Component-based reliability of a retrofitted reinforced concrete building using a series-parallel model and self-deconvolution scheme

This study presents a comprehensive system-level reliability assessment for existing Reinforced Concrete (RC) frames retrofitted with a dual system of aluminum shear links and eccentric steel braces. While the deterministic efficacy of this retrofit strategy has been previously established by the authors, the present work addresses the fundamental question of its probabilistic safety by evaluating the interaction of component failure modes. A detailed reliability framework is developed, idealizing the structure as a series system of its stories, wherein the original Moment-Resisting Frame (MRF) and the new bracing system act as parallel subsystems. Component fragility functions for the MRF, links, and braces are derived from nonlinear time-history analyses at both the Design Basis (DBE) and Maximum Considered Earthquake (MCE) hazard levels, using a novel self-deconvolution extrapolation scheme to ensure robust tail-end estimation. The results demonstrate a fundamental transformation of seismic safety. At the DBE level, the global system reliability against the serviceability objective is elevated from effectively zero in the original structure to 100% in the retrofitted configuration, signifying a complete mitigation of damage risk. Under the more severe MCE hazard, the retrofitted system maintains a significant global reliability of 30.2%, a monumental improvement from the original building's certain failure. The MCE-level analysis further quantifies a definitive failure hierarchy, confirming that the shear links are the most vulnerable component, followed by the MRF, which validates their intended role as sacrificial ductile fuses. This component-based framework provides a more detailed and mechanistically sound assessment of the retrofit’s contribution to probabilistic safety than a global fragility analysis alone.