Shake table testing of out-of-plane response of repaired bridge subassembly with simplified ABC-inspired cast-in-place joints

Abstract

Accelerated bridge construction (ABC) has been utilized in precast bridge structures because of its advantage to expedite on-site construction. In ABC, one of the main concerns is the joint connection as it needs to be well designed to maintain structural integrity. A recent study at the University of Nevada, Reno (UNR) was conducted to utilize ABC pocket connection concept in cast-in-place (CIP) cap beam-column bridge joint. The cap beam was constructed by having the cap beam longitudinal reinforcement bundled outside the pocket joint allowing the placement of the column reinforcement cage uninhibited. The specimen was tested in an inverted position at one of UNR’s shake tables and found to perform well under out-of-plane ground motion excitations, and the ductility of the column was confirmed through typical plastic hinge behavior. In this study, the specimen from the recent UNR test was further utilized by removing the damaged column in the cap beam through cutting and coring. A new column was constructed in the cap beam using the same reinforcement detailing from the original specimen. The repaired specimen was tested using the same loading protocol adopted from the 1994 Northridge earthquake as the original model. The objective of this study is to demonstrate that ABC-inspired CIP joints can provide a viable repair method after major earthquakes, where damaged columns can be replaced without affecting cap beam reinforcement. The repaired specimen performed well as the plastic hinge zone was developed in the column outside the joint, close to the interface of the cap beam, as desired and required by design. The cap beam remained essentially elastic, i.e. capacity-protected as required, throughout the test which is similar to the performance of the original model. High residual drift ratios were recorded at higher earthquake motions and were attributed to the slippage of the column in the joint. The paper also concludes with recommendations for the repair of CIP cap beam-column joints emulating ABC pocket connections.