Seismic behavior of chevron concentrically braced frames with weak beams

Abstract

Concentrically braced frames provide ductility and imparted seismic energy dissipation through yielding of tension braces and buckling of compression braces. In braced frames with chevron con guration, di erence of actions in tension and buckled brace results in considerable unbalanced force at brace-beam intersection, which is addressed in modern seismic design provisions. In this paper, the role of exural capacity of beam in carrying this unbalanced force and consequently, seismic behavior of braced frame were investigated by nite element analysis. Two-story and four-story chevron braced frames were modeled in ABAQUS software and studied by means of nonlinear cyclic pushover and nonlinear response history analysis methods. Results showed that inadequate exural strength of the beams reduced lateral sti ness and strength of braced frame signi cantly as lateral drift increased. Therefore, concentration of lateral deformation on one story might cause formation of soft and weak story. Furthermore, seismic behaviors of chevron braced frame and two-story X braced frames were compared.