Punching shear behavior of steel fiber reinforced recycled coarse aggregate concrete two-way slab without shear reinforcement

In this paper, the punching shear performance of 8 steel fiber reinforced recycled coarse aggregate concrete (SFRCAC) two-way slabs with a size of 1800 mm x 1800 mm x 150 mm was studied under local concentric load. The effects of RCA replacement ratio (rg) and SF volume fraction (Vf) on the punching shear performance of SFRCAC two-way slabs were investigated. Digital Image Correlation (DIC) measurement and Acoustic Emission (AE) technique were introduced to collect pictures and relevant data during the punching shear test. The test results show that the SFRCAC two-way slab mainly exhibits punching shear failure and flexure failure under local concentric load. The punching shear failure space area of SFRCAC two-way slab has no obvious change with increasing rg, however, show a gradual increase trend with increasing Vf. Both of the punching shear ultimate bearing capacity (Pu) and its deflection of SFRCAC two-way slab decrease with increasing rg and increase with increasing Vf, respectively. Finally, through the regression analysis of the results from this study and the data collected from related literature, the influence of rg and Vf on the Pu of two-way slabs were obtained, and the equations in GB 50010-2010, ACI 318-19, and Eurocode 2 Codes were amended, respectively. Furthermore, the amended equations were all applicable to predicted the ultimate bearing capacity of the ordinary concrete two-way slab, RCAC two-way slab, SFRC two-way slab, and SFRCAC two-way slab.