Influence of connection type on the effectiveness of CFRP wraps in seismic repair of precast GFRP-reinforced concrete columns

Abstract

The growing demand for accelerated construction and durable, low-maintenance structures has increased interest in precast concrete systems reinforced with glass fibre-reinforced polymer (GFRP). To support wider adoption, various connection systems have been developed to meet project requirements. Under seismic loading, damage is typically limited to the concrete, with severity depending on the connection type. Despite this, these structures generally exhibit limited residual drift and remain repairable after strong earthquakes. However, their post-repair behaviour remains insufficiently understood, limiting confidence in the long-term safety and resilience of repaired structures. To address this gap, this study investigates the structural performance of repaired precast column-to-footing connections under seismic loading and compares it with that of the original specimens. The connections include a corrugated duct connection (GCDC), a pocket connection with a non-contact lap splice filled with engineered cementitious composite (ECC), and bolted connections with stainless steel bolts of varying sizes. The specimens were repaired using patch mortar and confined with two layers of carbon-fibre-reinforced polymer (CFRP) wraps at the connection region. The results showed that the repair method was effective in nearly restoring the lateral capacity of bolted connections, while GCDC exceeded the original by 32 % and the pocket connection was 9 % lower. In addition, the drift capacity of the repaired systems, defined as the drift at the point corresponding to the peak load, outperformed the originals. The GCDC reached 10 % drift versus 3.2 % originally, the pocket connection 8 % versus 4 %, and bolted connections up to 8 %, compared to 5 % and 3.2 % for the original connections with larger and smaller bolts, respectively. The failure mode of all the repaired systems was improved, with the failure zone shifting away from the repaired region. This resulted in a gradual flexural failure, particularly mitigating the sudden failure observed in the original bolted connections. Finally, the repaired specimens were able to dissipate 1.96–2.38 times more energy than the originals, although the initial stiffness was only partially restored to 83–92 % of the original. Overall, the proposed repair method restores and improves the seismic performance of precast GFRP-RC structures with different connections, providing a reliable approach for post-earthquake repair.