Development of tension-stiffening model for the analysis of UHSFRC structures considering bond-slip effect

Abstract

This thesis presents analytical models to simulate the cracking behavior of reinforced concrete structures composed of normal strength concrete and ultra high strength concrete. The concrete behavior is designed by an orthotropic constitutive relationship presented in the axes of orthotropy, which coincide with the principal axes of the total strain, and rotate according to the loading history. An equivalent uniaxial stress-strain relationship with the tension-stiffening and compression-softening effects is also used for an effective simulation of the inelastic behavior induced from the concrete cracking. The proposed analytical models are composed of three kinds of models. Two models introduced in this thesis are slip models, namely, the anchorage slip model and shear connector slip model, which represent the bond-slip effect in structures. Because consideration of the bond-slip effect is virtually impossible in the finite element analysis as the reinforcing steels are uniformly distributed though the entire domain, slip models to implement the bond-slip effect are developed through this study. For the case of the anchorage slip model, a relationship between the steel stress and end-slip derived from an idealized pull-out specimen is implemented at the end face of RC structures instead of using the bond-link elements that connect the concrete and steel nodes with the spring elements along all steel elements. For the case of the shear connector slip model, condensed elements obtained from the condensation between the slab and spring elements are applied to the interface in a composite beam. The last proposed model is the tension-stiffening model of the ultra high strength fiber reinforced concrete beam. Since the engineering material properties of ultra high strength concrete are remarkably different from those of normal strength concrete, some mechanical characteristics, from the designation of the basic material properties such as the uniaxial stress-st...