LOAD DISTRIBUTION IN CONCRETE DECKS OF CABLE-STAYED BRIDGES

Abstract

The use of cable-stayed bridges with concrete girders stayed by steel cables, has been gaining popularity in India in recent years, Inclined eablea which enamate from one or more points on the supporting towers are used to hold large span stiffening girders of the bridge deck at intermediate locations between the main supports, Important characteristics of such a three-dimensional system include full participation of transverse system in the structural behaviour of the main structure in longitudinal direction, as well as integral action of the stiffening girders and the stay cables. The analysis of such bridges, being highly indeter-minate is too complicated, Many simplified assumptions have been made to analyse such bridges by various research workers, Such approximate analyses do not fully represent the actual 3-Dimensional behaviour of the structure One such two lane bridge with 130 m span is proposed to be constructed over new supply channel at Hardwar and is presently being designed in Civil Engineering Department, Incorporating the structural details of this bridge a para- metric study to investigate the influence of cable stiff- ness on bridge charact-e-ri-stiss is dome -,which "re-veals that the effect of cable stiff Yresue` on :va-rious stress resultants is onTly pronounce near actual cabl-e areas; At -iv- very large cable stiffnesses the contribution of the axial deformations of the deck and the tower becomes significant and stress resultants are not much effected, When the cable stiffnesses are reduced considerably the behaviour of the structure approaches to that of a bridge deck supported only on piers and abutments, Further a space frame analysis of the structure using stiffness approach has been carried out, which gives the design forces in the stiffening girders, transverse system, stay cables and towers. For the same structure a plane frame analysis has also been done and the design forces obtained, The comparison of these design forces in various elements of the bridge has been presented which shows that the space frame analysis is not only more _rational approach but also gives design forces smaller compared to 2-D analysis,