Progressive Collapse Analysis of Low Rise Steel Frame Structure With and Without Bracing System

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 01 | Jan -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 1186
Progressive Collapse Analysis of Low Rise Steel Frame Structure With
and Without Bracing System
Krishna Kant Chaubey1, A.B.Pujari2, Dr. Venkata Dilip Kumar P3
1 Krishna Kant Chaubey, Postgraduate student, KJ College of Engineering, Pisoli, Pune, Maharashtra.
2 A.B.Pujari, Professor, KJ College of Engineering, Pisoli, Pune, Maharashtra.
3 Associate Professor, School of civil engineering,Anurag group of institutions, Hyderabad.
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Abstract - Progressive Collapse is a local failure of a
primary structural component leads to collapse of adjoining
member which leads to additional collapse. Hence the total
damage is disproportionate to the original cause. The most
common local failure is framed structural is to be column
failure. This paper compares the influences of several
modelling approach for progressive collapse assessment of
steel frame structure, considering sudden column loss as
design scenario. A linear staticanalysisbasedontheGSA-2013
guidelines is used as preliminary study to determine
progressive collapse analysis of low rise steel frame structure
with and without bracing system. In thisstudy, acolumnatthe
different position and different story level is removed to
simulate an effect of an extreme event and the remaining
structure is analysed using a finite element software ETABS
2015. The structure is analysed for gravity load and seismic
load. Then the structure is checked for the Demand Capacity
Ratio as per GSA 2013.
Key Words: Progressive Collapse, Demand Capacity
Ratio, GSA-2013, Steel structure failure, ETABS 2015
etc.
1. INTRODUCTION
Progressive collapse is a catastrophic structural
phenomenon that can occur because of human-made or
natural hazards. In progressive collapsemechanism,a single
local failure may cause a significant deformation which may
then lead to collapse of a structure. If a structure has good
alternative loading path, the initial failure will not expand to
the other parts of the structure and the local damage will be
restricted. The American Society of Civil Engineering (ASCE,
2005) is the only mainstream standard which addresses the
issue of progressive collapse in some detail. The guidelines
for progressive collapse resistantdesignare noticeablein US
Government documents, General Service Administration
(GSA, 2003) and Unified Facility Criteria (UFC, 2009). The
GSA guidelines have provideda methodologytodiminishthe
progressive collapse potential in structures based on
Alternate Path Method (APM). It defines scenarios in which
one of the building’s columns is removed and the damaged
structure is analysed to studythesystemresponses.The UFC
methodology, on the other hand, is a performance-based
design approach, and is partly based on the GSA provisions.
GSA Guidelines the General Service Administration (GSA)
analysis includes removal of one column at a time from the
storey 1 above the ground floor. GSA provides criteria for
column removal for static analysis case. According to that a
column is removed as mentioned below for typical
structures. Exterior Column in the middle of longer side of
building Exterior column in the middle of shorter side of the
building Corner Column butinthepresentstudythe building
considered is a typical structure and has an
irregular/asymmetricplanandbaysize.HenceGSAsuggests,
an engineering judgment is to be done along with the above
mentioned column removal cases and additional critical
locations for removing column foranalysisaretobedecided.
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2. Literature Review:-
The Ronan Pointapartment in1968collapseprovokedactive
research in the engineering community in Europeand US for
better understanding of Progressive Collapse. Investigations
were conducted to find errors in design & construction
procedures, but the collapsed structure was designed using
the code provisions in places at the time. Although warning
about progressive collapse in a structure was issued prior to
the Ronan point apartment collapse extensive research
related to progressive collapse started after the Ronan Point
event. Bruce R. Ellingwood (2002)studied onloadresistance
factor criteria for progressive collapse .He describes design
strategies to minimize the likelihood of progressive collapse,
and prospects for the implementation of general provisions
in national standards such as ASCE ,Minimum Design Loads
for Buildings and Other Structures.[1] G. Tarțaa* and A.

Pinteaa(2012) madean attempt to investigateandevaluated
of multi-storey moment-resisting steel frames with stiffness
irregularities using standard and advanced pushover
methods. The results show that the adaptive pushover
methods give the bestapproximationintermsofmediumand
maximum errors of the interstory drifts. [2] Khandelwal ,K;
EL-Tawail, S;and F.(2009) studied on progressive collapse
analysis of seismically designed steel braced frames and
performed a research for evaluating the progressivecollapse
of steel braced frame through using models based on
validating computational simulation procedures through
applying alternative path method (APM). They conducted
their standard on a ten story building byremovingimportant
load bearing column and adjacent braces in order to define
the ability of the structure to resist the member loss. They
finally concluded thattheframethatwasbracedeccentrically
was a more resistant to progressive collapse than that was
braced concentrically.[3] H.R.Tavakoli and A.Rashidi Alashti
(2012) made an attempt to investigate and study whether
MRF steel structures that have been designed based on
seismic codes, are able to resist progressive collapse with
damaged columns in different locations under seismic
loading. For this purpose, 3-D and 2-D push-over analysis of
structures is carried out. This conclusion is reached without
taking into consideration the beneficial effect of slab action.
The panel zone in girder to column joints was assumed to be
rigid, and connection properties were not considered.
Althoughlumped plastic hinges can appear toprovideagood
solution to the modeling problem, they actually only shiftthe
difficulty elsewhere, by raising the question relative to the
numerical length of the hinge.[4] Kamel Sayed Kandil, Ehab
Abd ElFattah Ellobodyand HanadyEldehemy(2013)studied
and Experimental Investigation of Progressive Collapse of
Steel Frames and two new tests conducted to augment
available data highlighting the structural performance of
multistory steel frames under progressive collapse. The
comparison between the experimental results and the
existing results in the literature with finite element results
obtained in this study showed that the developed model
simulates the behavior of steel frames well. It showed that
the maximum lateral deflection measured for the edge-
column-removed case was higher than that when predicted
numerically because the fixation points of the steel frame
were not fully rigid. It also showed that the column adjacent
to the removed column underwent higher strains than other
columns, which implied the redistribution of forces from the
removed column to the nearest columns [5].
3. Research objective:-
A significant portion of the reported collapse includes
progressive collapse that often leads to large human and
property losses. In order to reduce the potential of
progressive collapse, detailed behavior of a structural
system is needed when a structural member is damaged.
 To find out the critical locations of the three
dimensional low rise (G+5 & G+10) moment
resisting frame.
 To find out detailed behavior of a structural system
when a structural member is damaged.
 Capturing realistic structural response of three
dimensional structures using various analyses.
Considering sudden column loss as a design
scenario.
Aim is to make such building which should be progressive
collapse free.
4. Research methodology:-
In this study a framework of low rise steel structure 5th and
10th story for progressive collapse, considering suddenloss
of column as a design scenario and the structure analysis to
minimize the collapse by using ‘V’ bracing at each outer face
of structure by using software .The steel frame structure
analyzed using Finite Element software ETABS-2015 the
linear static response with dynamic effects in a simple
method are carried out. The resisting capacity of moment
resisting frame using alternatepathmethodsforprogressive
collapse as per recommended in the GSA-2013 guidelines.
The linear static and Non-linear static analysis procedure
were carried out for comparison of basic model, removal of
column at different location at different floor with bracing
and without bracing. It was observed that in the linear static
analysis progressive collapse of steel frame structure were
minimized by using ‘V’ bracing at outer face of frame
structure. Also it is observed that the non-linear static
analysis provided larger structural responsesandtheresults
varied more significantly as comparison to linear static
analysis. However, the linear procedure provided a more
conservative decision for progressive collapse potential of
model frame structures. GSA stated DCR criteria for
acceptance of member,
DCR=Qud/Qce Eqn. 1
Model Description
In the present study, five story and ten story model were
prepared on ETABS-2015. Spacing of grid is 5metersin both
the directions and the floor to floor height to complete
structure is 3 meters. In both the cases before progressive
collapse of structures we have taken the demand capacity of
members as 0.5-0.9. Loading on structures are taken as Live
Load-2.5KN/m and Floor Finish-1.25KN/m. For 5 story
building we did not consider the wind load casewhereas,for
the 10 story we considered the wind load effect as per IS-
875-2007. Seismic loads are applied for both the structures
as per the IS-1893-2007.

Figure 1: Five Story Building. (6X6 Bay Size)
Figure2: Ten Story Building (6X6 Bay Size)
Loading cases:-
All loading cases are used according to GSA 2013 guideline
for Progressive Collapse.
For Linear Static
Increased Gravity Loads for Floor Areas above Removed
Column or Wall,
After removal of Column,
Glf = ΩLF [1.2DL+ (0.5LL)] Eqn. 2
Gravity Loads for Floor Areas Away From Removed
Column or Wall Before removal of Column:
Glf = 1.2DL+ (0.5LL) Eqn. 3
For Nonlinear Static
Increased Gravity Loads for Floor Areas above Removed
Column or Wall,
After removal of Column,
Glf = Ωn [1.2DL+(0.5LL) Eqn. 4
Gravity Loads for Floor Areas Away From Removed
Column or Wall Before removal of Column,
Ωn = 1.08+0.76/ [(θc⁄ θy)+0.83)] Eqn. 5
In this study we used linear static as well as nonlinear
analysis method to carry progressive collapse of a 3-
Dimensional 5th & 10th steel frame structure. We used a
primary structural bearing element component removed at
various critical locations recommended by the GSA-2013
guideline.
Figure 3: Column removal positions at 1st, 3rd & 1st, 5th
story for five story & ten story building.
5. Analysis and Interpretation:-
In this study we used linear static as well asnon-linearstatic
analysis method to carry progressive collapse of a three-
Dimensional 5th & 10th steel frame structure. We used a
primary structural bearing element component removed at
various critical locations as recommended by GSA-2013
guideline. We removed different critical columnfordifferent
floor level i.e. in 5th story at 1st and 3rd story whereas in 10th
story, we will analysis at 1st and 5th story. For every location
we analysed and record various parameters such as DCR,
Joint Displacement, Axial Forces and Bending Moment.

For Case C1: Analyse for the sudden loss of a column
situated at the corner of building for 5th story at 1st Story.
Chart -a: Joint Displacement of Column C1 removal.
Chart -b: DCR of Column C1 for Column C1 removal.
Chart -c: DCR of Column C2 for Column C1 removal.
From above graph (a) tograph(f)wecanseethevariation
in all story due to sudden removal of Column C1 at corner
locations at first story. The demand capacity ratio for linear
static as well as nonlinear static analysis shows that after
removal, DCR of column at next successive story get
increased hence column gets fails which leads to increase in
DCR of neighboring primary and secondary element. But in
account to minimize the effect of collapse after providing
Chart -d: DCR of Beam B1 for Column C1 removal.
Chart -e: Axial Force in Column C1 for C1 removal.
Chart -f: Bending Moment in Beam B1 for Column C1
removal.
Bracing DCR of these element can be bring down to safety
limit, same scenario can be observed in joint displacement,
axial force & bending moment graphs.

For Case C4: Analyse for thesuddenlossofacolumnsituated
at or near the middle of the one of the direction (Y-Direction)
of the building for 5th story at 1st story.
Graph (a) to (f): Variation of DCR, Joint Displacement,
axial force and bending Moment values for respective
Case C4. This indicates localized failure of member from
first story to last story and forces are increased in
comparison to original Structures. When we use bracing
then forces reached to approximate value in
correspondence to actual which means structure is in
Chart -d: Axial Force in Column C4 for C4 removal.
Chart -e: DCR of Beam B61 for Column C4 removal.
removal.
Safe, even DCR after bracing reached to1whichindicatethat
we minimize the failure by using bracing.

For Case C1 At 3rd Story: Analyse for the sudden loss of a
column situated at the corner of building for 5th story at3rd
Story.
From above graph (a) to graph (f) we can the variationin
all story due to sudden removal of ColumnC1at3rd story,
corner locations at first story. The demand capacity ratio
for linear static as well as nonlinear static analysisshows
that after removal, DCR of column at next successive
story get increased hencecolumngetsfailswhichleadsto
increase in DCR of neighboring primary and secondary
element.
removal.
For Case C4 at 3rd Story: Analyses for the sudden loss of a
column situated at or near the middle of the one of the
direction (Y-Direction) of the building for 5th story at 3rd
story.

Graph (a) to (d): Variation of DCR, Joint Displacement,
axial force, Shear Force, bending Moment values for
respective Case C4 at 3rd story. This indicates localized
failure of member from 3rd story to last story and forces
are increased in comparison to original Structures. When
Chart -d: DCR of Beam B61 for Column C4 removal
removal.
We use bracing then forces reached to approximate value in
correspondence to actual which means structure is in safe,
even DCR after bracing reached to 1 which indicate that we
minimize the failure by using bracing.
For Case C1 at 1st Story: Analyse for the sudden loss of a
column situated at the corner of building for 10th story at 1st
Story.

removal.
All graphs gives the sameresultforC1caseat10th storyas
5th story gives.

For Case C4 at 1st Story: Analyse for the sudden loss of a
column situated at or near the middle of the one of the
direction (Y-Direction) of the building for 10th story at 1st
story.
removal.
Graph (a) represent Joint Displacement in which at the
critical location increases tremendously and after using
bracing it decreases. Graph (b) and (c) represents DCR
whereas Graph (d), (e) and (f) represents axial forces and
bending moments.

For Case C1 at 5th Story: Analyse for the sudden loss of a
column situated at the corner of building for 10th story at 5th
Story.
removal.
In case C1 at 5th at 10th gives the same result as the 5th
story gives. Graph (a) represents Joint displacement and
Graph (b), (c) and (e) represents DCR. Graph (d) and (f)
represents axial force and bending moments.

Graph (a) indicates that when remove C4 column at 5th
story, Joint Displacement increase linearly to 4th story but
after 5th story it increase drastically. Graph (b), (c) and (d)
represents the DCR value which means after removal of
critical column i.e., C4 at 5th story, Adjoining beam and
column are maximum fail. After providing bracing, the
progressive collapse minimize. Graph (e) and (f), in this
firstly axial force decrease as we go to above floor and after
removing critical column it goes on decreasing which results
incapable of sustaining load but we increase it by providing
bracing in outer face of structures. It is alsosame for bending
moment case.
We also analyzed for the Case C9 for 5th and 10th story at
different floor level which results are not so much
satisfactory as after providing Bracing at outer face of
structurethere is no change in progressive collapse whereas
in other case progressive collapse can be minimized but in
Joint Displacement and DCR, the result are showing same
result.
6. Limitation of the study:-
a. In this study we are considering only the Steel
Structureswhereaswehavemanytypesofstructuresare
available such as RCC composites or Precast but our
complete aim to find out the results for the steel
structures only.
b. In this study will be considering the connection
between the structures will be the rigid connectiononly.
c. We used box section for column, I-section for beam
and angle section for bracing, different section can be
used for this like built up section or cold formed section
for bracing or composite section as beam or column.
d. Study is limited to only nonlinear static analysis
more accurate analysis can be performed on this study
like nonlinear dynamic analysis.
7. Conclusion:-
Several Past Researcher used only linear static
procedures for designing againstprogressivecollapsefor
only two dimensional structures. Earlier several
researcher considered first floor single column loss only,
but in this study various cases on different floor level at
different critical column position. Various increase
parameters such as joint displacement or nodal
displacement at removed locations i.e. there is increased
in joint displacement of removed column in linear static
as well as nonlinear static analysis and after providing
bracing there is decrease in joint displacement as it
transfers the load to the interconnected beam and
column.Nodal displacement of joint changes abruptly
which indicates that beam column junction becomes
critical. The demand capacity ratio for linear static as
well as nonlinear static with and without V bracing. The
DCR increases when we remove critical column at
different story for linear static as well as nonlinear static
which means structure fails at columnandbeamposition
and after providing V bracing we minimize the failure of
progressive collapse of framed structure in linear aswell
as nonlinear analysis. There is change in axial force as in
axial force when we removed the critical column there is
drastic decrease in axial force at the critical column
whereas in other columns there is increase in axial force
and after providing bracing there is decrease in axial
force. In bending moment case there is increase in
moment in clockwise direction for all adjoining beams
near the critical column linear static as well as nonlinear
static analysis, after providing bracing there is decrease
in bending moment as it transfers the load to the
interconnected beam and column. Sudden increase in
bending moment value indicate increase in the strength
of beam to avoid the progressive collapse in the
structure. Even though it isverybasicmodel simulationit
gives in depth fundamental understanding about the
progressive collapse. All the results discussed show the
change in failure pattern and the increase various
parameters in the member just in the vicinity of the
vertical element removed. Surely, alternative path
method would be one ofthe best remediesor precautions
to overcome the progressive collapse apart from the
other methods mentioned by various researchers in the
past. Further extension of this research work caninclude
similar portal frame analysis with and without bracing
system with different analysis techniques such as
nonlinear dynamic analysis forthreedimensional frames
are also being considered with material nonlinearity as
well as providing different types and combination of
bracing.
8. Future Scope:-
Further extension of this research work can include
similar portal frame analysis with and without bracing
system with different analysis techniques such as
nonlinear dynamic analysis forthreedimensional frames
are also being considered with material nonlinearity as
well as providing different types and combination of
bracing.
Nomenclature:-
Symbols Meaning
GSA General Service Administration
APM Alternative Path Method
UFC Unified Facility Criteria
LS Linear Static
NLS Nonlinear Static
Qud Actual load on column
Qce Capacity of column
DL Dead Load

LL Live Load
DCR Demand Capacity Ratio
Glf Gravity Load Increased Factor
Θc Connection Rotation
Θy Yield Rotation
References
1. Ellingwood, B. R.; Leyendeckar, E.V.()
H.R.Tavakoli∗,A.RashidiAlashti1(2012), Evaluation
of progressive collapse potential of multi-story
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stiffness irregularities using standardandadvanced
pushover methods, Procedia Engineering 40 (
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3. KhandelwalKapil,El-TawilSherif,SadekFahim(2009)
Progressive collapse analysis of seismically
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