Seismic Performance Evaluation of Reinforced Concrete Frame –Wall System Using Fragility Curve

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Addis Ababa University


According to the new Ethiopian building code ES EN 1998-1:2015, there is an adjustment in peak ground acceleration of Addis Ababa. The peak ground acceleration is updated to 0.1g which, were 0.05g in previsions EBCS8-1995. The variation will significantly affect the seismic performance of structure due to this, need to check buildings performance level and status against the new code predominant issue. Besides, building seismic performance and vulnerability analyses are probabilistic and vulnerability can be evaluated by developing fragility function which is expressed in the fragility curve. Works of literature provide a different technique to evaluate the fragility of structure: Empirical, Expert opinion, Analytical and Hybrid. Each of those methods is subjected to their on limitation, subjectivity in expert opinion, time-demanding in analytical and particularity in the empirical approach. With all its constraint, analytical fragility is the most dominate approaches employed in the research community and a simplified structural model which resembles the real structure behaviour can further reduce the time demand resulted from extensive nonlinear analysis. This research aspires to find a simplified analytical solution which minimizes time demand required under previous analytical fragility analyses. The resulted fragility curves are used to evaluate the performance of case study building in line with conventional pushover analysis. Before implementing fragility analysis, conventional pushover analysis of the case study building is performed in SAP 2000® and the effect of confinement is considered in determining the material nonlinearity of structural elements. The global level performance points of the building determined with Capacity spectrum method of FEMA 440 under different seismic demand and the selected capacity curve are used to generate Incremental Dynamic Analysis curves of the building. The conversion of the capacity curve to generate Incremental dynamic analysis curves was conducted by utilizing Static Pushover to Incremental Dynamic Analysis algorithm. The generated Incremental Dynamic Analysis curves were calibrated for its elastic stiffness by using statistical results of elastic stiffness computed from time history analysis. Further adjustment to Incremental Dynamic Analysis curves is also introduced to calibrate record to record variability at near collapse limit state with FEMA P695 requirement. At last, the uncertainty related to record-to- record variability of ground motion is extracted from calibrated Incremental Dynamic Analysis curves and combined modelling uncertainty of FEMA P695 recommendations. Finally, the seismic fragility curve of case study building developed for seismic hazard zones expressed in ES EN 1998-1:2015 and its probability damage states evaluated by considering SYNER-G damage limit state. Considering the lack of data regarding least allowable damage probability, the study adopts FEMA P695 requirement link with near collapse damage states.



Dual system, Pushover analysis, Capacity curve, Damage state, Uncertainties, Fragility analysis, Static Pushover to Incremental Dynamic Analysis