Optimization of extradosed concrete bridges subjected to seismic action

Abstract

An optimization algorithm is proposed to assist in the design of extradosed concrete bridges under static and seismic loading. This procedure is composed of structural analysis, sensitivity analysis and optimization modules. The finite element method is used for the three-dimensional analysis considering static loading (dead load and road traffic live load), geometrical nonlinearities, time-dependent effects and seismic action by using a modal response spectrum analysis. The design is formulated as a multi-objective optimization problem with objectives of minimum cost, deflections and stresses including service and strength criteria. The solution of the minimax problem is obtained by minimizing a convex scalar function obtained through an entropy-based approach. The design variables are the extradosed cables and tendons forces, the extradosed cables and tendons cross-sectional areas, the deck, towers and piers sizes. The analytical discrete direct method is used to find the structural response to changes in the design variables. A convex optimization strategy with multiple starting points finds minimum cost solutions with an adequate stiffness and mass distribution that satisfy the design criteria under both, static loading and seismic action. Numerical examples concerning the optimization of a real-sized extradosed concrete bridge illustrate the features and capabilities of the proposed method.