Parametric experimental investigation of unbonded post‐tensioned reinforced concrete bridge piers under cyclic loading

Abstract

The present paper investigates the cyclic performance of unbonded post‐tensioned reinforced concrete (PRC) rocking piers by a parametric experimental campaign. PRC rocking specimens are assembled by hybrid connections, containing an ungrouted post‐tensioned (PT) bar and grouted mild steel bars, that is, energy‐dissipation (ED) components. The properties of a benchmark PRC pier were defined according to a design procedure to control its strength, ductility, energy dissipation capacity, and self‐centering behavior. Five additional PRC piers with different ED bars amounts, initial PT force, and ED bars unbonded lengths were also tested to investigate the influence of these parameters on the cyclic performance. The test results show the superior cyclic performance of the PRC pier in limiting both damage and residual deformations. The parametric analysis highlighted that decreasing the initial PT force and/or ED bars amount enhances the PRC's ED capacity at the expense of the lateral force resistance and self‐centering behavior. Moreover, it has been observed that the influence of ED bars’ unbonded length only minimally affects the PRC pier's cyclic performance due to ED bars’ bond‐slip and concrete cover spalling of the pier shaft. Analytical models describing the PRC piers’ lateral force‐drift cyclic behavior were formulated and calibrated, showing a good agreement with test results for all specimens. The results and findings provide a valuable reference and solution for tailoring an efficient parameter recommendation of PRC rocking piers.

Enhanced Strategies for Seismic Resilient Posttensioned Reinforced Concrete Bridge Piers: Experimental Tests and Numerical Simulations

“…Figs. 1(d) and (e), respectively, show the final damage state of the pier base and force-drift cyclic response of a typical PRC bridge pier tested by Shen et al (2022b). This PRC bridge pier was identified as "Specimen PRC-P17.5E.79" in the previous experimental campaign, where 17.5 and .79 represent the initial PT force ratio (ηP = FPT_ini/fcAg, where FPT_ini is the initial PT force in the PT bar; fc and Ag are respectively the compressive strength of concrete and gross cross-sectional area of the pier) and the ED reinforcement ratio (ρED = AED/Ag, where AED is the amount of the ED bars), respectively.…”

“…It was designed to have ultimate strength and drift capacities superior to those of an equivalent monolithic RC pier as well as to improve the seismic resilience of the system. Five other PRC version models with different ED bars amounts, initial PT force, and ED bars unbonded lengths were also developed and tested by Shen et al (2022b) to investigate their influence on the pier's cyclic performance. Analytical models describing these PRC piers' lateral forcedrift cyclic behavior were formulated and further calibrated based on the test observations and results.…”

“…An unbonded length (Lu) was introduced at the pier-footing interface to avoid stress concentrations that could lead to the premature fracture of ED bars (Bu et al 2016b;Ou et al 2010;Wang et al 2018a). Lac and Lu were designed to be 550 mm and 250 mm, respectively, according to the procedure presented in Shen et al (2022b). The mortar bed in the PRC pier was cast by a 15 cm thick UHPC a to meet the design objective of keeping the mortar bed integrity for the rocking system (Shen et al 2021;Guerrini et al 2015).…”

“…Precast post-tensioned (PT) bridge piers can conform to the above needs (Piras et al 2022;Marriott et al 2009;Jeong et al 2008;Shim et al 2017;Bu et al 2016aBu et al , 2016bLi et al 2019;Shen et al 2022b;Ou et al 2010;Jia et al 2020) and also offer some intrinsic prefabrication advantages, that is, shortened construction periods, improved quality control, and reduced traffic disruption (Marsh et al 2011). This pier system incorporates PT technologies and energy dissipation (ED) solutions to control the rocking behavior and increase hysteretic damping.…”

“…The results highlighted that, compared with the conventional RC pier, the PRC is an effective and promising alternative solution, having stable ED and superior self-centering characteristics. The influence of some design parameters related to the ED and self-centering systems on the seismic response of the PRC pier was experimentally investigated by Shen et al (2022b). This study allowed the definition of design rules, including an optimal combination of initial PT force and ED amount.…”