A performance-based rehabilitation strategy for RC frame buildings in moderate seismic regions

Large parts of Asia, Europe, and the eastern USA have high population concentrations in moderate seismic regions (MSR), where very large earthquakes are rare. With rampant construction in the cities located in MSRs, a relatively moderate earthquake can turn into a catastrophe. Limiting the collapse has been the conventional performance objective for regions with high seismicity. However, this does not necessarily translate into a more desirable target of life-safety under design basis earthquake in MSRs. The present paper investigates the seismic performance of non-ductile reinforced concrete (RC) buildings that were common before the advent of modern design standards, and are found in very large numbers. An analytical model capturing the shear failure is employed using a drift-based limit state material. The results show that a hybrid index captures moderate damage more accurately than the prevalent drift-based index. The paper further shows that while a generic ground motion suite accurately estimates the median fragility, it fails to capture the uncertainty. A 7-story non-ductile RC archetype building was found to be at a collapse prevention risk of 2 \(\times\) $\times$ 10^–4. The seismic risk deaggregation reveals that seismic risk consistency can be enhanced by explicit specification of the seismic forces for retrofitting. The study shows that the stringent seismic risk targets can be met by non-ductile buildings in MSR, provided they are designed or retrofitted with constraints on strong column weak beam factors. The study will facilitate in developing a scheme for prioritizing and devising the retrofit of pre-modern code and non-ductile deficient buildings.