Response modification factor and displacement amplification factor of K-shaped eccentrically braced high-strength steel frames

Abstract

A K-shaped eccentrically braced high-strength steel frame is a novel structure. For such structures to exhibit good plastic deformation under severe earthquakes, the links are made of ordinary steel (fy≤345 MPa), whereas high-strength steel (fy≥460 MPa) is used in the frame beams and columns to reduce the cross section while ensuring the elasticity of the nonenergy consuming components. The response modification factor R is crucial to the performance-based seismic design. For an appropriate and economical seismic design, the R value and displacement amplification factor Cd should be reasonably selected. In China’s code for Seismic Design of Buildings R is uniform without considering high-strength steel, which is unreasonable. It is important to study R and Cd of K-shaped eccentrically braced high-strength steel frame. Therefore, structures with different stories (5, 10, 15, and 20 stories) and link lengths (900, 1000, 1100, and 1200 mm) were designed via the performance-based seismic design method. A static nonlinear pushover analysis and an increment dynamic analysis (IDA) were conducted. The R and Cd of each prototype were calculated using the capacity spectrum method. The effects of various factors in terms of the number of stories and link length were evaluated.