Incremental dynamic analysis for seismic fragility analysis
Published:
A vital component of the performance-based earthquake engineering (PBEE) is the so-called fragility function. In this post, I will discuss one method to calculate the fragility function using incremental dynamic analysis. A simplified single degree-of-freedom (SDOF) system is analysed in OpenSeesPy to illustrate the steps in determining the fragility function.
Seismic fragility function
One of the advantageous feature of PBEE is the transparent accounting of uncertainty in the design or assessment process. While the PBEE framework has evolved over the years, its original inception as part of the Pacific Earthquake Engineering Research (PEER) studies partitioned seismic assessment into four distinct analyses: seismic hazard, structural response, damage, and loss, while accounting for various levels of uncertainties at each step. The PBEE framework provides a sequential methodology that maps seismic hazard to eventual impacts that the stakeholders can use for decision-making.
The seismic hazard analysis, typically performed probabilistically, is characterized by an intensity measure (IM), which quantifies the severity of an earthquake scenario. Examples of IM include peak ground acceleration (PGA) and first-mode spectral acceleration $S_a(T_1)$. Seismic hazard curves which is derived by performing Probabilistic Seismic Hazard Analysis (PSHA) describes the annual rate of exceeding certain levels of ground-motion shaking (expressed as in terms of IM) at a specific site.
