Experimental Performance Assessment of Large-Scale Polyurethane-Enhanced Damage-Resistant Bridge Columns with Energy Dissipation Links. Ⅰ: Overview and Damage Assessment

摘要

This paper, which is the second of two companion papers, presents the results of a large-scale testing program on a novel bridge column design, termed polyurethane (PU)-enhanced rocking column with energy dissipation (ED) links. The experimental program included cyclic testing of large-scale (approximately 1:2.5) cantilever bridge columns, including (1) a rocking-only precast concrete column, which served as the reference column, (2) a PU-enhanced rocking column with a solid PU segment, and (3) a PU-enhanced rocking column with an axisymmetrically bilayered segment with an exterior PU layer to withstand seismic loads, an internal reinforced concrete core to sustain long-term gravity loads, and external ED links to provide energy dissipation and flexural stiffness and strength. The specimens were subjected to displacement-controlled lateral cyclic loading of increasing amplitude (exceeding a 10% drift ratio) at several drift ratio rates (up to 1 s(-1)). The tested PU column with ED links was further repaired via ED link release and retightening-the yielding of the ED links was small and did not justify replacement-to demonstrate its rapid reparability characteristics. The repaired column was subsequently retested to demonstrate that the original column properties had been practically recovered. This second companion paper experimentally quantifies the performance of all designs in terms of strength, ductility capacity, self-centering and energy dissipation capabilities, posttensioning losses, and ED link fracture capacity. It also quantifies the capability of ED link release and retightening (and, by extension, ED link replacement) in eliminating residual deformations and recovering the mechanical properties of the original/undamaged system. Compared to conventional RC rocking-only columns, the proposed PU-enhanced column design with ED links demonstrated higher energy dissipation and self-centering capabilities, while release and retightening of the ED links eliminated the residual deformations and resulted in the recovery of the mechanical properties of the original/undamaged column. While ED link release and retightening (i.e., ED link reuse) is adopted in this study, because the yielding of the ED links was small, as verified herein by the practically identical response of the original and repaired column, it can be deduced that ED link replacement (i.e., use of new/pristine ED links) would also restore the original column properties and eliminate residual deformations. (C) 2021 American Society of Civil Engineers.