Concepts to minimize earthquake-induced column axial shortening in steel moment-resisting frames

Capacity-designed steel moment-resisting frames (MRFs) dissipate the seismic action through inelastic flexural yielding of protected zones located at the beam ends and the first story column bottom end. During low-probability of occurrence seismic events, flexural yielding is typically followed by local and/or member buckling that could potentially lead to steel MRF global collapse. Experiments of steel columns under cyclic loading underscore the influence of residual axial shortening on the overall column stability. Particularly, residual column axial shortening may cause slab tilting. In turn, the ability for post-earthquake structural repairs in columns may also be significantly compromised. This paper explores an alternative concept aiming to protect the steel MRF column integrity and at the same time minimize axial shortening during an earthquake event. Unlike the traditional seismic design practice, column base connections are designed to dissipate the seismic demands by tuning a stable inelastic dissipation mechanism. The concept is explored by means of nonlinear response history analyses of a case-study steel MRF frame building. Limitations and suggestions for future work are also discussed.