Bend Beam Method for Determining Fracture Behavior of Concrete: II. Performance of the Fracture Models

Abstract

In this paper, test results and analytical data of other researchers were compared with those predicted by the fracture mechanics model based on bend beam method presented in the previous publication [1]. Although a large number of bend beam tests of concrete have been reported, the load vs. deflection responses and load vs. crack-mouth-opening displacement (CMOD) responses were rarely published in details. As investigated by researchers, error in load-line deflection measurement greatly affects the fracture energy (G_F) and the fracture parameters such as the critical crack length (a_c), the critical stress intensity factor (K_IC) and the critical energy release rate (G_C). Test data referred were selected to highlight the importance of the accurate measurement of the load-line deflections and also to verify the validity of the proposed fracture model. The analytical results concluded that a number of concrete fracture tests were carried out by using the erroneous measurements of beam deflections which often included the crushing at supports. By applying the reasonably assumed values of S₁for the true deflections and the empirically determined values of S₂ from the literature, the proper evaluation of the fracture behavior and the fracture properties of concrete can be obtained by using the load-CMOD response based on the proposed model.