Shear strengthening effects of core-filling method for hollow-core slabs considering relative slip

Core-filling method has been actively utilized to improve the shear capacity of hollow-core slabs (HCSs). However, when a high shear force is applied, slip may occur at the interface between HCS unit and core-filling concrete due to a poor bond condition, which can significantly reduce the shear strengthening effect of the core-filling method. Nevertheless, there has been no relevant research that quantitatively measured the slip between HCS unit and core-filling concrete and investigated its impact on the reduction of shear capacity. Therefore, in this study, shear tests were performed on a total of six HCS specimens reinforced with core-filling concrete, where the compressive strength of core-filling concrete and the number of filled cores were set as the key test variables. During shear testing, the slip between HCS unit and core-filling concrete was measured so that the effect of slip on the shear capacity was discussed in detail. In addition, the shear capacities of the specimens were evaluated based on the structural codes and the partial interaction shear capacity model (PISCM) proposed by the authors in previous research. The test and analysis results indicated that, as the compressive strength of core-filling concrete or the number of filled cores increased, the shear capacity of HCS tended to increase. However, when slip occurred at the interface of filled cores, the improvement of shear capacity was reduced, suggesting that the shear strengthening effect of the core-filling method cannot be fully expected unless the composite performance of the HCS unit and filled cores is secured.