Performance-Based Evaluation of Infill-Controlled Eurocode Limit States for Modern RC Frame Buildings

Abstract eng:
Past earthquakes in Southern Europe have caused damage to external enclosures of unreinforced clay masonry block in RC frame residential buildings. The construction of these buildings in these moderate seismic regions continues, though only with stringent seismic code provisions to mitigate early damage. Analytical tools currently under development by researchers are improving modeling of these buildings, but most studies target the existing building stockpile in their local region. Recent architectural requirements have brought thicker infill walls which are expected to be more resistive to outof-plane excitation but also effect the in-plane seismic response far more. Several full scale experiments targeting effects of damage on the out-of-plane response have shown a strong interaction between in-plane drift history and the out-of-plane strength and stiffness. A macro model has been developed and calibrated to the experiment data on different masonry typologies for implementation in nonlinear dynamic analysis. To precisely evaluate the different limit states as prescribed by the Italian National Annex, a full range of the response of the infill is needed--that is, an accurate representation of initial stiffness, the in-plane post-peak behavior, and the collapse of the infill out-of-plane. Local damping of the infill walls out-of-plane direction are updated as damage in the wall progresses. The damage limitation, ultimate, and collapse prevention limit states are verified by performing time history analyses on an archetype building model subject to a bidirectional ground motion suite with the strong infill typology. The susceptibility of premature damage and expulsion of debris has been estimated using drift indices recorded during the experiment. However, experiments on the wall were not carried out until collapse. Therefore, imminent collapse has been taken as the point at which the infill can no longer resist additional load, which has been shown to change with maximum in-plane drift. Discussion on the significance of the results and the effectiveness of the seismic provisions currently in the design code concludes the study.

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