Abstract:The splitting tensile test is a much used method to determine the tensile strength of concrete. The conventional test procedure is known to have a number of limitations related to size effect and boundary conditions. Furthermore, it has been reported to be impossible to determine the tensile strength of Fibre Reinforced Concrete (FRC) using the standard splitting tensile test method. The objective of this paper is to present a methodology to obtain a close estimate of the true tensile strength of FRC from an adjusted tensile splitting test procedure. Splitting tests were performed on cylindrical specimens of four FRC mixes. The transversal deformation perpendicular to the load direction was recorded during the tests. The experimental load-deformation curves thus obtained have two peaks, an initial one as a result of the tensile stresses at the centre of the specimen and a second peak due to secondary cracking outside the loading axis. The tensile strength can be calculated from the first peak which represents the elastic limit state for the material. The method is validated through numerical simulation of the splitting tests using a cohesive crack approach. It is concluded that it is possible to obtain a close estimate of the true tensile strength of FRC using the procedure developed in the paper.

In this paper a simple, but effective methodology to simulate opening mode fracture in high performance fibre reinforced concrete is presented. To obtain the specific fracture energy of the material, load-deflection curves from three point bending (TPB) experiments are extrapolated. The proposed extrapolation technique is an adaptation of an approach originally developed for plain concrete. The experimental part of the paper includes a size effect study on TPB specimens. The post crack behaviour of the material is modelled using a cohesive softening function with crack tip singularity. Numerical simulation of the experiments is performed by means of an embedded discontinuity method. The simulation provides satisfactory predictions of the fracture behaviour of the material and the size-effect observed in the experiments.

Asphalt pavements exhibit viscoelastic behavior resulting in deflections, strains, and stresses varying with both temperature and traffic speed. For structural thickness design against fatigue cracking, the material response is typically assumed to be linear elastic to simplify the calculation of the critical horizontal strain at the bottom of the asphalt layer. An asphalt modulus representing the response of the materials under average conditions for both temperature and traffic speed is generally adopted in the simplified pavement model. This paper presents a method to determine an equivalent asphalt modulus (EAM) for the asphalt layer. The EAM, when used in the linear elastic analysis of a pavement, will result in a resilient response in terms of the critical strain criterion that is equivalent to the response of that structure when calculated using viscoelastic modeling. The methodology of this paper included a qualitative comparison of the EAM approach with published field results. Two thick asphalt pavement configurations representative of typical French pavement designs were considered in this paper. Results showed expected trends of the equivalent asphalt modulus with changes in traffic speed and temperature. The application of time–temperature superposition principle allowed building pseudo-master curves for the EAM dataset. The effect of different asphalt temperature and different traffic speed on the viscoelastic strains was qualitatively validated against the trends observed under full-scale testing.

Cracking is a major source of distress in hot-mix asphalt (HMA) pavements. Various approaches have been proposed to describe crack initiation and propagation in HMA. This paper evaluates a finite element analysis technique that uses the embedded discontinuity method (EDM) for model cracking. The purpose of this study is to identify the strengths and potential weaknesses of the approach and investigate its applicability in general crack simulation for HMA pavements. An alternative formulation of EDM is adopted to make the approach easier to understand. The cohesive-crack model is used to describe development of HMA cracking. Numerical examples are presented to demonstrate the ability of EDM to simulate uniaxial-tension, three-point bending, and semicircular beam bending tests. It is shown that EDM is a promising finite element analysis technique, but additional research is needed to make it more robust.