Civil Engineering Association

PUSHOVER ANALYSIS OF AN EXISTING REINFORCED CONCRETE STRUCTURE

The main purpose of this study is to analyze the seismic response of a reinforced concrete structure which suffered damage in the South Iceland earthquakes in June 2000.
Two different methods are used to analyse the structure. First, a 3D linear elastic response spectrum analysis (RSA) is carried out in a finite element program, using response spectra within the European seismic design code (EC8). The response spectrum analysis is followed with a pushover analysis of one of the walls which suffered the most severe damage. A new finite element model is constructed where the nonlinear properties of the reinforced concrete are implemented. The pushover analysis is combined to the response spectra approach through the comprehensive N2 method, which is a novelty in EC8. Results of the pushover analysis are used to estimate the performance of the structure under the design earthquake load. Deformation of the structure, stress strain and evaluation of cracks in the reinforced concrete are reviewed. Damage obtained in the analysis and the actual reported damages are then compared. Finally, the effect of strengthening is estimated.
The study showed that despite serious damage, the structural wall is able to withstand the earthquake design load. However, the structure does by no means meet the design code requirements. Observed damage was fairly consistent with that actually reported, but according to the analysis the N2 procedure tends to be conservative. As shown in the study, the pushover analysis based on the N2 method is a desirable procedure in order to evaluate the seismic resistance of existing structures, especially if there is doubt that response spectrum analysis provides sufficient information.