Parametric study of various structural framing systems & effect of substructure modelling on super structure

PARAMETRIC STUDY OF VARIOUS STRUCTURAL FRAMING
SYSTEMS AND EFFECT OF SUBSTRUCTURE MODELLING ON
SUPERSTRUCTURE
A dissertation submitted to
The Maharaja Sayajirao University of Baroda
in partial fulfillment of the requirements for
the degree of
MASTER OF ENGINEERING (CIVIL)
in
STRUCTURAL ENGINEERING
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CERTIFICATE
This is to certify that the dissertation entitled,
“PARAMETRIC STUDY OF VARIOUS STRUCTURAL FRAMING
SYSTEMS AND EFFECT OF SUBSTRUCTURE MODELLING ON
SUPERSTRUCTURE”
Submitted by
SOHAIL S DHANPURWALA
in partial fulfillment for the award of degree of
MASTER OF ENGINEERING (CIVIL)
in STRUCTURAL ENGINEERING
to THE MAHARAJA SAYAJIRAO UNIVERSITY OF BARODA, is the record of the
work carried out by him under my supervision and guidance. The matter
presented here, to the best of my knowledge, has not been submitted
earlier for the award of any other degree.
EXTERNAL GUIDE
V. V. SHAH
Deputy Manager
Civil & Steel Structure Department,
LINDE Engineering Pvt. Ltd.,
Vadodara.
INTERNAL GUIDE
Dr. G. S. DOIPHODE
Associate Professor
Applied Mechanics Department,
Faculty of Technology & Engineering,
M. S. University of Baroda,
Vadodara.
HEAD
Dr. B. A. SHAH
Associate Professor
Applied Mechanics Department,
Vadodara.
DEAN
Prof. (Dr.) S. S. BHATTACHARYA
Vadodara.

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ACKNOWLEGMENTS
I would like to thank those who have contributed to the realization of my thesis
report. This work would not have been possible without the guidance and constant
support of the following persons, to whom I like to express my sincere gratitude.
To begin with, I would like to thank DIPAL OZA (Head, Civil & Steel Structure
Department, Linde Engineering) and VISHAL SHAH (Deputy Manager, Civil & Steel
Structure Department, Linde Engineering) for giving me the opportunity to work on this
project. They are the initiator of this dissertation topic based on “PARAMETRIC STUDY
OF VARIOUS STRUCTURAL FRAMING SYSTEMS AND EFFECT OF SUBSTRUCTURE
MODELLING ON SUPERSTRUCTURE”. During the time working on my thesis he guided
me, was very critical and had given me a lot of feedback, which gave me a better
understanding of the broad subject that this thesis covered.
I also would like to thank VIPUL PATEL (Deputy Manager, Civil & Steel Structure
Department, Linde Engineering) who also guided me, especially in the intermediate
phase of the thesis. During my time working on my thesis at Linde Engineering I got a lot
of support from the wonderful employees. I am also very thankful for the Geotechnical
expert, Dr. KANNAN IYER (Deputy Manager, Civil & Steel Structure Department, Linde
Engineering) who provided me with a lot of practical knowledge in geotechnical
engineering.
I would also like to thank my mentor Dr. G. S. DOIPHODE (Associate Professor,
Applied Mechanics Department) from the Faculty of Technology & Engineering (M.S.
University) for helping me in the starting phase with the documents I had to prepare for
beginning my thesis.
I further extend my thanks to Dr. B. A. SHAH, Head, Applied Mechanics
Department for providing the facilities for research work and extending all help for the
research.
Finally I would like to thank Salim Dhanpurwala my father, Sakina Dhanpurwala
my loving mother. Brothers Roshan and Hussain. I would also like to thank all my friends
at MSU for helping me during my studies in the Vadodara. With your love and support I
was able to finish my study.
July 2016 Sohail S. Dhanpurwala

ii
ABSTRACT
This thesis contains complete study in two parts which is as follows:
Part I (Parametric Study of Various Structural Framing Systems)
Parametric study has been carried out to illustrate the impact of various types of
external loading pattern on various types of structural framing systems. The study
includes parameters such as frame with different support condition, frame with
different height to width ratio, frame with change in elevation of load point, frame
with single bay and multiple bay, frame with different plan bracing system and
different structural systems under action of vertical and horizontal load. Comparison
of deflection and structural weight is done for the selected parameters.
Part II (Effect of Substructure Modelling on Superstructure)
A steel frame has been analysed with different foundation condition to study the
effect of modelling of substructure on superstructure. Plane frame is analysed with
pinned condition at base plate level, fixed condition at the top of foundation,
foundation modelled with plate elements and pile foundation modelled with plate
elements. Winkler‘s spring base is applied in software by assigning nodal springs
having value equal to soil stiffness at the base of discretized plate for isolated
foundation and by assigning nodal springs having value equal to pile stiffness at the
base of discretized plate for pile foundation. The parameters varied for the study are
the modulus of subgrade reaction of the soil, pile stiffness, depth of foundation, height
of superstructure, unsymmetrical gravity load, extent of substructure modelling and
type of connection at interface. A comparison of the displacements of the frame is

iii
done. A comparison of the lateral displacement of top node of the frame is carried out
for each case.
The results of the study will help Structural and other discipline engineers to
understand impact of loads on structure which is essentially required for selection of
right structural system and assessing impact of changes in loads on structures to
adopt overall economical approach for structural arrangement.

iv
Table of Contents
ACKNOWLEGMENTS...........................................................................................................................................i
ABSTRACT...........................................................................................................................................................ii
List of Figures ...................................................................................................................................................vii
List of Tables......................................................................................................................................................ix
List of Graphs.....................................................................................................................................................xi
Notations & Abbreviations ..............................................................................................................................xii
PART - I
INTRODUCTION TO PART I.............................................................................................................................1
GENERAL ..............................................................................................................................................11.1
OBJECTIVE ............................................................................................................................................21.2
SELECTION OF PARAMETERS FOR RESULT COMPARISION ..................................................................31.3
1.3.1 Deflection.............................................................................................................................. 3
1.3.2 Structural weight................................................................................................................... 4
SELECTION OF 2-D FRAME..............................................................................................................................6
INDUSTRIAL PROCESS STRUCTURE ......................................................................................................62.1
STEEL SECTIONS ...................................................................................................................................82.2
STRENGTH AND SEVICEABILITY CHECK................................................................................................92.3
STRUCTURAL SYSTEMS & LOAD ACTIONS................................................................................................ 10
CHAPTER OVERVIEW......................................................................................................................... 103.1
STRUCTURAL FRAMING SYSTEMS..................................................................................................... 103.2
3.2.1 Braced frame (vertical) ....................................................................................................... 10
3.2.2 Moment frame.................................................................................................................... 11
3.2.3 Partial braced frame ........................................................................................................... 13
3.2.4 Combined frame ................................................................................................................. 14
3.2.5 Concrete and steel composite frame.................................................................................. 15
3.2.6 Plan bracing system ............................................................................................................ 16
STRUCTURAL ASPECTS ...................................................................................................................... 173.3
3.3.1 Base condition – Fixed ........................................................................................................ 18
3.3.2 Base condition – Pinned...................................................................................................... 18
FRAMING OPTIONS........................................................................................................................... 193.4
3.4.1 Height to width ratio........................................................................................................... 20
3.4.2 Multiple bay frames............................................................................................................ 21

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LOAD ACTIONS.................................................................................................................................. 223.5
3.5.1 Vertical load ........................................................................................................................ 22
3.5.2 Horizontal load.................................................................................................................... 24
PARAMETRIC STUDY AND RESULTS.......................................................................................................... 26
EFFECT OF VERTICAL LOAD ON DIFFERENT FRAMING SYSTEM........................................................ 264.1
4.1.1 Moment frame, Combined frame and Partial braced frame comparison.......................... 26
4.1.2 UDL and Point load comparison for moment frame........................................................... 29
EFFECT OF HORIZONTAL LOAD ON DIFFERENT FRAMING SYSTEM .................................................. 334.2
4.2.1 Braced frame, Moment frame, Combined frame and Partial braced frame comparison.. 33
4.2.2 Support condition comparison ........................................................................................... 37
4.2.3 Effect of frame Height to Width ratio................................................................................. 42
4.2.4 Effect of Elevation of Load point......................................................................................... 45
4.2.5 Single bay moment frame and Multiple bay frame comparison........................................ 48
4.2.6 Composite frame and Steel frame comparison.................................................................. 52
4.2.7 Plan bracing system ............................................................................................................ 55
4.2.8 Vertical bracing in frame..................................................................................................... 61

vi
PART - II
INTRODUCTION TO PART II ........................................................................................................................ 65
GENERAL ........................................................................................................................................... 655.1
OBJECTIVE ......................................................................................................................................... 665.2
SOIL MODELS USED IN SOIL STRUCTURE INTERACTION................................................................... 665.3
5.3.1 NUMERICAL MODELS.......................................................................................................... 67
LITERATURE REVIEW................................................................................................................................... 71
PRELIMINARY REMARK ..................................................................................................................... 716.1
LITERATURE STUDIED........................................................................................................................ 716.2
MODELLING AND ANALYSIS ........................................................................................................................ 77
METHODOLOGY ................................................................................................................................ 777.1
CODAL PROVISIONS .......................................................................................................................... 797.2
PARAMETRIC STUDY & RESULTS............................................................................................................... 81
TYPE OF SOIL ..................................................................................................................................... 828.1
DEPTH OF FOUNDATION................................................................................................................... 878.2
HEIGHT OF SUPERSTRUCTURE AND TYPE OF ANALYSIS ................................................................... 918.3
8.3.1 Height of superstructure..................................................................................................... 91
8.3.2 Type of analysis................................................................................................................... 96
UNSYMMETRICAL GRAVITY LOAD..................................................................................................... 998.4
TYPE OF CONNECTION AT INTERFACE ............................................................................................ 1048.5
PILE MODELING............................................................................................................................... 1088.6
DECISION MATRIX....................................................................................................................................... 112
FUTURE SCOPES.............................................................................................................................. 1149.1
REFERENCES........................................................................................................................................... 115

Parametric Study of various Structural Framing Systems Page vii
List of Figures
FIG. 1 OVERVIEW OF PIPE RACK ....................................................................................................... 7
FIG. 2 OVERVIEW OF TECHNOLOGICAL STRUCTURE.......................................................................... 7
FIG. 3 TYPES OF BRACED FRAMES .................................................................................................. 11
FIG. 4 MOMENT FRAME................................................................................................................... 12
FIG. 5 PARTIAL BRACED FRAME ..................................................................................................... 13
FIG. 6 COMBINED FRAME ................................................................................................................ 14
FIG. 7 COMPOSITE FRAME............................................................................................................... 15
FIG. 8 ALTERNATIVE PLAN BRACING ARRANGEMENT .................................................................... 17
FIG. 9 BASE CONDITION - FIXED ..................................................................................................... 18
FIG. 10 BASE CONDITION - PINNED ................................................................................................. 19
FIG. 11(A) 3 TIER FRAME ................................................................................................................ 20
FIG. 11(B) 2 TIER FRAME ................................................................................................................ 20
FIG. 12(A) SINGLE BAY FRAME....................................................................................................... 21
FIG. 12(B) MULTIPLE BAY FRAME .................................................................................................. 21
FIG. 13 UNIFORMLY DISTRIBUTED LOAD (UDL) ............................................................................ 23
FIG. 14 POINT LOAD........................................................................................................................ 23
FIG. 15 FRAME WITH HORIZONTAL / LATERAL LOAD...................................................................... 25
FIG. 16 FRAMING SYSTEMS SUBJECTED TO UDL ............................................................................ 26
FIG. 17 MOMENT FRAMES WITH UDL & POINT LOAD .................................................................... 29
FIG. 18 DEFLECTION & STRENGTH RATIO COMPARISON................................................................. 30
FIG. 19 FRAMING SYSTEMS SUBJECTED TO HORIZONTAL LOAD ..................................................... 33
FIG. 20 FRAMES WITH FIXED & PINNED SUPPORT CONDITION........................................................ 37
FIG. 21 STRENGTH RATIO COMPARISON........................................................................................... 38
FIG. 22 COLUMN SIZE COMPARISON ................................................................................................ 39
FIG. 23 SUPPORT REACTION............................................................................................................ 40
FIG. 24 FRAMES WITH SAME USEABLE SPACE................................................................................. 42
FIG. 25 FRAMES WITH CHANGE IN ELEVATION OF LOAD POINT...................................................... 45
FIG. 26 SINGLE BAY & MULTIPLE BAY MOMENT FRAME............................................................... 48
FIG. 27 COMPOSITE FRAME & STEEL FRAME .................................................................................. 52

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FIG. 28 FRAME WITH NO PLAN BRACING ........................................................................................ 55
FIG. 29 DIFFERENT PLAN BRACING SYSTEM ................................................................................... 56
FIG. 30 PLAN VIEW OF FRAMES FOR STRUCTURAL WT. COMPARISON............................................ 59
FIG. 31 SIGN CONVENTION FOR SUPPORT REACTION ...................................................................... 63
FIG. 32 MODELLING OF FOUNDATION ............................................................................................. 78
FIG. 33 FRAMES WITH DIFFERENT BASE SUPPORT .......................................................................... 81
FIG. 34 SELECTED FRAME FOR CASE 8.1......................................................................................... 83
FIG. 36 SELECTED FRAMES FOR CASE 8.3 ....................................................................................... 92
FIG. 37 SECOND-ORDER EFFECTS IN A VERTICAL CANTILEVER ...................................................... 96
FIG. 39 SELECTED FRAME FOR CASE 8.5....................................................................................... 104
FIG. 40 PILE MODELLING WITH SPRING AT REGULAR INTERVAL .................................................. 108
FIG. 41 PILE MODELLED AS EQUIVALENT SINGLE SPRING SUPPORT............................................. 109
FIG. 42 FRAMES WITH FULL PILE MODELLED & SINGLE POINT PILE STIFFNESS ........................... 109
FIG. 43 DECISION MATRIX ............................................................................................................ 113

ix
List of Tables
TABLE 1 STRUCTURAL WT. COMPARISON FOR FRAMES SUBJECTED TO UDL .................................. 28
TABLE 2 STRUCTURAL WT. COMPARISON FOR FRAMES WITH UDL & POINT LOAD......................... 31
TABLE 3 DEFLECTION COMPARISON FOR FRAMES SUBJECTED TO HORIZONTAL LOAD..................... 34
TABLE 4 STRUCTURAL WT. COMPARISON FOR FRAMES SUBJECTED TO HORIZONTAL LOAD ............ 35
TABLE 5 DEFLECTION COMPARISON FOR FIXED & PINNED BASE FRAME......................................... 38
TABLE 6 STRUCTURAL WT. COMPARISON FOR FIXED & PINNED BASE FRAME ................................ 39
TABLE 7 REACTION COMPARISON FOR FIXED & PINNED BASE FRAME ............................................ 40
TABLE 8 DEFLECTION COMPARISON FOR FRAMES WITH SAME USEABLE SPACE ............................... 43
TABLE 9 STRUCTURAL WT. COMPARISON FOR FRAMES WITH SAME USEABLE SPACE ...................... 44
TABLE 10 DEFLECTION COMPARISON FOR CHANGE IN ELEVATION OF LOAD POINT ......................... 46
TABLE 11 STRUCTURAL WT. COMPARISON FOR CHANGE IN ELEVATION OF LOAD POINT................. 47
TABLE 12 DEFLECTION COMPARISON FOR SINGLE BAY & MULTIPLE BAY FRAME........................... 49
TABLE 13 STRUCTURAL WT. COMPARISON FOR SINGLE BAY & MULTIPLE BAY FRAME.................. 50
TABLE 14 DEFLECTION COMPARISON FOR COMPOSITE & STEEL FRAME ......................................... 53
TABLE 15 STRUCTURAL WT. COMPARISON FOR COMPOSITE & STEEL FRAME................................. 54
TABLE 16 DEFLECTION COMPARISON FOR FRAME WITHOUT PLAN BRACING ................................... 57
TABLE 17 DEFLECTION COMPARISON FOR FRAME WITH X-TYPE PLAN BRACING ............................. 57
TABLE 18 DEFLECTION COMPARISON FOR FRAME WITH GIRDER TYPE PLAN BRACING .................... 57
TABLE 19 DEFLECTION COMPARISON FOR FRAME WITH DIAMOND TYPE PLAN BRACING................. 57
TABLE 20 HORIZONTAL DRIFT RATIO COMPARISON FOR FRAMES WITH OR WITHOUT PLAN BRACE. 58
TABLE 21 STRUCTURAL WT. COMPARISON FOR FRAMES WITH & WITHOUT PLAN BRACING............ 59
TABLE 22 SUPPORT REACTION COMPARISON FOR (+ VE) FORCES .................................................... 64
TABLE 23 SUPPORT REACTION COMPARISON FOR (- VE) FORCES ..................................................... 64
TABLE 24 SELECTED SUBGRADE MODULUS.................................................................................... 83
TABLE 25 FOUNDATION DETAILS FOR FRAME IN FIG. 34 ................................................................ 83
TABLE 26 CHANGE IN DEFLECTION WITH TYPE OF SOIL [ISOLATED FOUN.].................................... 84
TABLE 27 SELECTED PILE STIFFNESS.............................................................................................. 85
TABLE 28 CHANGE IN DEFLECTION WITH TYPE OF SOIL [PILE FOUN.] ............................................ 86
TABLE 29 FOUNDATION DETAILS FOR FRAME IN FIG. 35 ................................................................ 88
TABLE 30 CHANGE IN DEFLECTION WITH DEPTH OF FOUN. [ISOLATED FOUN.]............................... 89

x
TABLE 31 CHANGE IN DEFLECTION WITH DEPTH OF FOUN. [PILE FOUN.]........................................ 90
TABLE 32 FOUNDATION DETAILS FOR FRAMES IN FIG. 36 .............................................................. 91
TABLE 33 CHANGE IN DEFLECTION WITH HT. OF SUPERSTRUCTURE [ISOLATED FOUN.- 1ST
ORDER] . 94
TABLE 34 CHANGE IN DEFLECTION WITH HT. OF SUPERSTRUCTURE [PILE FOUN. -1ST
ORDER].......... 95
TABLE 35 CHANGE IN DEFLECTION WITH HT. OF SUPERSTRUCTURE [ISOLATED FOUN. - 2ND
ORDER] 97
TABLE 36 CHANGE IN DEFLECTION WITH HT. OF SUPERSTRUCTURE [PILE FOUN. - 2ND
ORDER] ........ 98
TABLE 37 FOUNDATION DETAILS FOR FRAME IN FIG. 38 .............................................................. 100
TABLE 38 CHANGE IN DEFLECTION WITH UNSYMMETRICAL LOAD [ISOLATED FOUN.]................. 101
TABLE 39 INCREASE IN DEFLECTION DUE TO UNSYMMETRICAL LOAD [ISOLATED FOUN.]........... 101
TABLE 40 CHANGE IN DEFLECTION WITH UNSYMMETRICAL LOAD [PILE FOUN.] ......................... 102
TABLE 41 INCREASE IN DEFLECTION DUE TO UNSYMMETRICAL LOAD [PILE FOUN.].................... 103
TABLE 42 FOUNDATION DETAILS FOR FRAME IN FIG. 39 .............................................................. 105
TABLE 43 CHANGE IN DEFLECTION WITH CONNECTION TYPE [ISOLATED FOUN.]......................... 106
TABLE 44 CHANGE IN DEFLECTION WITH CONNECTION TYPE [PILE FOUN.] ................................. 106
TABLE 45 PILE STIFFNESS AT DIFFERENT DEPTH.......................................................................... 110
TABLE 46 SINGLE POINT PILE SPRING STIFFNESS ......................................................................... 111
TABLE 47 DEFLECTION COMPARISON FOR FRAME WITH DIFFERENT PILE MODEL........................ 111

xi
List of Graphs
GRAPH 1 STRUCTURAL WT. COMPARISON FOR FRAMES SUBJECTED TO UDL.................................. 28
GRAPH 2 STRUCTURAL WT. COMPARISON FOR FRAMES WITH UDL & POINT LOAD ........................ 32
GRAPH 3 DEFLECTION COMPARISON FOR FRAMES SUBJECTED TO HORIZONTAL LOAD ................... 34
GRAPH 4 STRUCTURAL WT. COMPARISON FOR FRAMES SUBJECTED TO HORIZONTAL LOAD........... 35
GRAPH 5 DEFLECTION COMPARISON FOR FIXED & PINNED BASE FRAME ........................................ 38
GRAPH 6 STRUCTURAL WT. COMPARISON FOR FIXED & PINNED BASE FRAME................................ 39
GRAPH 7 DEFLECTION COMPARISON FOR FRAMES WITH SAME USEABLE SPACE .............................. 43
GRAPH 8 STRUCTURAL WT. COMPARISON FOR FRAMES WITH SAME USEABLE SPACE...................... 44
GRAPH 9 DEFLECTION COMPARISON FOR CHANGE IN ELEVATION OF LOAD POINT........................... 46
GRAPH 10 STRUCTURAL WT. COMPARISON FOR CHANGE IN ELEVATION OF LOAD POINT ................ 47
GRAPH 11 DEFLECTION COMPARISON FOR SINGLE BAY & MULTIPLE BAY FRAME.......................... 49
GRAPH 12 STRUCTURAL WT. COMPARISON FOR SINGLE BAY & MULTIPLE BAY FRAME ................. 50
GRAPH 13 DEFLECTION COMPARISON FOR COMPOSITE & STEEL FRAME......................................... 53
GRAPH 14 STRUCTURAL WT. COMPARISON FOR COMPOSITE & STEEL FRAME................................ 54
GRAPH 15 DRIFT RATIO COMPARISON FOR FRAMES WITH OR WITHOUT PLAN BRACE...................... 58
GRAPH 16 STRUCTURAL WT. COMPARISON FOR FRAMES WITH & WITHOUT PLAN BRACING ........... 60
GRAPH 17 DEFLECTION V/S TYPE OF SOIL [ISOLATED FOUN.]......................................................... 84
GRAPH 18 DEFLECTION V/S PILE STIFFNESS [PILE FOUN.]............................................................... 85
GRAPH 19 DEFLECTION V/S DEPTH OF FOUNDATION [ISOLATED FOUN.] ......................................... 89
GRAPH 20 DEFLECTION V/S DEPTH OF FOUNDATION [PILE FOUN.].................................................. 89
GRAPH 21 DEFLECTION V/S SUPERSTRUCTURE HEIGHT [ISOLATED FOUN.] .................................... 93
GRAPH 22 DEFLECTION V/S SUPERSTRUCTURE HEIGHT [PILE FOUN.]............................................. 94
GRAPH 23 DEFLECTION V/S SUPERSTRUCTURE HEIGHT [ISOLATED FOUN. - 2ND
ORDER] ................. 97
GRAPH 24 DEFLECTION V/S SUPERSTRUCTURE HEIGHT [PILE FOUN. - 2ND
ORDER] ......................... 98
GRAPH 25 DEFLECTION V/S UNSYMMETRICAL LOAD [ISOLATED FOUN.]...................................... 101
GRAPH 26 DEFLECTION V/S UNSYMMETRICAL LOAD [PILE FOUN.] ............................................... 102
GRAPH 27 DEFLECTION V/S CONNECTION AT INTERFACE [ISOLATED FOUN.]................................ 105
GRAPH 28 DEFLECTION V/S CONNECTION AT INTERFACE [PILE FOUN.] ........................................ 106

xii
Notations & Abbreviations
 For column beam framing connection, shows rigid connection (moment connection).
 For column beam framing connection, shows simple connection (shear connection).
 In different structural framing system, or shows bracing member.
 RCC : Reinforced Cement Concrete
 WT. or Wt. : Weight
 Ht. : Height
 foun. : Foundation
Notes:
 All dimensions are in Meters except specified.
 All loads are in kN except specified.
 Deflection values are in mm.

Parametric Study of various Structural Framing Systems Page 1
INTRODUCTION TO PART I
GENERAL1.1
The process of designing a structural framing system in plant involves lot of
consideration and coordination between different disciplines and groups involved in the
project. The major groups involve are Process, Piping, Stress, Static & Rotating
equipment, Electrical & Instrumentation and Civil & steel structural. The initial study
begins with Process department which gives input in the form of Piping &
Instrumentation diagram and 2D-layout to piping department. Piping department does
preliminary 3D modelling, which is input for stress department. The stress department
performs the stress analysis for critical lines and calculates the load generated by the
critical lines, which is then passed to the civil & structural department. Civil & Structural
department designs the foundation based on the load input received from stress
department. The structural design is incorporated in the other discipline to check if it is
acceptable with them. If there are any constraints in the design by any discipline the
points are discussed & mutually agreed and resolved respectively. The finalization of the
design will require the above to be repeated again & again.
In all the projects, often the final piping, raceway and equipment information are
available at later stage of project. Civil & steel structural department is the last to get
input and need to give output first. Thus, civil & structural department use judgment
based on experience when applying or allowing for loads that are not known, justifying
CHAPTER 1

Introduction to Part I Chapter 1
them in the design basis under design philosophy. But at the later stage of the project
when all the load details become available, actual load values may contradict with the
load values used for design thus, there is need for redesign. Parametric study of
structural framing systems commonly encountered in industrial plants has been carried
out. It explains the behaviour of different framing system under different load actions.
Up to certain extent, this study will be helpful to know the effect of revised input (new
load values) on the structural frame. This dissertation work helps in identifying better
structural framing system from selected for study under various conditions.
OBJECTIVE1.2
This study intends to explain effect of different types of external loading patterns on
various types of structural framing systems. Parametric study has been carried out to
illustrate the effect. The results of the study will help Structural and other discipline
engineers to understand impact of loads on structure, which is essentially required for
selection of right structural system and assessing impact of changes in loads on
structures to adopt overall economic approach for structural arrangement. The study
includes parameters such as change in value of horizontal load, change in form of vertical
load, change in elevation of horizontal point load on structural framing system etc. Such
study will help structural engineer to understand the impact of change in these
parameters on structural framing system and it will also be helpful to structural to take
decision of any change in parameter.

SELECTION OF PARAMETERS FOR RESULT COMPARISION1.3
Values of top point lateral displacement and structural weight for different structural
framing systems are evaluated and compared. Structural framing weight is compared to
check economy of the structural system and Deflection is compared as it impacts main
component of the plant i.e. equipment & piping. Excessive deflection also impacts
structural and functional requirement of the framing system.
1.3.1 Deflection
Due to lateral deflection of frame there will be loss of serviceability. Loss of serviceability
includes misalignment of piping and industrial equipment. In pressure piping, pipe
risers may fail due to inter-story drift between adjacent floors, that is, differential
movement between the points of support located on different floors of the building. Or
else instead of whole failure the pipes or pipe joints may fail and leak. Improperly
supported pipes can become dislodged and fall. Joints may fail due to sway of frame in
floor mounted pipes. Also differential settlement can lead to excessive internal forces /
stresses in piping.
Piping system account for a significant portion of the total plant cost, at times as much as
one-third of the total investment. Pipe rack failures could cause serviceability problems
for plant operations. Failures of pipe support systems could potentially impact the
health, welfare, and safety of plant personnel due to pipe breakage or leaks. The failure of
pipe supports or excessive deflection of support may result into following problems with
piping:

 Piping stresses in excess of those permitted in the Code.
 Leakage at joints.
 Excessive thrusts and moments on connected equipment.
 Excessive interference with thermal expansion and contraction in piping.
 Unintentional disengagement of piping from its supports.
The lateral deflection value has a particular importance of serviceability requirement.
The following problems are associated with large values of lateral deflection.
 Structural damage: Deflection related investigations have shown that during
earthquake, large damage potential is observed with large values of deflection
irrespective of design and detailing of the structure.
 Non – structural damage: Larger deflection may damage the cladding; create
problems like bending of doors and windows frames.
 Discomfort to occupants: The occupants feel discomfort with the large lateral
deflection / drift although no structural damages are observed.
1.3.2 Structural weight
Selection of an appropriate structural framing system in steel structures is one of the
important factor affecting the weight of consumed steel and consequently, the economics
of the project. The study involves comparison of structural weight of different framing
system, comparison of same structural system with different structural aspect. In other
words, it is attempted to evaluate and compare the weight of consumed steel. Today, one
of the indicators that affect the quality of construction is final cost. Consequently, one of

the criteria for design of the structure is to reduce weight and making the plant more and
more economical. In steel structures with the industrial utility, weight of consumed steel
is an appropriate basis for decision of investors and constructors. Weight of consumed
steel in steel structures is affected by structural system. Therefore, selection of a suitable
structural system is one of the important and effective decisions in achieving economy of
the project.

SELECTION OF 2-D FRAME
INDUSTRIAL PROCESS STRUCTURE2.1
Pipe rack and Technological structure are commonly encountered in oil and gas industry.
Pipe rack is used to carry pipes (process and utility) to process area. Technological
structure is used to support process equipment and their connected piping. Generally, in
pipe rack, transverse frames are spaced at 5.0 – 7.0 m, this spacing is chosen based on
the maximum allowable spans for the pipes or cable trays being supported. Spacing can
vary based on the estimated size and allowable deflection limits of the pipe being
supported.
Longitudinal struts are usually offset from the beams used to support the pipes. Levels of
the pipe rack are assumed to be fully loaded with pipe, and when the pipes need to exit
the rack to the side to connect to equipment, a flat turn cannot be used as this would
clash with the other pipes on the same level. The pipe is typically routed to turn either up
or down and then out of the rack at the level of the longitudinal struts where the pipe can
be supported on the longitudinal struts before exiting the rack. In technological
structure, spacing of structural frames is decided based on layout of the equipment on
the structure and ground.
Fig. 1 and Fig. 2 shows an isometric view of the pipe rack and technological (equipment
supporting) structure respectively.
CHAPTER 2

Selection of 2-D frame Chapter 2
Fig. 1 Overview of Pipe Rack
Fig. 2 Overview of Technological structure
The typical frame is chosen and modelled based on idealized conditions. A width of
6.0 m is chosen to allow one-way traffic along corridor. The height of the first level of the
structure is set at 5.0 m to provide sufficient height clearance along the access corridor.
In this study spacing between two transverse frames is set as 6.0 m c/c. Here 2-D frames

selected for the study are assumed to be braced in minor direction and effect of same is
considered in the design.
Based on D. A. Nelson (W. W. University, 2008) results of the isolated moment frame
and the entire pipe rack segment, relatively small differences were observed. Because the
braced bay supports any longitudinal loading, relatively very little weak axis column
moment or longitudinal deflection occurs that would affect the design of the columns or
beams that are part of the transverse frame. Ratios of demand to capacity showed errors
of less than 5% on member design, when using the single frame compared to the full pipe
rack structure. Therefore, analysis of a single transverse frame will be used to simplify
calculations. 2-D frames are used for the study of the behaviour of framing
arrangements. However, derived conclusions and underlining principles are applicable
to 3-D structures. Hence, concepts explained in the different cases can be applied by
engineers suitably to plant structures.
STEEL SECTIONS2.2
European steel sections are used throughout this study. Equal angle sections are used for
bracing member and I – section are used for column and beam members. In this study
HE sections are used, which are classified as A, B and M e.g. HE200A, HE200B and
HE200M respectively. HE _A sections are only used in this thesis.

STRENGTH AND SEVICEABILITY CHECK2.3
Strength and serviceability checks are performed in STAAD.Pro V8i, where RATIO
parameter (Permissible ratio of actual load to allowable load) is set to be 1.0. The
strength checks are based on AISC 360-05.
Serviceability checks are made using the calculated deflections from STAAD.Pro V8i.
Various limits on serviceability are based on specific project requirements. For checking
serviceability criteria adopted deflection as per AISC 360-05 limits are:
 For horizontal drift = Height/200 [AISC Cl. L4]
 For vertical deflection = Length/360 [AISC Cl. L]

STRUCTURAL SYSTEMS & LOAD ACTIONS
CHAPTER OVERVIEW3.1
The different structural framing systems which are commonly used in the industrial
plants have been selected for study and are explained in this chapter as mentioned
below:
 Braced frame (Vertical / Elevation)
 Moment frame
 Partial braced frame
 Combined frame
 Composite frame
 Plan bracing system
The brief information on different types of support conditions at base plate level and
different framing options is also included in this chapter. This chapter also covers
different load actions on these structural framing systems, which are of horizontal and
vertical point loading and UDL respectively.
STRUCTURAL FRAMING SYSTEMS3.2
3.2.1 Braced frame (vertical)
A Braced frame is a structural system, which is designed primarily to resist lateral
forces i.e. wind and earthquake forces. Bracing members in the frame are designed to
resist tension and compression, which is same as truss. As per literature braced frames
have much higher initial strength and stiffness. Bracing is a much effective than rigid
CHAPTER 3

Structural systems & Load actions Chapter 3
joints at resisting deformation of the frame. Braced frames use less material and have
simpler connections than moment-resisting frames. Fig. 3 shows different braced
frames.
Fig. 3 Types of Braced Frames
The bracing members can be arranged in different forms to carry solely tension or
alternatively tension and compression. When it is designed to take tension only, the
bracing is made up of crossed diagonals. Depending on the wind direction, one diagonal
will take all the tension while the other remains inactive. Tensile bracing is smaller than
the equivalent strut and is usually made up of flat - plate, channel or angle sections and
rod. When designed to resist compression, the bracings become struts and the most
common arrangement is the ‗K‘ brace/Chevron bracing.
3.2.2 Moment frame
Moment frames are rectilinear assemblages of beams and columns, with the beams
rigidly connected to the columns. Moment frame involves constructing very rigid beam-

to-column connections that permit moment transfer across the joint. Resistance to
lateral forces is provided primarily by rigid frame action - that is, by the development
of bending moment and shear force in the frame members and joints. By virtue of the
rigid beam-column connections, a moment frame cannot displace laterally without
bending the beams or columns depending on the geometry of the connection. The
bending rigidity and strength of the frame members is therefore the primary source of
lateral stiffness and strength for the entire frame. Fig. 4 shows Moment frame.
Fig. 4 Moment Frame
A typical moment-resisting beam-to-column steel-framed connection involves
transferring horizontal loads through the beam flanges directly to the column flanges by
using angles and column web stiffener plates. The analysis of the connection is fairly
complex, labour-intensive and expensive to construct and is not as good as other

methods of stabilization. In comparison with braced frames, moment frames have more
deformation capacity with less stiffness.
3.2.3 Partial braced frame
Partial braced frame can be obtained by providing an element called "knee" in between
the beam and column. Partial braced frames are modified form of braced frame in which
braced element is cut short and connected to the adjacent column. The key component of
the Partial braced frame is the knee element, which controls the initial elastic stiffness of
the frame and also limits interstorey drifts. Moment at the beam-column junction may
be released partially or fully. Fig. 5 shows Partial braced frame.
Fig. 5 Partial Braced Frame
Due to vertical (gravity) load, knee bracing is under compression and due to lateral load;
knee bracing is under compression or tension, depending upon the direction of the
lateral load. Hence, knee bracing and its connection with the beam-column are to be

designed for compressive load as well as for tensile loads. In the beam and column, at the
junction of knee bracing, the design force in the knee bracing may be resolved in two
components i.e. horizontal and vertical. These components will cause bending in the
beam and column. Hence, beam and column are to be designed for bending at the
junction of knee bracing.
3.2.4 Combined frame
This framing system provides resistance to lateral loads and provides stability to the
structural system, by combination of bracing and rigid connection. This frame can be
used to reduce horizontal deflection. The key component of the combined frame is the
bracing in the bottom storey, which provides higher initial strength and stiffness to the
complete frame.
Fig. 6 Combined Frame
Combined frame is very useful where lateral load at bottom storey is higher compared to
all other storey. This structural system can also be used where height of bottom story is

quiet more compared to other storey and bottom storey column governs in slenderness.
Fig. 6 shows Combined frame.
3.2.5 Concrete and steel composite frame
In this framing system, lower part is made of RCC column. Pinned condition is
considered at RCC and steel column junction. The frame shown in Fig. 7 is a Composite
frame. The concrete column in bottom part increases stiffness of the frame. Due to
higher stiffness of concrete part, deflection at top node is less compared to steel frame.
This structural system is very useful where there is fire resistance requirement in the
bottom part of the frame. The concrete part can be either column only or it can have
concrete frame where the beam can be either be simply supported or console (in case of
precast) or have rigid connection with column.
Fig. 7 Composite Frame

3.2.6 Plan bracing system
In most commercial buildings, floor and roof diaphragms are used to distribute loads in
the horizontal plane of the structure to the lateral load resisting system. Due to the open
nature of most industrial structures, diaphragms are not present, and horizontal bracing
is often used to distribute the loads in the horizontal plane. Horizontal bracing is also
used in heavily loaded commercial structures, where a diaphragm is not present, or
where the strength or stiffness of the diaphragm is not adequate. When horizontal
bracing is used, the beams at that elevation become members in a horizontal truss
system, carrying axial loads in addition to the normal bending and shear loads. From
design point of view attention should be paid to the beam end connections within the
truss system, because the axial loads transferring through the connections is of higher
magnitude. A bracing system contributes to the distribution of load and provides
restraint to compression flanges or chords where they would otherwise be free to buckle
laterally. A small tonnage of steel bracing can be used to provide huge increases in the
bending resistance of the main beams. Plan bracing is perhaps the most obvious way to
prevent lateral buckling of a compression flange and plan bracing also provides lateral
restraint, i.e. it restrains the compression flanges of beams from moving sideways. Plan
bracing takes the form of diagonal members, usually angle sections, connecting the
compression flanges of the main beams, to form a truss when viewed in plan. This makes
a structure very stiff in response to lateral movement. Most plan bracing will be at top

flange level. Error! Reference source not found. shows different plan bracing
arrangements.
Without bracing, beams vulnerable to buckling
With plan bracing, buckling is controlled
Fig. 8 Alternative Plan Bracing Arrangement
STRUCTURAL ASPECTS3.3
There are two base conditions – fixed and pinned which are considered for the study. In
the study base condition refers to support condition at the base plate level in the framing
system. Detailed description is given below.

3.3.1 Base condition – Fixed
A fixed base column is more of a special situation base connection, has a lot of stiffness
which resist horizontal, vertical, and moment loads. The additional stiffness at the base
and in the columns, means less stiffness is required from the rest of the building
members. The foundations may need to be larger than the pinned base because of
moment transferred at base. The fabrication and installation of fixed base columns can
also be more difficult because of the additional plates on the column and anchor rods
required. Typically, fixed base columns are recessed below finished floor. The Fig. 9
shows fixed base column. There are a few options for this condition depending on the
size of the building and the loading.
Fig. 9 Base Condition - Fixed
3.3.2 Base condition – Pinned
A pinned base column is the standard column base found in most steel buildings. This
connection is pinned because it has enough stiffness to apply horizontal and vertical

loads to the foundations, but enough flexibility not to apply moment. Due to loading
when deflection requirements is very stringent, pinned base will require much more steel
than fixed base. The pinned base is typically very easy to install. Pinned base will have
smaller foundation size compared to fixed based. For pinned base condition, anchor
bolts are placed within section of column while for fixed base connections, anchor bolts
are placed outside the section. So higher pedestal sizes are expected in case of fixed base
conditions. Fig. 10 shows pinned type base connection.
Fig. 10 Base Condition - Pinned
FRAMING OPTIONS3.4
Two framing options namely frames with different height to width ratio and multiple bay
frames are considered in the present study. These two framing options are explained in
detail below.

3.4.1 Height to width ratio
An elevated multi-level pipe rack may be required for plant layout, equipment or process
reasons. As long as the required space beneath the pipe rack for accessibility and road
crossings has been taken into account, the rack can remain single level. However, in
most cases, multiple levels will be required. Within plant units, most process pipes are
connected to related unit equipment. Placing these pipes in the lower levels results in
shorter pipe runs, savings on piping costs and better process flow conditions. In this
aspect of structural system effect of frame height to width ratio has been checked.
Useable space of the frame is kept same while height and width are changed.
(a) 3 Tier Frame (b) 2 Tier Frame
Fig. 11
If horizontal clearance is available, width of the transverse frame is increased and
number of tiers can be decreased. But if sufficient space is not available one can decrease
the width and increase number of tier as per requirement. Example for the same is as

shown above. 3 tier-6.0 m wide transverse frame is shown in Fig. 11.a, useable space in
this frame is 18 m. 2 tier-9.0 m wide transverse frame is shown Fig. 11.b, useable space in
this frame is 18 m. Useable space in both the frames shown in Fig. 11 is almost same but
height to width ratio for 3 tier - 6.0 m wide frame is 1.83 (i.e. 11/6) and that for 2 tier -
9.0 m wide frame is 0.89 (i.e. 8/9) .
3.4.2 Multiple bay frames
In this aspect of structural system effect of number of bays has been checked. Useable
space of the frame is kept same while comparing number of bays. Example for the same
is shown below. Fig. 12.a shows 1 bay – 9.0m wide frame having useable space of 27.0 m
and Fig. 12.b shows 2 bays – 5.0m wide frame having useable space of 30.0 m. But
useable space for both the frames is almost same as second frame involves one additional
column. Multiple bay frame will require one additional foundation per every increase of
one additional bay while steel sections are lighter in multi bay frame.
(a) Single bay frame (b) Multiple bay frame
Fig. 12

LOAD ACTIONS3.5
In oil and gas sector structures are different than general building structures. Moreover,
frames have different loading as compared to general buildings structure. For these
structures, certain types of loading (e.g. piping load, equipment loads, etc…) are not
clearly mentioned in standard codes. These structures resist gravity loads as well as
lateral loads from either pipes, equipments, cable trays or wind and seismic loads. Loads
present in these kind of structures includes Dead Load (DL) of the structure, Live Load
(LL) on the structure, Temperature Load on Structure, Earthquake Load, Wind Load,
Pipe/ equipment Load (empty, operating & hydro test), Pipe Anchor / Guide Load, Pipe
Friction Load, Cable tray loads, etc.
3.5.1 Vertical load
The vertical load includes, Dead Load of the structure, Live Load on the structure, Pipe /
equipment (Empty, Operating, Hydro test), cable trays load, etc. These vertical loads can
be generated in the form of uniformly distributed load or Point load.
a. Uniformly Distributed Load (UDL)
At proposal stage of engineering, getting actual "Point loads" of all critical/non critical
lines is difficult and time consuming. So at this stage of project, generally loading is
available in the form of UDL (Typically Pipe size 10" and below). During stage of detail
engineering also, loads of small-bore lines (typically 6‖ below) available in the form of
UDL. For small-bore line, having loads in form of UDL is advantages because it will take
care of change in size/location of pipe or spacing between pipes. For example, in a bunch

of 7 lines, if some line sizes increase/decrease effective change in UDL would be less and
in case of change in the spacing between pipes changes or line is moved across the
section of rack, the UDL will have no or little changes. The example of uniformly
distributed load (UDL) is shown in Fig. 13 with beam having UDL throughout its span.
Fig. 13 Uniformly Distributed Load (UDL)
b. Point load
As the project develops, actual loads and locations become known, the structural design
should be carried out based on the actual data. Generally, a concentrated load should be
added for pipes that are 300 mm (12 inch) and larger in diameter. This assumption
needs to be verified by piping group for each project. The beam with point load /
concentrated load is shown in Fig. 14.
Fig. 14 Point Load
q 0
q 0
P
P

3.5.2 Horizontal load
Earthquake load, Wind load, Temperature load on structure, Pipe Anchor / Guide load,
Pipe Friction load etc. are considered as horizontal load acting on the structure. Wind
load on structural members, piping, electrical trays, equipment, platforms, and ladders
should be determined in accordance with project approved design code. Horizontal wind
should typically be applied to structural framing, cable tray vertical drop (if any), large
diameter pipes vertical drop (if any) and equipment only. The effects of longitudinal
wind on piping and trays running parallel to the wind direction should be neglected.
Seismic forces generated by the pipes, raceways, supported equipment, and structure
should be considered and should be based on their operating weights. Friction forces
caused by hot lines sliding across the pipe support during startup and shutdown are
assumed to be partially resisted through friction by nearby cold lines. Therefore nominal
unbalance friction force acting on a pipe support is considered in the design. Friction
between piping and supporting steel should not be relied upon to resist wind or seismic
loads. Industrial structures in oil and gas sector should be checked for anchor and guide
loads as determined by the pipe stress group. It may be necessary to use horizontal
bracing if large anchor forces are encountered. In this study horizontal load is applied
only in X-direction (major axis of the section).

Fig. 15 Frame with Horizontal / Lateral Load

PARAMETRIC STUDY AND RESULTS
The present work attempts to study impact of load action on different framing system. As
mentioned in chapter 1, two parameters namely Deflection and Structural weight of
different framing system like Moment frame, Braced frame, Partial braced frame,
Combined frame and Composite frame are compared. Structural weight is compared to
check economy of the structural system and deflection is compared as it impacts main
component of the plant i.e. piping as explained in previous chapter. Comparison of
different structural framing system along with different structural aspects is mentioned
below.
EFFECT OF VERTICAL LOAD ON DIFFERENT FRAMING SYSTEM4.1
4.1.1 Moment frame, Combined frame and Partial braced frame
comparison (subjected to vertical load)
A-1 A-2 A-3
Moment frame Combined frame Partial braced frame
Fig. 16 Framing Systems Subjected to UDL
CHAPTER 4

Parametric study & Results Chapter 4
In this case three different framing systems, Moment frame (A-1), Combined frame (A-2)
and Partial braced frame (A-3) have been selected and vertical load in form of UDL is
applied as shown in Error! Reference source not found. and height of each frame is
11.0 m. Generally in the industrial process structure process lines are passing through
bottom most tier and utility lines and cable tray are placed on tier above that, hence first
tier in the above framing systems is loaded with higher load compared to second and
third tier. The load on the first tier is 6.0 kN/m2 and that on second and third tier is 3.0
kN/m2. As structural frame are considered to be spaced at 6.0 m c/c, the load applied
during analysis is 36 kN/m on first tier and 18 kN/m on second and third tier in the form
of uniformly distributed load. Effect on structural weight is studied by satisfying
Strength and serviceability criteria for above framing systems. Serviceability is checked
for the beam member by restricting the vertical deflection to span/360 while stress ratio
(utilization of member strength) is restricted to 1.0 in order to satisfy strength criteria for
every member in the frame. Results of structural weight comparison are shown below in
Table 1 as well as in graphical form in Graph 1. Here P-1 and P-2 is applied vertical load
to the frame. Following points are observed from Table 1:
 For same load, structural weight of frame A-3 (Partial braced frame) is least while
that of frame A-1 (moment frame) is highest.
 Structural weight required for moment frame is 12% more compared to Partial braced
frame.

Table 1 Structural Wt. comparison for frames subjected to UDL
P-1
(kN/m2)
P-2
(kN/m2)
STRUCTURAL WEIGHT (kg)
(A-1)/(A-2) (A-1)/(A-3) (A-2)/(A-3)
A-1 A-2 A-3
3 6 1856 1670 1661 1.11 1.12 1.01
Graph 1 Structural Wt. comparison for frames subjected to UDL
CONCLUSION
 Vertical bracing members of either 'chevron' type (Frame A-2) or 'knee brace' type
(Frame A-3) provides support to beams in resisting vertical loads. Hence, by adding
bracing members, vertical deflection and thereby size of the beams can be reduced.
 Because of nature of moment frame higher weight (section sizes) are required while as
for remaining two frame because of presence of bracing lower section sizes are
required.
 Combined frame or partial braced frame are economical than moment frame.
 Fabrication and erection cost may get higher in Combined frame and partial braced
frame as compared to moment frame.
 The use of combined frame/ Partial braced frame blocks the passage for access and
piping.
1856
1670 1661
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
A-1 A-2 A-3
STRUCTURALWT.(kg)
STRUCTURE

4.1.2 UDL and Point load comparison for moment frame
A-1 A-2 A-3 A-4
Fig. 17 Moment Frames with UDL & Point Load
Fig. 17 shows four moment frames having similar geometry with different types of
vertical loading. However, total vertical loads remain same in all four frames. In Frame
A-1 vertical load is applied in the form of UDL at each level. In frame A-2 same UDL as in
frame A-1 is applied in the form of point load at midspan of the beam. In frame A-3, two
point loads are applied at each level. One at 1/3rd length of the beam while other at 2/3rd
length of the beam respectively. In frame A-4, single point load at 1/3rd span of the beam
is applied at each level. Vertical deflection, strength ratio and structural weight are
compared to study the effect of uniformly distributed load and point load on the
structural frame. In frame A-1, UDL on the first tier is 6.0 kN/m2 and on the second and
third tier is 3.0 kN/m2 which is applied as 36 kN/m on the first tier and 18 kN/m on
Moment frame
with UDL
Moment frame
with Point load
at mid span
Moment frame
with Point load at
1/3rd & 2/3rd span
Moment frame
with Point load
at 1/3rd span

second and third tier considering transverse frames are spaced at 6.0 m c/c. On frame
A-2, point load equivalent to UDL in frame A-1 is applied at the centre of the beam. On
frame A-3, two point load each having half the magnitude that in frame A-2 is applied at
1/3rd and 2/3rd span of the beam. On frame A-4, point load having same magnitude as
that in frame A-2 is applied at 1/3rd span of the beam. Support condition at the base i.e.
at junction of pedestal and base plate is considered as pinned.
a. Effect on Deflection and Strength ratio
For these frames, effect on Strength ratio and deflection has been studied while keeping
same member sizes in each frame. The strength ratio and maximum deflection of the
beam (in mm) in each frame is shown below in line diagram. The deflection values are
indicated by ( )* and strength ratio value by [ ]*. Following points are observed from
Fig. 18:
 Maximum deflection is observed in frame A-2 subjected to point load at centre and
least deflection is observed in frame A-1 subjected to UDL.
Fig. 18 Deflection & Strength ratio comparison

 Strength utilization is maximum in frame A-2 subjected to single point load at centre
and least in frame A-1 subjected to UDL.
b. Effect on Structural weight
Effect on structural weight is studied by satisfying strength and serviceability criteria for
above framing systems. Serviceability is checked for the beam member by restricting the
vertical deflection to span/360, while stress ratio is restricted to 1.0 in order to satisfy
strength criteria for every member in the frame. Results of structural weight comparison
are shown below in Table 2 as well as in graphical form in Graph 2. Here P-1 and P-2 are
applied vertical point load. Following points are observed from Error! Reference
source not found.
 Structural weight requirement is maximum for frame subjected to vertical load in the
form of point load at the midspan i.e. frame A-2 and minimum for frame subjected to
vertical load in the form of UDL i.e. frame A-1.
Table 2 Structural Wt. comparison for frames with UDL & Point load
P-1 (kN) P-2 (kN)
(A-2)/(A-1) (A-3)/(A-1) (A-4)/(A-1)
A-1 A-2 A-3 A-4
108 216 1951 2164 2050 2115 1.11 1.05 1.08

Graph 2 Structural Wt. comparison for frames with UDL & Point load
 Frame A-2 requires about 12% higher steel compared to frame A-1.
CONCLUSION
 Disposition of vertical load affects bending moment and deflection of beams.
 When load is acting as a single concentrated load, its effect on beam deflection and
strength ratio will be higher as its location is closer to mid-point of the beam.
 When load is acting more uniformly distributed way, i.e. more no. of point loads or
UDL (Uniformly Distributed Load), deflection and strength ratio of beam will reduce.
 For small diameter pipe it will be economical to apply load in the form of UDL.
 For large diameter pipe the load can be distributed to UDL for pipe shoe length or
can be applied as point load depending on the decision of structural engineer.
1951
2164
2050
2115
1800
1850
1900
1950
2000
2050
2100
2150
2200
A-1 A-2 A-3 A-4
STRUCTURALWT.(kg)
STRUCTURE

EFFECT OF HORIZONTAL LOAD ON DIFFERENT FRAMING SYSTEM4.2
4.2.1 Braced frame, Moment frame, Combined frame and Partial braced
frame comparison (subjected to horizontal load)
A-1 A-2 A-3 A-4
Braced frame Moment frame Combined frame Partial braced frame
Fig. 19 Framing Systems Subjected to Horizontal Load
Four different framing system, Braced frame (frame A-1), Moment frame (frame A-2),
Combined frame (frame A-3) and Partial braced frame (frame A-4) have been selected
and same horizontal load in the form of point load is applied at beam column junction in
every frame as shown in Fig. 19.
a. Effect on Deflection
Lateral load is applied at each tier level in order to study effect on deflection of each
structural framing system. For comparing the deflection of above framing systems,
section sizes are kept same in every frame except addition of some bracing members.
Strength and serviceability checks are satisfied for minimum value of lateral load i.e.
10kN and then load is increased from 10kN to 40kN at interval of 10kN without

considering strength and serviceability criteria in order to see change in behaviour of
deflection when stiffness of the beams and columns are kept same in each framing
system. Results of lateral deflection at top level are shown below in Table 3 as well as in
graphical form in Graph 3. Following points are observed from Table 3:
 Deflection in moment frame (frame A-2) is maximum and least in braced frame
(frame A-1).
 Deflection in Partial braced frame and combined frame is less than moment frame
but more than braced frame.
Table 3 Deflection comparison for frames subjected to Horizontal load
Graph 3 Deflection comparison for frames subjected to Horizontal load
A-1
A-2
A-3
A-4
0
50
100
150
200
250
0 10 20 30 40 50
STRUCTUREDEFLECTION(mm)
LOAD (kN)
A-1
A-2
A-3
A-4

Effect on structural weight with increase in loading is studied by restricting the sway to
permissible limits i.e. H/200 (H is height of frame) and stress ratio not exceeding 1.0.
Horizontal deflection in each structural framing system is kept same for same value of
loading. Results of structural weight comparison are shown below in Error! Reference
source not found. as well as in graphical form in Graph 4. Here P is applied horizontal
load to the frame. Following points are observed from Table 4:
 Structural weight of moment frame is maximum and braced frame is minimum.
 The structural weight requirement for Partial braced frame and Combined frame is
less than Moment frame but higher than Braced frame.
Table 4 Structural Wt. comparison for frames subjected to Horizontal load
Graph 4 Structural Wt. comparison for frames subjected to Horizontal load
A-1
A-2
A-3
A-4
0
500
1000
1500
2000
2500
3000
3500
4000
4500
0 10 20 30 40 50
STRUCTURALWT.(kg)
LOAD (kN)
A-1
A-2
A-3
A-4

CONCLUSION
 Braced frame (A-1) offers high lateral load resisting capacity. When lateral load value
increases it undergoes less change compared to other type of frames.
 Partial braced frame (A-3) offers better behaviour than Moment frame (A-2). This
framing solution can be adopted for piperack structures, wherever possible. However
connection feasibility need to be checked for Partial braced frame. Partial braced
frame used in minor axis of the column will have significantly reduced stiffness (and
hence effectiveness to resist deflection) as compared to Braced frame.
 If clear space is available provide bracing in major direction as well.
 Bracing in the framing system will increase cost of fabrication and erection.
 Deflection is minimum in Braced frame, which is in line with the assumption made
for the stress analysis of the piping system.
 If possible, providing partial brace or bracing at bottom level to reduce deflection and
tonnage.

4.2.2 Support condition comparison
A-1 A-2
Fixed Base Pinned Base
Fig. 20 Frames with Fixed & Pinned Support Condition
Two frames A-1 and A-2 are with same structural arrangement but with different support
condition at base plate level, i.e. A-1 with fixed base and A-2 with pinned base are
compared for deflection, strength ratio, structural weight, column sizes and support
reaction. Horizontal load P is applied at beam column junction in both the frames as
shown in Fig. 20.
a. Effect on Deflection and Strength ratio
Effect on strength ratio and deflection value is studied for same section size and same
load. Result of horizontal deflection at the top of the frame is shown below in Table 5 as
well as in graphical form in Graph 5. The ratio of actual load to allowable load is known
as strength ratio. The strength ratio of each member is shown below in line diagram in

Graph 5 Deflection comparison for Fixed Fig. 21 Strength ratio comparison
Here P is applied horizontal load to the frame.
Table 5 Deflection comparison for Fixed & Pinned base frame
P (kN)
STRUCTURE DEFLECTION (mm)
(A-2) / (A-1)
A-1 A-2
30 30.3 77.8 2.57
Graph 5 Deflection comparison for Fixed Fig. 21 Strength ratio comparison
& Pinned base frame
b. Effect on Structural weight and Column size
Effect on structural weight is studied by applying same lateral load of 30kN at each tier
level in both the frames. Strength and serviceability criteria are satisfied for both the
frames. Horizontal deflection in both the frames is kept same and within permissible
limits i.e. H/200 (H is height of frame) and stress ratio is restricted to 1.0. Column sizes
are also compared for this value of structural weight. Column sizes are compared to
know which frame offers higher useable space. Smaller the section size higher is the
useable space. Results of structural weight comparison are shown below in Table 6 as
30.3
77.8
0
20
40
60
80
100
A-1 A-2
STRUCTUREDEFLECTION
(mm)
STRUCTURE

well as in graphical form in Graph 6. Column sizes for both the frames are shown in line
diagram in Graph 6 Structural Wt. comparison for Fixed Fig. 22 Column size
comparison Here P is applied horizontal load to the frame.
Table 6 Structural Wt. comparison for Fixed & Pinned base frame
P (kN)
(A-2) / (A-1)
A-1 A-2
30 3068 3642 1.19
Graph 6 Structural Wt. comparison for Fixed Fig. 22 Column size comparison
& Pinned base frame
c. Effect on Reactions
Effect on reaction by changing base condition is studied here. Support reaction of both
the frames for same loading on both the frames is tabulated below. Here P is applied
horizontal load to the frame.
3068
3642
2600
2800
3000
3200
3400
3600
3800
A-1 A-2
STRUCTURALWT.(kg)
STRUCTURE

Fig. 23 Support Reaction
Table 7 Reaction comparison for Fixed & Pinned base frame
P (kN)
Base Fixed Base Pinned
HA VA MA HB VB MB HA VA MA HB VB MB
30 44.9 -68.8 153.3 45.1 68.8 153.9 45 -120 0 45 120 0
CONCLUSION
 Column base type effects bending moment and lateral deflections of the columns. i.e.
with fixed type of base conditions, deflection and column size (thereby structural
weight) is lower than that of pinned base frame for same set of loadings.
 The nature and magnitude of loads transferred to foundation changes with base
connection type. Fixed type of base transfers moments and lower tension force to
foundation. This will directly effect design of base plate and foundation, which has to
be investigated while selection of base condition.
 Based on above, for fixed type of base condition the foundation will be bigger than
pinned type base condition. For pinned type of base condition sizes / weight of
structural member will be higher than fixed type base condition.

 Deflection of the frame is less for fixed type base condition, which is favourable
condition for piping system.
 For fixed base condition, anchoring system will be higher so that pedestal size will
increase and because of that space requirement will be higher.
 Foundation sizes for fixed base will be higher compared to pinned base which may
create interface issue with underground utilities.

4.2.3 Effect of frame Height to Width ratio
A-1 A-2
2 tier – 9.0m wide frame 3 tier – 6.0m wide frame
Fig. 24 Frames with Same Useable Space
Two frames with same structural framing system have been selected and horizontal load
P is applied at beam column junction. Total horizontal load applied on both the frames is
same (i.e. horizontal load is equally distributed at each tier level). Load on frame A-1 is
45 kN at each tier and on fame A-2 is 30 kN at each tier. As shown in Fig. 24, height and
width of frame A-1 is 8.0 m and 9.0 m respectively. Height and width of frame A-2 is
11.0 m and 6.0 m respectively. Hence height to width ratio for frame A-1 is 0.89 while
that for frame A-2 is 1.83.
In order to study effect on deflection, of height to width ratio of frames, weight of both
the structural frames is kept same. Permissible deflection for frame A-1 is 40 mm and for

frame A-2 is 55 mm. As both the frames having total horizontal load P and having
different height, to make the results of deflection comparable, ratio of actual deflection to
the permissible deflection of the top node for respective frame is compared. Results of
deflection comparison are shown below in Table 8 as well as in graphical form in
Graph 7.
Table 8 Deflection comparison for frames with same useable space
P (kN)
Actual Deflection / Permissible Deflection
(%) (A-2)/(A-1)
A-1 A-2
90 82.64 88.33 1.07
Graph 7 Deflection comparison for frames with same useable space
Effect on structural weight is studied by restricting the sway to permissible limits i.e.
H/200 (H is height of frame) and stress ratio not exceeding 1.0. Strength and
serviceability criteria are satisfied for both the frames. Lateral deflection is the governing
criteria for design in both the frames A-1 and A-2, hence while comparing the structural
weight, ratio of actual deflection to the permissible deflection is kept same. Results of
82.64
88.33
60
70
80
90
A-1 A-2
ACTUAL/PERMISSIBLE
DEFLECTION(%)
STRUCTURE

structural weight comparison are shown below in Table 9 as well as in graphical form in
Graph 8. Here P is total applied horizontal load to the frame.
Table 9 Structural Wt. comparison for frames with same useable space
P (kN)
(A-2)/(A-1)
A-1 A-2
90 3829 3901 1.02
Graph 8 Structural Wt. comparison for frames with same useable space
CONCLUSION
 Broader the base of the structure i.e. lower height/ width ratio higher the stiffness of
the frame against lateral loads. Higher height / width ratio of frame results in higher
deflection and tonnage.
 Lower height / width ratio will occupy higher space in the plant while higher height /
width ratio will have more number of connections compared to frame with lower
height / width ratio.
3829
3901
3500
3600
3700
3800
3900
4000
A-1 A-2
STRUCTURALWT.(kg)
STRUCTURE

4.2.4 Effect of Elevation of Load point
20 kN @ each tier 30 kN @ 1st tier 30 kN @ 2nd tier 30 kN @ 3rd tier
A-1 A-2 A-3 A-4
Fig. 25 Frames with Change in Elevation of Load Point
In frame A-1, 20 kN load is applied at each tier of frame. Now load is increased at
different level. The effect of this change in magnitude of the load is studied on deflection
and structural weight. In frame A-2, point load is increased to 30 kN at first tier level
while keeping other point load same. In the same way, point load is increased to 30 kN at
second and third tier level in frame A-3 and A-4 respectively while loads at other level
are kept 20 kN. Same is shown in Fig. 25.
In order to study effect on deflection with change in height of load point on frames,
section sizes are kept constant for all the frames i.e. A-1, A-2, A-3 and A-4. Lateral
deflection at top node of the frame is measured. Results of deflection comparison are

shown below in Table 10 as well as in graphical form in Graph 9 It is observed from
Table 10 that frame A-1 has least deflection and frame A-4 has maximum deflection.
Table 10 Deflection comparison for change in elevation of load point
(A-2) / (A-1) (A-3) / (A-1) (A-4) / (A-1)
A-1 A-2 A-3 A-4
53.8 57.8 62.1 68.4 1.07 1.15 1.27
Graph 9 Deflection comparison for change in elevation of load point
Effect on structural weight with change in height of load point on frames is studied by
restricting the sway to permissible limits i.e. H/200 (H is height of frame) and stress
ratio not exceeding 1.0. Hence strength and serviceability criteria are satisfied in each
case. Also utilization in each case is restricted to same value so that structural weight of
frames A-1, A-2, A-3 and A-4 can be made comparable. Results of structural weight
comparison are shown below in Table 11 as well as in graphical form in Graph 10. It is
observed from Table 11, that frame A-1 has least structural weight and frame A-4 has
maximum structural weight.
53.8
57.8
62.1
68.4
0
10
20
30
40
50
60
70
80
A-1 A-2 A-3 A-4
STRUCTURE

Table 11 Structural Wt. comparison for change in elevation of load point
(A-2) / (A-1) (A-3) / (A-1) (A-4) / (A-1)
A-1 A-2 A-3 A-4
3052 3131 3223 3320 1.03 1.06 1.09
Graph 10 Structural Wt. comparison for change in elevation of load point
CONCLUSION
 As the point of application of lateral loads moves away from base (higher elevation
from ground), its effect on structural frame increases due to higher lever arm.
 The same incremental load occurring at higher elevation results significantly higher
effect on structural behaviour. If load is to be increased than, to minimize its effect on
steel structure, it should be preferred to do so at lower level of the structure.
3052
3131
3223
3320
2900
3000
3100
3200
3300
3400
A-1 A-2 A-3 A-4
STRUCTURALWT.(kg)
STRUCTURE

4.2.5 Single bay moment frame and Multiple bay frame comparison
A-1 A-2 A-3 A-4
Fig. 26 Single Bay & Multiple Bay Moment Frame
This exercise is done to understand the behaviour and cost effectiveness of multiple bay
frame with different structural arrangement compared to single bay frame. Useable
space in single bay frame and multiple bay frames is kept same. Different multiple bay
frames are compared with single bay moment frame. Frame A-1 is single bay moment
frame and all the connections in frame A-1 are rigid connection. Frame A-2 is multiple
bay frame having two bays. One bay in frame A-2 has shear connection while other bay
has rigid connection. Frame A-3 is multiple bay combined frame in which bracing is
provided at lower level in one of the bay. Shear connection are provided at lower level
and in the bay with bracing in frame A-3 while all other connections are rigid connection.
Frame A-4 is multiple bay frame with two bays having all rigid connections. Same is
shown in Fig. 26.
Single bay
Moment frame
Multiple bay
frame with 1-bay
Moment
connection
Multiple bay
Combined frame
Multiple bay
Moment frame

Each of the structural framing system shown above is applied same lateral load to study
effect on deflection. Structural weight for every framing system is kept same while
comparing deflection. Results of deflection comparison are shown below in Table 12 as
well as in graphical form in Graph 11. Here P is applied horizontal load to the frame.
Following points can be observed from Table 12:
 It is observed that frame A-3 i.e. Multiple bay combined frame has minimum
deflection of 31.3 mm while frame A-2 i.e. Multiple bay frame with 1-bay moment
frame has maximum deflection of 79 mm.
 Single bay moment frame i.e. frame A-1 has about 86% more deflection compared to
Multiple bay combined frame i.e. frame A-3.
Table 12 Deflection comparison for Single bay & Multiple bay frame
P (kN)
(A-2)/(A-1) (A-1)/(A-3) (A-1)/(A-4)
A-1 A-2 A-3 A-4
30 58.3 79.0 31.3 45.3 1.36 1.86 1.29
Graph 11 Deflection comparison for Single bay & Multiple bay frame
58.3
79.0
31.3
45.3
0
10
20
30
40
50
60
70
80
90
A-1 A-2 A-3 A-4
STRUCTURE

Structural weight of different multiple bay frames and single bay frame is compared by
keeping the utilization same in every frame. Strength and serviceability criteria are
satisfied for each frame. Lateral deflection is restricted to permissible limits i.e. H/200
(H is height of frame). Stress ratio is restricted to 1.0, so that strength criteria are
satisfied. Results of structural weight comparison are shown below in Table 13 as well as
in graphical form in Graph 12. Here P is applied horizontal load. Following points can be
observed from Table 13:
 It is observed that structural weight of multiple bay combined framed is least and
multiple bay frame with 1 bay moment connection is maximum.
 Structural weight of single bay moment frame is about 33% more compared to
multiple bay combined frame.
Table 13 Structural Wt. comparison for Single bay & Multiple bay frame
P (kN)
(A-2)/(A-1) (A-1)/(A-3) (A-1)/(A-4)
A-1 A-2 A-3 A-4
30 4570 5021 3447 4388 1.10 1.33 1.04
Graph 12 Structural Wt. comparison for Single bay & Multiple bay frame
4570
5021
3447
4388
0
1500
3000
4500
6000
A-1 A-2 A-3 A-4
STRUCTURALWEIGHT(kg)
STRUCTURE

CONCLUSION
 Additional column requires additional foundation, hence in assessment of cost
effectiveness; cost of the superstructure and substructure should also be taken in to
account. Additional column in the frame also helps in lateral load resistance of the
frame.
 From serviceability and strength point of view, Multiple bay combined frame
(frame A-3) is most economical.

4.2.6 Composite frame and Steel frame comparison (subjected to horizontal
load)
A-1 A-2
Fig. 27 Composite Frame & Steel Frame
As shown in Fig. 27, two frames dimensionally similar but frame A-1 having RCC column
of 3.5 m in the lower part while frame A-2 made completely from steel is subjected to
horizontal point load at beam column junction. The size of RCC column in frame A-1 is
800 x 600 mm and connection at the junction of RCC and steel column is taken as
pinned connection.
Beam and column steel sections used in both the frames are same while comparing
deflection of both the frames. Results of deflection comparison are shown below in
Table 14 as well as in graphical form in Graph 13. Here P is applied horizontal load to the
Concrete - Steel
Composite frame
Steel frame

frame. It is observed from Table 14, that frame A-1 has less deflection compared to frame
A-2.
Table 14 Deflection comparison for Composite & Steel frame
P (kN)
(A-2) / (A-1)
A-1 A-2
30 31.2 51.8 1.66
Graph 13 Deflection comparison for Composite & Steel frame
Effect on structural weight is studied by applying same loading on both the frame at
same load point and satisfying design requirements. Lateral deflection is restricted to
permissible limits i.e. H/200 (H is height of frame). Stress ratio is restricted to 1.0 so
that strength criteria are satisfied. Utilization of both the frames is kept same and within
permissible limit while comparing the structural weight. Results of structural weight
comparison are shown below in Table 15 as well as in graphical form in Graph 14. It is
observed from Table 15, that structural steel requirement for frame A-1 is less compared
to frame A-2.
31.2
51.8
0
10
20
30
40
50
60
A-1 A-2
STRUCTUREDEFLECTION
(mm)
STRUCTURE

Table 15 Structural Wt. comparison for Composite & Steel frame
P (kN)
(A-2) / (A-1)
A-1 A-2*
30 1720 2624 1.53
* Weight of A-2 frame is considered above 3.5 m.
Graph 14 Structural Wt. comparison for Composite & Steel frame
CONCLUSION
 Concrete columns offer higher resistance to lateral loads due to higher stiffness.
Hence Composite frame results in to lesser deflection and lesser structural steel (with
additional concrete).
 Due to higher size of concrete column compared to steel section, useable space will be
reduced comparatively while anchoring requirement will be less in concrete - steel
composite frame (frame A-1) compared to steel frame (frame A-2).
1720
2624
0
500
1000
1500
2000
2500
3000
A-1 A-2*
STRUCTURALWEIGHT(kg)
STRUCTURE

4.2.7 Plan bracing system
Plan view 3D view
Fig. 28 Frame with No Plan Bracing
Fig. 28 shows Plan view and 3D view of frame with no plan bracing. Error! Reference
source not found. shows the position of vertical bracing. In middle frame vertical
bracing is absent. The arrangement of the vertical bracings remain same for all four cases
shown in the following sections. All the Beam – column connection in X – direction are
shear connection while that in Y – direction are rigid connection.
a. Effect on horizontal drift
Fig. 29 shows plan view of different structural systems. There is no plan bracing in frame
A-1 while in frame A-2, A-3 and A-4 different types of plan bracing is present. The load
P-1, P-2 and P-3 are horizontal load applied at top level of the frame and beam – column
junction in all the frames at top level has been numbered as shown in Fig. 29.

A-1 A-2
No Plan Bracing Plan Bracing (X Type)
A-3 A-4
Plan Bracing (Girder Type) Plan Bracing (Diamond Type)
Fig. 29 Different Plan Bracing System
In this case comparison of horizontal deflection is done for different load cases and
results are shown in Table 16 to Table 19. Also comparison of horizontal drift is done to
check which plan bracing give better diaphragm effect. The ratio of maximum horizontal

deflection to the minimum horizontal deflection at top level of the frame is termed as
horizontal drift. Result of horizontal drift at top of the frame is shown below in
Error! Reference source not found. as well as graphical form in Graph 15. The
sample calculation of horizontal drift for case 1 of frame A-1 is shown below.
Horizontal drift = 23.9/0.7 = 35.8
Table 16 Deflection comparison for frame without plan bracing
Frame
A-1
LOAD (kN)
HORIZONTAL DEFLECTION
(mm)
P-1 P-2 P-3 NODE 1 NODE 2 NODE 3
CASE 1 25 25 25 0.7 23.9 0.7
CASE 2 25 50 25 0.9 29.1 0.9
CASE 3 50 25 25 1.1 24.2 0.7
Table 17 Deflection comparison for frame with X-type plan bracing
Frame
A-2
LOAD (kN)
(mm)
CASE 1 25 25 25 0.7 0.8 0.7
CASE 2 25 50 25 0.9 1.0 0.9
CASE 3 50 25 25 1.1 1.0 0.7
Table 18 Deflection comparison for frame with Girder type plan bracing
Frame
A-3
LOAD (kN)
(mm)
CASE 1 25 25 25 0.7 2.8 0.7
CASE 2 25 50 25 0.9 4.7 0.9
CASE 3 50 25 25 1.1 3.0 0.7
Table 19 Deflection comparison for frame with Diamond type plan bracing
Frame
A-4
LOAD (kN)
(mm)
CASE 1 25 25 25 0.7 1.0 0.7
CASE 2 25 50 25 0.9 1.5 0.9
CASE 3 50 25 25 1.1 1.2 0.7

Table 20 Horizontal Drift ratio comparison for frames with or without Plan brace
LOAD (kN) DRIFT RATIO
P-1 P-2 P-3 A-1 A-2 A-3 A-4
CASE 1 25 25 25 35.8 1.1 4.0 1.5
CASE 2 25 50 25 32.4 1.1 5.0 1.7
CASE 3 50 25 25 36.2 1.6 4.3 1.8
Graph 15 Drift ratio comparison for frames with or without Plan brace
b. Effect on structural weight
Fig. 30 shows plan view of different structural systems. Frame A-1 has no plan bracing
and has only grating beams. Frame A-2 has X type plan bracing arrangement. Frame A-3
has plan bracing in the form of girder of 1.5m width. It also has tie beam connected to
grating beam, which helps in reducing effective length (ly) of grating beams i.e. beam
parallel to Y- axis. Frame A-4 has diamond type bracing arrangement. All the frames are
subjected to horizontal load P at beam – column junction at the floor level. In addition to
that, frames are also subjected to vertical load of 10 kN/m2. Effect on structural weight is
studied by restricting the sway to permissible limits i.e. H/200 (H is height of frame) and
strength ratio not exceeding 1.0.
0
5
10
15
20
25
30
35
40
A-1 A-2 A3 A4
DRIFTRATIO
STRUCTURE
CASE 1
CASE 2
CASE 3

A-1 A-2
No Plan Bracing Plan Bracing (X Type)
A-3 A-4
Plan Bracing (Girder Type) Plan Bracing (Diamond Type)
Fig. 30 Plan View of Frames for Structural Wt. Comparison
Results of structural weight comparison (floor weight only) are shown below in
Table 21 as well as in graphical form in Graph 16.
Table 21 Structural Wt. comparison for frames with & without Plan bracing
P (kN)
STRUCTURAL WEIGHT* (kg)
(A-2)/(A-1) (A-2)/(A-3) (A-2)/(A-4)
A-1 A-2 A-3 A-4
25 6652 6796 5150 4673 1.02 1.32 1.45
* Floor weight only.

Graph 16 Structural Wt. comparison for frames with & without Plan bracing
CONCLUSION
 Absence of plan bracing induces high torsion in the structure. Due to plan bracing
floor works as rigid diaphragm and because of that deflection shared by each column.
 System A-2, shows uniform distribution of horizontal deflection as compared to
system A-3.
6652 6796
5150
4673
0
1500
3000
4500
6000
7500
A-1 A-2 A-3 A-4
STRUCTURALWT.(kg)
STRUCTURE

4.2.8 Vertical bracing in frame
In this case effect of change in location of vertical bracing has been studied. In frame A-1,
vertical bracings are placed in one bay and from frame A-2 to A-5 bracings are placed in
different bays. Same is shown in below figures.
A-1
A-2

A-3
A-4
A-5

a. Effect on support reactions
Effect on support reactions is studied, when position of bracing is changed from one bay
to other in the frame. Here P is applied horizontal load at first and second level of the
frame and 2P is the applied horizontal load on third and fourth level of the frame.
Support reaction of all the frames for same loading on all the frames is tabulated in
Table 22 for positive direction of forces and in Table 23 for negative direction of forces.
Below shown line diagram of frame explains direction of support reaction FX and FY.
Fig. 31 Sign Convention for Support Reaction

Table 22 Support reaction comparison for (+ ve) forces
P (kN) FRAME
SUPPORT REACTION (kN)
NODE 1 NODE 2 NODE 3 NODE 4 NODE 5 NODE 6
FX1 FY1 FX2 FY2 FX3 FY3 FX4 FY4 FX5 FY5 FX6 FY6
30
A- 1 0.0 0.0 0.0 0.0 -30.0 -105 -30.0 105 0.0 0.0 0.0 0.0
A- 2 0.0 0.0 0.0 0.0 -30.0 -75.0 -30.0 45.0 0.0 30.0 0.0 0.0
A- 3 0.0 0.0 0.0 0.0 -30.0 -75.0 -30.0 55.4 0.0 9.3 0.0 10.3
A- 4 0.0 0.0 0.0 0.0 -30.0 -49.2 -30.0 23.5 0.0 -4.2 0.0 29.9
A- 5 0.0 0.0 -30.0 -49.0 -30.0 24.0 0.0 6.0 0.0 9.0 0.0 10.0
Table 23 Support reaction comparison for (- ve) forces
P (kN) FRAME
SUPPORT REACTION (kN)
NODE 1 NODE 2 NODE 3 NODE 4 NODE 5 NODE 6
FX1 FY1 FX2 FY2 FX3 FY3 FX4 FY4 FX5 FY5 FX6 FY6
30
A- 1 0.0 0.0 0.0 0.0 30.0 105 30.0 -105 0.0 0.0 0.0 0.0
A- 2 0.0 0.0 0.0 0.0 30.0 75.0 30.0 -45.0 0.0 -30.0 0.0 0.0
A- 3 0.0 0.0 0.0 0.0 30.0 75.0 30.0 -55.4 0.0 -9.3 0.0 -10.3
A- 4 0.0 0.0 0.0 0.0 30.0 49.2 30.0 -23.5 0.0 4.2 0.0 -29.9
A- 5 0.0 0.0 30.0 49.0 30.0 -24.0 0.0 -6.0 0.0 -9.0 0.0 -10.0
CONCLUSION
 When vertical bracings are kept in one bay only throughout the height of the frame
than load is distributed only in two columns.
 When vertical bracings are arranged in multiple bays, each column will share push
pull where vertical bracings are placed.
 Foundation become lighter when vertical bracings are scattered.
 More number of foundations affected when loads increased, at latter stage of project,
in case of scattered vertical bracing.

Effect of Substructure modelling on Superstructure Page 65
INTRODUCTION TO PART II
GENERAL5.1
In conventional analysis of any civil engineering structure the super structure is usually
analysed by treating it as independent from foundation and soil medium on the
assumption that no interaction takes place. This usually means that by providing fixity at
the support structural analyst simplifies soil behaviour, while geotechnical engineer
neglects structural behaviour by considering only the foundation while designing.
When a structure is built on soil some of the elements of the structure are in direct
contact with the soil. When the loads are applied on the structure, internal forces are
developed in both the structure and as well as in soil. This results in deformations of
both the components (structure and soil) which need to be compatible at the interface as
they cannot be independent of each other. Because of this mutual dependence, which is
termed as interaction, the stress resultants in structure and, stresses and strains in soil
are significantly altered during the course of loading. Therefore it becomes imperative to
consider the structure-foundation and soil as components of a single system for analysis
and design of the structure and its foundation. The analysis that treats structure
foundation - soil as a single system is called as Soil Structure Interaction (SSI)
analysis.
The effect of soil immediately beneath and around the structure, on the response of the
structure when subjected to external loads is considered in soil structure interaction. In
CHAPTER 5

Introduction to Part II Chapter 5
this case, the soil and structure are considered as components of one elastic system.
During the analysis soil can be modelled using various soil models such as Linear elastic
soil model, Winkler‘s soil model etc.
OBJECTIVE5.2
The study intends to find effect of substructure on superstructure. The objective of the
study is to check the requirement to model substructure along with superstructure
during analysis and design. The parameter varied for the study are extent of substructure
modelling, modulus of subgrade reactions of soil, pile stiffness, depth of foundation,
height of super structure, unsymmetrical vertical load and type of connection at
interface. A comparison of the displacements of the frame is done in this study. In the
present work, analysis is carried out using Winkler‘s soil model. Foundation is modelled
using Finite Element Method. Method by considering soil structure interaction is
compared with the Conventional analysis.
SOIL MODELS USED IN SOIL STRUCTURE INTERACTION5.3
The behaviour of soil must be defined initially to study soil structure interaction by
which further analysis part becomes less complicated. For this purpose soils must be
modelled. In soil structure interaction soil mass is considered as an elastic material.
The soil structure interaction can be studied by,
1) Numerical modelling.
2) Centrifuge modelling.

In present work numerical modelling is used and hence detail explanation of numerical
modelling is given below.
5.3.1 NUMERICAL MODELS
The numerical models give the relationship between the applied forces and resulting
displacement. These relationships are given by linear functions, which are further used
for analysis. In the soil-structure interaction problem, for the numerical analysis
modelling of the soil to represent its real behaviour is very important. In order to
simulate this condition, different models are developed and grouped into discrete and
continuum models. [6]
a. Discrete models
1) Winkler’s model
The analysis of the soil-structure interaction, including the problem of a plate on an
elastic foundation, has a wide range of application in structural and geotechnical
engineering. Owing to the complexity of the actual behaviour of the foundation, many
idealized foundation models have been proposed. The simplest of the models, proposed
in 1867 by Winkler, a German engineer, assumes that the soil medium consists of a
system of mutually independent spring elements capable of resisting only compressive
forces. This is popularly known as the Winkler model. Winkler represented the case of a
finite soil layer resting on a basement rock by a family of linear springs resting on a rigid
base. One can be pushed down without affecting its neighbours. This model is only a
crude representation of the behaviour of the real soil wherein deformation is continuous.

In this model soil mass is replaced by a bed of closely spaced elastic, identical and
independent springs. The shear resistance in soil is neglected. The soil outside the loaded
area does not undergo any deflection. This model is based on simple assumption that
contact pressure (p) is proportional to deflection (y) of elastic system.
p α y … (1)
considering constant one can write
p = k y … (2)
k = Modulus of sub grade reaction.
p and y are mutually dependent. This mutual dependency is the essence of interaction.
The value of k is dependent on material and dimensions of foundations. From the above
assumptions we can conclude that, the value of k remains same whatever be the value of
p and y. The above assumptions are collectively referred as Winkler‘s model. It has been
assumed that soil bed is considered as medium of elastic, identical and independent
springs. By elastic it ensures that there is linear relationship between p and y. Identical
ensures that the value of k remains same whatever be the value of p and y may be.
Independent means that each spring deflects independently due to load coming on it,
without the interference of adjacent springs. The value of modulus sub grade reaction
can be determined experimentally from load settlement diagram obtained plate load test.
2) Two parameter soil foundation model
The inherent deficiency of the Winkler model in depicting the continuous behaviour of
the semi-infinite medium led to the development of the two parameter elastic models.

When a load is applied to the surface of a linear elastic half-space, the surface deflects
under the load, but it also moves down in the unloaded area adjacent to the load, the
displacement diminishing with distance. This occurs because the material is represented
as a connected continuum. A linear elastic isotropic continuum is described by two
material properties namely, Young‘s modulus and Poisson‘s ratio but the Winkler model
is described by the spring stiffness, k. A few important two parameter models are
Filonenko-Borodich model, Hetenyi model, Pasternak model, Vlazov model, Reissner
model.
b. Continuum Models
The surface deflections which occur in the Winkler model are limited to the loaded
region. It is a common experience that in the case of the soil media, surface deflections
will occur not only immediately under the loaded region but also within certain limited
zones outside the loaded region. It attempts to account for this continuous behaviour,
the soil media have often been idealized as three-dimensional continuous elastic solids
or elastic continua. Generally the distribution of the displacements and the stresses in
such media remain continuous under the action of external force systems. The initial
impetus for the continuum representation of the soil media stemmed from the work of
Boussinesq (1885), who analysed the problem of a semi-infinite homogeneous isotropic
linear elastic solid subjected to a concentrated force which acts normal to the plane
boundary.

1) Elastic half space model
The elastic half space model for soil is superior to the Winkler‘s model, as the continuity
present in the soil medium is accounted for in the model. Also advantage of this model is
its versatility in transferring horizontal shear stresses beneath the foundation. Soil is
assumed to be homogenous, isotropic elastic and semi-infinite. Displacement will not
only occur in loaded area but also within certain limited zones outside the loaded area.

LITERATURE REVIEW
PRELIMINARY REMARK6.1
Literature has been proved always boosting and stepping-stones for further research
work. The papers presented here helped me to resolve the major issue in multidirection.
In this chapter literature regarding modelling foundation and different research papers
for the subject have been studied and abstracts from the same are listed below.
LITERATURE STUDIED6.2
Ankit Suri, “ANALYSIS OF STRUCTURE SUPPORTED BY ELASTIC
FOUNDATION”, In this paper structure supported on elastic foundation with different
soil types is analysed. The raft is modelled with the structure, with total area of the raft is
divided into finite number of plates. The plate - foundation system is idealized as a thin
elastic plate resting on a linearly elastic foundation. It has been observed that the stiff
stratum at the base does not change the design forces significantly. As the stiffness of the
soil strata increased, structure behaviour became closer to that observed for rigid
supports. For seismic forces, magnitude of bending moments in the columns and beams
of the structure increase with the increase in modulus of subgrade reaction. The relative
displacements between successive floors are less for structure on soft soils, but
significant increase in displacements of the structure can occur when subjected to lateral
forces. The softer the soil, the more the differential settlement. This differential
settlement resulted in an increase in bending moments of raft slab.
CHAPTER 6

Literature review Chapter 6
Jenifer Priyanka R.M, SaravanaBhaarathi .S, Varun .J, “STUDY ON LATERAL
DEFLECTION OF BUILDINGS WITH FIXED SUPPORT UNDER VARIOUS SOIL
CONDITIONS”, In this paper multi-storeyed building frames with fixed support
subjected to seismic force were analysed for different soil conditions. The response of
regular buildings was compared with response of vertical irregular buildings. The lateral
deflections values increased when type of soil changes from hard to medium and
medium to soft soil. The lateral deflection value for vertical irregular building is higher
compared to regular building subjected to soft soil condition under fixed support. Hence
suitable soil condition has to be adopted along with the type of foundation while
designing building for earthquake resistant.
R. M. Jenifer Priyanka, N. Anand, Dr. S. Justin, “STUDIES ON SOIL STRUCTURE
INTERACTION OF MULTI STOREYED BUILDINGS WITH RIGID AND FLEXIBLE
FOUNDATION”, In this paper multi-storeyed building frames with fixed and flexible
base subjected to seismic forces were analysed and designed for different soil conditions.
The seismic response of the building frames such as Lateral deflection, Storey drift, Base
shear and Moment values were compared for both type of building frames. Lateral
deflection, Storey drift, Base shear and Moment values increases when the type of soil
changes from hard to medium and medium to soft for fixed and flexible base buildings.
Lateral deflection, Storey drift, Base shear and Moment values of fixed base building was
found to be lower as compared to flexible base building. Hence suitable foundation

system considering the effect of soil stiffness has to be adopted while designing building
frames for seismic forces.
Kuladeepu M N, G Narayana, B K Narendra, “SOIL STRUCTURE INTERACTION
EFFECT ON DYNAMIC BEHAVIOR OF 3D BUILDING FRAMES WITH RAFT
FOOTING”, In this paper the dynamic behaviour of building frames over raft footing
under seismic forces uniting soil structure interaction is considered. For the interaction
analysis of space frame, foundation and soil are considered as parts of a single
compatible unit and soil is idealized using the soil models for analysis. The soil system
below a raft footing is replaced by providing a true soil model (continuum model). In
continuum model, soil is considered as homogeneous, isotropic, elastic of half space for
which dynamic shear modulus and Poisson‘s ratio are the inputs. Influence of number of
parameters such as number of storey‘s, soil types and height ratio for seismic zone-V is
considered in study. For the increment in shear modulus and number of stories the
maximum lateral displacement of the structural element discovered to be expanded. The
estimations of maximum lateral displacement resulting from a fixed base analysis are
impressively improved when interaction analysis of the system is considered.
B. Darmian, M.A. Moghaddam, H.R.Naseri, “SOIL–STRUCTURE INTERACTION IN
STEEL BRACED STRUCTURES WITH FOUNDATION UPLIFT”, In this paper the
nonlinear behaviour of various steel braced structures placed on different types of soil
with varying hardness has been investigated. Results showed that for structures allowed

to foundation uplift, the softer the soil, the higher will be changes in seismic response.
Comparison of rate of uplift for various structures showed that maximum uplift occurred
for the foundation of exterior columns of the structure. This part of foundation carries
the brace‘s load too. It is also noted that with an increase in the height of structure the
foundation uplift increases. Foundation uplift causes the greatest increase of story drift
ratio. This can cause an overturn of the tall structures. The greatest story drift ratio
increase occurs for the structures located on the soft soil.
Bhojegowda V T, Mr. K G Subramanya, “SOIL STRUCTURE INTERACTION OF
FRAMED STRUCTURE SUPPORTED ON DIFFERENT TYPES OF FOUNDATION”, In
this paper study for building with Isolated, mat and pile foundations for different soil
conditions like soft, medium and hard strata, and a comparison between the regular and
irregular buildings. Response of the structure increases with change in soil type from
hard to medium and soft irrespective of height of structure and type of foundation.
Framed structure with pile foundation resting on hard, medium and soft soil can be
treated as fixed since no much variation in the response of the structure. Framed
structure with mat foundation possesses high foundation stiffness in comparison with
isolated foundation hence base shear for mat foundation has increased and other
parameters like displacement, bending moment and time period have reduced in
comparison to structure with isolated footing. As the height of the structure increases,
proportionally the base shear, time period and response also increases. Hence the tall

structure supported on soft soil will have more displacement and it needs to be more
flexible.
Dr. S. A. Halkude, Mr. M. G. Kalyanshetti, Mr. S. H. Kalyani, “SOIL STRUCTURE
INTERACTION EFFECT ON SEISMIC RESPONSE OF R.C. FRAMES WITH
ISOLATED FOOTING”, In this paper the effect of soil flexibility on the performance of
building frame. Two SSI modes are considered for the analysis; one is replacing soil by
spring of equivalent stiffness (Discrete Support) and second by considering the whole
soil mass (Elastic Continuum). Natural period, Roof displacement, Base shear, Beam
moment and Column moment are observed to be increasing with increase in soil
flexibility. The variations are less for low storey building and goes on increasing with
increase in storey height. Difference in spring model (Discrete Support) and FEM model
(Elastic continuum) is less up to medium hard soil. For soft soils this difference is high.
Therefore one can employ spring models for hard soil and FEM models for soft soil.
Finite Element Method has proved to be a very useful method for studying the effect of
SSI. However to reduce the complexity for practical purpose, at least Winkler hypothesis
should be employed to consider SSI instead of fixed base.
MohammedSaeem B Vohra, Prof.K.N.Sheth, “ A PARAMETRIC STUDY FOR
ANALYSIS OF SPACE FRAME WITH ISOLATED FOOTINGS SUPPORTED ON
WINKLER’S SPRING BASE WITH REFERENCE TO IDEALIZED FIXED/HINGED
BASE”, In this paper a G+3 storied reinforced concrete Space frame located in seismic
zones IV and V with the fixed, hinged and flexible foundation is analysed. The building

with the flexible foundation has been analysed incorporating soil-structure interaction
(SSI) effects. For flexible foundation frame is supported by isolated footing on Winkler‘s
spring bed. The space frame is subjected to various combinations of gravity and
earthquake loads. The parameter varied for the study is the modulus of subgrade
reaction of the soil. A comparison of the displacements of the frame and the time period
of the whole structure is done. For this particular frame maximum displacement is least
for the fixed base condition while increasing the value of subgrade modulus the
displacement is decreasing for the building on Winkler‘s spring base. The value of time
period decreases as per increase of the soil subgrade modulus value for SSI effects as per
both the methods.

MODELLING AND ANALYSIS
METHODOLOGY7.1
A typical 2-D steel frame is used for comparison purpose, however derived results and
underlining principles are applicable to 'real life' 3-D frames and structures. Hence,
concepts explained in the different cases can be applied by engineers suitably to steel
structures.
In the present work, analysis is carried out using Winkler‘s soil model, the method of
analysis being used is Finite Element Method. Lateral deflection by considering soil
structure interaction is compared with the Conventional analysis. This dissertation work
deals with a comparative study of effect of soil structure interaction on Isolated
foundation and Pile foundation using Finite Element Method. While considering SSI
effect as of Winkler‘s spring model, first from support reactions size of foundation is
proportioned and designed for the appropriate loads. Then after the isolated foundation
is modelled in the software as 3D plate element beneath the pedestal at certain depth and
subgrade is modelled as springs. For pile foundation size of pile cap is proportioned and
designed for the appropriate loads. Then after pile cap foundation is modelled in the
software as 3D plate element beneath the pedestal at certain depth and pile is modelled
as pile spring stiffness. 4 piles are modelled below each column.
Finite Element Analysis (FEA) is used for analysing this problem of plate resting on
springs. FEA is numerical technique for understanding the behaviour of engineering
structures, where in a structure is discretized into many small elements and each
CHAPTER 7

Modelling and Analysis Chapter 7
element is analysed individually using loading and boundary conditions. While
modelling foundation thickness of the plate is given thickness equal to the thickness of
foundation. Meshing is done in the foundation considering aspect ratio lies between
1 to 2 and below each meshed element vertical spring is modelled at each discretized
node having value equal to soil subgrade modulus in case of isolated foundation.
Modelling of Isolated foundation is done as shown in Fig. 32(a)
(a) Isolated Foundation (b) Pile Foundation
Fig. 32 Modelling of Foundation
While modelling pile foundation thickness of the plate is given thickness equal to the
thickness of pile cap. Meshing is done of the pile cap considering aspect ratio lies
between 1 to 2. Spring having stiffness equal to Vertical and horizontal stiffness of pile is
modelled at 4 discretized node representing exact location of pile with edge distance and
centre to centre spacing of piles. Four piles are used below every column pile cap each

pile having diameter of 300 mm and centre to centre spacing of pile is kept as 1.0 m. The
edge distance of pile is 350 mm. Fig. 32(b) shows model of Pile foundation.
CODAL PROVISIONS7.2
 IS 1904 : 1986 Code Of Practice For Design And Construction Of Foundations In
Soils : General Requirements states that, the design of the foundation, super-
structure and the characteristics of the ground are inter-related. In order to obtain
maximum economy, the supporting ground, foundation and super-structure should
be studied as a whole.
 Clause 19.6 of IS 456 : 2000 Plain And Reinforced Concrete - Code Of Practice states
that, account shall be taken of Foundation movement if they are liable to affect
materially the safety and serviceability of the structure.
 Clause 4.3.4 of IS 800 : 2007 General Construction In Steel — Code Of Practice states
that, in the analysis of all structures the appropriate base stiffness about the axis
under consideration shall be used.
 Clause 12.13.3 of ASCE 7 – 05 Minimum Design Loads for Buildings and Other
Structures also highlights about considering stiffness of foundation while analysis
and design of structure. Clause 12.13.6.7 of same code highlights about pile soil
interaction and states that Pile moments, shears, and lateral deflections used for
design shall be established considering the interaction of the shaft and soil.
 Clause 2.3.2.1 of BS 8004: 1986 Code of Practice for Foundation states that, to obtain
maximum economy the supporting ground, substructure and superstructure should

be studied as a whole. In general it will be necessary to consider the overall stiffness
of a structure together with its substructure and their interrelation with ground
settlements.
 In Clause 2.6 of EN 1992-1-1:2004 - Design of concrete structures, it is mentioned
that where ground – structure interaction has significant influence on the action
effects in the structure, the properties of the soil and the effects of the interaction
shall be taken into account.
 Clause 6.8 from EN 1997-1:2004 states that, a more detailed analysis of soil –
structure interaction may be used to justify a more economic design. The distribution
of bearing pressure beneath a flexible foundation may be derived by modelling the
foundation as a beam or raft resting on a deforming continuum or series of springs,
with appropriate stiffness and strength.

PARAMETRIC STUDY & RESULTS
Four frames shown in Fig. 33 namely A-1, A-2, A-3 and A-4 with different substructure
and support condition have been selected for this study.
A-1 A-2 A-3 A-4
Fig. 33 Frames with Different Base Support
Support condition is pinned in frame A-1 at base plate level. In frame A-2, substructure
is modelled as isolated foundation and soil is modelled with the help of appropriate
spring stiffness. In frame A-3, substructure modelling is done only up to top of
foundation. Fixed support condition is considered in frame A-3 at the top of foundation
level. Substructure modelled in frame A-4 is pile foundation. Pile is modelled with the
help of vertical and horizontal spring having stiffness equivalent to that of stiffness of
pile.
CHAPTER 8

As mentioned earlier, parameters mentioned below have been selected to study its effect
of modelling of substructure with superstructure. Same are studied one by one in the
subsequent sections.
 Type of soil
 Depth of foundation
 Height of superstructure and type of analysis
 Unsymmetrical gravity load
 Type of connection at interface
 Pile modelling
TYPE OF SOIL8.1
In this case type of soil over which the frame is considered to be resting is changed while
depth of foundation, size of foundation and loading on frame is kept constant. Dense
soil, Medium dense Soil and Soft soil are the three types of soil over which the frame is
considered to be resting. The modulus of subgrade reaction constant k for each soil type
is taken as shown in Table 24, representing soft, medium dense and dense soil. Fig. 34
shows frame used for this comparison. The height of the frame is 15.0 m and it is loaded
with UDL of 36 kN/m on first storey, 18 kN/m on second and third storey and with UDL
of 30 kN/m on forth storey. The horizontal load is applied at beam – column junction as
shown in Fig. 34. Foundation is designed as per the loading on the frame and their sizes
are shown in Table 25. Net allowable bearing pressure of the soil is taken as 250 kN/m2

and depth of foundation is considered to be 2.0 m. Comparison of maximum lateral
deflection at top node of the frame for different types of soil is done in this case.
Table 24 Selected Subgrade Modulus
Type of soil
Modulus of subgrade reaction
(kN/m2/m)
Soft Soil K = 10000
Medium Dense Soil
K = 20000
K = 30000
Dense Soil
K = 40000
K = 55000
Fig. 34 Selected Frame for Case 8.1
Table 25 Foundation Details for Frame in Fig. 34
Type of footing Footing Depth ABP (kN/m2) Foundation Geometry
Isolated Foundation
- - Length Width Thickness
2.0 m 250 2.350 m 1.350 m 0.500 m
Pile Foundation
Footing Depth Pile Spacing
Pile - cap Geometry
Length Width Thickness
2.0 m 1.0 m 1.700 m 1.700 m 0.450 m

Graph 17 shows comparison of lateral deflection of frame with pinned support at base
plate level and frame with isolated foundation resting on different kind of soils. Table 26
shows percentage increase in deflection with decrease in modulus of subgrade against
pinned base foundation. It is observed from Error! Reference source not found.
that percentage increase in deflection for dense soil is 10.3% which is minimum and
percentage increase in deflection for soft soil is 49.5% which is maximum.
Graph 17 Deflection v/s Type of Soil [Isolated foun.]
* PINNED connection is considered at base plate level.
Table 26 Change in Deflection with Type of Soil [Isolated foun.]
DIFFERENCE BETWEEN
% INCREASE IN DEFLECTION
Dense soil Medium dense soil Soft Soil
K = 55000 K = 40000 K = 30000 K = 20000 K = 10000
ISOLATED & PINNED* 10.3 13.5 17.5 25.5 49.5
Graph 18 shows comparison of top node lateral deflection of frame with pinned support
at base plate level, fixed support at the top of foundation and frame with pile foundation
having different pile stiffness as mentioned in Table 27.
K =
55000
K =
40000
K =
30000
K =
20000
K =
10000
Dense Soil Medium Dense Soil Soft Soil
ISOLATED 70.8 72.9 75.5 80.6 96.0
PINNED* 64.2 64.2 64.2 64.2 64.2
50.0
60.0
70.0
80.0
90.0
100.0
STRUCTURELATERALDEFLECTION
(mm)

Table 27 Selected Pile Stiffness
VERTICAL STIFFNESS
KY (kN/m)
HORIZONTAL STIFFNESS
KX (kN/m)
63000 7660
90000 7660
125084 7660
135000 7660
Table 28 shows percentage increase in deflection with decrease in vertical stiffness of
pile. It is observed from Table 28 that percentage difference in deflection between frame
with pile foundation and pinned support condition is 7.7% for higher vertical stiffness of
pile and 11.8% for lower vertical stiffness of pile.
Graph 18 Deflection v/s Pile stiffness [Pile foun.]
* FIXED connection is considered at the top of foundation.
** PINNED connection is considered at base plate level.
KX (kN/m)
7660
KX (kN/m)
7660
KX (kN/m)
7660
KX (kN/m)
7660
KY (kN/m)
135000
KY (kN/m)
125084
KY (kN/m)
90000
KY (kN/m)
63000
PILE 69.1 69.3 70.3 71.8
FIXED* 64.7 64.7 64.7 64.7
PINNED** 64.2 64.2 64.2 64.2
50.0
55.0
60.0
65.0
70.0
75.0
(mm)

Table 28 Change in Deflection with Type of Soil [Pile foun.]
DIFFERENCE
BETWEEN
KY (kN/m)
135000
KY (kN/m)
125084
KY (kN/m)
90000
KY (kN/m)
63000
KX (kN/m)
7660
KX (kN/m)
7660
KX (kN/m)
7660
KX (kN/m)
7660
PINNED** & FIXED* 0.8 0.8 0.8 0.8
PILE & FIXED* 6.8 7.1 8.6 10.9
PILE & PINNED** 7.7 8 9.5 11.8
CONCLUSION
From above results it can be said that,
For Isolated foundation
 Considerable increase in lateral deflection occurred when foundation is located on
soft soil. As the stiffness of the soil strata increases, structure behaviour became
closer to that observed for rigid supports. For foundation resting on soft soil, it will be
better to model foundation along with superstructure.
For pile foundation
 For pile foundation resting on different types of soil, change in lateral deflection is
less when foundation is modelled. So behaviour of structure can be treated as fixed
(i.e. fixed at top of foundation). Modelling of foundation up to top of foundation will
give more or less same results as fixed support.

DEPTH OF FOUNDATION8.2
In this case depth of foundation is changed while all other parameters such as loads on
frame, allowable bearing pressure of soil are kept same. Different depths of foundation
are considered like 1.0 m, 1.5m, 2.0m, 3.0m, 3.5m and 4.0m. Fig. 35 shows frame used
for this case.
The height of the frame is 15.0 m and it is loaded with UDL of 36 kN/m on first storey,
18 kN/m on second and third storey and with UDL of 30 kN/m on forth storey. The
horizontal load is applied at beam – column junction as shown in Fig. 35. Foundation is
designed as per the depth of foundation and loading on the frame. Table 29 shows
footing dimension and pile cap details for various depth of foundation. Net allowable
bearing pressure of the soil is taken as 250 kN/m2. Net allowable bearing pressure is

assumed to be constant and does not vary with depth of foundation. Subgrade modulus
used is 40000 kN/m2/m for isolated foundation irrespective of depth of foundation. For
pile foundation stiffness of pile is used. The stiffness values are KY = 63000 kN/m and
KX = 10000 kN/m which remain same for every depth of foundation. For each depth of
foundation, maximum lateral deflection at top node for plane frame is measured.
Type of footing Footing Depth ABP (kN/m2) Foundation Geometry
Isolatedfoundation
1.0 m
250
2.100 m 1.350 m 0.450 m
1.5 m 2.250 m 1.350 m 0.500 m
2.0 m 2.350 m 1.350 m 0.500 m
3.0 m 2.650 m 1.350 m 0.575 m
3.5 m 2.800 m 1.350 m 0.600 m
4.0 m 2.900 m 1.350 m 0.625 m
Pilefoundation
Footing Depth
(m)
Pile Spacing
(m)
Pile - cap Geometry
1.0 1.0 1.700 m 1.700 m 0.450 m
1.5 1.0 1.700 m 1.700 m 0.475 m
2.0 1.0 1.700 m 1.700 m 0.500 m
3.0 1.0 1.700 m 1.700 m 0.525 m
3.5 1.0 1.700 m 1.700 m 0.550 m
4.0 1.0 1.700 m 1.700 m 0.575 m
Graph 19 shows comparison of structure lateral deflection at top node of the frame with
pinned support at base plate level and frame with isolated foundation having different
depth of foundation. Table 30 shows percentage increase in deflection with increase in
depth of isolated foundation. It is observed from Table 30 that percentage increase in
deflection is 11.5% for 1.0 m depth of foundation and this increase goes on increasing
with depth. For 4.0 m depth of foundation percentage increase in deflection is 20.9%.

Graph 19 Deflection v/s Depth of foundation [Isolated foun.]
Table 30 Change in Deflection with Depth of foun. [Isolated foun.]
DIFFERENCE BETWEEN
1.0 m 1.5 m 2.0 m 3.0 m 3.5 m 4.0 m
ISOLATED & PINNED* 11.5 12.0 13.5 17.6 19.2 20.9
Graph 20 Deflection v/s Depth of foundation [Pile foun.]
* FIXED connection is considered at the top of Pile cap.
1.0 m 1.5 m 2.0 m 3.0 m 3.5 m 4.0 m
ISOLATED 71.6 71.9 72.9 75.5 76.6 77.6
PINNED* 64.2 64.2 64.2 64.2 64.2 64.2
50.0
55.0
60.0
65.0
70.0
75.0
80.0
(mm)
1.0 m 1.5 m 2.0 m 3.0 m 3.5 m 4.0 m
PILE 68.9 69.8 71.1 75.3 77.9 81.1
FIXED* 64.3 64.5 64.7 65.6 66.2 67.1
PINNED** 64.2 64.2 64.2 64.2 64.2 64.2
50.0
55.0
60.0
65.0
70.0
75.0
80.0
85.0
(mm)

Graph 20 shows comparison of top node structure lateral deflection of frame with pinned
support at base plate level, fixed support at the top of foundation and frame with pile
foundation having same pile stiffness but different depth of foundation. Table 31 shows
percentage increase in deflection with increase in depth of Pile foundation. It is observed
from Table 31 that percentage difference in deflection between frames with base pinned
and with pile foundation is 7.3% for 1.0 m depth of foundation and 26.3 % for 4.0 m
depth of foundation.
Table 31 Change in Deflection with Depth of foun. [Pile foun.]
DIFFERENCE BETWEEN
1.0 m 1.5 m 2.0 m 3.0 m 3.5 m 4.0 m
PINNED** & FIXED* 0.2 0.4 0.8 2.1 3.2 4.5
PILE & FIXED* 7.1 8.3 9.9 14.8 17.7 20.9
PILE & PINNED** 7.3 8.7 10.8 17.2 21.4 26.3
CONCLUSION
 For Isolated foundation, percentage difference in deflection increases with increase in
depth of foundation. When depth of the foundation is more than 2.0 m it will be
better to model foundation.
For pile foundation
 Percentage difference in deflection is less up to 2.0 m but increase is noticeable
beyond 2.0 m depth of foundation.

HEIGHT OF SUPERSTRUCTURE AND TYPE OF ANALYSIS8.3
Two parameters Height of superstructure and Type of analysis are discussed in this
section. In 8.3.1, Height of superstructure is changed and results are compared for 1st
order analysis. In 8.3.2, results are compared for 1st order and 2nd order analysis with
same frames used for in 8.3.1.
8.3.1 Height of superstructure
In this case height of superstructure is changed whereas depth of foundation is kept
constant for every frame i.e. A-1, A-2, A-3, A-4 & A-5 shown in Fig. 36. The height of
superstructure is varied from 20 m to 60 m. The bottom most storey of each frame is
loaded with UDL of 36 kN/m and rest all other storey are loaded with UDL of 18 kN/m.
Horizontal load is applied at beam column junction.
Table 32 Foundation Details for Frames in Fig. 36
Type of
footing
Height of
Superstructure
Footing
Depth
ABP (KN/m2) Foundation Geometry
Isolated
foundation
20 m
2.0 m 250
1.800 m 1.250 m 0.400 m
30 m 2.150 m 1.450 m 0.475 m
40 m 2.400 m 1.650 m 0.550 m
50 m 2.600 m 1.850 m 0.575 m
60 m 2.750 m 2.150 m 0.625 m
Pile
foundation
Footing
Depth
Pile Spacing
(m)
Pile - cap Geometry
20 m
2.0 m
1.0 1.700 m 1.700 m 0.550 m
30 m 1.0 1.700 m 1.700 m 0.600 m
40 m 1.0 1.700 m 1.700 m 0.625 m
50 m 1.0 1.700 m 1.700 m 0.650 m
60 m 1.0 1.700 m 1.700 m 0.675 m

A-1 A-2 A-3 A-4 A-5
Ht. = 20 m Ht. = 30 m Ht. = 40 m Ht. = 50 m Ht. = 60 m
Fig. 36 Selected Frames for Case 8.3
The horizontal load of 11.0 kN is applied at bottom most storey and horizontal load at all
other stories is 5.5 kN. Foundation for each frame is designed as per the load on the
frame. Table 32 shows footing dimension and pile cap details for different height of

frame. Net allowable bearing pressure of the soil is taken as 250 kN/m2. Depth of
foundation is taken as 2.0 m and remains constant for every frame. The subgrade
modulus used is 20000 kN/m2/m for isolated foundation irrespective of height of
superstructure. For pile foundation stiffness of pile is used. The stiffness values are
KY = 63000 kN/m and KX = 10000 kN/m which remain same for every frame.
Comparison of maximum lateral deflection at top node for every plane frame structure is
done with different support conditions.
Graph 21 shows comparison of structure lateral deflection of frames with pinned support
at base plate level and frames (i.e. A-1, A-2, A-3, A-4 & A-5) with isolated foundation.
Graph 21 Deflection v/s Superstructure Height [Isolated foun.]
Table 33 shows percentage increase in deflection with increase in height superstructure
for isolated foundation. It is observed from Table 33 that percentage increase in
deflection for 20 m height of structure is 13.5% which is lesser compared to that for 60 m
height of the structure for which increase in deflection is 24.1%.
20 m 30 m 40 m 50 m 60 m
ISOLATED [I order] 103.7 156.2 213.6 277.1 340.3
PINNED* [I order] 91.4 136.3 181.4 228.4 274.2
50.0
100.0
150.0
200.0
250.0
300.0
350.0
400.0
(mm)

Table 33 Change in Deflection with Ht. of Superstructure [Isolated foun.- 1st order]
DIFFERENCE BETWEEN
20 m 30 m 40 m 50 m 60 m
ISOLATED & PINNED* 13.5 14.6 17.8 21.3 24.1
Results of comparison of structure lateral deflection of frames (i.e. A-1, A-2, A-3, A-4 and
A-5) with pinned support at base plate level, fixed support at the top of foundation and
with pile foundation having same pile stiffness for all the frames are shown in Graph 22.
Table 34 shows percentage increase in deflection with increase in height superstructure
for pile foundation. It is observed from Table 34 that difference in deflection between
pinned base and foundation with pile spring stiffness, for 20 m height of structure is
3.2% which is lesser compared to that for 60 m height of the structure for which increase
in deflection is 12.6%.
Graph 22 Deflection v/s Superstructure Height [Pile foun.]
* FIXED connection is considered at the top of Pile cap.
20 m 30 m 40 m 50 m 60 m
PILE [I order] 94.3 142.6 193.6 249.7 308.7
FIXED* [I order] 91.8 136.9 182.4 229.9 276.3
PINNED** [I order] 91.4 136.3 181.4 228.4 274.2
90.0
140.0
190.0
240.0
290.0
(mm)

Table 34 Change in Deflection with Ht. of Superstructure [Pile foun. -1st order]
DIFFERENCE BETWEEN
% Increase in Deflection
20 m 30 m 40 m 50 m 60 m
PINNED** & FIXED* 0.4 0.4 0.6 0.7 0.8
PILE & FIXED* 2.7 4.1 6.1 8.6 11.7
PILE & PINNED** 3.2 4.6 6.7 9.3 12.6
CONCLUSION
 With an increase in structure‘s height, percentage difference will also increase. So
when height of the structure is significant (more than 30 m) it will be better to model
foundation together with superstructure.
For Pile foundation
 Percentage difference in deflection is less up to 50 m but it increase beyond 50 m
height of structure. So foundation modelling can be ignored upto 50 m height of
structure when you are going for pile foundation.

8.3.2 Type of analysis
The type of analysis refers to First and Second order analysis. Second-order analysis
accounts for additional forces induced in the frame due to the axial forces acting
eccentrically to the assumed member centroids as the frame deflects under load. These
secondary effects, often referred to as ‗P-Delta‘ effects, can be best illustrated by
reference to Fig. 37 of a simple cantilever. As can be seen, the second-order effects
comprise an additional moment of P due to the movement of the top of the cantilever,
, induced by the horizontal force, H. In addition to a moment within the member of P
due to deflection of the member itself between its end points.
Fig. 37 Second-order Effects in a Vertical Cantilever
2nd order analysis (P-Delta analysis) is also carried out on same frames shown in Fig. 36
with other parameters such as loading, depth of foundation, bearing pressure, subgrade
modules, pile stiffness etc. remaining same as explained 8.3.1

Graph 23 shows comparison of structure lateral deflection of frames with pinned support
at base plate level and frames (i.e. A-1, A-2, A-3, A-4 & A-5) with isolated foundation for
2nd order analysis. Table 35 shows percentage increase in deflection with increase in
height of superstructure for isolated foundation for P-Delta analysis.
Graph 23 Deflection v/s Superstructure height [Isolated foun. - 2nd order]
Table 35 Change in Deflection with Ht. of Superstructure [Isolated foun. - 2nd order]
DIFFERENCE BETWEEN
20 m 30 m 40 m 50 m 60 m
ISOLATED & PINNED* 13.8 15.6 19.3 23.5 26.7
Results of comparison of structure lateral deflection of frames (i.e. A-1, A-2, A-3, A-4 and
A-5) with pinned support at base plate level, fixed support at the top of foundation and
with pile foundation having same pile stiffness for all the frames are shown in Graph 24
for 2nd order analysis. Table 36 shows percentage increase in deflection with increase in
height of superstructure for pile foundation when 2nd order analysis is carried out.
20 m 30 m 40 m 50 m 60 m
ISOLATED [II order] 115.3 174.0 238.7 311.5 384.7
PINNED* [II order] 101.4 150.5 200.1 252.2 303.5
50.0
100.0
150.0
200.0
250.0
300.0
350.0
400.0
(mm)

Graph 24 Deflection v/s Superstructure Height [Pile foun. - 2nd order]
Table 36 Change in Deflection with Ht. of Superstructure [Pile foun. - 2nd order]
DIFFERENCE BETWEEN
20 m 30 m 40 m 50 m 60 m
PINNED** & FIXED* 0.1 0.3 0.5 0.6 0.8
PILE & FIXED* 2.8 4.3 6.6 9.4 12.7
PILE & PINNED** 2.9 4.7 7.0 10.0 13.6
CONCLUSION
For Isolated foundation & Pile Foundation
 Increase in deflection is higher in 2nd order compared to first order analysis and these
difference increases with height of the superstructure. So when height of the structure
is significant, it will be better to model foundation together with superstructure and
carry out 2nd order analysis.
20 m 30 m 40 m 50 m 60 m
PILE [II order] 104.3 157.5 214.1 277.4 344.8
FIXED* [II order] 101.5 151.0 201.0 253.7 305.9
PINNED** [II order] 101.4 150.5 200.1 252.2 303.5
100.0
150.0
200.0
250.0
300.0
350.0
(mm)

UNSYMMETRICAL GRAVITY LOAD8.4
In this case structural frame is subjected to unsymmetrical gravity load. For that point
load P is applied to the frame as shown in Fig. 38. The value of P changes from 150 kN to
600 kN with interval of 150 kN. In addition to that frame is subjected to the vertical and
horizontal load of 36 KN/m and 11 kN respectively at 1st storey. And vertical and
horizontal load on all other stories is 18 kN/m and 5.5 kN respectively. Unsymmetrical
load results in sway of frame and differential settlement of the frame.

Foundation is designed as per loading on the frame. Table 37 shows footing dimension
and pile cap details for different P values. Net allowable bearing pressure of the soil is
taken as 250 kN/m2. The subgrade modulus used is 20000 kN/m2/m for isolated
foundation. For pile foundation stiffness of pile is used. The stiffness values are
KY = 63000 kN/m and KX = 10000 kN/m. For each load value maximum lateral
deflection at top node for plane frame is measured.
Type of
footing
Unsymmetrical
vertical load
(kN)
Footing
Depth
ABP
(KN/m2)
Foundation Geometry
Isolated
foundation
150
2.0 m 250
2.150 m 1.650 m 0.550 m
300 2.250 m 1.850 m 0.550 m
450 2.450 m 1.950 m 0.575 m
600 2.500 m 2.150 m 0.575 m
Pile
foundation
Unsymmetrical
vertical load
(kN)
Footing
Depth
Pile
Spacing
(m)
Pile - cap Geometry
150
2.0 m
1.0 1.700 m 1.700 m 0.550 m
300 1.0 1.700 m 1.700 m 0.600 m
450 1.0 1.700 m 1.700 m 0.625 m
600 1.0 1.700 m 1.700 m 0.650 m
Graph 25 shows comparison of structure lateral deflection for selected frame with pinned
support at base plate level and structural frame with isolated foundation for different
values of unsymmetrical gravity load. Table 38 shows percentage increase in deflection
with increase in unsymmetrical vertical load for isolated foundation. It is observed from
Table 39 that when value of unsymmetrical vertical load is 150 kN difference of

percentage increase in deflection is 4.3% which increases to 11.0% when value of
unsymmetrical load is 600 kN.
Graph 25 Deflection v/s Unsymmetrical Load [Isolated foun.]
Table 38 Change in Deflection with Unsymmetrical Load [Isolated foun.]
DIFFERENCE BETWEEN
0 kN* 150 kN 300 kN 450 kN 600 kN
ISOLATED & PINNED* 20.1 24.4 27.7 29.7 31.2
*No unsymmetrical gravity load
Table 39 shows difference of percentage increase in deflection for frames with
unsymmetrical gravity load and no unsymmetrical gravity load. Hence results obtained
for no unsymmetrical gravity load (0 kN) shown in Table 38 is considered as datum for
comparison (i.e. 20.1%).
Table 39 Increase in Deflection Due to Unsymmetrical Load [Isolated foun.]
LOAD 150 kN 300 kN 450 kN 600 kN
Difference of % Increase
in Deflection
4.3 7.5 9.5 11.0
0 kN 150 kN 300 kN 450 kN 600 kN
ISOLATED 154.0 173.1 193.4 214.1 236.3
PINNED* 128.2 139.1 151.5 165.1 180.1
50.0
70.0
90.0
110.0
130.0
150.0
170.0
190.0
210.0
230.0
250.0
(mm)

Graph 26 shows comparison of structure lateral deflection for selected frame with
pinned support at base plate level, fixed support at the top of foundation and with pile
foundation having pile stiffness. Table 40 shows percentage increase in deflection with
increase in unsymmetrical vertical load. It is observed from Table 41 that when value of
unsymmetrical vertical load is 150 kN difference of percentage increase in deflection
between pinned base and foundation with pile spring stiffness is 2.4% which increases to
8.7% when value of unsymmetrical load is 600 kN.
Graph 26 Deflection v/s Unsymmetrical load [Pile foun.]
Table 40 Change in Deflection with Unsymmetrical Load [Pile foun.]
DIFFERENCE BETWEEN
0 kN* 150 kN 300 kN 450 kN 600 kN
PINNED** & FIXED* 0.4 0.5 0.6 0.8 0.8
PILE & FIXED* 5.2 7.4 9.6 11.6 13.4
PILE & PINNED** 5.6 8.0 10.3 12.4 14.4
*No unsymmetrical gravity load
0 kN 150 kN 300 kN 450 kN 600 kN
PILE 135.4 150.3 167.1 185.5 206.0
FIXED* 128.7 139.9 152.5 166.3 181.6
PINNED** 128.2 139.1 151.5 165.1 180.1
125.0
135.0
145.0
155.0
165.0
175.0
185.0
195.0
205.0
(mm)

Table 41 shows difference of percentage increase in deflection for frames with
unsymmetrical gravity load and no unsymmetrical gravity load. Hence results obtained
for no unsymmetrical gravity load (0 kN load) shown in Table 40 is considered as datum
for comparison.
Table 41 Increase in Deflection Due to Unsymmetrical Load [Pile foun.]
Difference of % Increase in Deflection
DIFFERENCE BETWEEN 150 kN 300 kN 450 kN 600 kN
PINNED** & FIXED* 0.1 0.3 0.4 0.5
PILE & FIXED* 2.2 4.4 6.4 8.2
PILE & PINNED** 2.4 4.7 6.8 8.7
CONCLUSION
 From Table 39 it can be said that, sway is increased considerably after unsymmetrical
vertical load of 450 kN. So in that case it is better to model foundation along with
superstructure.
For Pile foundation
 From Table 41 it can be said that, there is no significant increase in sway so in that
case there is no requirement to model foundation.

TYPE OF CONNECTION AT INTERFACE8.5
Here interface refers to connection at base plate level. There can be either pin connection
or fixed connection at base plate level. In this case structural frame shown in Fig. 39 is
compared with fixed and pinned type connection at base plate level. The loads on the
frame remain same while connection is pinned or fixed at base plate. The height of the
frame is 15.0 m and it is subjected to horizontal and vertical load as shown in Fig. 39.
Foundation is designed as per loading on the frame. Table 42 shows footing dimension
and pile cap details for same loading on the frame but different connection at base plate
level. Depth of foundation is kept 2.0 m and Net allowable bearing pressure of the soil is
taken as 250 kN/m2. Subgrade modulus of soil while modelling isolated footing is kept

20000 kN/m2/m and stiffness of pile for pile foundation is kept KY = 63000 kN/m and
KX = 10000 kN/m. In this case comparison of maximum lateral deflection at top node of
frame with and without soil structure interaction with different base plate level
connection is made.
Type of
footing
Footing
Depth (m)
Type of
connection at
Base plate
ABP
(kN/m2)
Foundation Geometry
Isolated
foundation
- - - Length Width Thickness
2.0 m Fixed 250 3.500 m 2.250 m 0.600 m
2.0 m Pinned 250 2.350 m 1.350 m 0.500 m
Pile
foundation
Footing
Depth (m)
Type of
connection at
Base plate
Pile
Spacing
(m)
Pile - cap Geometry
2.0 m Fixed 1.0 1.700 m 1.700 m 0.550 m
2.0 m Pinned 1.0 1.700 m 1.700 m 0.450 m
Graph 27 shows comparison of structure lateral deflection for frame shown in Fig. 39
with different support condition at base plate level and structural frame with isolated
foundation.
Graph 27 Deflection v/s Connection at Interface [Isolated foun.]
PINNED FIXED
ISOLATED 80.7 77.4
AT BASE PLATE 64.2 64.9
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
(mm)

Table 43 Change in Deflection with Connection Type [Isolated foun.]
Type of Connection at
Interface
PINNED FIXED
Increase in Deflection
(%)
25.7 19.3
Graph 28 shows comparison of structure lateral deflection for frame shown in Fig. 39
with different support condition at base plate level, fixed support at the top of foundation
and with pile foundation having pile stiffness as mentioned above.
Graph 28 Deflection v/s Connection at Interface [Pile foun.]
*Free headed pile is used.
** FIXED connection is considered at the top of foundation.
Table 44 Change in Deflection with Connection Type [Pile foun.]
DIFFERENCE BETWEEN
INCREASE IN DEFLECTION (%)
PINNED FIXED
BASE PLATE & FIXED* 0.8% 3.1%
PILE & FIXED* 10.4% 31.0%
PILE & BASE PLATE 11.3% 35.1%
PINNED FIXED
PILE* 71.5 87.7
FIXED** 64.7 66.9
AT BASE PLATE 64.2 64.9
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
(mm)

CONCLUSION
From above results it can be concluded that,
 Even if fixed condition is considered at base plate level increase in deflection is about
19%, so it will be better to model foundation.
For pile foundation (Free headed pile)
 Fixed connection at base plate level has more effect (i.e. increase in deflection)
compared to pin connection at base plate level.

PILE MODELING8.6
While considering soil interaction for pile foundation, either the pile can be modelled a
whole full length or else it can be just modelled with the help of spring at the bottom of
pile cap with springs having equivalent stiffness as that of pile. Fig. 40 shows example of
pile modelling in which whole pile is modelled beneath superstructure and vertical and
horizontal stiffness is assigned at regular interval. The alternative of considering soil
structure interaction in pile foundation is considering appropriate horizontal and vertical
pile spring stiffness at a single point instead of modelling pile as shown in Fig. 41.
Fig. 40 Pile Modelling with Spring at Regular Interval

Fig. 41 Pile Modelled as Equivalent Single Spring Support
As shown in Fig. 42, comparison of lateral displacement at top node is made for same
frame with same loading but one modelled with pile (Fig. 42.a) while other with only
single point pile spring stiffness (Fig. 42.b).
Fig. 42 Frames with Full Pile Modelled & Single Point Pile Stiffness

The height of the structure is 30.0 m and its bottom storey is loaded with 36 kN/m and
11 kN vertical and horizontal load respectively. All other storeys are loaded with 18 kN/m
and 5.5 kN vertical and horizontal load respectively. Four steel piles each of length
18.25 m (60 ft) are provided below each column. HP 14 X 73 American steel section is
used as pile. Depth of fixity of pile is considered as 4.9 m (16 ft), below that depth pile
has no resistance to lateral forces and horizontal stiffness of pile below that depth is
taken zero. Pile is modelled with horizontal and vertical stiffness provided at regular
interval of 0.5 m up to depth of fixity and after that stiffness values are provided at every
1.5 m. Horizontal and vertical stiffness of pile at this depth is derived from load
settlement curve of pile and their values are shown in Table 45. The horizontal and
vertical stiffness of single point pile stiffness at pile tip are shown in Table 46. The
comparison of lateral deflection at top node for plane frame with full pile modelled and
pile modelled as equivalent single spring support is shown in Table 47
Table 45 Pile Stiffness at Different Depth
DEPTH
Horizontal stiffness (kN/m) Vertical stiffness -
KY (kN/m)Major Direction - KX Minor Direction - KZ
0.0 955 573 524
0.5 860 516 3110
1.0 764 459 5696
1.5 669 401 8282
2.0 573 344 11031
2.5 478 287 13789
3.0 382 229 16547
3.5 287 172 19382
4.0 191 115 22226
4.5 96 57 25070
5.0 0 0 27914
6.5 0 0 40067

8.0 0 0 62044
9.5 0 0 81668
11.0 0 0 93733
12.5 0 0 106152
14.0 0 0 119941
15.5 0 0 131788
17.0 0 0 134374
18.25 0 0 180375
Table 46 Single Point Pile Spring Stiffness
Horizontal stiffness (kN/m)
Vertical stiffness
- KY (kN/m)Major Direction -
KX
Minor Direction -
KZ
5254 3152 102157
Table 47 Deflection Comparison for Frame with Different Pile Model
STRUCTURE LATERAL
DEFLECTION (mm)
Full Pile modelled 140.2
Pile modelled as equivalent single
spring support
141.4
% Difference in Deflection 0.8
CONCLUSION
 The results in Table 47 shows that difference in lateral deflection is less than 1% when
full pile is modelled and pile is modelled as equivalent single spring support. Thus it
can be concluded that while taking soil structure interaction into consideration
during pile foundation, analysis can be carried out only by modelling single point pile
stiffness instead of modelling the whole pile.

DECISION MATRIX
The Decision matrix has been developed based on various parameter studied in Part II of
the thesis. This Decision matrix will help in taking decision regarding modelling of
substructure (Isolated foundation) along with superstructure while analysis and design
of structure. This decision matrix is developed in Microsoft Excel and is user friendly. It
allows user to select values of different parameters as per the requirement. The following
parameter can be selected by the user.
(1) Depth of foundation
(2) Modulus of subgrade of soil
(3) Height of superstructure
(4) Enter type of analysis: I order OR II order
(5) Is Unsymmetrical gravity load present: Yes OR No. If Yes enter value of
unsymmetrical gravity load.
After entering above mentioned parameters, the decision matrix will give its opinion on
modelling of substructure with superstructure. However final decision lies in the hand of
the user. Fig. 1 shows pictorial view of Decision matrix.
CHAPTER 9

Decision matrix Chapter 9
Fig.43DecisionMatrix

Decision matrix Chapter 9
FUTURE SCOPES9.1
Since present research leaves few questions unanswered, a short list of suggestions for
future work is given below:
PART I
 The study can be extended for connections in this structural framing system and then
economy of the frame should be compared.
 Parametric study of selected structural framing can be done for different height of the
frame.
PART II
 Similar Decision matrix can be developed for pile foundation.
 Study for different configuration of pile group and different end condition at pile tip
can be done.
 Effect of substructure modelling on superstructure can be studied for few other types
of foundation such as raft foundation, compound foundation etc.

REFERENCES
Reference of Research Papers & Books
[1] Ankit Suri, ―Analysis of structure supported by elastic foundation‖, Department of
Structural Engineering, Malaviya National Institute of Technology, Jaipur, 2011.
[2] Bhojegowda V T, Mr. K GSubramanya, ―Soil structure interaction of framed
structure supported on different types of foundation‖, International Research
Journal of Engineering and Technology, Volume 2, Issue 5, 2015.
[3] Bo Dowswell, Allen Brice, and Brian Blain, ―Modern steel construction‖, July 2010.
[4] Boostani Darmian, M.Azhdary Moghaddam, H.R.Naseri, ―Soil–structure interaction
in steel braced structures with foundation uplift‖, IJRRAS, Volume 7, Issue 2, 2011.
[5] Buick Davison & Graham W. Owens, ―Steel Designer‘s Manual‖, 6th Edition, 2003
[6] Chandrasekaran.V.S, ―Numerical and centrifuge modelling in soil structure
interaction‖, Indian Geotechnical Journal, Volume 31 No 1, 2011.
[7] Dr. S. A. Halkude, Mr. M. G. Kalyanshetti, Mr. S. H. Kalyani, ―Soil structure
interaction effect on seismic response of R.C. frames with isolated footing‖,
International Journal of Engineering Research & Technology, Vol 3, Issue 1, 2014.
[8] Jenifer Priyanka R.M, SaravanaBhaarathi .S, Varun .J, ―Study on lateral deflection of
buildings with fixed support under various soil conditions‖, International Journal of
Engineering Research and Development, Volume 10, Issue 4, 2014, PP.36-40.

[9] Kuladeepu M N, G Narayana, B K Narendra, ―Soil structure interaction effect on
dynamic behavior of 3D building frames with raft footing‖, International Journal of
Research in Engineering and Technology, Volume 4, Issue: 07, 2015.
[10] MohammedSaeem B Vohra, Prof.K.N.Sheth, ―A parametric study for analysis of
space frame with isolated footings supported on winkler‘s spring base with reference
to idealized fixed/hinged base‖, International Journal for Scientific Research &
Development, Vol. 3, Issue 01, 2015.
[11] Nathan Miller, ―Tips from engineering‖, NBS-IN, Issue 1.14.
[12] R. M. Jenifer Priyanka, N. Anand, Dr. S. Justin, ―Studies on soil structure interaction
of multi storeyed buildings with rigid and flexible foundation‖, International Journal
of Emerging Technology and Advanced Engineering, Volume 2, Issue 12, 2012.
[13] Richard M. Drake, Robert J., ―Design of structural steel pipe racks‖, Walter
Engineering Journal, Fourth quarter, 2010.
[14] Shah H.J., ―Reinforced Concrete Vol.-I‖, Charotar Publishing House, India; 2000.
[15] Shrabony Adhikary, Yogendra Singh, D. K. Paul, ―Modelling of soil – foundation
structure system‖, Department of Earthquake Engineering, IIT Roorkee.

Reference of National & International Codes
[1] AISC 360-05, ―Specification for Structural Steel Buildings‖, American Institute of
Steel Construction; 2005.
[2] ASCE 7–05, ―Minimum Design Loads for Buildings and Other Structures‖, American
Society of Civil Engineers; 2005.
[3] BS 8004, ―Code of Practice for Foundation‖ British Standard Institution; 1986.
[4] EN 1992-1-1 Euro code 2, ―Design of Concrete Structures - Part 1-1: General rules
and rules for buildings‖; 2004.
[5] FEMA 74, ―Reducing the Risks of Non-structural Earthquake Damage‖; 1994.
[6] IS 1904, ―Code of Practice for Design and Construction of Foundations in Soils:
General Requirements‖ B.I.S., New Delhi; 1986.
[7] IS 456, ―Plain and Reinforced Concrete – Code of Practice‖, B.I.S., New Delhi; 2000.
[8] IS 800, ―General Construction in Steel — Code of Practice‖ B.I.S., New Delhi; 2007.

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