Multi-objective optimization of dual-purpose outriggers in tall buildings to reduce lateral displacement and differential axial shortening

Abstract

Maximum lateral displacement (LAT) and differential axial shortening (DAS) are important criteria to be considered in the design of tall buildings. Outrigger (OR) systems have proven to be efficient for reducing LAT and DAS in tall buildings. We developed a hybrid multi-objective optimization (MOO) method to determine the optimal locations of ORs to minimize LAT and DAS. Because minimizing LAT and DAS are conflicting objectives, multiple Pareto-front solutions are provided by the proposed method. Finite element analysis was used to evaluate the LAT and DAS of arbitrary shaped buildings. The steepest descent method was used to perform a gradient-based line search. To overcome the integrality requirements introduced by the integer design variables, piecewise quadratic interpolation was used to relax the integer variables. The scalarization of two objective functions was performed by using the weighted-sum method. Elite populations identified during scalarized optimization are stored and compared to apply the advantages of evolutional optimization to the MOO problem. It is demonstrated that the Pareto front obtained by the proposed method provides the same results as an exhaustive search.