Initial shape analysis of cable-stayed bridges during construction by the cantilever method

Abstract

Initial shape analysis of cable-stayed bridges during construction by cantilever method is under investigation in this study. The main objective is to improve the calculation procedure, given in recent studies, for finding the initial shape of such bridges. A finite element computational algorithm is formulated for the analysis of the bridges at each construction stage using substructuring technique. Forward process analysis in accordance with the actual construction sequence is performed and geometric nonlinearity due to the cable sag is taken into account. Successive over-relaxation (SOR) technique is employed to accelerate the convergence rate of the shape iteration in finding the initial shape of the bridges. Four different types of cable-stayed bridges are examined as case studies. The results from these case studies show that the convergence rate of the shape iteration, for finding the initial shape of the bridges during construction, can be improved by using the SOR technique. However, the optimum value of the over-relaxation factor cannot exactly be determined since it varies from problem to problem and is often determined empirically. Nevertheless, appropriate over-relaxation factor found in the case studies ranges between 1.1 and 1.9. For the bridges with a small number of cables, the value of the over-relaxation factor from 1.1 to 1.4 may be used. A large value of the over-relaxation factor tends to be suitable for the bridges with a large number of cables and significant improvement of the convergence of the shape iteration can be achieved especially for nonlinear analysis