Multi-objective optimal design of steel MRF buildings based on life-cycle cost using a swift algorithm

This paper proposed a swift multi-objective optimization algorithm for the performance-based design of steel moment-resisting frame (MRF) buildings considering life-cycle cost (LCC). Two components of the life-cycle cost, including the initial construction cost and the lifetime seismic damage cost of the building, are considered as two separate objectives of the optimization problem and are minimized simultaneously using the proposed algorithm. The proposed algorithm called Multi-objective Uniform Damage Optimization (MUDO) is an adaptive method that utilizes the concept of uniform damage (deformation) theory. MUDO leads to design alternatives for the building that are optimal (minimum) for both mentioned objectives. These alternatives, called Pareto optimal designs, allow decision-makers to choose the optimal investment option according to the project goals and by the trade-off between optimization objectives. The proposed algorithm is used to optimize three steel MRF buildings with 3, 6, and 9 stories. The lifetime seismic damage cost is calculated by assessing seismic losses at several ground motion intensities and using a probabilistic approach presented in HAZUS. A Monte Carlo analysis is used in this research to account for inherent uncertainties in structural response. The results demonstrate that MUDO can find competitive Pareto optimal designs in a much shorter time compared to a well-known metaheuristic algorithm called non-dominated sorting genetic algorithm II (NSGA-II).