Numerical Analysis On The Seismic Performance Of Precast Segmental And Hybrid Bridge Columns

Earthquakes have been a significant concern for bridge structures due to their complex and destructive nature.The increasing rate of severe earthquakes has propelled the engineers to look for alternative bridge design and concepts to mitigate these concerns.Due to the lack of design codes and knowledge about the performance of precast columns,the application of segmental piers is limited to low-medium seismic regions.The need for designing and analyzing structural systems that can perform efficiently in high seismic regions is becoming a necessity due to the constant threat imposed by intense earthquakes.This research investigates the seismic performance of prefabricated segmental bridge columns(PSBCs)with hybrid post-tensioned tendons and energy dissipation(ED)bars.PSBCs with unbonded,hybrid bonded prestressed tendons and columns incorporating ED bars were designed to improve the lateral strength,energy dissipation and limit the residual drift.The PSBCs under cyclic loading was investigated by using three-dimensional finite element(FE)modeling platform ABAQUS.The FE model was calibrated with experimental results with an overall error of less than 10%.The seismic performance of the proposed PSBCs was evaluated based on critical parameters,including lateral strength,residual plastic displacement,and energy dissipation capacity.The results show that bonding the tendons in the plastic hinge region as opposed to the overall bonding along the column leads to better cyclic performance.The lateral strength and recentering abilities are further improved by bonding tendons 75% in the plastic hinge region along with 100-300 mm in the footing.It was also found that selecting a longitudinal length of ED bars crossing multiple precast segmental joints and having a circumferential spread of 70-90% of core concrete results in higher bearing capacity,energy dissipation as compared to ED bars crossing the single joint.The emulative hybrid bridge columns(HBCs)combining the structural configurations of monolithic bridge columns(MBCs)and precast segmental bridge columns(PSBCs)were designed.The comparative analysis between HBCs and PSBCs under cyclic loadings were carried out to study the influence of different design parameters on the cyclic performance of these precast column systems.The parameter of interest included axial load ratio,post-tensioned tendon area,the combined influence of the orientation of post-tensioned tendons and increasing axial load ratio,and influence of hybrid post-tensioned tendons.HBCs at various axial loads were found to perform better than their PSBCs counterparts.The energy dissipation capacities and lateral strengths of HBCs were found to increase profoundly.The combined analysis of axial load ratio and positioning of post-tensioned tendons highlighted that,when the axial loads were limited under1.5,post-tensioned tendons placed at geometric center displayed improved lateral strength and energy dissipation capacities in PSBCs.In contrast,when the axial load ratio was over 1.5,the post-tensioned tendons should be placed at the middle-and-edges to negate the strength degradation and drop in energy dissipation capacities.The post-tensioned tendons placed at the mid-section of HBCs exhibited extensive damage to the concrete and reinforcements,softening,and strength degradation of lateral curves.Therefore,the post-tensioned tendons should be placed at the middle-and-edges or only edges of piers to acquire efficient performance.Finally,the usage of hybrid bonded tendons in the HBCs showed a significant increase in the energy dissipated,but with much larger residual plastic deformations.