Optimization study on the parameter design of double-layer steel truss bridges based on the response surface method

To optimize the design parameters of double-layer steel truss bridges, ensuring structural safety while minimizing material usage. A combination of the finite element method (FEM) and the response surface method (RSM) is employed to perform rational parameter optimization. From the analysis results and the mechanical characteristics of the structure, four key influencing factors-elastic modulus of steel, deck thickness, truss height, and side-to-midspan ratio were selected as optimization parameters. The objective functions considered included the midspan deflection of the main and side spans, maximum axial forces in the upper and lower chords and diagonal members, as well as material usage in the deck and diagonal members. The AdaDelta optimization method was then applied to optimize the design parameters, and the results were validated using the multi-objective genetic algorithm NSGA-II. After optimization, the midspan deflection of the main span decreased by 24.81%, while the side span deflection increased by 20.53% but remained lower than that of the main span. Additionally, the maximum axial force in the lower chords was reduced by 24.6%, and the maximum axial force in the diagonal members dropped by 15.34%. Furthermore, material usage in the deck and diagonal members was reduced by 2.92%.