Seismic repair of deficient and code compliant bridge wall piers

Abstract

Reinforced concrete bridge wall piers constructed using older codes perform inadequately during strong earthquakes; deficiencies include short reinforcement lap splices, insufficient steel reinforcement in the longitudinal and transverse direction and seismic detailing. A half-scale wall pier with an aspect ratio of 4.0 was constructed using as-built reinforcement details conforming to older bridge codes; a second pier with the same dimensions was constructed using modern code seismic reinforcement details. A total of four quasi-static cyclic tests were conducted about the weak axis of the wall piers: (i) as-built pier, (ii) modern code-compliant pier, (iii) repair of as-built pier using mild steel NSM bars, horizontal CFRP anchors and CFRP jackets, and (iv) repair of modern code-compliant pier using a CFRP shell and vertical headed steel bars for plastic hinge relocation. The repair method for the as-built pier increased initial stiffness by 50% and load-carrying capacity by 73% with similar hysteretic energy dissipation; the repaired as-built pier reached a 4.0% drift ratio before failure. The repair method for the modern code-compliant pier increased initial stiffness by 31%, load-carrying capacity by 15%, and hysteretic energy capacity by 55%; the repaired modern code-compliant pier reached a 6.0% drift ratio before failure.