Case studies of damage to 19‐storey irregular steel moment‐frame buildings under near‐source ground motion

Earthquake Engineering & Structural Dynamics (Impact Factor: 1.9). 06/2007; 36(7):861 - 885. DOI: 10.1002/eqe.657

ABSTRACT This paper describes the three-dimensional nonlinear analysis of six 19-storey steel moment-frame buildings, designed per the 1997 Uniform Building Code, under strong ground motion records from near-source earthquakes with magnitudes in the range of 6.7–7.3. Three of these buildings possess a reentrant corner irregularity, while the remaining three possess a torsional plan irregularity. The records create drift demands of the order of 0.05 and plastic rotation demands of the order of 4–5% of a radian in the buildings with reentrant corners. These values point to performance at or near ‘Collapse Prevention’. Twisting in the torsionally sensitive buildings causes the plastic rotations on the moment frame on one face of the building (4–5% of a radian) to be as high as twice of that on the opposite face (2–3% of a radian). The asymmetric yield pattern implies a lower redundancy in the lateral force-resisting system as the failure of the heavily loaded frame could result in a total loss of resistance to torsion. Copyright © 2006 John Wiley & Sons, Ltd.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In 2008, there was a significant campaign undertaken in southern California to increase public awareness and readiness for the next large earthquake along the San Andreas fault that culminated in a large-scale earthquake response exercise. The USGS ShakeOut scenario was a key element to understanding the likely effects of such an event. In support of this effort, a study was conducted to assess the response of tall steel structures to a M7.8 scenario earthquake on the southern San Andreas Fault. Presented here are results for two structures. The first is a model of an 18-story steel moment frame building that experienced significant damage (fracture of moment-frame connections) during the 1994 Northridge earthquake. The second model is of a very similar building, but with a structural system redesigned according to a more modern code (UBC 97). Structural responses are generated using three-dimensional, non-linear, deteriorating finite element models, which are subjected to ground motions generated by the scenario earthquake at 784 points spaced at approximately 4 km throughout the San Fernando Valley, the San Gabriel Valley and the Los Angeles Basin. The kinematic source model includes large-scale features of the slip distribution, determined through community participation in two workshops and short length-scale random variations. The rupture initiates at Bombay Beach and ruptures to the northwest before ending at Lake Hughes, with a total length of just over 300 km and a peak slip of 12 m at depth. The resulting seismic waves are propagated using the SCEC community velocity model for southern California, resulting in ground velocities as large as 2 m/s and ground displacements as large as 1.5 m in the region considered in this study. The ground motions at the sites selected for this study are low-passed filtered with a corner period at 2 seconds. Results indicate a high probability of collapse or damage for the pre-1994 building in areas of southern California where many high-rise buildings are located. Performance of the redesigned buildings is substantially improved, but responses in urban areas are still large enough to indicate a high-probability of damage. The simulation results are also used to correlate the probability of building collapse with damage to the structural system.
    9th National Conference on Earthquake Engineering, Toronto; 01/2009
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This work represents an effort to develop one plausible realization of the effects of the scenario event on tall steel moment-frame buildings. We have used the simulated ground motions with three-dimensional nonlinear finite element models of three buildings in the 20-story class to simulate structural responses at 784 analysis sites spaced at approximately 4 km throughout the San Fernando Valley, the San Gabriel Valley, and the Los Angeles Basin. Based on the simulation results and available information on the number and distribution of steel buildings, the recommended damage scenario for the ShakeOut drill was 5% of the estimated 150 steel moment-frame structures in the 10–30 story range collapsing, 10% red-tagged, 15% with damage serious enough to cause loss of life, and 20% with visible damage requiring building closure. [
    Earthquake Spectra 05/2011; 27(2):375-398. DOI:10.1193/1.3563621 · 1.00 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The mechanism of collapse of tall steel moment frame buildings is explored through three-dimensional nonlinear analyses of two 18-story steel moment frame buildings under earthquake excitation. Both fracture-susceptible as well as perfect-connection conditions are investigated. Classical energy balance analysis shows that only long-period excitation imparts energy to tall buildings large enough to cause collapse. Under such long-period motion, the shear beam analogy alludes to the existence of a characteristic mechanism of collapse or a few preferred mechanisms of collapse for these buildings. Numerical evidence from parametric analyses of the buildings under a suite of idealized sawtooth-like ground motion time histories, with varying period (T), amplitude (peak ground velocity, P GV), and duration (number of cycles, N), is presented to support this hypothesis. Damage localizes to form a "quasi-shear" band over a few stories. When the band is destabilized, sidesway collapse is initiated and gravity takes over. Only one to five collapse mechanisms occur out of a possible 153 mechanisms in either principal direction of the buildings considered. Where two or more preferred mechanisms do exist, they have significant story-overlap, typically separated by just one story. It is shown that a simple work-energy relation applied to all possible quasi-shear bands, combined with plastic analysis principles can systematically identify all the preferred collapse mechanisms.
    Journal of Structural Engineering 11/2012; 138(11). DOI:10.1061/(ASCE)ST.1943-541X.0000573 · 1.49 Impact Factor

Full-text (5 Sources)

Available from
Nov 20, 2014