Performance-based Life-cycle Seismic Multi-objective Optimization Research Of Reinforced Concrete Bridges Based On MOPSO

Both the amount and scale of bridge projects increase rapidly with the development of economics in our country for the last decades. Engineering experiences show that seriously damaged bridges under strong earthquake attack usually cause enormous losses. The performance-based seismic design of bridges combined with life-cycle multi-objective optimization, which can consider the economic efficiency and rational of the project comprehensively. In order to improve the efficiency of seismic design and scheme selection in engineering practice, the multi-objective optimization method is incorporated with performance-based life-cycle seismic design by adopting nonlinear static analysis method(Pushover Analysis), which could provide a series of schemes that satisfy the seismic design specification under given constraints and sufficient choices.Under the support of the national key basic research development "973" project (2011CB013605-4), the national science fund project (51178079) and the excellent talents support project in Liaoning province (2014020012). The Multi-Objective Particle Swarm Optimization algorithm (MOPSO) with well convergence and reliability and a life-cycle cost model of bridge with three functions are employed to analysis the performance under different seismic fortification levels. And the main research works in this thesis are listed as follow:(1) The failure of different bridges under earthquake attack and theoretical and practical development of bridge seismic design are reviewed in literature. Advantage and rational applicability of the performance-based seismic design of bridges are also discussed intensively, and the seismic design process under two fortification levels according to the bridge seismic code is presented in detail.(2) The development of multi-objective optimization algorithm is reviewed in literature. The details and superiority of Multi-Objective Particle Swarm Optimization algorithm (MOPSO) when tackling with multi-objective optimization problems are presented extensively, and the influence of repository and special mutation operator on the algorithm is also analyzed.(3) The research progress of life-cycle design method for bridges is reviewed in literature, and comparison of different life-cycle design models are carried out. A three functions model that takes the initial cost, the expectation loss under earthquake and the cost of demolition, is employed to analysis the bridge pier under earthquake.(4) The MOPSO algorithm and seismic design process of reinforced concrete circular cross section bridge pier are coded with MATLAB. By verifying the seismic performance and the maximum displacement angle ratio at the top of the pier by Pushover under two horizontal seismic fortification levels(E1 and E2), and combined with the bridge failure probability under three seismic fortify levels in order to calculates the expectation loss under earthquake, the initial cost and the cost of demolition. Numerical results show that the MOPSO algorithm is validated in analysis the seismic performance of the bridge pier during the whole life, and Pareto optimal solutions are obtained.(5) The reliability and stability of the algorithm proposed in the research are analyzed intensively, and reasonable parameters of the algorithm are recommended. The method presented herein that transfers the traditional bridge pier seismic design into a multi-objective optimization problem within certain constraints, is applicable and a good choice in engineering design practice.