Cyclic Behavior of Retrofitted Low- and High-Strength Concrete Scaled Bridge Piers under Quasistatic Loading

Bridges are vulnerable to devastation in the earthquake, resulting in the closure of the whole transport system of the particular region. Generally, pre-Kashmir earthquake bridges in Pakistan were not designed according to present seismic zoning requirements. Therefore, it is critical to evaluate their seismic performance and accordingly enhance their strength, stiffness, and thus reliability. Seismic retrofitting of existing bridges with CFRPs (carbon fiber-reinforced polymers) may be planned for typical bridge types of Pakistan. High-strength concrete (HSC) is now widely used in bridge construction, and the seismic behavior of typical bridge piers being a key component needs to be assessed. This investigation aims to evaluate the seismic performance of HSC piers before and after retrofitting in association with the earlier research in Pakistan on low-strength concrete prototypes. An experimental program was executed wherein scaled-down (4 : 1) HSC (6192 psi) RC bridge pier prototypes with axial load at the top were subjected to quasistatic cyclic loadings (QSCLs) under controlled drifts. The damaged pier prototypes were retrofitted with CFRP sheets beside another set of undamaged retrofitted models. The samples were tested under QSCL against several drift levels ranging from 0 to 5%. Hysteresis loops were drawn for each sample. The tests were studied for the assessment of the structural behavior of the prototypes. The results for the control models, damaged retrofitted models, and undamaged retrofitted models of low-strength concrete (LSC, 1800 psi and 2400 psi) obtained from doctoral research by Ali and Iqbal were compared with corresponding models of high-strength concrete (6192 psi). The outcomes clearly show a noteworthy increase in lateral load carrying capacity, ductility, strength, and energy absorption on an increase in concrete strength and retrofitting of the prototypes. The numerical modeling of these piers was in consistence with the experimental results. When retrofitted with CFRP, the existing bridge piers will enable the bridge stock to withstand high-intensity future earthquakes and lessen their seismic vulnerability against prospective damages.