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×1800 mm×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.

Dynamic Deformation Behaviors and Constitutive Relations of High-Strength Weldox700E Steel

High-strength Weldox700E steel has been increasingly applied to dynamic environment because of its high strength and good toughness. The plastic deformation behaviors of Weldox700E steel at strain rates ranging from 10^-4 to 6200 s^-1 are investigated by the quasistatic and dynamic uniaxial compression tests. The Weldox700E steel exhibits rate-related plastic behavior, work hardening and thermal softening behaviors. Due to the nonlinear strain rate effect of the material and the adiabatic temperature rise caused by high-speed impact compression, the properties of material are greatly affected. By improving the strain rate enhancement term and temperature term in the Johnson-Cook constitutive model, a new constitutive model was proposed to describe the dynamic mechanical behavior of Weldox700E steel. This constitutive equation was implemented into the finite element software, ABAQUS, via an explicit user material subroutine utilizing the stress update algorithm. The simulation results at different strain rates were in good agreement with the experimental data, verifying the validity of the constitutive model.