Seismic performance of exterior beam-column joints constructed with engineered cementitious composite: Comparison with ordinary and steel fibre reinforced concrete

Joint and plastic hinge regions of a ductile frame structure must be carefully detailed to ensure that the required ductility could be provided as intended, particularly when a high level of ductility is aimed for. However, the stringent detailing requirements for ductility often result in densely spaced transverse reinforcement which adds to construction difficulties. This paper presents an attempt to relax some requirements in transverse reinforcement spacing in the joint and potential plastic hinges of ductile moment-resisting frame structures using a damage-tolerant concrete known as the engineered cementitious composite (ECC). Results of reversed cyclic loading tests on two ECC beam-column joints are presented and compared with the response of companion specimens constructed with ordinary and steel fibre reinforced concretes (SFRC). Detailed documentation of key seismically important features is presented, along with a series of digital crack maps to provide a fuller understanding of the evolution and extent of damage under loading. It is shown that the seismic performance of the ECC specimens with relaxed detailing was similar and, in some cases, better than the companion concrete specimen which was designed in accordance with seismic design provisions. The ECC specimens displayed a considerably thicker hysteresis response with less pinching and smaller residual drifts, whereas the SFRC specimen retained a similar overall profile of the concrete joint. Throughout the testing, it was found the joint in the ECC specimens remained intact, while that in the concrete specimens displayed severe cracking under large displacement reversals.