Modelling the flexural behavior of reinforced-fiber-reinforced concrete members

Incorporation of concrete tensile behavior is necessary to evaluate the flexural strength of Reinforced Fiber Reinforced Concrete (RFRC) structural members. Similarly, traditional analysis models do not include the ability to model the increased FRC ductility in compression. A key step in developing analytical tools for RFRC is the formulation of a more general and powerful analysis tool to evaluate the flexural behavior of such members and can be extended to the a beam-column member. A computer model named LAYER has provided this capability to evaluate the capacity of a general RFRC section using general compressive and tensile stress-strain distributions and has the capability to develop the interaction diagram for any given RFRC member.; Program LAYER was first used to extract the tensile stress-strain distributions from the detailed load versus deflection data available from some well-conducted modulus of rupture tests of FRC using a step-wise trial-and-error procedure.; In a parametric study for each combination of fiber type and volume content, including the no-fiber case, a series of beam shapes and sizes were studied using analyses by LAYER for each of several amounts of conventional reinforcement ranging from none through the balanced amount. From the moment curvature beams' behavior, for lightly reinforced beams, the tensile stress-strain properties of FRC are most important in the fibers effect on beam response, with the maximum moment resistance occurring soon after yielding of the conventional reinforcement and before significant pullout of fibers has occurred. For beams with the higher reinforcement ratios, the increased compressive ductility of FRC is dominant in the determining the strength and ductility increases achieved with FRC. The maximum moment resistance in such cases occurs at a maximum compressive strain higher than 0.003 used with conventional concrete. For the interactive diagram, the curves shape are largest near the balanced conditions and when the increased compression ductility of FRC is recognized through the use of a of a larger maximum concrete strain value.