IRJET- Study on Cable Stayed Bridge using Csibridge Software

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 05 | May 2019 www.irjet.net p-ISSN: 2395-0072
© 2019, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 694
Study on Cable Stayed Bridge using CSiBridge Software
Dr. Laju Kottalil1, M Merin Sabu2, Maria S Mathew2, Megha Pavanan2, Swaleeh Ali Ramzan V K2
1Prof, Department of Civil Engineering, Mar Athanasius College of Engineering, Kothamangalam, Kerala, India
2Student, Department of Civil Engineering, Mar Athanasius College of Engineering, Kothamangalam, Kerala, India
---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - Cable-stayed bridges have emerged as the
dominant structural system for long span bridge crossings
during the past thirty years. This success is due to a
combination of technical advancements and pleasing
aesthetics attributes. The interaction of the variousstructural
components results in an efficient structure which is
continuously evolving and providing new methods to increase
span lengths. The objective of this project is to conduct a
parametric study on the behaviour of bridges under loading
conditions. The results were compared and evaluated interms
of allowable displacement and bending moment. Out of
various softwares, CSi bridge software is used due to its
advanced modeling features and highly sophisticated design.
Key Words: Cable Stayed Bridge, CSi Bridge Software,
Parametric Study, Analysis, Modelling
1. INTRODUCTION
Bridges may be classified by how the actions of tension,
compression, bending, torsion and shear are distributed
through their structure. Cable stayed bridges are one of a
kind. Structural analysis can evaluate whether a specific
structural design will be able to withstand external and
internal stresses and forces expected for the design.
1.1 Cable stayed bridge
Cable stayed bridges are one of the most used bridge
typologies for spans between 200 m to about 1100m due to
their structural efficiency, cost and aesthetics. The major
factors that contributed to the development of cable stayed
bridges were the introduction of high strength steels,
orthotropic type decks, development of welding techniques
and progress in structural analysis.
Cable stayed bridge consists of a deck supported by a set of
stay cables connecting it to one or more towers; this
geometry combined with high strength materials used in its
construction results in very slender and flexible structures
that are very sensitive to traffic, wind and seismic loads .It is
a structural system with a continuous girder supported by
inclined stay cables from the towers. From the mechanical
point of view, the cable-stayed bridge is a continuous girder
bridge supported by elastic supports .The main cable is
eliminated and the cables are connected directly from the
deck to the tower. This way, all steel cables are in tension
and are used to their full efficiency. Due to the direct
connection of cables to the pylon, all forces acting on the
members are axial. The steel cable is stretched straight
between the pylon and the deck which means it is subjected
to axial tension, and the pylon has half ofthetotal loadacting
on either side of it which means the resulting force is direct
compression. The structural components of a cable-stayed
system behave in the followingmanner:Thestiffeninggirder
transmits the load to the tower throughthecables,whichare
always in tension. The stiffening girder is subjected to
bending and axial loading. The tower transmits the load to
the foundation under mainly axial action.
The cable-stayed bridge has spanning capacity longer than
that of cantilever bridges, truss bridges, arch bridges, and
box girder bridges, but shorter than that of suspension
bridges. In this range, the cable-stayed bridge is very
economical and has elegant appearance due to therelatively
small girder depth and has proved to be very competitive
against other bridge types. The bending moment in cable
stayed bridge is very less, due to the direct forces. This
reduces the amount of steel and concrete requiredbya large
scale, making the bridge more efficient and more economic
than the suspension bridge by reducing the cost of
maintenance. With the reduced bendingmoments,thewidth
of deck can also be reduced. It has much greater stiffness
than the suspension bridge, so that deformationsofthedeck
under live loads are reduced. They can be constructed by
cantilevering out from the tower – the cables act both as
temporary and permanent supports tothe bridgedeck.Fora
symmetrical bridge (i.e. spans on eithersideofthetower are
the same), the horizontal forces balance and large ground
anchorages are not required.
1.2 CSiBridge Software
The design and analysis of thistypeof bridgeisdoneusing
the software CSi bridge. Over the past thirty-five years,
Computer and Structures, Inc, has introduced new and
innovative ways to model complex structures.CSiBridge, the
latest innovation, is the ultimate integrated tool for
modeling, analysis, and design of bridge structures.Theease
with which all of these tasks can be accomplished makes
CSiBridge the most versatile and productive bridge design
package in the industry. CSi Bridge is specialized analysis
and design software tailored for the engineering of bridge
systems. Suspension, cable-stay, elevated-roadway, and
other types of bridge systems can be modelled and designed
to suit many purposes. Automated seismic design, one of
CSiBridge’s many features, incorporates the recently
adopted AASHTO Guide Specification for LRFD Seismic

Bridge Design 2nd Edition, 2011.CSiBridgeallowsengineers
to define specific seismic design parameters that are then
applied to the bridge model during an automated cycle of
analysis through design.
2. MODELLING OF THE BRIDGE
CSiBridge is a specialized analysis and design software
tailored for the engineering of bridge systems. Suspension,
cable-stay, elevated-roadway, and other types of bridge
systems may be modeled and designed to suit any one of a
variety of purposes, including means for crossing water,
linking points between shear terrain, or extending over
highway infrastructure. Customized controls and features
integrate across a powerful object-based modeling
environment to offer an intuitive, practical, and productive
computational tool for bridge engineering. Advanced
modeling features and sophisticated analysis techniques
account for dynamic effects, inelastic behavior, and
geometric nonlinearity. It implements a parametric object-
based modeling approachwhendevelopinganalytical bridge
systems. This enables designers to assign bridge
composition as an assembly of objects; ie, roadway
superstructure, substructure, abutments, piers, foundation
system, etc. CSiBridge is the premier software for bridge
engineering.
The major steps involved in the modelling process include:
Create the Layout Line(s):Layout lines are reference lines
used for defining the horizontal andvertical alignmentofthe
bridge and the vehicle lanes. Layout lines are defined using
stations for distance, bearings for horizontal alignment, and
grades for vertical alignment. Layout lines may be straight,
bent or curved, both horizontally and vertically.
Define lanes on the bridge: Lanes must be defined before a
bridge model can be analyzed for vehicle live loads. Lanes
are used in the definition of bridge live type load patterns
that are used in static and dynamic multi-step load cases.
Lanes can be defined with reference to layout lines or
existing frame objects. Typically, when using the bridge
modeler, lanes should be defined from layout lines.
Define Superstructure components:These component
definitions include deck section,diaphragmsandparametric
variations. The deck section definition includes the section
property, material property, the slab and girder thicknesses
etc. Various precast girders are available which can be
modeled to our requirement and rigid links have been used
to join the disconnected beams together. The software also
allows us to prestress the beams to the required
compression. Parametric variations define variations in the
deck section along the length of the bridge. Almost all
parameters used in the parametric definition of a deck
section can be specified to vary. The variations may be
linear, parabolic or circular. After a variation has been
defined, it can be assigned as part of the deck section
assignment to bridge objects. In this study we have
considered only linear variations.
Design of pylons: Function of Pylon or tower is to support
the cable system and transfer the forces to foundation.
Therefore, it is subjected to high axial forces and bending
moments and also depend upon support conditions. The
material of construction and cross section can be varied
depending upon soil condition,designloadetc.Herewehave
considered steel pylons of pipe section. There are also
different boundary conditions prevailing for the connection
and this study involves fixed condition.
Define vehicle loads :In CSiBridge, vehicles must be defined
to analyze a bridge model for vehicle loads. Those vehicle
loads are applied to the structure through lanes. In addition,
vehicles classes must be defined to analyze a bridge model
for vehicle live loads using a moving load load
case. Numerous standard vehicle types are built into the
program. In addition, the General Vehicle feature allows
creation of customized vehicle definitions. Each vehicle
definition consists of one or more concentrated or uniform
loads.
Define load patterns: A load pattern is a specified spatial
distribution of forces, displacements, temperatures, and
other effects that act upon the bridge. A load pattern by
itself does not cause any response in the bridge. Load
patterns must be applied in load cases in order to produce
results. One special type of load pattern available in
CSiBridge is the Bridge Live Load pattern.Inthattypeofload
pattern, one or more vehicles that move across the bridge
can be specified. For each vehicle, the following can be
specified: a time that the vehicle starts loading the bridge,
the initial vehicle location, and the directionoftravel andthe
speed of the vehicle. When used in a multi-step static or
multi-step dynamic (direct integration time history) load
case, this type of load pattern is useful in evaluating special
vehicle loads.
Define load cases for analysis: A load case defines how loads
are to be applied to the structure (e.g., statically or
dynamically), how the structure responds (e.g., linearly or
nonlinearly), and how the analysis is to be performed (e.g.,
modally or by direct-integration). Any load case type can be
used when analyzing a bridge model. There are several
analysis options that are specialized for analysis of vehicle
live loads. Moving load load cases compute influence lines
for various quantities and solve all permutations of lane
loading to obtain the maximum and minimum response
quantities. Multi-step static and multi-step dynamic (direct
integration time history) load cases can be used to analyze
one or more vehicles moving across the bridge at a specified
speed. These multi-step load cases are defined using special
bridge live load patterns that define the direction, starting
time and speed of vehicles moving along lanes.

Figure -1: A 3-D Representation of the modelled cable
stayed bridge
3. PARAMETRIC STUDY
Basic design data:
Span of the bridge : 200m
Deck material : Concrete of M50 grade
Pylon Material : Steel of grade Fe350
Depth of deck : 1.8m
Width of deck : 8.4m
To find out best possible dimension of the bridge various
parameters were varied and the response quantities like
bending moment, shear force, torsion and axial force were
analysed. The study was carried out for cables,deck slaband
pylons which form major structural component for both
linear case and dynamic cases.
The parameters considered in the study include cable
diameter, number of cables, distance between the pylon,
number of pylons, pylon height and wall thickness of the
pylon
3.1 Variation In Number of Cables
Table -1: Model design data
Parameters Model 1 Model 2
Span 200m 200m
Deck width 8.4m 8.4m
Number of cables 7 x 2 9 x 2
Cable diameter 0.06m 0.06m
Distance between
pylons
8.4m 8.4m
Figure -2: Moment about horizontal axis of model 1
Figure -4: Vertical displacement of model 1

Table -2: Result comparison
Number of
cables
Maximum
moment
about
horizontal
axis
Maximum
vertical
displacement
Model 1 7 X 2 74325.53
kNm
2.5951m
Model 2 9 X 2 73611.28
kNm
2.3315 m
3.2 Variation in cable diameter
Parameters Model 1 Model2
Span 200m 200m
Distance between
pylons
8.4m 8.4m
Cable
diameter
Maximum
moment
about
horizontal
axis
Maximum
vertical
displacement
Model
1
0.04 m 74325.53
kNm
2.5951 m
Model
2
0.06 m 66893.53
kNm
1.7267 m
3.3 Variation in distance between the pylons
Parameters Model 1 Model 2
Sspan 200m 200m
Distancebetween
pylons
8.4m 12m

Figure-13: Vertical displacement of model 2
Distance
between
pylons
Maximum
moment
about
horizontal
axis
Maximum
vertical
displacement
Model 1 8.4m 73611.28
kNm
1.726 m
Model 2 12 m 64513.76
kNm
1.461 m
3.4 Variation in pylon wall thickness
Figure -14:Moment about horizontal axis of model 1
Parameters Model1 Model 2 Model 3
Total span
Centre span
End spans
200m
100m
50m
200m
100m
50m
200m
100m
50m
Deck width 8.4m 8.4m 8.4m
Number of
cables
9 x 2 9 x 2 9 x 2
Cable
diameter
0.04m 0.04m 0.04m
Distance
between
pylons
8.4m 8.4m 8.4m
Pylon wall
thickness
0.3m 0.2m 0.1m

Pylon wall
thickness
Maximum
moment about
horizontal axis
Maximum
vertical
displacement
Model 1 0.3m 23856.264kNm 0.4233 m
Model 2 0.2m 23977.873 kNm 0.4264 m
Model 3 0.1m 24225.28 kNm 0.4318 m
Bending moment and displacement value was found to be
decreasing with reduction in number of cables. Momentand
vertical displacement found tobedecreasingasthediameter
of cables decreased. Values for maximum moment and
displacement had a considerable amount of reductionasthe
distance betweentwopylons increased.Momentandvertical
displacement found to be decreasing as the pylon wall
thickness increased.
4. CONCLUSIONS
Considering the first parametric study wherein the number
of cables have been changed, it is seen that the maximum
moment and displacement has decreased while increasing
the number of cables.
In the second parametric study, the cable diameters have
been changed. Moment and displacement was found to be
decreasing as the cable diameters increases.
Thus, it has been concluded that prestressing the deck and
pretensioning the cables will reduce the moment and
displacement values. Prestressing of deck was done and
considerable reduction in maximum moment and
displacement values were found.
In the third parametric study, the distance between the
pylons has been changed. The values of maximum moment
and displacement has a considerable amountofreduction as
the distance between pylons increased.
The next study was conducted by considering two pylons
instead of a single pylon and three cases were considered by
changing the wall thickness. It has been obtained that the
maximum moment and displacement has reduced with
increase in the wall thickness.
REFERENCES
[1] Gurajapu Naga Raju, J Sudha Mani. Analysis And
Design Of Cable Stayed Bridge. International
Journal For Technological Research In Engineering
Volume 5, Issue 4, ISSN: 2347 – 4718,2017
[2] Elizabeth Davalos. Structural Behaviour of Cable-
stayed Bridges Submitted to the Department of
Civil and Environmental Engineering on May 5,
2000 in partial fulfillment of the requirements for
the degree of Master of Engineering in Civil and
Environmental Engineering.
[3] Lin W & Yoda T, Text Book on Cable-StayedBridges.
Bridge Engineering, 175–194, 2017
[4] Krishna Raju N, ‘Design Of Bridges’, Oxford & IBH
publishing co. pvt. Ltd., ISBN 81-204-0344-4
[5] Umang A. Koyani, Kaushik C. Koradia, ‘Parametric
Study Of Cable Stayed Bridge’ Journal of Emerging
Technologies and Innovative Research (JETIR) ,
ISSN-2349-5162
[6] T. P. Agrawal, ‘Cable Stayed Bridges-Parametric
Study’, Journal Of bridge Engineering, ASCE, ISSN
1084-0702/97/0002-0061

IRJET- Study on Cable Stayed Bridge using Csibridge Software

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