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

Abstract

SUMMARYThis 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 accelerationsensitive 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.

Earthquake-Induced Collapse Risk and Loss Assessment of Steel Concentrically Braced Frames

“…Note that in this case the effect of the numerical model choice on the EALs is insignificant. These values are slightly larger but consistent with EALs of steel frame buildings with moment-resisting frames [32]. It is also evident that losses due to acceleration-sensitive nonstructural component repair primarily governs the EALs regardless of the numerical model choice and the seismic design category.…”

Proposed Methodology for Earthquake-Induced Loss Assessment of Instrumented Steel Frame Buildings: Building-Specific and City-Scale Approaches

“…P(C|IM) is the probability of collapse conditioned on the seismic intensity IM=im. More details about the mathematical formulation of the building-specific loss estimation methodology can be found in [59,60].…”

Fragility Curves for Wide-Flange Steel Columns and Implications for Building-Specific Earthquake-Induced Loss Assessment

“…It should be noted from the same figure that although the employed steel column fragilities affect the computed EALs, these are still dominated by repairs due to non-structural damage in acceleration-sensitive components followed by those in drift-sensitive ones. This is attributed to the fact that EALs are usually dominated by frequently occurring earthquakes rather than seismic events with a low-probability of occurrence (Hwang and Lignos 2017). It is likely that the EAL contributions may be quite different in steel frame buildings with MRFs designed in areas of moderate seismicity.…”

“…The number of the different structural and nonstructural components in this building, as well their fragility and repair cost estimates, can be found in Hwang and Lignos (2017). It should be noted that no repair cost was assigned to DS 1 .…”

“…This is due to (1) the limited amount of experimental data on seismically compact steel wide-flange columns till recently; and (2) the assumption that steel columns in capacity-designed buildings, remain elastic during earthquakes (FEMA 2012). In that respect, steel beam fragility curves are typically utilized to quantify the extent of column damage for buildingspecific loss assessment of steel MRFs (Hwang and Lignos 2017). Experimental research on the seismic behavior of wide-flange steel columns (Popov et al 1975;MacRae et al 1990;Newell and Uang 2006;Suzuki and Lignos 2015;Elkady and Lignos 2016;Lignos et al 2016;Ozkula et al 2017) suggests that steel column limit states are fairly different than those observed in steel beams.…”