摘要

This paper presents a five-step algorithm to determine the reasonable state of suspension bridges with spatial cables without theoretical derivation or original programming. The algorithm is extended from the common FEM analysis method with additional algebraic operation and flow control. The five-step algorithm is an efficient and convenient method for the general bridge designers in normal engineering practice and can be summarized as follows. In the first four steps, a main cable-only model is used considering the couple of the spatial main cable and inclined hangers. First, a set of ideal vertical components of the hanger forces is obtained by the rigid-supported continuous beam method. Second, the shape of the main cable in the midspan is calculated iteratively based on the designated sag. Third, the reasonable state of the main cable in the side span is determined by the force equilibrium of the IP point. Fourth, the anchor span is solved by the equilibrium of the splay saddle. Finally, a full-bridge model is activated and specially handled to complete the analysis. Next, a 1,588-m midspan suspension bridge with spatial cables is introduced as a case study. Several details and strategies are also presented. It is proved that the algorithm can avoid the theoretical derivation and simplify the programming on the premise of the necessary numerical precision.