In-plane optimization of truss arch footbridges using stability and serviceability objective functions

This paper investigates the use of stability and serviceability objective functions in the shape optimization of truss arch footbridges prone to in-plane snap-through buckling. The objective functions evaluated relate to global linear buckling, geometrically nonlinear response, fundamental frequency, linear compliance, and maximum deflection. These objective functions are applied to help define the global structural shape for the 2D configuration of a truss arch footbridge subjected to its governing code-defined load combination. The strength criterion of maximum axial force, the global stability responses of critical linear buckling load and nonlinear limit load, and the serviceability responses of fundamental frequency and unfactored live load deflection are used to evaluate the optimized topologies. These structural performance results are compared to those of a benchmark structure prone to in-plane snap-through buckling. The results highlight that improvement in stability and serviceability behavior can be obtained by altering the global structural form according to the presented objective functions. Stable optimized topologies, which are not prone to in-plane snapthough buckling, are achieved without the use of computationally expensive, geometrically nonlinear analysis functions.