Experimental study on the seismic performance of precast segmental unbonded post-tensioned frame piers

Abstract

Prefabricated assembly technology offers significant benefits for the construction of urban bridges, including shortened construction periods and reduction of traffic congestion. It can be used to construct precast concrete structures that are capable of withstanding seismic loads. However, studies on the seismic performance of precast segmental unbonded post-tensioned frame concrete piers are lacking. Therefore, there is an urgent need to evaluate the seismic performance of piers under different prestressing degrees. In the study, three prefabricated frame concrete piers were designed and subjected to quasi-static tests: unbonded post-tensioned tendons (UPT) with the prestressing degrees of 0.5 and 0.7 combined with grouted splice sleeves (UPT-0.5 specimen, UPT-0.7 specimen); and grouted splice sleeve connection (a reference specimen PC-S). The seismic performance of the UPT-0.5, UPT-0.7, and PC-S specimens was evaluated based on various evaluation indexes such as bearing capacity, residual displacement, displacement ductility, displacement of column segments, stiffness degradation, and energy dissipation (ED) capacity. The test results showed that the three piers exhibited flexural failure; however, the damage to the UPT-0.5 specimen was the most severe. With the increase of prestressing force, the hysteresis curve of the UPT-0.7 specimen was greater, the yield load and peak load of UPT specimens both increased by more than 18%, the initial stiffness and failure stiffness increased by more than 10%, but the impact on the ductility, residual displacement, and displacement of column segments was relatively small. At the end of the test, the cumulative energy dissipation (ED) values of specimens UPT-0.5 and UPT-0.7 were 76% and 53% lower than those of the PC-S specimen, respectively. The combination of grouted splice sleeves and unbonded post-tensioned tendons endows precast segmental frame piers with the characteristics of rapid construction and excellent self-centring ability. These characteristics are particularly advantageous for the efficient post-earthquake rehabilitation of urban bridges in low-to-medium seismic areas.