Seismic Performance of Weak-Base Strong Column Steel Moment Frames

Abstract eng:
Steel moment frames in seismically active regions are designed as strong-base weak-column systems, such that yielding is concentrated in the lower region of the column member, thereby protecting the base connection itself. This is achieved through capacity design of the base connection. This necessitates an expensive base connection, since heavy detailing is required to develop the forces associated with column yielding. However, recent research by the authors and others has shown that column base connections may be highly ductile with excellent dissipative characteristics. The research explores the possibility of a weak-base system that leverages these characteristics. The study is conducted in a Performance Based Earthquake Engineering (PBEE) framework, by examining the effect of base strength on various performance metrics – including probabilities of collapse, and of exceeding critical member forces and interstory drifts. The results indicate promise for these types of systems, but also highlight issues, which arise due to reduce base stiffness that accompanies the weaker base. Limitations of the study are discussed along with directions for future work.

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