Damage evaluation of composite-special moment frames with concrete-filled tube columns under strong seismic loads

Abstract

Concrete Filled steel Tube (CFT) columns have been widely used in moment resisting frame structures located on non-seismic zones or high seismic zones. This paper discusses the design of such composite members based on the advanced methods which are introduced in the 2005 America Institute of Steel Construction (AISC) Specification and the 2005 AISC Seismic Provisions. These design specifications explicitly allow the use of the full plastic capacities of CFT columns, and so they require column members with more slender steel walls than ones allowed in previous specification. In addition, this study focuses particularly on damage evaluation following nonlinear frame analyses. The paper begins with an examination of design interaction curves including the length effect and the full plastic strength demand in CFT beam-column members. Based on advanced computational simulations of a series of 3-, 9-, and 20-story SAC composite-special moment frames, this paper then investigates new techniques to evaluate the damage of CFT columns during a strong earthquake. The paper concludes with some discussion of (a) step by step procedures to compute the interactive ratios of the individual CFT beam-columns and (b) member vs. seismic performance evaluation.