Optimizing steel arch bridge components using multi-objective harmony search

Abstract

Steel arch bridges have excellent aesthetics and load-resisting performance, but they have complex structural behavior characteristics depending on their structural shape. Therefore, much effort is needed to determine an efficient section by considering safety and economy due to changes in the cross-section or steel grade of members. In this study, a method for determining the cross-section and steel grade of members of steel arch bridges was proposed by applying a multi-objective harmony search algorithm, considering economy, safety, and workability. In the Harmony search algorithm, steel grades and cost coefficients considering various yield strength levels were considered to evaluate the economy, and structural analysis was included for safety evaluation. In addition, Pareto optimality and crowding distance concepts were applied to determine the cross-section specifications and steel grade for multi-objective functions. Optimization to determine the cross-sectional dimensions and steel grades of the steel arch bridge was conducted separately for cases with two and three objective functions. Variations in cost coefficients for hanger members and steel grades were analyzed to examine differences in the results. The analysis revealed that cross-sections can be determined based on cost scenarios, and box-type cross-sections were evaluated to be more advantageous for hanger members in terms of the considered objective function. From the optimization process proposed in this study, the optimized cross-sectional dimensions and steel grades for the steel arch bridge could be considered to provide effective solutions that meet the design criteria while addressing the trade-offs between economy, safety, and workability. © 2025 Institution of Structural Engineers