Analytical model validation and influence of column bases for seismic responses of steel post-tensioned self-centering MRF systems

The first generation for the post-tensioned (PT) self-centering (SC) system, which incorporates the PT technology to beam-to-column connections, exhibits good seismic performance with small residual deformations except for the first floor. Instead of using the fixed column base, the column PT to the base affects the seismic performance of frames, especially for residual deformations. Recently, the seismic response of a SC frame subassembly, which applied the PT technology to the connection and column base, was verified in shake table tests. In this paper, a three-dimensional analytical model with rotational springs in the PT connection and PT column base was introduced to capture shake table test results of the frame subassembly. The same modeling approach was adopted to one MRF and three SC frames to study the effects of column bases on the seismic responses of frames under the design-based and maximum-considered earthquakes. The monotonic, cyclic pushover, and time-history analyses were conducted for these frames. Analytical results showed that (1) the residual drift of the First floor could be significantly minimized by using the PT column base but the maximum interstory drift in the SC frame increased with decreasing fixity at the column base, (2) the largest maximum interstory drifts of the SC frames were larger than those of the MRF due to the low-to-medium structural period and high yield strength, and (3) the SC frame with the PT column base effectively decreased column restraining forces to the first floor compared to that with the fixed column base. (C) 2011 Elsevier Ltd. All rights reserved.