Seismic performance of steel chevron braced frames designed according to Japanese practice

Numerical simulation of the cyclic‐loading behavior of steel chevron‐braced moment‐resisting frames

“…Weak beam mechanism: $$$$ {\beta}_0=\frac{\kappa +x\cdotp {r}_0}{2+x\cdotp {r}_0} $$$$ The above equations are consistent with Seki et al 15 . In these equations, $$$ x={N}_u/{N}_y $$$ is the compressive‐to‐tensile strength ratio of the brace.…”

“…Furthermore, $$$ \kappa $$$, $$$ 1.0\le \kappa \le 2.0 $$$, is the assumed limit for the maximum possible unbalanced vertical force over the plastic resistance of the beam, $$$ {V}_{b0}=4{M}_p/l $$$, when subject to reverse end moments $$$ {M}_p $$$. The factor $$$ \kappa $$$ addresses the beam end moments that act in combination with the unbalanced vertical force 3,4,15 . The maximum value$$$ \kappa =2.0 $$$ corresponds to the case when both end moments $$$ {M}_p $$$ act in the direction to oppose the unbalanced vertical force.…”

“…A key design issue for chevron‐braced MRFs is that $$$ \kappa $$$ should reflect the cyclic loading history experienced by the system, and therefore, the plastic mechanism by pushover monotonic loading analysis shown in Figure 1 may not necessarily represent the behavior realized by real earthquake demands. One objective of this paper is to examine whether $$$ \kappa =1.5 $$$, assumed by Seki et al., 15 would result in adequate performance.…”

“…A key focus of the project was the beams intersected by braces. Unlike the beams in chevron CBFs that are simply supported at the ends, the beams in chevron‐braced MRFs cannot be evaluated straightforwardly 3,4,15 . Their resistance against unbalanced vertical forces depends on the bending moments developed at the beam ends, which in turn is a function of the cyclic loading history experienced by the structural system.…”

“…This paper summarizes the computational component of the project whose objective was to further the understanding obtained from the experimental observations. In the following, the plastic strength of chevron‐braced MRFs is discussed in association with the weak‐beam versus strong‐beam mechanism, the experimental program by Seki et al 15 . is summarized, a numerical simulation procedure is described, then the simulation procedure is validated against experimental data.…”