Experimental and numerical investigation on the dynamic performance of cast-in-place and precast hollow ultra-high piers under longitudinal impact

•Large-scale cast-in-place hollow ultra-high piers (CIPUHP) were tested under multiple longitudinal impact loads.•Large-scale precast hollow ultra-high piers connected with grouted sleeves (PCUHP-GS) were tested and compared with CIPUHP.•Under longitudinal impact loads, the CIPUHP and PCUHP-GS exhibited flexural failure, but the grouted layer and grouted sleeve joints in the PCUHP-GS remain as weak interfaces under impact.•The proposed simplified FE model can provide reasonably accurate predictions of the dynamic responses for CIPUHP and PCUHP-GS. The probability of bridge piers, particularly cast-in-place hollow ultra-high piers (CIPUHPs) and precast hollow ultra-high piers connected with grouted sleeves (PCUHP-GSs), being impacted by falling rocks has increased significantly in mountainous areas. In this study, two 1/20-scale hollow ultra-high pier (UHP) specimens were designed and manufactured to conduct impact tests using a pendulum system. The UHPs under longitudinal impact were compared and analysed in terms of the failure mode and dynamic response. On this basis, a numerical study was conducted on continuous rigid-frame bridges with hollow ultra-high piers (CRFB-UHPs). The results show that both the CIPUHP and PCUHP-GS exhibit flexural failure at the impact point, but the grouted layer and grouted sleeve joints in the PCUHP-GS remain as weak interfaces under impact. Under the same impact velocity, the CIPUHP and PCUHP-GS exhibit the same impact force, owing to the unchanged local stiffness at the impact point. However, the PCUHP-GS exhibits greater deformation than the CIPUHP. Moreover, the energy-dissipation ratios are smaller for the CIPUHP bridge (69.3 %) than for the PCUHP-GS bridge (75.3 %), owing to cracking in the grouted layer. The bending moment at the grouted layer in the PCUHP-GS bridge is also smaller. In addition, the proposed simplified numerical model of the CRFB-UHP can achieve an 87.5 % improvement in computational efficiency and can be used in a parametric study on the impact performance of CRFB-UHPs. The parametric study results show that increasing the longitudinal reinforcement and stirrup ratios can effectively reduce deflection and local damage at the impact point. An excessively large axial load ratio may aggravate reinforcement buckling and increase deformation at the impact point, whereas increasing the interface failure strength of the PCUHP-GS can reduce residual displacements at the impact point.