Uniaxial concrete tension damage evolution using acoustic emission monitoring

The tension damage function is an important component in concrete constitutive models. However, it is difficult to experimentally establish the complete tensile response due to the brittle behavior of concrete. This paper utilizes an acoustic emission (AE) monitoring method to determine the strain energy release within the fracture process zone (FPZ) of concrete. A total of 12 specimens with three different concrete strengths were subjected to three-point bending tests. The fracture mode, micro cracking initiation and propagation, strain energy release and macro-crack development of the specimens were identified by the AE technique. Based on the definition of the proposed tension damage function, an empirical expression was developed by using the strain test data in the FPZ and the monitored AE energy data. The proposed model is validated using experimental data from uniaxial monotonic and cyclic loading tests as well as comparison with existing models in the literature. The results show that the proposed model can reliably predict the strength, softening branch, unloading and stiffness degradation of concrete in uniaxial tension.