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I JSRD - I nternational Journal for Scientifi c Research & Development| Vol. 3, I ssue 11, 2016 | ISSN (onli ne): 2321-0613

All rights reserved by www.ijsrd.com 411

Effect of the Different Shapes of Pylons on the Dynamic Analysis of Cable

Stayed Bridge using SAP 2000Hussain Hararwala1 Dr. Mrs. Savita Maaru2

1M.E. Student (CASDD) 2Professor1,2Department of Civil Engineering

1,2

Govt. Engineering College, Ujjain - 456001, India Abstract — This paper deals with the modelling of Cable

Stayed Bridges with different shapes of pylons. The cable

stayed bridge is one of the modern bridges which were built

for the longer spans. There is a need of study on the effect of

shape of pylon on the dynamic response of cable stayed

bridge, for this, the bridge span dimension and other

parameters are kept constant, and only the pylon shape is

varied i.e. A type, H type, inverted Y type, Single pylon,

Diamond or Pyramid shapes & Double Diamond or Spread

Pylon shapes. The height of the pylon is kept constant for allthe shapes for comparison purpose. The modelling of bridge

is prepared on SAP 2000 software. For this, the arrangement

of cable stay has been taken as semi fan type as well as fantype for the purpose of comparison. The study reveals the

following points such as the spacing of cables, theinclination of pylon legs & spacing of intermediate supports

which needs to be considered for the modelling of bridge.

Key words: Cable Stayed Bridge, Pylons, Semi Fan & Fan

Type, SAP 2000

I. I NTRODUCTION

Many cable stayed bridges have been successfully built

around over the world in only last two decades of the 20th

century. Due to their highly appreciable appearance &significantly utilized structural materials, cable stayed

bridges have been taken as one of the most popular type of bridges in last decades. With increasing span length, the

modern cable stayed bridges are more acceptable & flexible

strong enough to the effect wind as compare to ever. A

typical cable stayed bridge consists of deck with one or two pylons erected above the piers in the middle of the span. The

cables are attached diagonally to the girder to provide

additional supports.

In recent years, several cable-stayed bridges have

been constructed with different shapes of pylons such as H-

shaped, A-shaped, Diamond shaped, Inverted Y-shaped etc.

which results in a great demand to evaluate the effects of

different shapes of pylon on cable stayed bridges under the

consideration of wind effect. Therefore, there is a need tostudy the behaviour of the bridge system having

conventional pylons under vehicular and wind loading. Forstudy of such phenomenon the two steps have been

generally computed:

1) Computational analysis of bridges using finite

element programmes

2) By performing wind tunnel test on the prototype of

such bridges.The purpose of the pylons is to support the cable

system and transfer forces to the foundations. They are

loaded with high compressions and bending moments that

depend on the stay cable layout and the deck-pylon support

conditions. Pylons can be made of steel or concrete, being

the latter generally more economic considering similar

stiffness conditions. Thus, the dynamic response of the

pylons will be conditioned by several aspects, and in

addition to the previous idea, the geometric shape of the

pylons, which depends on the applied loads, cable-stay

system and aesthetic conditions, is a very important aspect.

Fig. 1: Different tower /Pylons available for cable stayed

bridgeThe dynamic effects under the effect of wind were

studied by the software SAP 2000. SAP is finite element

based program and is recognized by international

community for the research purpose. The modelling of cable

stayed bridge in SAP is prepared as per following

procedure:

II. MODELING PROCEDURE ON SAP

Draw the geometry of the bridge either by inserting

coordinates or by linking the nodes through member

length.

Define the sections and materials for the members. Define the loading values and load combinations to be

applied on the structures.

Define the time history to be used for the dynamic

analysis and include it in the analysis case.

Now assign the defined section to the members.

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, base reactions,

deck force, forces in cables and pylons, mode shapes etc.

III. MODELING OF BRIDGE

In the analysis of the bridge the most important part ismodelling. Different components of bridges like deck,

pylon, cables etc must be modelled as per the actual forces

they are subjected. The dimension of bridge which was

taken in consideration here was situated at river Ravi in

Jammu Kashmir, India. The various shapes of pylon have

been considered in this paper are Diamond shaped, A-shaped, H-shaped, Inverted Y-shaped, single pylon shaped

& Double Diamond or Pyramid-Shaped. There are different

types of cable-stayed bridges which are distinguished on the

basis of the arrangement of stay cables; they are called asharp arrangement, fan arrangement, and semi-fan

arrangement. In this paper, the considerations of the fan &



Effect of the Different Shapes of Pylons on the Dynamic Analysis of Cable Stayed Bridge using SAP 2000

(IJSRD/Vol. 3/Issue 11/2016/099)


semi fan arrangement of cables have been taken, & the

analyses will be computed for concrete pylons as well as for

steel pylons. The pylons which have been modelled foranalysis purpose having their section rectangular as well as

circular.

Different elements of cable supported bridge like

deck, pylon, and cable-stays are discussed below:

Bridge deck: Deck is model as a frame section

with cross sectional properties as mentioned in the

following tables for different types of bridges.

Pylon: Pylon and pylon beam is modelled as a

frame section where the pylon with the vertical

orientation and pylon beam with horizontal

orientation.

Cables: Cables of the cable stayed bridge aremodelled as cable element. The cable elements act

as axial load transfer element only.

The details are given in Table 1 will be remains

constant for all the shapes of pylon. The details of different

shapes and dimensions of pylons will be given in Table 3while the entire cross sectional properties of the components

will be given in Table 2.

S.

No.Component Material Shape

Dimension

(in m.)

1. Cable Steel Circular 0.24

2. Deck Concrete Rectangular

Depth- 0.4

Width-

13.15

Length-592

3. End Beams Steel I-Section

1 x 0.4

Tf = 0.15

Tw= 0.15

4.Intermediate

BeamsSteel I-Section

0.7 x 0.25Tf = 0.1

Tw= 0.1

5 Girders Steel I-Section

3 x 0.7

Tf = 0.05

Tw= 0.03

Length-

592

6Side

SupportsConcrete I-Beam 3 x 12.5

Table 1: Details of the cable stayed bridge

S.

No. Component

Cross

Sectiona

l Area(m2)

Momen

t of

Inertia(m4)

Shear

Area(m2)

Torsiona

lConstant

1. Deck 3.985 58.52 0.16 0.24

2. Cable .04521.62 x

10-4

0.040

7

3.2 x 10-

4

3. End Beams .2251.79 x

10-30.15

1.36 x

10-3

4.Intermediat

e Beams0.1

3.02 x

10-40.07

2.7 x 10-

4

5. Girders 0.1572.86 x10-3

0.098.16 x10-5

6.Side

Supports22.5 8.22 16.86 17.01

Table 2: Details of cross sectional properties of various

components

Fig. 2: Different 3D models of Cable Stayed Bridge with

different types of Pylons

Fig. 3: Typical Bridge Span Configuration

Fig. 4: Main Span Typical Section

Fig. 5: Pylon Geometry






S. No. Pylon Shape Material Shape Dimension (in m.)

1. ‘Diamond’ Shape

Concrete

Steel

Hollow Rectangular

Hollow Circular

Hollow Rectangular

Hollow Circular

2.5 x 3.5 – (0.6 x 0.6)

(3.0)2 -

(0.4)2

2.5 x 3.5 – (0.6 x 0.6)

(3.0)2 -

(0.4)2

2. ‘H’ Shape

Concrete

Steel

Hollow Rectangular

Hollow Circular

Hollow Rectangular

Hollow Circular

2.5 x 3.5 – (0.6 x 0.6)(3.0)2 -

(0.4)2

2.5 x 3.5 – (0.6 x 0.6)

(3.0)2 -

(0.4)2

3. ‘Inverted Y’ Shape

Concrete

Steel

Hollow Rectangular

Hollow Circular

Hollow Rectangular

Hollow Circular

2.5 x 3.5 – (0.6 x 0.6)

(3.0)2 -

(0.4)2

2.5 x 3.5 – (0.6 x 0.6)

(3.0)2 -

(0.4)2

4. ‘A’ Shape

Concrete

Steel

Hollow Rectangular

Hollow Circular

Hollow Rectangular

Hollow Circular

2.5 x 3.5 – (0.6 x 0.6)

(3.0)2 -

(0.4)2

2.5 x 3.5 – (0.6 x 0.6)

(3.0)2 -

(0.4)2

5. ‘Double Diamond’ Shape

Concrete

Steel

Hollow Rectangular

Hollow Circular

Hollow Rectangular

Hollow Circular

2.5 x 3.5 – (0.6 x 0.6)

(3.0)2 -

(0.4)2

2.5 x 3.5 – (0.6 x 0.6)

(3.0)2 -

(0.4)2

6. ‘Single Pylon’ Shape

Concrete

Steel

Hollow Rectangular

Hollow Circular

Hollow RectangularHollow Circular

2.5 x 3.5 – (0.6 x 0.6)

(3.0)2 -

(0.4)2

2.5 x 3.5 – (0.6 x 0.6)

(3.0)2 -

(0.4)2

Table 3: Details of dimensions and other parameters for different shape of Pylons

IV. CONCLUSION

In this study, the modelling of cable stayed bridge has been

done for six different types of pylon’s shape i.e. A-type, H-type, Diamond type, Inverted Y-type, Double diamond type

and single pylon type on SAP 2000 software. The models of

bridge which have been prepared were having side supports

as well as end supports at both the ends of side span. The

following points which were used to carry out for the

modelling are as follows:

1)

The angles which have been made by inclined

pylons with deck shall be lies between “600 - 750”.

2) The minimum spacing between cables which was

jointed at pylon shall not be less than H/100 in

meters where H= height of pylon from the ground

level.

3) The intermediate supports which were used as side

span supports shall have the minimum spacing of

20 meters between them.

These conclusions are based on the models which

were prepared using SAP software therefore; anexperimental verification has been performed on these

before implementing these in practice.

R EFERENCES

[1] N D Shah & Dr. J A Desai 2010, “Nonlinear Aerostatic

Analysis of Self Anchored & Bi-stayed Cable Stayed

Bridges using sap 2000”, ISSN: 0975-6744 Volume 1,

Issue 1.

[2] Siddharth G. Shah, Desai.J.A & Solanki.C.H 2010,

“Effect of Pylon Shape on seismic response of Cable

stayed bridge with soil structure interaction”, ISSN:

0976-4399 Volume 1, Issue 3.[3] Olfat Sarhang Zadeh 2012, “Comparison between

three types of Cable Stayed Bridges using StructuralOptimisation”, M.E. thesis, School of Graduate and

Postdoctoral Studies, The University of Western

Ontario London, Ontario, Canada.

[4] Atul K. Desai 2013, “Siesmic Time History Analysis

for Cable Stayed Bridges considering different

geometrical configuration for near field earthquakes”,Volume 7.

[5] A.M.S. Freire, J.H.O. Negrap & A.V. Lopes 2006,

“Geometrical Nonlinearities on the static analysis of

highly flexible steel Cable Stayed Bridges”, ISSN:

2128-2140.






[6] R. Kao, “A comparison of N.R. Methods &

Incremental Procedures for Geometrically Nonlinear

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Spans”, Journal of Bridge Engineering, Aug 1996,

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[8] SAP2000, “Structural Analysis Programme” Integrated

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Computers and Structures Inc. Berkeley, California,1998.

[9] Desai A. K. & Desai J. A.(2009), “Effects of pylon

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