Genetic Algorithms-Based Optimization of Cable Stayed Bridges

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carried out using genetic algorithms. The following con-

clusions are drawn from the present work:

GA can handle more number of variables easily. The

developed GA program is more general to accommo-

date discrete and continuous variables

Effect of bridge material study reveals that for 60 m

bridge length decrease in relative cost for steel bridge

is around 25%. As bridge length increases from 60 m

to 500 m there is increase in the reduction in steel

bridge cost up to 45% as compared to concrete bridge

cost.

Due to inclusion of cable grouping concept in the

current optimization approach, reduction in the rela-

tive cost is observed. As bridge length increases from

60 m to 500 m the reduction in relative optimum cost

varies between 5% to 13%. It is expected more when

the bridge length increases beyond 500 m and in

situations where cable numbers are more.

By incorporating the geometric nonlinearity in the

analysis of cable stayed bridge in optimization ap-

proach up to 200 m bridge length there is hardly any

difference in optimum relative cost. An increase in

optimum relative cost was observed for bridge length

ranging from 250 m to 500 m up to 13%.

It is observed, by restricting the tower height, that the

optimum tower height-to-main span ratio is shifted

from 0.2 to 0.4 as bridge length increased from 60 m

to 500 m.

The effect of optimum side-to-main span ratio on op-

timum relative cost study revealed that the optimum

side-to-main span ratio is changing from 0.55 to 0.35

as bridge length increases from 60 m to 500 m. The

side-to-main span ratio is shifted towards 0.35 fol-

lowing s-curve pattern.

When the cable layout is restricted to radial type only,

up to 300 m bridge length the difference in optimum

relative cost is neglig ible. Beyond 300 m length , it has

been observed that radial-type cable layout can result

in reduction of the optimum cost by 5% - 12% from

the bridge with harp type cable layout.

The data base prepared for various practical bridge leng-

ths will be beneficial for designers to estimate the cost of

cable stayed bridges.

REFERENCES

[1] M. S.Troitsky, “Cable-Stayed Bridges: Theory and De-

sign,” Crosby Lockwood Staples, London, 1972.

[2] M. Y. H. Bangash, “Prototype Bridge Structures: Analysis

and Design,” Thomas Telford Publisher, London, 1999.

[3] W. Podolny and J. B. Scalzi, “Construction and Design of

Cable Stayed Bridges,” John Wiley and Sons, New York,

1986.

[4] P. Krishna, A. S. Arya and T. P. Agrawal, “Effect of Ca-

ble Stiffness on Cable-Stayed Bridges,” Journal of Struc-

tural Engineering, Vol. 111, No. 9, 1985, pp. 2008-2020.

[5] H. I. A. Hegab, “Parametric Investigation of Cable Stayed

Bridges,” Journal of Structural Engineering, Vol. 114, No.

8, 1988, pp. 1917-1928.

doi:10.1061/(ASCE)0733-9445(1988)114:8(1917)

[6] D. Shi and Y. M. Xu, “Optimum Design of Cable Stayed

Bridges with Multi Variables. Computing in Civil and

Building Engineering,” Pahi & Werner Edition, Rotter-

dam, 1995.

[7] P. K. Singh and P. K. Mallick, “Optimum Cost Solution

for Cable-Stayed bridges,” Journal of the Indian National

Group of the International Association for Bridge and

Structural Engineeri ng, Vol. 32, No. 1, 2002, pp. 51-72.

[8] C. S. Krishnamoorthy, P. P. Venkatesh and R. Sudarshan,

“Object-Oriented Framework for Genetic Algorithms with

Application to Space Truss Optimization,” Journal of Soft

Computing in Civil Engineering, Vol. 16, No. 1, 2002, pp.

66-75. doi:10.1061/(ASCE)0887-3801(2002)16:1(66)

[9] A. Upadhyay and V. Kalyanaraman, “Optimum Design of

Fibre Composite Stiffened Panels Using Genetic Algo-

rithms,” Engineering Optimization, Vol. 33, 2000, pp.

201-220.

[10] V. Srinivas and K. Ramanjaneyulu, “An Integrated Ap-

proach for Optimum Design of Bridge Decks Using Ge-

netic Algorithms and Artificial Neural Networks,” Ad-

vances in Engineering Software, Vol. 38, No. 7, 2007, pp.

475-487. doi:10.1016/j.advengsoft.2006.09.016

[11] L. M. C. Simoes and J. H. O. Negrao, “Sizing and Ge-

ometry Optimization of Cable-Stayed Bridges,” Compu-

ters and Structures, Vol. 52, No. 2, 1994, pp. 309-321.

doi:10.1016/0045-7949(94)90283-6

[12] J. H. O. Negrao and L. M. C. Simoes, “Optimization of

Cable Stayed Bridges with Three Dimensional Model-

ing,” Computers and Structures, Vol. 64, No. 1-4, 1997,

pp. 741-758. doi:10.1016/S0045-7949(96)00166-6