Earthquake-induced loss assessment of steel frame buildings with special moment frames designed in highly seismic regions

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Wiley-Blackwell, 2017
Article

Résumé

This paper discusses an analytical study that quantifies the expected earthquake-induced losses in typical office steel frame buildings designed with perimeter special moment frames in highly seismic regions. It is shown that for seismic events associated with low probabilities of occurrence, losses due to demolition and collapse may be significantly overestimated when the expected loss computations are based on analytical models that ignore the composite beam effects and the interior gravity framing system of a steel frame building. For frequently occurring seismic events building losses are dominated by non-structural content repairs. In this case, the choice of the analytical model representation of the steel frame building becomes less important. Losses due to demolition and collapse in steel frame buildings with special moment frames designed with strong-column/weak-beam ratio larger than 2.0 are reduced by a factor of two compared with those in the same frames designed with a strong-column/weak-beam ratio larger than 1.0 as recommended in ANSI/AISC-341-10. The expected annual losses (EALs) of steel frame buildings with SMFs vary from 0.38% to 0.74% over the building life expectancy. The EALs are dominated by repairs of acceleration-sensitive non-structural content followed by repairs of drift-sensitive non-structural components. It is found that the effect of strong-column/weak-beam ratio on EALs is negligible. This is not the case when the present value of life-cycle costs is selected as a loss-metric. It is advisable to employ a combination of loss-metrics to assess the earthquake-induced losses in steel frame buildings with special moment frames depending on the seismic performance level of interest.

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,
Wiley-Blackwell, 2017
Article

Résumé

Official source

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In recent years, there is an increasing need to quantify earthquake-induced losses throughout the expected life of a building in order to evaluate alternative design options such that we can minimize repairs in the aftermath of an earthquake. This paper discusses an analytical study that quantifies the expected economic losses in a portfolio of archetype steel frame buildings designed with perimeter special moment frames or special concentrically braced frames in urban California in accordance with current seismic provisions in the U.S. The expected economic losses associated with repair are computed based on an established loss estimation framework within the context of performance-based earthquake engineering. It is shown that repair costs in the aftermath of earthquakes vary significantly depending on the employed lateral load-resisting system, seismic design considerations as well as the analytical model representation of the archetype frame building itself.

American Society of Civil Engineers2015

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This paper quantifies the collapse risk and earthquake-induced economic losses of steel-frame buildings with special concentrically braced frames designed in urban California. A probabilistic building-specific loss estimation methodology that can explicitly account for the main sources of variability related to seismic hazards and structural response is used for this purpose. It is shown that, depending on the choice of the loss metric, at seismic events with low probability of occurrence (i.e., 2% probability of occurrence in 50 years), losses because of demolition and structural collapse in steel-frame buildings with special concentrically braced frames designed in highly seismic zones may be significantly overestimated when ignoring the contribution of the composite floor and gravity framing system to the analytical model building representation. For frequent and moderately frequent seismic events (i.e., 50 and 10% probability of exceedance over 50 years of building life expectancy), acceleration-sensitive nonstructural component repairs govern building losses regardless of the analytical model representation used. For the same seismic events, an appreciable contributor to total losses in steel-frame buildings with special concentrically braced frames is structural repairs because of steel brace flexural buckling. It is suggested that dual-parameter rather than drift-based steel brace fragility curves should be used in loss computations conditioned on a single seismic intensity. Otherwise, the expected annual losses should be used as a metric for building-specific loss assessment of steel-frame buildings with special concentrically braced frames.

Asce-Amer Soc Civil Engineers2017

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Improving the collapse risk of steel structures with high-performance steel

Dimitrios Lignos

With the advent of material science, high-performance steel materials have been developed for seismic applications that potentially reduce the earthquake-induced collapse risk of steel frame buildings. The High Yield Point (HYP400) steel is one of those materials that is developed based on thermomechanical control process. Both its yield strength and notch toughness is enhanced compared to conventional seismic-resistant steels. This is achieved through refinement of the microstructural grain size. The application of such material in steel columns facilitates economic design and enhances the collapse capacity of steel moment resisting frames during severe seismic events. This paper first discusses the key aspects of the HYP400 steel and illustrates its potential through detailed nonlinear analyses and earthquake-induced collapse simulations of a steel frame building. The material cyclic hardening prior to the onset of local buckling is characterized on the basis of uniaxial cyclic coupon tests. Finite element studies are then conducted to investigate the pre- and post-buckling behavior of hollow structural section steel columns made of HYP400 steel under various loading histories. A versatile fiber-based deterioration model is then utilized that captures the steel material potential and facilitates computationally efficient collapse simulations. The effectiveness of the HYP400 steel for enhancing the collapse capacity of a steel moment resisting frame is demonstrated through incremental dynamic analysis of a case study steel moment-resisting frame.

2018

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