Probabilistic seismic demand and capacity models and fragility curves for reticulated structures under far-field ground motions

Abstract

This paper aims to develop probabilistic seismic demand models (PSDMs), probabilistic seismic capacity models (PSCMs) and fragility curves for the widely-constructed reticulated structures using far-field earthquake records. The ground motion variability and prevailing uncertainties in structural design and modeling are considered, via performing incremental dynamic analyses (IDAs) on sample models of eighteen generic reticulated shells under forty far-field three-dimensional ground motions. A seismic energy demand-based damage index (DIE) is introduced and then employed together with the peak ground acceleration (PGA), to develop PSDMs and PSCMs for the reticulated shells considered, on the basis of statistical evaluation of the IDA results. The effects of two key structural design parameters, i.e., rise-to-span (or -width) ratio and roof load, on the PSDMs are investigated, and the normalized values for the PSCMs are also recommended. Fragility curves are derived and plotted to examine the difference among reticulated shells with different design parameters. It is concluded that DIE has strong correlation with PGA, and is more appropriate for developing PSDMs for the reticulated shells; and it also suggests that the reticulated shells with bigger rise-to-span (or -width) ratios or larger roof loads are more likely to damage or collapse during earthquakes. These results and conclusions will facilitate the performance-based seismic design and seismic vulnerability assessment of reticulated structures.