Initial shape of cable-stayed bridges

Abstract

A finite element computation procedure for determining the initial shape of cable-stayed bridges under the action of the dead load of girders and pretension in inclined cables is presented. The system equation of cable-stayed bridges including the nonlinearities due to large displacement, beam-column, and cable sag effects is first set up and then solved using the Newton-Raphson method in an increment-iterationwise approach. Based on a reference configuration and an assumed cable pretension force, the equilibrium configuration under dead load is found. Further, by adjusting cable forces, a ‘shape iteration’ is carried out and a new equilibrium configuration, i.e., a more reasonable initial shape, can be determined. The shape iteration is repeated until the desired tolerance is achieved. Numerical results show that a more accurate initial shape having reasonable prestress distribution and less deflection of girders can easily be determined by the proposed procedure.