Single Beam Specimens Research Articles

Cohesive fracture model for functionally graded fiber reinforced concrete

A simple, effective, and practical constitutive model for cohesive fracture of fiber reinforced concrete is proposed by differentiating the aggregate bridging zone and the fiber bridging zone. The aggregate bridging zone is related to the total fracture energy of plain concrete, while the fiber bridging zone is associated with the difference between the total fracture energy of fiber reinforced concrete and the total fracture energy of plain concrete. The cohesive fracture model is defined by experimental fracture parameters, which are obtained through three-point bending and split tensile tests. As expected, the model describes fracture behavior of plain concrete beams. In addition, it predicts the fracture behavior of either fiber reinforced concrete beams or a combination of plain and fiber reinforced concrete functionally layered in a single beam specimen. The validated model is also applied to investigate continuously, functionally graded fiber reinforced concrete composites.

DETERMINATION OF TENSION SOFTENING DIAGRAMS OF CONCRETE BY MEANS OF BENDING TESTS

The establishment of test methods for determination of the tension softening diagrams of concrete has been desired. In this contribution, following the discussions on the existing J-integral approaches a simple and handy test method for determination of the tension softening diagrams from bending tests on notched beams is proposed. The method has the following features: (1) the tension softening diagrams can be determined from a single beam specimen, (2) the method can be combined with the RILEM method for determination of the fracture energy GF, (3) only the load, the loading point displacement and the crack opening at the notch tip are necessary to be measured, (4) the second derivative of the potential energy is introduced to improve the accuracy of the estimation of the diagrams. The proposed method is applied to concretes including high strength concrete and light weight concrete to determine tension softening diagrams, and the validity of the method is certified.