NONLINEAR ANALYSIS OF CABLE STRUCTURES

Abstract

Cable structures provide structurally efficient, aesthetical and economical solution for medium to large span structures. The cable structures consist of cable elements and in addition can have beam column elements also. The deformational characteristics of cable structures are affected by various sources of nonlinearities. In this dissertation only geometrical nonlinearity has been considered. Three main sources of geometrical nonlinearities namely the cable sag, the axial force-bending moment interaction (beam column effect) and the large deflection effect have been chosen for the present study. Stiffness approach has been used to analyse a cable structure. For this purpose a program has been developed. Two examples, one of cable truss and second one of cable stayed bridge (Second Hooghly bridge) have been selected. From the linear as well as nonlinear analysis of cable truss and cable stayed bridge one may conclude the following: (1) For a cable truss, the main source of nonlinearity is large deflection effect. The effect of nonlinearity on the vertical deformation of cable truss is 2% to 7% in comparison to linear analysis results. (2) For a cable stayed bridge the main sources of nonlinearity are cable sag as well as the beam column effect. They increase the vertical deformation of the girder in central span by 2% to 3% and the horizontal displacement of tower top node by 1% to 6% . (3) The nonlinearity due to large deflection effect predominates as the cable rigidity or girder rigidity decreases.