INITIAL SHAPE OF CABLE-STAYED BRIDGES

A finite element computation procedure for determining the initial sha pe of cable-stayed bridges under the action of dead load of girders an d pretension in inclined cables is presented. The system equation of c able-stayed bridges including the nonlinearities due to large displace ment, beam column, and cable sag effects is first set up and then solv ed using the Newton Raphson method on increment-iterationwise. Based o n a reference configuration and an assumed cable pretension force, the equilibrium configuration under dead load is found. Further, by adjus ting cable forces, a 'shape iteration' is carried out and a new equili brium configuration, i.e., a more reasonable initial shape, can be det ermined. The shape iteration is repeated until the desired tolerance i s achieved. Numerical results show that a more accurate initial shape having reasonable prestress distribution and less deflection of girder s can easily be determined by the proposed procedure.