Composite Beam Analogy Fracture Model for Concrete

A new model for the determination of fracture-mechanics parameters in concrete is developed. Application of this method requires merely knowledge of peak load and peak crack-mouth–opening displacement (CMOD) values. The interrelationship between the damaged and undamaged sections within the microcracked zone is drawn through an analogous composite beam section. The extent of damage material within the process zone is assumed to vary linearly from its maximum level at the crack tip all the way to the boundary of the undamaged section. Hence, the fracture-process zone is defined as a composite material with a linearly variable modular ratio within its boundary. By using this approach, it is possible to determine a number of important fracture parameters from the knowledge of peak load and CMOD at peak load alone. These parameters include the fracture-process–zone size ( r _p ), critical fracture-energy release rate ( G _IC ), fracture toughness ( K _IC ), and fracture energy ( G _F ). Furthermore, use of the proposed methodology makes it possible to construct the entire load CMOD, deflection diagrams from the peak load, and CMOD data alone. Fracture-mechanics parameters and load-displacement relationships obtained through analysis by the present approach compare very well with a number of available experimental results.