Simplified Estimation of Economic Seismic Risk for Buildings

Abstract

A seismic risk assessment is often performed on behalf of a buyer of commercial buildings in seismically active regions. One outcome of the assessment is that a probable maximum loss (PML) is computed. PML is of limited use to real-estate investors as it has no place in a standard financial analysis and reflects too long a planning period. We introduce an alternative to PML called probable frequent loss (PFL), defined as the mean loss resulting from shaking with 10% exceedance probability in 5 years. PFL is approximately related to expected annualized loss (EAL) through a site economic hazard coefficient (H) introduced here. PFL and EAL offer three advantages over PML: (1) meaningful planning period; (2) applicability in financial analysis (making seismic risk a potential market force); and (3) can be estimated using a single linear structural analysis, via a simplified method called linear assembly-based vulnerability (LABV) that is presented in this work. We also present a simple decision-analysis framework for real-estate investments in seismic regions, accounting for risk aversion. We show that market risk overwhelms uncertainty in seismic risk, allowing one to consider only expected consequences in seismic risk. We illustrate using 15 buildings, including a 7-story nonductile reinforced-concrete moment-frame building in Van Nuys, California, and 14 buildings from the CUREE-Caltech Woodframe Project.

A Seismic Performance Classification Framework to Provide Increased Seismic Resilience

“…Interestingly, there are two loss estimates for this building, the aforementioned study by Krawinkler (2005) and another conducted by Porter et al (2004). The two estimates of EAL for the Van Nuys hotel are displayed in Table 11.4 showing the estimate of Porter et al (2004) to be approximately one third (0.77 % vs. 2.2 %) of that reported by Krawinkler (2005).…”

“…the 3 D's) expressed in a variety of metrics. These metrics can be annualized, such as expected annual loss (EAL), to allow losses to be treated as an expense within cash flow analysis (Porter et al 2004), based on a given intensity such as that corresponding to a design level event, or based on a given scenario possibly recreating a previous or anticipated event of known magnitude and distance (ATC 2011a). Further, loss metrics can be expressed based on input from decision makers such as the annual or 50 year probability that losses will exceed a given value, such as probable maximum loss (PML).…”

“…The large difference is most likely attributed to the number of damageable assemblies considered in the study and the manner in which their repair costs are distributed. Reportedly, the damageable assemblies (with subsequent fragilities and consequence functions) in Porter et al (2004) consist of select structural and non-structural typologies from the collection of fragility and repair cost information within Beck et al (2002). Conversely, the fragilities for the Krawinkler (2005) study consider a, comparatively, exhaustive list of non-structural components as identified by Taghavi and Miranda (2003) as well as numerous structural elements with distinct seismic fragility and consequences.…”

Cost-Effectiveness of Stronger Woodframe Buildings

“…Subsequent study suggests that a more appropriate value would have been 40%; see Porter et al ͑2002b͒ for details. ͑In Beck et al 2002 andPorter et al 2004, our stochastic structural models also accounted for uncertainty in the force-deformation behavior of structural elements. Here we used the differences between the performance of the poor-quality, typical-quality, and superior-quality variants to examine the effect of strength variability.͒ In each analysis, we randomly selected a ground-motion component pair, scaled it to the desired S a value, and randomly paired it with one of the 20 simulated structural models.…”

Computational and rapid expected annual loss estimation methodologies for structures

“…This method has gained considerable acceptance since its inclusion in emerging regulations [10]. Other simplified methods have been proposed by Porter and Beck [11], who by assuming that seismic risk is dominated by non-structural damage from moderate events, proposed a simple linear elastic analysis to replace the often cumbersome non-linear dynamic analysis. The non-linear dynamic procedure is considerably more time consuming and requires uncommon skills for practicing engineers, whereas the linear approach is relatively simple.…”