A numerical study on special truss moment frames with Vierendeel openings

A two-phase numerical study was undertaken to address some design issues related to special truss moment frames (STMFs). In the first phase, the design approaches for distribution of shear strength among stories were examined. Multistory STMFs sized, based on elastic and plastic analysis, were evaluated from a performance point of view. A set of time history analyses was conducted to investigate performance parameters such as the interstory drift ratio and the plastic rotation at chord member ends. The results of the analysis reveal that the maximum interstory drifts are not significantly influenced by the design philosophy adopted while considerable differences are observed for plastic rotations. In the second phase, the expected shear strength at Vierendeel openings was studied using three dimensional finite element modeling. The results from finite element analysis reveal that the expected shear strength formulation presented in the AISC Seismic Provisions for Structural Steel Buildings is overly conservative. Based on the analysis results, an expected shear strength formula was developed and is presented herein.

Research highlights
► Designs based on different load distributions are compared.
► The AISC Equation for shear strength is overly conservative.
► A new equation for shear strength is developed.
► Practical recommendations are given.