Optimization of relative-span ratio in rocking steel braced dual-frames

Abstract

Controlled rocking concentrically steel braced frame (CR-CSBF) is an earthquake-resisting system that is effectively capable of reducing structural damage after earthquakes and causes resilience in the structure. Post-tensioning (PT) strands and fuse members are two important elements in CR-CBSFs to provide frame self-centering and energy dissipation, respectively. This study firstly purposes to evaluate the nonlinear response history analysis with five different relative-span ratios (A/B = 1.5, 2.0, 2.5, 3.0, 3.5). Various amounts of four parameters consist of the yield strength and modulus of elasticity of the fuse, the initial force of the PT cable, and the gravity load on the rocking column are also considered as design valuable factors in the analysis. Additionally, it is considered to involve the influence of frame height with 3-, 6- and 9-story and earthquake different characteristics. The second aim of the study is to investigate about optimizing the seismic response of CR-CSBFs, in order to determine the optimal A/B for each height of structures. In addition to previous valuable research, this study has taken a more innovational approach and aims to complement them. A statistical multi-objective optimization methodology is used to distinguish the design of the spanning ratio required to minimize the peak story drift ratio (PSD), peak roof displacement (PRD), peak roof acceleration (PRA) and peak base shear (PBS), which are considered seismic response demand factors. The results demonstrate that the optimal relative-span ratio or A/B for the three-story controlled rocking concentrically steel braced dual-frame is equal to 1.5, and for the six- and nine-story frames is equal to 3.5.