Existing reinforced concrete slab strengthening by reinforced spray mortar and shear connectors

초록

Reinforced spray mortar is an effective and convenient method for enhancing the structural performance of existing slabs. However, interface slip between a slab and reinforced spray mortar should be prevented to ensure composite behavior. Four existing slab specimens were tested under two-point vertical loading to verify the proposed strengthening method using spray mortar. The test parameters were the application of reinforced spray mortar and the installation method of shear connectors. Based on the test results, the initial flexural stiffness and peak strength of an existing slab were increased by using the reinforced spray mortar. However, interface slip between the existing slab and reinforced spray mortar occurred at a small vertical deflection of delta = 10.11 mm. In contrast, in the specimens with shear connectors, the peak strength increased and flexural yielding occurred without interface slip. Based on the test results, a parametric study was conducted using a finite element model to investigate the effects of the design parameters on the interface shear resistance mechanisms of an existing slab reinforced with spray mortar. According to the analysis results, as the number of shear connectors or reinforcement ratio of the existing slab increased, the horizontal shear strength of the interface increased. Furthermore, regardless of the number of shear connectors or the reinforcement ratio of the existing slab, interface slip occurred in a critical curvature range of phi= 0.014-0.036 1/m. Based on the test and parametric analysis results, the horizontal shear strength of the interface with shear connectors was evaluated.

키워드