Shear friction capacity of monolithic construction joints reinforced with self-prestressing reinforcing steel bars

Abstract

This study examined the shear friction capacity of a monolithic concrete interface reinforced with newly developed self-prestressed reinforcing steel bars (SPRBs). Twelve push-off specimens with SPRBs were prepared according to the different compressive strengths of concrete (f′c) by applying compressive stresses (σx) on a monolithic concrete interface. To compare the shear friction capacities of monolithic concrete interfaces reinforced with conventional reinforcing bars, four companion specimens were prepared. The test results showed that the shear cracking and shear friction capacities were high for specimens with high f′c and σx values, resulting in the highest values for specimens with f′c = 40 MPa and σx = 0.5fy, where fy is the yield strength of the reinforcing steel bar. The test results confirmed that at a similar (ρvffy+σx)/f′c, a σx of more than 0.35fy is required for the SPRBs to achieve a λn value comparable to that of the specimens reinforced with conventional reinforcing bars, where ρvf is the transverse reinforcement ratio and λn is the shear friction capacity. The prediction models ACI 318-19 and AASHTO significantly underestimated the shear friction capacity with low accuracies. In particular, the difference between the experimental and underpredicted values became large as the (ρvffy+σx)/f′c value increased. However, the Mattock's model well-estimated the measured shear friction capacities of all the specimens tested in this study, irrespective of ρvffy and σx. Thus, the mean and standard deviation values of the measured-to-predicted shear friction capacity ratio were 1.07 and 0.13, respectively.