Flexural behavior of UHPC-filled longitudinal connections with non-contacting lap-spliced reinforcements for narrow joint width

Abstract

In this study, the longitudinal connections between precast concrete box girders were closure-poured by ultra-high performance concrete (UHPC), where were reinforced by three anchorage details of non-contacting lap-spliced reinforcements including straight bars, U-bars, and headed bars. UHPC made it possible to narrow the joint width because of its high mechanical properties. A testing procedure of four-point loading scheme was adopted to evaluate the flexural behavior of the UHPC-filled longitudinal connections. For comparison, the connections filled with fast-setting concrete (FSC) and self-compacting concrete (SCC) were also investigated. Experimental results indicated that 300-mm-width connections filled by UHPC materials efficiently accommodated the development length of lap-spliced reinforcements, performed a more deformable behavior, and obtained a higher flexural capacity. When a narrower joint width less than 200 mm was adopted, however, headed bars were not fully developed in UHPC-filled joint panels. UHPC-filled joint panels controlled interfacial cracks better and showed a 50% increase of cracking load than FSC-filled and SCC-filled joint panels. In terms of flexural capacity, the panels with U-bars exhibited the highest value, followed by those with headed bars and straight bars, regardless of different filling materials. A strut-and-tie model, considering the effective compressive strength and the effective height of concrete strut, was proposed to evaluate the flexural capacity of joint panels. The average ratio of experimental values to the calculated ones of all joint panels was 1.10.