Parametric Study On Cable-Stayed Suspension Hybrid Bridge: Shreekunj Vasantbhai Patel
Parametric Study On Cable-Stayed Suspension Hybrid Bridge: Shreekunj Vasantbhai Patel
Parametric Study On Cable-Stayed Suspension Hybrid Bridge: Shreekunj Vasantbhai Patel
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A Thesis Submitted To
Indus University in Partial Fulfilment of the
Requirements For the Degree of
Master of Technology
In
Structural Engineering
May 2019
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This is certify that research work embodied in this thesis entitled “Parametric Study On
Cable Stayed Suspension Hybrid Bridges” was carried out by Mr. shreekunj patel
(IU17512100019) at INDUS UNIVERSITY for partial fulfilment of Master of
Technology in Structural Engineering to be awarded by Indus University. This
research work has been carried out under my guidance and supervision and it is up to
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Date:
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Mr. Tejas N. Rathi Dr. Tejendra G. Tank Dr. Anupam Kumar Singh
(Guide) HOD - Civil Engineering, Director,
Assistant Professor, IITE, IITE,
Civil Engineering Department, Indus University, Indus University,
IITE, Ahmedabad. Ahmedabad,
Indus University,
Ahmedabad.
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_______________________ _______________________
SHREEKUNJ PATEL Mr. TEJAS N. RATHI
(IU175121009) Assistant Professor,
Civil Engineering Department,
IITE, Indus University,
Ahmedabad.
ABSTRACT
The requirement of long span bridge has increased with development of infrastructure
facility in every nation. Long span bridge could be achieved with use of high strength
materials and innovative techniques for analysis of bridge. Generally, cable supported
bridges comprising both viz. suspension and cable-stayed bridge, has addressed the
need. The combination of the above mentioned systems, i.e. Cable stayed suspension
hybrid bridge is a recent advancement in the bridge engineering which provides the
flexibility of increasing span length for bridge decks.
The present study is concentrated towards the behavioral analysis of hybrid bridges
under dead loads and moving loads for serviceability criteria. Different cable systems
viz. Fan shaped and Semi Harp shape are used for representing cable stayed systems
with the combination of different shapes of pylon. Influence of span length on the
choice of cable system and pylon shape has also been observed.
Results of analysis reflects that for the span length up to 1200 m a combination of
inverted Y-shaped pylon and Fan system of cable stayed bridges have yielded better
performance under dead loads and moving loads, whereas for the span of 1400 m A
shaped Pylon with modified fan system is effective.
6
Acknowledgement
I take this golden opportunity to express my sincere thanks to all who have helped me
in completion of thesis.
I like to show my greatest appreciation to my guide Mr. Tejas Rathi. I cannot say thank
you enough for his great support and help. I feel inspired and encouraged every time I
attend his meeting. Without his guidance this thesis would not have materialized.
I am thankful to Prof. Tejendra Tank, Head of Civil Engineering Department for his
motivation and constant monitoring. Also thankful of all the faculty members of civil
engineering department of Indus University, Ahmedabad.
I would like to thank for the guidance Mr. Suketu Unagar, Former Student, Indus
University, for his guidance, suggestions and constructive criticism.
_______________
Shreekunj patel
(IU1751210009)
Structural Engineering
INDUS UNIVERSITY
CONTENTS
8
List of figures
Figure 1:NORMANDIE BRIDGE, FRANCE...............................................................7
Figure 2: hybrid cable-stayed suspension bridge.............................................................8
Figure 3 :3rd Bosphorus Bridge, Turkey.........................................................................9
Figure 4:CABLE STAY BRIDGE AND SUSPENSION BRIDGE..............................11
Figure 5:.Components of bridge....................................................................................12
Figure 6: Typical H-type pylon......................................................................................13
Figure 7: Y-type pylon...................................................................................................13
Figure 8: Inverted V-type pylon.....................................................................................13
Figure 9: Delta type towers............................................................................................13
Figure 10:Composite deck.............................................................................................14
Figure 11:Typical cross section of parallel wire standsLocked coil strand...................15
Figure 12:Typical cross section of locked coil strands Helically-wound strand...........15
Figure 13:Fan type arrangement....................................................................................16
Figure 14:Albert Bridge, London fan type arrangement................................................16
Figure 15:Typical Harp type arrangement.....................................................................17
Figure 16:Abdoun Bridge, Amman, Jordan...................................................................17
Figure 17:: Typical arrangement of Semi Harp type arrangement................................17
Figure 18:The Okutama Cable-stayed Bridge,Tokoyo,Japan........................................17
Figure 19:Typical arrangement of star type...................................................................18
Figure 20:Ormiston Road Bridge by Moller Architects in New Zealand:.....................18
Figure 21:: cable stayed suspension hybrid bridge........................................................31
Figure 22:3rd bosphorus bridge.....................................................................................34
Figure 23:: A shape pylon..............................................................................................34
Figure 24:: steel deck section.........................................................................................35
Figure 25:User interface of SAP2000 v 20....................................................................35
Figure 26:3-D finite element model of A -shaped pylon C.S.S.H bridge.....................36
Figure 27:. A-shape pylon,.............................................................................................36
CHAPTER 1: INTRODUCTION
10
1. Introduction
1.1. History
Bridges are one of the oldest types of structures ever to be built in the world. The
idea of the bridge was invented when man wanted to reach points which were
inaccessible due to the presence of a physical obstacle like bay, river etc.
In recent decades the use and construction of cable supported bridge is more
popular due to their aesthetic appearance and economical construction for long span
bridges compare to conventional bridge system. Cable stayed bridges have good
stability, optimum use of structural materials, aesthetic, relatively low design and
maintenance costs, and efficient structural characteristics. Therefore, this type of
bridges are becoming more and more popular and are usually preferred for long span
crossings compared to suspension bridges. A cable-stayed bridge consists of one or
more towers with cables supporting the bridge deck. In terms of cable arrangements,
the most common types of cable stayed bridges are fan, harp, and semi fan bridges.
Because of their large size and nonlinear structural behavior, the analysis of these
types of bridges is more complicated than conventional bridges. In these bridges, the
cables are the main source of nonlinearity. An optimum design of a cable-stayed
bridge with minimum cost while achieving strength and serviceability requirements is
a challenging task.
12
Figure 1: Arc Bridge Figure 2: Beam Bridge Figure 3: Truss Bridge
These two bridges support the load of the roadway in very different ways. The
difference lies in how the cables are connected to the towers. In suspension bridges,
the cables ride freely across the towers, transmitting the load to the anchorages at
either end. In cable-stayed bridges, the cables are attached to the towers, which alone
bear the deck load.
14
length for bridge construction with more economical way, And for that we are talking
here a new hybrid cable support system, which have advantages over both old cable
support systems. The general geometry for cable stayed suspension hybrid bridge is as
follow:
Buckling stability improves because the axial force in the girder decreases
because of the reduced number of stayed cables (in cases of externally
anchored suspension cable).
It leads to a longer span because of the above mentioned reason (in cases of
externally anchored suspension cable).
Its advantages are in cable erection and vibration problems because of short
stayed cables length.
The height of pylons can be short for the reduced number of stayed cables.
16
1.6.1.1. Tower Design
Usually the towers of cable supported bridges uses two vertical shafts and two
planes of cables, for an example H shape. But a few cable supported bridges have also
been designed with an A or an inverted Y form of towers.
The pylons can be arranged to support one axial layer of cable stays or two lateral
layer of cable stays. The following figures shows arrangement of pylons for single and
double layer of cable stays.
Figure 13: Transverse Arrangement of Pylons for Single Plane Cable System
Figure 14: Transverse Arrangement of Pylon for Two Layer of Cable System
18
Saddle System Crossing of Stay Cables
Box girders may be rectangular or trapezoidal in form, i.e. with web plates vertical or
sloping. The trapezoidal section is often used in order to keep the bottom flange area
to the desired size, whilst the support to the deck plate from the webs is provided at
an optimum position. Although fabrication costs of the inclined web plates are
higher, an overall saving can often be achieved. Both plate girder and box section
main girders are used for cable-stayed bridges, but it is felt that box sections have a
further advantage due to their better torsional stiffness. Unsymmetrical live loading
and wind forces can produce high torsional moments and box sections are inherently
better suited to carry this type of loading and therefore reduce torsional rotations in
the deck.
Truss Girder
During the last decade trusses have rarely been used
in the construction of cable-Supported bridges.
Compared to solid web girders, trusses present an
unfavorable visual appearance; they require a great
deal of fabrication and maintenance, and protection
against corrosion is difficult. Thus, except in special
circumstances, a solid web girder is more
satisfactory both from an economical and an
Figure 17: Truss Girder
aesthetic viewpoint. However, trusses may be used
instead of girders for aerodynamical reasons. Also, in the case of combined highway
and railroad traffic, when usually double deck structures are used, trusses should be
provided as the main carrying members of such bridges.
20
Reinforced or prestressed concrete girders
During the last decade a number of
cable-stayed bridges have been
built with a reinforced or
prestressed concrete deck and main
girders. These bridges are
economical, possess high stiffness
and exhibit relatively small
deflections. The damping effect of
these monolithic structures is very Figure 18: Prestressed Concrete Box Girder
high and vibrations are relatively small. Such outstanding structures as, for instance,
the Maracaibo Bridge in Venezuela, indicate that this new bridge system possesses
many excellent characteristics.
1.6.4. Cable System
Cables are one of the main parts of a cable-stayed bridge. They transfer the dead
weight of the deck to the pylons. These cables are usually post-tensioned based on the
weight of the deck. The cables post-tensioned forces are selected in a way to
minimize both the vertical deflection of the deck and lateral deflection of the pylons.
These cables are made of high tensile steel wire, and having the diameter ranging
from 3 to 7mm. General characteristic of steel used in cable is as follow:
Yield Strength: 1180 MPA
Tensile Strength: 1570 MPA
Strain at breaking: 4%
Modulus of elasticity: 205 GPA
Chemical Composition: 0.8% C, 0.2% Si, 0.6% Mn, 0.05% Cu, 0.05% Ni,
0.05% Cr, 0.03% P, 0.02% S.
This steel has a much higher yield stress and tensile strength than normal steel used
in construction (approx. five times and four times higher values respectively), but
they have much lower ductility, due to its high carbon content. This steel cannot be
welded.
Various types of cable cross section available in industry are as follow:
Name Shape of Section Structure
Spiral Rope Wires are stranded in several
layers mainly in opposite lay
directions
The wires laid straight and
parallel throughout the complete
cable length
Six strands made of several
wires are closed around a core
strand
Deformed wires are used for the
outside layers of Spiral Rope
and the final layers are made up
of interlocking Z-shapes wires
Figure 19: Cable Cross Section
Fan Arrangement
In this pattern, all the stay cables are attached to a single point at top of each
pylon as shown in Fig. 1.11a. The relatively steep slope of the stay cables results in
smaller cable cross section in comparison to the harp type. Moreover, the horizontal
cable forces in the deck in this arrangement is less than the harp type. However, by
increasing the number of the stay cables, the weights of the anchorages increase and
attaching the stay cables to anchorage becomes difficult. Therefore, the fan patterns
are suitable only for moderate spans with a limited number of stay cables.
22
Harp Type
In a harp arrangement, the cables are made nearly parallel by attaching them to
different points on the pylon as shown is in Fig. 1.11b. From economical point of
view, this type cable stayed bridges is not efficient for long span bridges. This is
because such an arrangement requires more steel for the cables, gives more
compression in the deck, and produces bending moments in the pylon. However, in
terms of aesthetics it is attractive in comparison to other types of cable stayed
bridges. The parallel cables give a most pleasant appearance to the harp arrangement.
The need for taller pylons is one of the disadvantages of this type of cable stayed
bridges.
Semi Harp Type
Several modern cable supported bridges have been built around the world using
mixed arrangement due to its efficiency. As shown in Fig. 1.11c, in this system, the
cables are distributed over the upper part of the pylon, which are more steeply
inclined close to the pylon. The world largest cable-stayed bridge (Sutong Bridge in
Jiangsu, China) was designed as a mixed arrangement using A-shape pylons. The
mixed arrangement has better appearance in comparison to the fan arrangement.
Star Type
The star system may be preferred due to its unique aesthetic appearance. However, it
contradicts the principle that the points of attachment of the cables should be
distributed as much as possible along the main girder.
Harp Arrangement
Fan Type
Semi Harp
Star Type
Figure 20: Cable Arrangement in Longitudinal Direction
24
and bending moment into the deck structure. Also, the substructure, especially
the piers for the towers, has to be longer, because in this case the towers stand
apart and outside the cross-section of the bridge.
Where the cables and towers lie within the cross-section of the bridge, the
area taken up cannot be utilized as part of the roadway and may be only partly
used for the sidewalk. Thus, an area of the deck surface is made non-effective
and has to be compensated for by increasing the overall width of the deck.
26
2. To check the influence on cable forces with variation in cable system and pylon
shape.
28
2.1. Static and dynamic analysis of cable stayed suspension hybrid bridge and
validation
Author: Dr A.K. Desai, Dr S.V.Vasanwala, Prof. G. M. Savaliya
Journal: International Journal of Advanced Research in Engineering and
Technology
Abstract:
The requirement of long span bridge is increase with development of
infrastructure facility in every nation. Long span bridge could be achieved with
use of high strength materials and innovative techniques for analysis of bridge.
Generally, cable supported bridges comprise both suspension and cable-stayed
bridge. Cable supported bridges are very flexible in behaviour These flexible
systems are susceptible to the dynamic effects of wind and earthquake loads.
The cable-stayed bridge could provide more rigidity due to presence of tensed
cable stays as a force resistance element. The suspension bridge could assigned
more span in the field of bridge. So, combination of above two structural
system the innovative form of cable-stayed suspension hybrid bridge could be
the better option to provide more span. Here, attempt is made to analyse long
span cable-stayed suspension hybrid bridge. The literature survey on the topic
of analysis of cable-stayed suspension hybrid bridge is presented in the current
paper. Modeling of cable-stayed suspension hybrid bridge in SAP2000
software and its validation is carried out. The nonlinear static analysis are carry
out. The time period of bridge for different mode shape is presented to compare
the result of research paper with Sap 2000 software.
Conclusions:
As compared to cable-stayed bridges with the same span length, the cable-
stayed portion is also greatly shortened. These results, the reduced height of
tower, length of stays and the axial forces in the deck. stems.
It is found from the review carried out related to development and analytical
techniques that there is wide scope for the seismic analysis of hybrid cable-
stayed suspension bridge.
2.2. Effect of Pylon Shape on seismic response of Cable stayed bridge with soil
structure interaction
Author: Siddharth shah, J.A. Desai, Solanki
Journal : International journal of civil and structural engineering
Abstract:
Cable stayed bridge are the most flexible bridge and getting popularity because
of its economy for longer spans and aesthetics. Here focus is given on the effect
of shape of pylon on the seismic response of cable stayed bridge, for this, the
bridge span dimension and other parameters are kept constant, and only the
pylon shape is varied viz. A type, H type, portal frame, spread pylon and
pyramid shapes. The height of the pylon is kept constant for all the shapes for
comparison purpose. The 3D bridge model is prepared on SAP 2000 software
and bridge is analyzed seismically by Bhuj 2001, Earthquake India. The bridge
response in terms of pylon displacement, acceleration and base moment is
obtained. The study reveals that the shape of the pylon has great influence in
the seismic response of cable stayed bridge. spread pylon shape are better for
resisting earthquake in longitudinal direction but weak in lateral direction, but
pyramid shape pylon is better because of its geometry in resisting earthquake
30
force from any direction and also SSI effects are minimum in this case. SSI
effects are predominant for soft soil conditions for all pylon shapes.
Conclusions:
In this study, the cable stayed bridge Quincy bay view bridge, is analyzed for
four different shapes of pylons on SAP 2000 software by time history method.
The analysis was carried out for three different soil conditions namely, soft,
medium and hard soil to study the Soil structure interaction effects and against
the fixed base of structure-i.e. without SSI case. The response in terms of
displacement max acceleration, and moment was plotted.
Abstract:
This paper presents the construction of the 3rd Bosphorus Bridge to be built in
Istanbul, Turkey. The 3rd Bosphorus Bridge has a unique construction that is
regarded as the bridge of the firsts. It is going to be the widest suspension
bridge in the world with a width of 60 meters and the longest spanning one that
has 8 lanes of motorway and 2 lanes of railway on it, with a main span of 1408
meters. Another first of the bridge is that it is the suspension bridge with the
highest bridge pylons of the world, with a height of 322 meters. A hybrid
system that consists of two different construction techniques which are cable-
stayed and suspension bridge is used for the 3rd Bosphorus Bridge
The construction of the bridge includes three main parts. Side spans including
anchorage and approach block, main span and pylons. Anchorage and approach
blocks are built up by conventional methods. Pylons triangular in cross section
and with 1.50 m wall thickness, are raised up by slip forming up to elevation
+208.00 and then continue with climbing form up to elevation +322.00. A
special formwork was produced by Bygging International, the Swiss company,
and used in the construction of pylons.
Conclusions:
The 3rd bridge has some significant skills that can be seen at first glance. It will
be the widest suspension bridge in the world when it is completed. Another
skill of the bridge is that it is the suspension bridge with the highest bridge
pylons of the world, with a height of 322 meters. A hybrid system that consists
of two different construction techniques is an advantage for the bridge. Large
scale suspension and cable stayed bridge has many complex details Even
though more studies Needs to be done more for these types of construction,
they still find a wide application.
Abstract
32
Conclusions:
Abstract:
Because a large longitudinal force exists in hybrid girder cable-stayed bridges
due to the cable tension, its transfer mechanisms on the steel-concrete
combination segment would be an important issue.
Conclusions:
The load distributing mode could be used to instruct preliminary engineering
designs, and the finite-element modeling method could be used to verify it.
Abstract:
A parametric analysis of the nonlinear static behavior of self-anchored long-
span bridges is here carried out by using a 3D nonlinear finite element model of
the bridge. Both cable-stayed bridges with a fan-shaped arrangement of stays
and combined cable-stayed-suspension bridges are considered in the numerical
investigations.
The importance of an accurate description of geometrically nonlinear effects,
arising from the cables nonlinear behavior in coupling with the instability effect
of axial compression in girder and pylons, is pointed out by means of
comparisons with results obtained by using different cable models.
The strong role of nonlinear cables response, in coupling with the notable
influence of the relative girder stiffness on the stability bridge behavior is
analyzed.
For the self-anchored combined cable-stayed-suspension bridges the influence
of the dead load distribution factor on the limit load evaluation is also
accounted.
Conclusions:
In the case of the self-anchored combined cable-stayed-suspension bridges the
influence of the coupling stayed-suspension parameter r on the maximum load
for the bridge is analyzed.
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Results evidence the conservative prediction of the limit load in the case of
suspension bridge (r=1) with respect to the cable-stayed system (r=0).
Abstract:
The paper presents finite element approach for the geometric nonlinear
aerostatic analysis of self anchored cable-stayed bridges with different pylon
configurations along with vehicular interaction. In the recent years cable stayed
bridges have received more attention than any other bridge mainly due to Cable
stayed bridge are the most flexible bridge and getting popularity because of its
economy for longer spans and aesthetics. The results showed that these factors
have significant influence on the aerostatic behavior and should be considered
in the aerostatic analysis of long span cable stayed bridges. Analysis results will
be useful for the designers to consider the shape of pylon at the initial stage of
design. Again the results indicate the significant influence of pylon shapes on
aerostatic behavior of such long span. A cable stayed bridge consists of one or
more towers with cables supporting the bridge deck. In terms of cable
arrangements, the most common type of cable stayed bridges are fan, harp, and
semi fan bridges. Because of their large size and nonlinear structural behavior,
the analysis of these types of bridges is more complicated than conventional
bridges An optimum design of a cable-stayed bridge with minimum cost while
achieving strength and serviceability requirements is a challenging task
Conclusions:
The finite element method is discussed to find out the efficient pylon
configuration from comparison of analysis results during aerostatic analysis of
cable stayed bridges. The following conclusions are deduced from the
parametric results:
Nonlinearity effect is predominant in long span bridges and gives
approximately 20 to 60% higher results than linear analysis.
The displacement due to wind is reduced by approximately 20 to 35% when
live load due to IRC loads is considered.
The concept of anchoring of top cable to the earth proved effective in reducing
the forces in cable
The results show that both in self-anchored and bi-stayed bridges, the forces
and moments are found minimum in A frame pylon configuration due to tripod
action.
The costs of cables are very high in case of cable-stayed bridges which can be
reduced using the concept of partially earth anchored bridges.
36
CHAPTER 3: METHODOLOGY
3.1. Sap2000 software:
3.2 Material and Sectional properties Details
3.3 Methods of analysis
3.4. Modeling of Hybrid Bridge with SAP2000
3.5. Structural modeling analysis
38
No. weight ratio of ultimate tensile
(kN/m³) elasticity strength (MPa)
(GPa)
1 Pylon RCC 25 0.25 35 35
2 Deck RCC 25 0.25 35 35
slab
3 Girder steel 77 0.3 200 450
4 Cable steel 77 0.3 210 1600
40
3.3. Methods of analysis:
In order to analyse a cable-stayed bridge an appropriate idealization or
modeling of the structure must be made. The restraints, if any, present at each
joint in the structure should be determined in order to mathematically model the
structure. The stiffness or flexibility of each member must be known or be
determined by the analysis. Connections between the cables, girders, and
towers are idealized at their points of intersection.
For a single-plane system the structure may be idealized as a two-dimensional
plane frame, and torsional forces acting on the girder would have to be
superimposed on the girder. A two-plane system may be idealized as a three-
dimensional space frame with torsional forces included in the analysis
Several methods have been employed in the analysis of cable-stayed bridges. A
mixed method of analysis, where the unknowns in the matrix formulation
include displacements and forces, has been developed by Stafford Smith. A
transfer matrix method has been developed in West Germany. Troitsky and
Lazar have used the flexibility approach while Podolny and Fleming used a
stiffness approach. Several general computer programs, such as ANSYS,
STRUDEL, SAP2000, etc. are available which use either the stiffness or
flexibility approach. A stiffness approach incorporating an iterative procedure
was used by Podolny and Fleming to compensate for the nonlinearity of the
cables and Tang applied the transfer matrix to the nonlinearity of cable-stayed
bridges.
Where K is the stiffness matrix, r is the vector of applied loads, and u is the
vector of resulting displacements. In long span cable-stayed bridges, dead load
is often dominant feature; the pre-strain on the stay cable controls the internal
force distribution in the deck and tower as well as the bridge alignment. The
initial deformed equilibrium configuration of the bridge is important since it is
the starting position to perform the succeeding modal and time history analysis.
It is realized by manipulating the initial tension force in each stay cable. For the
final analysis the most common approach is to model either a half or the entire
structure as a space frame. The pylon, deck and the stays will usually be
represented within the space frame model by bar elements.
The stays can be represented with a small inertia and a modified modulus of
elasticity that will mimic the sag behavior of the stay. Achieving the deformed
equilibrium configuration due to dead load is indeed one of the most difficult
tasks involving multiple trial and errors.
42
3.4. Modeling of Hybrid Bridge in SAP2000
3.4.1. Modeling Procedure on SAP
Draw the geometry of the frame either by inserting coordinates or by linking
the nodes through member length.
Draw the required fixed support or spring according to the case.
Select the stiffness of the spring for hangers Which is taken as 200kN/m
Define the sections and materials for the members.
Now assign the defined section to the members
Define the loading values and load combinations to be applied on the structures
Define the moving load case to be used for the static analysis and include it in
the analysis case.
Define the moving load case to be used for the static analysis and include it in
the analysis case.
Assign the loads to the joints or members as per the case
After assigning everything, set the analysis to be carried out and press run
analysis SAP program will Generate the various results like joint
Displacements joint forces, joint reactions.
44
3.2.4. Pylon or Towers:
Our tower has a height of 330 meters which is approximately 1/5 of the length
of the main span. As the tower has a considerable height this will allow us to
reduce the required amount of cable steel and the compression forces in the
bridge beaup to a cable inclination of 45º.
Our tower in 3D model will have an “A” shape since we are dealing with long
spans, proportioning us high torsional frequencies and permitting the two
planes of cables be arranged in a symmetrical pattern
3.2.5. cable systems
The cable arrangement we will make use of a semi-harp system in the
longitudinal direction and a two-plane system arranged in a symmetrical
pattern. For very long spans where the tower is very high and needs high lateral
stiffness it’s better to use the two lateral plane system.
Therefore, in the transversal direction, taking into account the problems that the
other systems cause selecting the semi-harp system seems to be the best
solution.
Thus, the disposition of the cables is given by the angle that these conform to
the tower and the deck. The angles between the cables and the deck goes from
22,71º until 75,38 º and the total length of the cables varies between 1431 m for
the shorter cable and 586 m for the larger one.
46
3.2.6. Models of the studied cable-stayed bridge and data
The following figures contain model views of the studied bridge created
usingSAP2000-V19 structural analysis software:
Figure 33:3-D finite element model of Inverted Y-shaped pylon hybrid bridge with different cable systems
Figure 34:Material properties
48
Figure 36:deck properties
50
Figure 42:Class 70R Vehicle data in SAP2000
52
CHAPTER 4 : RESULTS OF ANALYSIS
4.1Results of static dead load analysis
Dead loads of all the components of the bridge like cables, girder, deck, pylon,
etc. are considered as dead load of the bridge. In the design of cable-stayed
bridges, the dead load often contributes to most of the bridge load. Dead loads
are indeed the most important for the preliminary analysis in cable-stayed
bridges. In this analysis, the type of analysis considered is Non-linear static
Moving loads on bridge deck cause the superstructure comprising beams and slabs to
deflect from its equilibrium position relatively quickly. The mass and inherent
54
elasticity of the structure tends to restore the bridge deck to its equilibrium position
thus causing a series of vibrations due to the motion of vehicles on the bridge deck.
The normal practice generally followed in several national codes to safeguard the
bridge deck from the destructive effects of dynamic loads is to provide for impact
factors for live loads which amplify the design static loads by a certain percentage.
Consequently, the bridge is rendered more rigid so that the dynamic effects are safely
resisted with increased mass and elasticity of the structure.
In a present study, number of lanes are 2. For these lanes, 2 live load cases are
described in cl. 204.3, Table no. 6-A, IRC 6: 2016. They are: - Case 1: CLASS 70-R
(W), Case 2: CLASS A – 2 lane
The type of vehicle considered for dynamic analysis is IRC class A wheeled vehicle at
a speed of 27.77 km/hour.
5. CONCLUSIONS
The pylon shapes and height in cable supported bridges are important parameters to
consider for analysis of cable supported bridges.
In the present study, two types of pylon shapes namely A-shape and Inverted Y-shape,
with two different cable system, Fan type and modified fan system have been
considered for analysis under different loads viz; dead load, moving vehicular load.
The following results were obtained after the analysis in SAP2000 software:
For 1400 m
For A-shape pylon,
Target force required in Fan System is lower by 0.42% than Semi-Harp
System.
Displacement in Fan System is lower by 10.85% than M-Fan System
Pylon Reaction in Fan System is lower by 21.77% than M-Fan System
For 1200 m
Target force required in Fan System is lower by 0.42% than Semi-Harp
System.
Displacement in Fan System is lower by 597.5% than M-Fan System
56
Pylon Reaction in Fan System is lower by 1459% than M-Fan System
For 1000 m
For A-shape pylon,
Target force required in Fan System is lower by 0.42% than Semi-Harp
System.
Displacement in Fan System is lower by 102.94% than M-Fan System
Pylon Reaction in Fan System is lower by 176.31% than M-Fan System