Transition from energy dissipative processes to displacement discontinuities during concrete failure

Abstract

Fracture in concrete beams is mainly governed by two processes: energy dissipation and discontinuous displacement fields or discrete cracks. In the existing literature, the fracture process in quasi-brittle materials, like concrete, is considered by either one of the two processes. In this study we discuss the simultaneous development of both types of fracture. Energy dissipation and crack openings are analyzed during the fracture development by acoustic emission and digital image correlation. The analysis of local failure processes thus indicates three processes which describes overall failure mechanism: (1) high energy dissipation domain during which energy release rate increases. (2) Continuum – dis-continuum phase where energy dissipation rate attains its maximum value, and (3) dis-continuum phase where energy dissipation rate drops and displacement discontinuities start increasing. A new approach is then presented to model fracture of concrete based on transient and steady-state behavior of a local damaging stress.