ABSTRACT
The failure of constructions such as concrete buildings and bridges or cemented pavements due to mechanical impacts is one of the most noticeable problems in engineering in that it directly affects human safety, the usability of the constructions, and farther the economic efficiency of structural designs. Structural collapse is the collective results of localised fractures occurred at specific places in the structure encountering critical stress. At these localised positions, the behaviour of materials practically depends on their intrinsic features. Based on their mechanical responses, materials are categorised into three groups: perfectly brittle, quasi-brittle and ductile. Quasi-brittle materials are distinct from perfectly brittle materials by the present of gradual reduction of load carrying capacity after reaching a peak stress. This phenomenon has been observed in many experiments (Carol et al., 2001, Carpinteri et al., 2003, Ouyang and Shah, 1991). In fact, the residual response of quasi-brittle materials is associated with the propagation of micro-cracks and the frictional interaction of micro-cracked surfaces. These mechanisms are in turn determined by the microstructural properties of the materials.
