Fiber orientation factor on rectangular cross-section in concrete members

In order to predict the post-cracking tensile behavior of fiber reinforced concrete, it is necessary to evaluate the fiber orientation factor which indicates the number of fibers bridging a crack. For investigation of fiber orientation factor on a rectangular section, in this paper, dog-bone fiber reinforced concrete specimens were prepared with the variables of concrete compressive strength, rectangular cross-section size, fiber type, and fiber volumetric ratio. After direct tension tests, the fiber orientation factor could be evaluated through counting the number of fibers on a crack. From the test results, it was investigated that the fiber orientation factor was larger than 0.5 which is generally adopted for large members, as fibers distribution is affected by the specimen size. For rational prediction of the fiber orientation factor on a rectangular concrete section, a simple model was derived from the Diverse Embedment Model (DEM), which is a rigorous model to predict the tensile behavior of steel fiber reinforced concrete. From the comparison of the measured data and the predicted values, it was found that the actual fiber orientation factor was well predicted by the proposed model.