The Efficiency of Reduced Beam Section Connections for Reducing Residual Drifts in Moment Resisting Frames

Abstract

In most framed structures anticipated deformations in accordance with current codes fall into acceptable limit states, whereas they go through substantial residual deformations in the aftermath of severe ground motions. These structures seem unsafe to occupants since static imminent instability in the immediate post-earthquake may be occurred. Moreover, rehabilitation costs of extensive residual deformations are not usually reasonable. Apparently, there is a lack of detailed knowledge related to reducing residual drift techniques when code-based seismic design is considered. In this paper, reduced beam section connections as a positive approach are taken action to mitigate the huge amount of residual drifts which are greatly amplified by P-Δ effects. To demonstrate the efficacy of RBS, a sixteen-story moment resisting frame is analyzed based on a suite of 8 single-component near field records which have been scaled according to the code provisions. The results are then processed to assess the effects of RBS detailing on drift profile, maximum drift, and residual drift. Besides, a special emphasis is given to estimate overall trend towards drift accumulation in each story in the presence of RBS assembly. A main conclusion is that using this connection predominantly alleviates the adverse effects of P-Δ on amplifying residual drifts.

Pushover Analysis of Steel Seismic Resistant Frames with Reduced Web Section and Reduced Beam Section Connections

“…The 4-, 8-and 16-storey frames presented in this paper have become a benchmark for the validation of pushover analyses (Ghassemieh and Kiani, 2012;Kildashti et al, 2012), which this study will similarly validate against. The three MRFs are designed according to American design code and consequently use American beam and column sections.…”

“…Previously, RBSs have been studied in steel frames in research presented by Kildashti et al (2012) and Ghassemieh and Kiani (2012), finding RBSs reduced inter-storey drifts in the lower storeys of multistorey structures, as well as reducing the overall capacity curve of the frames.…”

“…Previous studies of RBSs (Jin and El-Tawil, 2004;Ghassemieh and Kiani, 2012;Kildashti et al, 2012) have used three steel MRFs of varying height; 4-, 8-, and 16-storey. This study will use these frames to validate results against, and then further develop the frames to incorporate RWSs.…”

“…The storey mass for the roof and floor levels is calculated as 496 and 757 tonnes, respectively. In combination with this, the full dead load, accompanied with 25% of the live load is included for the pushover analysis (Kildashti et al, 2012). Pachoumis et al (2009) established that it is unsuitable to use codes developed for American sections to design European sections, due to the inherent differences in section geometry.…”

“…This study will use these frames to validate results against, and then further develop the frames to incorporate RWSs. The RBSs are also modeled using non-linear hinges defined by moment-rotation data from the validation study (Kildashti et al, 2012), which designed the RBSs in accordance to the recommendations proposed by FEMA 350 (2000b). The frames, initially introduced by Jin and El-Tawil (2004), are designed in accordance with FEMA 302 (1997), FEMA 350 (2000a, and American Institute of Steel Construction, Inc. (2016); the beam and column sizes were selected due to limitations on inter-storey drifts and to promote the "weak beam-strong column" mechanism.…”