With the advancement in earthquake engineering in the recent decade, catastrophic structural collapses during moderate intensity earthquakes are relatively rare in modern engineered buildings. However, financial losses due to earthquake damages are still relatively high with estimated annual earthquake-related losses at $4.4 billion USD per year. While the aim of the modern seismic codes is collapse prevention, many damaged buildings are deemed non-repairable after a moderate earthquake.
This paper presents a fresh look at the way that irreparability is perceived in the context of advanced performance-based earthquake engineering (PBEE). Customary prescriptive design approaches tend to overlook the issue of reparability in the process of seismic design of buildings.
One of the most commonly used PBEE loss estimation frameworks in recent years is known as the FEMA P-58 methodology which includes a three-module Monte Carlo Simulation (MCS) procedure to assess the seismic performance of buildings. In each realization of MCS, ‘collapse state’ is checked first followed by ‘reparability state’ check. If neither of these states occurred, in other words, no collapse and repairable, a detailed ‘loss estimation’ is conducted. In the current FEMA P-58 framework, irreparability is based solely on one of the structural responses, specifically residual drift. In reality, a building is condemned for demolition following an earthquake depends on various factors which include structural, strategic and financial decision variables. In order to overcome the observed shortcomings, firstly, it is proposed the arrangement of three modules of the methodology set forth by FEMA P-58 be reworked to emulate the common practice of assessment of earthquake-induced losses to a building in the field. In the new revised framework, ‘irreparability’ is excluded from the loss estimation and is considered as a post loss estimation decision making variable.
In this presentation, a brief yet methodical review of irreparability assessment approaches will be presented including a discussion on the drawbacks of irreparability model in FEMA P-58. Several factors commonly used by insurance adjusters to quantify the chance of irreparability will be presented and discussed. Finally, several illustrative examples will be presented whereby the vulnerability functions for select building types (steel and RC moment frames and light-frame wood) are assessed and compared using the proposed new method and FEMA P-58 approach.
The target audience for this presentation are engineers, catastrophe loss analyst, and researchers. Engineers may use the new information to design buildings that are less susceptible to financial losses. Loss analysists may use the information to develop more accurate loss functions for setting insurance premium.