Time dependent seismic fragility and serviceability assessment of reinforced concrete frames under chloride induced...

Chloride-induced corrosion represents a critical deterioration mechanism for reinforced concrete (RC) structures, yet its time-dependent impact on structural reliability remains insufficiently investigated. This study integrates a corrosion progression model with finite element analysis and the First-Order Reliability Method (FORM) to evaluate the seismic performance and serviceability of a single-bay, single-story RC frame throughout a 60-year service life. Nonlinear dynamic, static, and modal analyses were conducted using OpenSees and MATLAB to quantify failure probabilities for both drift-based seismic damage states and serviceability criteria (deflection and vibration). The results demonstrate that corrosion significantly amplifies failure risk: for slight, moderate, and extensive seismic damage states, failure probability increases by approximately 46-56%, 52-55%, and 34-47%, respectively, compared to an uncorroded frame. Serviceability reliability similarly deteriorates, with corrosion raising the probability of deflection and floor vibration failure by approximately 30-37% over the 60-year period. A sensitivity analysis identified the corrosion initiation time, chloride diffusion coefficient, and rebar diameter as governing uncertainties affecting the reliability index. Notably, the influence of corrosion-model parameters (such as time to initiation) on reliability is pronounced during early years but diminishes at later stages of the service life. These findings highlight the significant long-term vulnerability of RC frames in chloride-rich environments and underscore the value of probabilistic approaches for assessing structural resilience under progressive corrosive deterioration.