Seismic Performance Of Buckling-Restrained Braced Frame With Masonry Walls And Design Method Concerning Energy Dissipation Ratio

Compared to frame system, frame-brace system is a dual lateral-force-resisting structure system. In such system, the lateral stiffness of the structure is increased, and the displacement under earthquakes is reduced. The buckling-restrained brace (BRB) does not buckle when compressed, enabling it to avoid the weak story problem caused by the fact that conventional braces tend to buckle when compressed, and to dissipate seismic energy.The masonry walls in frame can affect or change structural seismic performance, making the actual seismic performance different from design. Meanwhile, the damage of real structures shows masonry walls’ destruction can cause significant loss to life and property.Based on the two facts above, researches done in this paper are as follows:(1) The existing design methods of BRB and the impact of masonry walls on the structure are summarized. Current researches of BRB and masonry wall are reviewed.(2) FEM models are built to reveal the influence of masonry walls and the arrangement of BRBs. Four arrangements of BRB are applied. Autoclaved aerated concrete is chosen to be the material of masonry walls. Three-strut model is applied to simulate masonry walls. Based on time-history analysis, the difference of fundamental period, inter-story displacement angle and column internal force are summarized and analyzed.(3) Based on energy balance principle, a design method of BRB concerning energy dissipation ratio is presented. The section area and yield displacement of BRBs are design parameters. First, the maximum inter-story displacement angle and energy dissipation ratio are acquired; then, the relationship surfaces of section area-yield displacement-maximum inter-story displacement angle/energy dissipation ratio are gained; last, according to target angle, the final result is given concerning energy dissipation ratio.(4) The idea that BRB can work as the first defending line is proposed. BRBs are designed so that they yield before walls fail. Structure based on this idea remains well protected under earthquakes. When earthquake intensity is one degree higher, the masonry walls are damaged, but inter-story displacement angles can still meet the code requirement.