ScholarWorks@성균관대학교

초록

This study conducted fundamental loading tests on rib-plus precast concrete slabs (RPSs) with cast-in-place (CIP) topping concrete subjected to combined flexure and shear. Each precast pretensioned concrete unit was prefabricated using slip-forming machine differing from the typical extrusion method to form a hollowed light-weight section. This automated fabrication technique allows providing shear reinforcements directly to concrete webs in a precast unit during section-forming process in factory. To evaluate the structural performance of composite RPS members, three specimens were carefully designed and fabricated, where one specimen was tested for flexural testing, and the other two were tested to investigate the shear strength including composite action between the precast unit and the CIP topping concrete. The flexural specimen showed a typical ductile response with substantial deformation capacity, and failure mode of the shear test specimens were dominated by diagonal tension cracking in concrete webs. The shear strength of the specimen, in which the lattice was fully anchored through both transverse and longitudinal reinforcing bars, was 17% higher than that of the specimen, where only longitudinal reinforcement bars were welded to anchor the lattice. This suggests that the placement of transverse reinforcement through the lattice enhances its anchorage within the member. Notably, the RPS unit and CIP concrete exhibited excellent composite performance even without any special surface roughening treatment on the RPS units before casting the CIP topping concrete. This study also presents nonlinear flexural analysis and shear capacity estimation models that account for the unique dimensional and non-uniform material properties of the RPS composite slabs. These models were validated by comparing with the experimental results, demonstrating that the nonlinear flexural analysis model accurately estimated the stiffness and capacity of the specimens with an average test-to-analysis ratio of 0.99. Moreover, the shear capacity model predicted the shear strengths of the composite RPS specimens conservatively, with an average ratio and a coefficient of variation (COV) of 1.12 and 0.18, respectively.

키워드