Seismic behavior of buckling-restrained braced frames

In this study the seismic performance of buckling restrained braced frames in steel structures in Turkey are addressed. A set of three (low rise), six (mid rise) and ten (high rise) buildings is assessed and compared. Buildings were designed and modeled in three different configurations as concentrically braced, eccentrically braced with short link and eccentrically braced with long link braced frames to investigate the response of structure under lateral loading. In order to have a good estimation about the behavior of the structures, two seismic design approaches namely "nonlinear static" and "nonlinear dynamic" according to the FEMA 356 is performed. The governing criterion for evaluation of the buildings is inter-story drift and maximum residual displacement. Comparison among three types of configurations in case of seismic behavior and their response is done to evaluate the most efficient configuration in low, mid and high rise buildings. For the case study, 3 types of steel structures in 3D modeled and designed in compliance with FEMA 356 provision implementing conventional braces to obtain the proper cross section needed for the buildings and in the second phase for simplification, one end bay of the structure as a 2D frame selected and the response of frame under nonlinear static and nonlinear dynamic procedures are examined to obtain the maximum axial force demand of the braces. In the next step, the behavior of the braces has changed according to research results and assigned for brace members and nonlinear static (pushover) and nonlinear dynamic analyses perform over the braced frames. Results compared to have a good understanding of the response of the three configurations in terms of maximum displacement and inter-story drift. The important point in response of the buckling restrained braced frame is that primary elements such as beam and columns to remain elastic during a seismic activity. In order to achieve this goal braces are expected to absorb the maximum energy of the earthquake through the yielding under cyclic loading.