Experimental, numerical, and theoretical study of punching shear capacity of corroded reinforced concrete slab-column joints

Rebars in reinforced concrete (RC) slab-column systems are susceptible to corrosion in unfavorable environments, making slab-column joints (SCJs) more prone to punching shear (PS) failure. In this study, experimental, numerical, and theoretical studies of the PS capacity of corroded RC SCJs were conducted. Four RC SCJ specimens were constructed, and their reinforcement bars were exposed to accelerated corrosion using an electrochemical process. Subsequently, monotonic load tests were performed to determine the PS capacity of the RC SCJs with various corrosion levels. The test results demonstrated that rebar corrosion significantly reduces the PS capacity of the SCJs. Based on this outcome, an extended numerical study is executed to get a broader understanding of the corrosion effect on RC SCJs. A finite element model was devolved using Abaqus software, and the accuracy of the model was validated by the results of the four experimental specimens in the current study. Additionally, experimental results of large-scale specimens from the literature were also used to validate the numerical simulation. A two-level factorial design (TLFD) was used to examine the main and interactive parameters influencing the PS capacity and the ultimate deflection of the corroded RC SCJs. The parameters that were considered are the corrosion ratio, corrosion area, column rectangularity, slab thicknesses, reinforcement ratio, compressive strength of concrete, yield strength of reinforcement, and supporting distance. Based on the TLFD, the numerical parametric study was performed. The results of the numerical study show that corrosion can change the failure mode of the joints from flexural failure to punching shear failure and significantly reduces the PS capacity. The results indicate that increasing the rebar corrosion ratio or the corroded zone size decreases the PS capacity of a corroded SCJ. While increasing the slab thickness reduces the negative effect of rebar corrosion on the PS capacity. In addition, increasing the reinforcement ratio has a slight impact on improving the PS capacity. However, increasing the column rectangularity decreases the PS capacity of a corroded RC SCJ significantly. Based on the results of the experimental and numerical studies, an analytical model was developed to predict the punching shear capacity of the corroded RC SCJ. The reliability of the developed model was verified through the comparison with four different code provisions: ACI 318-19, CSA 23.3-14, BS 8110-97, and Eurocode 2, and three empirical models from the literature.