Precast concrete connections for alleviating reinforcement congestion: A state-of-the-art review

Abstract

In prefabricated structures, densely distributed stirrups and splicing of longitudinal reinforcement extending from precast components can result in rebar congestion in precast concrete connections, obstructing the assembly of precast components and proper concrete compaction. To address these issues, five types of joint details less susceptible to reinforcement congestion have been thoroughly reviewed. Mechanical connectors, as a substitute for lap splices of protruding rebars, are incorporated in dry and hybrid connections, which exhibit semi-rigid behavior under seismic loading. Notched connections, typified by evenly spaced notches at the side surfaces of precast components, employ post-installed connecting bars to replace projecting reinforcement. Design guides for notch geometry and anchorage length of connecting bars inserted in notches were proposed based on pull-out test results. Precast rocking systems with self-centering capability can be established by unbonded post-tensioning, which clamps structural components together without the necessity for rebar splicing. Energy dissipation is achieved by metallic, viscoelastic, or friction dampers. Furthermore, the ultra-high bond strength of reinforcing bars anchored in UHPC allows for short lap-spliced joints, while employing ECC as grouting materials enhances joint confinement and shear strength, enabling a reduction or total elimination of stirrups in precast concrete connections. Reinforcement congestion can be also relieved by separating beam-to-column connections into beam-to-beam and column-to-column joints, which effectively reduces the amount of reinforcement intersecting in the joint core.