Hanger pre-tensioning force optimization of steel tied-arch bridges considering operational loads

Full design analysis of a bridge usually has lots of load cases and leads to the analysis process, which is extremely time-consuming. To reduce the computational cost, the existing hanger pre-tensioning force optimization approaches for cable-supported bridges always consider only a few critical load cases. This study presents an efficient approach for hanger pre-tensioning force optimization of steel tied-arch bridges, which can include all the operational loads and their combinations based on the code requirements. The proposed method develops a load decoupling approach (LDA) to enhance the computational efficiency of structural analysis in optimization and utilize the particle swarm optimization algorithm to search the global optimal design. The LDA divides the structural analysis procedure into two systems: (1) iteration-varying and (2) iteration-invariant. The former evaluates the structural responses induced by different hanger forces using unit load method (ULM) and the latter solely needs a single finite element (FE) analysis before iteration to calculate the structural responses caused by the other loads. The superposition principle combines the results from the two systems to identify the minimum safety margin of the bridge under the ultimate limit state. A practical bridge is examined to compare the proposed method with three traditional hanger force determination approaches. The obtained results illustrate that the proposed method not only owns high efficiency but also leads to a safer design and has a broader application range.