Period elongation-based framework for operative assessment of the variation of seismic vulnerability of reinforced concrete buildings during aftershock sequences

• Modeling of time-variant seismic vulnerability of reinforced concrete buildings.
• Damage states are defined using thresholds of eigenperiod elongation.
• Transition of damage states as a Markov process.
• Cumulative probability of exceeding damage states as a function of time.

Safety assessment of structures and/or critical infrastructures is a key factor in post-seismic decision-making. In this context we present a performance-based framework for modeling time-variant vulnerability of reinforced concrete buildings during aftershock sequences. Structural damage is associated with first eigenperiod elongation, a performance metric whose measurement can complement visual inspection and assessment of structural health as a post-seismic operative tool. The proposed framework is applied for a series of reinforced concrete building models and two aftershock sequences. Damage states are defined using thresholds of period elongation. Numerical models of the buildings in each damage state are considered and their fragility curves are computed. The time-variant vulnerability is modeled with Markov chain as a function of the characteristics of the aftershocks sequence. Finally, the probabilities of the damage states are computed as a function of time during two real aftershock sequences.