Effect of the Different Shapes of Pylons on the Dynamic Analysis of Cable Stayed Bridge Using SAP200

IJSRD - International Journal for Scientific Research & Development| Vol. 3, Issue 11, 2016 | ISSN (online): 2321-0613

Effect of the Different Shapes of Pylons on the Dynamic Analysis of Cable Stayed Bridge using SAP 2000 Hussain Hararwala1 Dr. Mrs. Savita Maaru2 1 M.E. Student (CASDD) 2Professor 1,2 Department 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 all the 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 fan type for the purpose of comparison. The study reveals the following points such as the spacing of cables, the inclination 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

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 bridge The 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:

I. INTRODUCTION 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 Hshaped, 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 to study the behaviour of the bridge system having conventional pylons under vehicular and wind loading. For study 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

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 is modelling. 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, Ashaped, 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 as harp arrangement, fan arrangement, and semi-fan arrangement. In this paper, the considerations of the fan &

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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 for analysis 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 are modelled 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 3 while the entire cross sectional properties of the components will be given in Table 2.

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

1.

Cable Steel Circular 0.24 Depth- 0.4 Width2.

Deck Concrete Rectangular 13.15 Length592 1 x 0.4 3.

End Beams Steel I-Section Tf= 0.15 Tw= 0.15 0.7 x 0.25 Intermediate 4.

Steel I-Section Tf= 0.1 Beams Tw= 0.1 3 x 0.7 Tf= 0.05 5 Girders Steel I-Section Tw= 0.03 Length592 Side 6 Concrete I-Beam 3 x 12.5 Supports Table 1: Details of the cable stayed bridge Cross Momen S. Shear Torsiona Sectiona t of No Component Area l l Area Inertia . (m2) Constant (m2) (m4) 1.

Deck 3.985 58.52 0.16 0.24 1.62 x 0.040 3.2 x 102.

Cable .0452 10-4 7 4 1.79 x 1.36 x 3. End Beams .225 0.15 10-3 10-3 Intermediat 3.02 x 2.7 x 104.

0.1 0.07 e Beams 10-4 4 2.86 x 8.16 x 5.

Girders 0.157 0.09 10-3 10-5 Side 6.

22.5 8.22 16.86 17.01 Supports 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

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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)

S. No.

1.

2.

3.

4.

5.

6.

Pylon Shape

Material

Shape

Concrete

Hollow Rectangular Hollow Circular

‘Diamond’ Shape Steel

Hollow Rectangular Hollow Circular

Concrete

Hollow Rectangular Hollow Circular

‘H’ Shape Steel

Hollow Rectangular Hollow Circular

Concrete

Hollow Rectangular Hollow Circular

‘Inverted Y’ Shape Steel

Hollow Rectangular Hollow Circular

Concrete

Hollow Rectangular Hollow Circular

‘A’ Shape Steel

Hollow Rectangular Hollow Circular

Concrete

Hollow Rectangular Hollow Circular

‘Double Diamond’ Shape Steel

Hollow Rectangular Hollow Circular

Concrete

Hollow Rectangular Hollow Circular

‘Single Pylon’ Shape

Dimension (in m.)

2.5 x 3.5 – (0.6 x 0.6) đ?œ‹ đ?œ‹ (3.0)2 - (0.4)2 4

4

2.5 x 3.5 – (0.6 x 0.6) đ?œ‹ đ?œ‹ (3.0)2 - (0.4)2 4 4 2.5 x 3.5 – (0.6 x 0.6) đ?œ‹ đ?œ‹ (3.0)2 - (0.4)2 4

4

2.5 x 3.5 – (0.6 x 0.6) đ?œ‹ đ?œ‹ (3.0)2 - (0.4)2 4 4 2.5 x 3.5 – (0.6 x 0.6) đ?œ‹ đ?œ‹ (3.0)2 - (0.4)2 4

4

2.5 x 3.5 – (0.6 x 0.6) đ?œ‹ đ?œ‹ (3.0)2 - (0.4)2 4 4 2.5 x 3.5 – (0.6 x 0.6) đ?œ‹ đ?œ‹ (3.0)2 - (0.4)2 4

4

2.5 x 3.5 – (0.6 x 0.6) đ?œ‹ đ?œ‹ (3.0)2 - (0.4)2 4 4 2.5 x 3.5 – (0.6 x 0.6) đ?œ‹ đ?œ‹ (3.0)2 - (0.4)2 4

4

2.5 x 3.5 – (0.6 x 0.6) đ?œ‹ đ?œ‹ (3.0)2 - (0.4)2 4 4 2.5 x 3.5 – (0.6 x 0.6) đ?œ‹ đ?œ‹ (3.0)2 - (0.4)2 4

4

2.5 x 3.5 – (0.6 x 0.6) đ?œ‹ đ?œ‹ (3.0)2 - (0.4)2 4 4 Table 3: Details of dimensions and other parameters for different shape of Pylons Steel

Hollow Rectangular Hollow Circular

IV. CONCLUSION

REFERENCES

In this study, the modelling of cable stayed bridge has been done for six different types of pylon’s shape i.e. A-type, Htype, 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; an experimental verification has been performed on these before implementing these in practice.

[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 Structural Optimisation�, 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.

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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)

[6] R. Kao, “A comparison of N.R. Methods & Incremental Procedures for Geometrically Nonlinear Analysis”, Computer & Structures 1974; 4: 1091-1097.

[7] Uwe S., “Cable Stayed Bridge Concpet of Longer Spans”, Journal of Bridge Engineering, Aug 1996, Volume 1, 99-103.

[8] SAP2000, “Structural Analysis Programme” Integrated Finite element Analysis and design of structures, Computers and Structures Inc. Berkeley, California, 1998.

[9] Desai A. K. & Desai J. A.(2009), “Effects of pylon shapes on dynamic behaviour of cable-stayed bridges subjected to seismic loading” , Ph D Thesis, Dept of Applied Mechanics SVNIT-Surat ,78-103.

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