Precast column-to-foundation specimens using grouted corrugated steel conduits were tested under cyclic lateral load combined with axial compression by Belleri and Riva and Popa et al. Research studies to address the aforementioned concerns and the use of grouted noncontact lap splices in plastic hinge regions of structural elements have been completed in recent years. Similarly, ACI 318-14 specifies that application of such splices in plastic hinge requires demonstration through laboratory testing that the spliced precast structural element shows an equivalent response to its cast-in-place counterpart. In China, the connection of this type is not recommended to be used in primary earthquake-resistant members. The continuity of the longitudinal reinforcement is achieved through the noncontact lapping when the lower projecting bars are inserted and grouted into the corrugated duct. The steel conduits are positioned adjacent to the embedded longitudinal bars. The connection system (Figure 1) is based on the use of consecutive column segments provided each with longitudinal bars protruding from the upper end and corrugated steel conduits encased in the lower end. Rebar lapping in grout-filled conduit is enormously used in construction of precast concrete structures. Based on the experimental results and the development length specified in ACI 318-14, a revised equation with a reduction factor of 0.76 was proposed to predict the required minimum lap length of spirally confined lap splice. Compared with the spiral bar diameter, the spiral pitch distance provides more dominant effect on the tensile strength of the connection. As the spiral pitch distance is not greater than 75 mm, the tensile strength generally improves with the increment of volumetric spiral reinforcement ratio due to the higher confinement provided by the spiral bar. The experimental results show that bond failure splices are always failed by the pullout of the preembedded bar other than the grouted bar. Deformed bars lapped through a grout-filled corrugated duct, and a spiral reinforcement was preembedded in the connection to improve tensile strength of the splice. The results also confirm the applicability of the method for strengthening lap-spliced regions of wide elements-such as slabs, shear walls, and wall-bridge piers-without having to provide any confinement.This paper discusses the behavior of grouted noncontact lap splices under monotonic tension load. The results demonstrate that an appropriate casting method combined with a self-compacting UHPFRC with an appropriate fiber content ensure the efficiency of the strengthening technique for providing for the continuity of lapped bars and for enabling a high ductility capacity under monotonic or cyclic loading. The levels of ductility reached for the highest fiber content meet the requirements for high ductility demand, such as in seismic design. The result indicates that UHPFRC with a fiber content of 2 or 3% can significantly increase the bond strength of splice bars without confinement. The beam specimens are tested at four points, bending with a constant-moment region along the splice length. For isolating the UHPFRC contribution, the splice regions are free of any confinement. One type of fiber, three fiber contents, two bar diameters, and two bar arrangements are considered. The strengthening technique consists of replacing normal concrete around lapped bars in the splice region by UHPFRC, which allows for keeping the original member geometry. Specimen reinforcement consists of two pairs of deformed bars spliced at midspan on both tension and compression faces. The objective of this experimental work is to determine the efficiency of this strengthening technique on wide flexural elements (beams, slabs, walls, or wall columns) subjected to reverse cyclic loading. The experimental program is based on the findings of previous test series carried out in the same research program that demonstrated the ability of UHPFRC to eliminate bond failure in deficient lap splices of beams and wall-type bridge columns. The cyclic behavior of six full-scale reinforced concrete (RC) beams with a deficient lap splice strengthened with ultra-high-performance fiber-reinforced concrete (UHPFRC) is experimentally investigated.
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