Probabilistic evaluation of behaviour factors in EC8-designed R/C frames

A methodology for the probabilistic assessment of reinforced concrete (R/C) frames which takes into account material variability, confinement model uncertainty and the uncertainty in local and global failure criteria is applied for the derivation of vulnerability curves for the serviceability and ultimate limit states of a multi-storey frame designed to Eurocode 8. By combining the uncertainties affecting structural vulnerability and seismic hazard, the seismic reliability is quantified in terms of the probability of failure for any given design life period. It is found that, while adequate safety margins exist for the ULS, the reliability against the SLS strongly depends on the structural criterion adopted for the definition of this state. The variability in the actual behaviour factor of this frame is also estimated, and the appropriateness of the EC8 specified value is assessed.