Optimum design of the long‐span continuous steel truss rail beams of straddle monorails

Abstract

To understand the influences of beam height and side-to-midspan ratio on the mechanical characteristics of straddle monorail large-span continuous steel truss rail beams, the first phase of Wuhu Rail Transit Line 2, a section of continuous steel truss rail beams, is taken as the engineering background. The specific numerical values of the beam heights and side-to-midspan ratios of some large-span bridges, which have been built in China and abroad, are analyzed and counted. Combined with the unique characteristics of continuous steel truss rail beams, the two design variables of side-to-midspan ratio and beam height are scientifically valued. The two-variable direct grid search method is used, and the finite element software Midas Civil is employed to calculate and analyze the mechanical properties of the selected structural system. The main beam deflection, vertical fundamental frequency, beam end corner, and six other aspects are taken as the research focus of the optimization analysis. The above six aspects coordinate bridge strength, stiffness, and stability. They also consider comprehensively and enhance the scientificity of the results. Data indicate that when the side-to-midspan ratio and beam height are small, it is beneficial to the structural stress and deformation. However, to prevent the occurrence of the reaction force of the support, the side-to-midspan ratio should be greater than 0.2; when the beam height is constant, the ratio increases from 0.56 to 0.74, and the safety factor increases by about 14%. The side-to-midspan ratio of 0.56 and the beam height of 1.86 m are the recommended solutions. The scheme features reasonable structural stress and deformation, material saving, and low cost.