Seismic Collapse Safety of Reinforced Concrete Buildings. I: Assessment of Ductile Moment Frames

Abstract

This study applies nonlinear dynamic analyses to assess the risk of collapse of reinforced concrete (RC) special moment frame (SMF) buildings, with the goal of quantifying the seismic safety implied by modern building codes. Thirty archetypical RC SMF buildings, ranging in height from 1 to 20 stories, are designed according to ASCE 7-02 and ACI 318-05 for a high seismic region. The results of performance-based seismic assessments find that, on average, these buildings have an 11% probability of collapse under ground motion intensities with a probability of exceedance of 2% in 50 years. The average mean annual rate of collapse of 3.1x10-4 collapses/year corresponds to an average 1.5% probability of collapse in 50 years. The study further examines the influence of specific design provisions on collapse safety. In particular, changes to the minimum seismic base shear requirement between ASCE 7 2002 and 2005 editions and variations in ACI 318 strong-column weak-beam

Seismic performance assessment of conventional steel and steel-concrete composite moment frames using CFST columns

“…A similar technique was applied in the FEMA P695 project (FEMA [20]). As proposed by Haselton et al [21], a general ground motion record suite was selected without taking into account the  values, with the results being post-processed to account for the expected  at a specific site and hazard level. Records were selected using SelEQ (Macedo and Castro [22]), which allowed for a very good correlation between the mean/median spectrum of the selected ground motions and the code spectrum.…”

An improved CWT-based algorithm for the generation of spectrum-compatible records

“…The continuum and fiber models can accurately capture the effects such as cracking of concrete and yielding of reinforcement bars but they are unable to capture the strength degradation effects associated with reinforcement bar buckling, bond-slip and shear failure causing strain softening (Haselton et al 2007(Haselton et al , 2011. As these effects are more critical for the structural collapse assessment, the lumped-plasticity models have gained more popularity for seismic response simulation of RC buildings (Haselton and Deierlein 2007;PEER/ATC 72-1 2010;Haselton et al 2011;Farsangi and Tasnimi 2016). In lumped-plasticity models, the force-deformation behaviour of an element is confined by an envelope, known as the "backbone curve".…”

“…Further, none of the studies, except for the one by Haselton et al (2011), examined adequacy of the existing code provisions on the SCWB ratio in terms of their effect on collapse probability. Consequently, there is no consensus about the values for the SCWB ratio for seismic design of RC frame buildings.…”

“…Until now, only few studies (Dooley and Bracci 2001;Kuntz and Browning 2003;Ibarra and Krawinkler 2005;Haselton et al 2011 andCagurangan 2015) have been conducted in which the adequacy of SCWB design provision of seismic design codes is assessed. In the context of seismic design of new buildings, the influence of the SCWB ratio on the collapse performance of buildings has already been identified as a high-priority study (NIST 2012).…”

“…Ibarra and Krawinkler (2005) focused on 9-to 18-storied RC frame buildings and observed that, to avoid column hinging, a SCWB ratio as high as 3 is required. Haselton et al (2011) studied the effect of SCWB ratio on the seismic performance and the inherent collapse probability of RC frame buildings. They observed that for a 4-storied building, a SCWB factor of 1.2 is adequate, whereas for a 12-storied building the building performance continues to improve up to a SCWB ratio of 3, and therefore, suggested a dependency of the SCWB ratio on the building height, too.…”