Seismic Vulnerability and Fragility of Steel Buildings

Abstract eng:
The main goal of this article is to evaluate the structural behavior of steel buildings. The seismic performance of a specific steel building located in the campus of the National University of Colombia in Manizales is assessed. The seismic demand is characterized by a peak effective acceleration of 0.25 g. Pushover analysis applied to a low-rise steel moment-resitant frame building and a low-rise steel braced frame building has shown the inadequate seismic behaviour of moment-resistant frame buildings, althoug the increase of the stiffness of braced frame buildings may induce seismic damage to non-structural elements sensitive to spectral acceleration. We have obtained fragility curves and damage probability matrices for the seismic demand anticipated by the Colombian seismic code for Manizales. We obtain specific relationships between yielding and ultimate capacity spectral displacements and damage states’ thresholds. These relationships can be applied to low-rise moment resistant frame and low-rise braced frame buildings. The comparison of the obtained expected mean damage states and the vulnerability classes provided by the EMS-98 macro-seismic scale leads us classifying low-rise steel braced frame buildings and low-rise steel moment resistant frame buildings respectively into the vulnerability classes C and D-E. We clearly show that, stiffening buildings with concentric braces leads to more earthquake-resistant structures, and therefore with a significantly lower seismic vulnerability.

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