Sensitivity of the Fragility Curve on Type of Analysis Methods, Applied Ground Motions and Their Selection Techniques

Fragility curves are the primary way of assessing seismic risk for a building with numerous studies focused on deriving these fragility curves and how to account for the inherent uncertainty in the seismic assessment. This study focuses on a three-story steel moment frame structure and performs a fragility assessment of the building using a new approach called SPO2FRAG (Static Pushover to Fragility) that is based on pushover analysis. This new approach is further compared and contrasted against traditional nonlinear dynamic analysis approaches like Incremental Dynamic Analysis and Multiple Stripe Analysis. The sensitivity of the resulting fragility curves is studied against multiple parameters including uncertainties in ground motion, the type of analysis method used and the choice of curve fitting technique. All these factors influence the fragility curve behavior and this study assesses the impact of changing these parameters.

Fragility Curve Analysis of Medium Cable Stayed Bridge

The seismic performance of a bridge can be shown by analyzing the vulnerability of the structure in resisting an earthquake motion and then developing into fragility curves. This study presents a convenient method to establish the fragility curve for the cable-stayed bridge. For this purpose, three spans cable-stayed bridge is assessed using a series of seismic loads in different intensities to ensure that the structure was experiencing damage in several conditions. The fragility curve was obtained by analyzing the structure using Nonlinear Time History (NTHA) and Pushover Analysis. The ground motions of the earthquake were subjected to the bridge in different intensities, which were scaled from the initial ground motion. Hereafter, the structure’s ductilities were developed into the fragility curves as the responses of the bridge. HAZUS standard is used for classifying the damages of the bridge, which are grouped into; slight, moderate, extensive, and complete due to the seismic load. The values of the damage states were generated to the fragility curves using the probabilistic values of the damage states. To ensure the validity of the data statistically, Kolmogorov-Smirnov test was conducted to the fragility function. The result revealed that the fragility curve was qualified as the lognormal distribution.

Assessing Material Fragility using Nanoscale Incremental Dynamic Analysis

A new methodology to assess material failure subjected to stochastic loads is proposed, titled Nanoscale Incremental Dynamic Analysis (NIDA), which is adopted from performance-based assessment in structural engineering. Using full atomistic molecular dynamics, proof-of-concept simulations produce the material fragility curve of a simple carbon nanotube.

Assessing Material Fragility using Nanoscale Incremental Dynamic Analysis

A new methodology to assess material failure subjected to stochastic loads is proposed, titled Nanoscale Incremental Dynamic Analysis (NIDA), which is adopted from performance-based assessment in structural engineering. Using full atomistic molecular dynamics, proof-of-concept simulations produce the material fragility curve of a simple carbon nanotube.

Seismic Fragility Analysis of Base Isolated Structure Subjected to Near-fault Ground Motions

In order to better evaluate the performance of the base isolated structure under the near-fault earthquakes, this paper takes into consideration an existing engineering case study in China as the prototype, and uses OpenSEES platform to establish the nonlinear finite element model of the base isolated structure. The nonlinear response of the isolated structure under the near-fault earthquake is analyzed. The incremental dynamic analysis (IDA) method is used to calculate the damage probability of the structure under the near-fault earthquake, and the fragility curve of the base isolated structure is established. The fragility equation is obtained by nonlinear regression, and the error of fragility equation is analyzed. The results show that the maximum value of the inter-story drift of the upper structure under the action of near-fault earthquake is significantly greater than that under the action of far-fault earthquake. With the increase of seismic intensity, the damage probability of base isolated structure increases nonlinearly, and the maximum response value of horizontal displacement of bearing and inter-story drift of superstructure increases generally. In addition, the exceeding probability of the fragility curve based on PSDA is greater than that based on EDP criterion. When the sample points of the two methods are the same, the exceeding probability points calculated based on PSDA can be regarded as accurate values. The fragility curve based on PSDA may overestimate the exceeding probability to some extent, and the overestimation may be enlarged with the increase of failure stage.