- مبلغ: ۸۶,۰۰۰ تومان
- مبلغ: ۹۱,۰۰۰ تومان
Seismic fragility functions are essential for performance-based seismic design of structures. Global demand parameters, such as peak roof displacement or maximum drift over the height of the building, are commonly used to estimate seismic fragility. However, in case of buildings with vertical irregularities, the global demand parameters may not suffice since maximum demand in such building is mostly concentrated at the level of irregularity. The current study focuses on one of the most common forms of vertically irregular reinforced concrete (RC) buildings, known as open ground story buildings, where irregularity lies at the ground story. Nonlinear dynamic analyses of RC frames subjected to a number of ground motions, each scaled-up for different PGA, are carried out to estimate the component level and global drift demands, also known as engineering demand parameters (EDPs). Seismic fragilities developed for the frames based on both the component and global EDPs are presented. Finally, the importance of component-based fragilities for estimation of seismic fragility of irregular frames is emphasized. The component level EDP-based fragility is found to be effective in predicting the actual damage scenarios in such buildings observed during past earthquakes.
Seismic fragility of three common typologies of concrete moment frames, broadly categorized as frame with unreinforced masonry infill walls and those without infill walls are studied. Different configuration of masonry infill walls in the frame may sometimes render the frame highly irregular, for example, open ground story frames in which masonry infill walls are not provided in the ground story. Experience during past earthquakes suggests that the open ground story buildings behave poorly during earthquake shaking. Such buildings suffered severe damage in the ground story columns but no noticeable damage was observed in the upper stories. It is observed in the nonlinear time history analyses of the considered frames for six ground motions that the conventional engineering demand parameters (EDP), for example, top level displacement or drift, cannot capture this behavior of open ground story frames, and hence, the fragility estimated using such EDP will not be realistic.
The primary objective of the study is to establish an EDP that correctly interprets the behavior of irregular frames for fragility assessment. This is accomplished by considering both displacement and inter-story drift as engineering demand parameters for fragility assessment of regular and irregular frames. Equal importance is laid on the effect of infills and its presence or absence in the ground story of the frames. It is obviously observed in the fragility estimation that the absence of infills in the ground story makes the frame more vulnerable as compared to a frame without any infill in any story (bare frame). Further, a frame with infill walls in all the stories becomes vulnerable once the ground story infills fail, which otherwise, behaves as a regular frame.