Predicting Crack Widths In Frc/Reinforced Concrete Members Using Small Deformation Post-Crack Parameters

Fibers are now accepted as a means of reducing flexural and direct tension crack widths when used in combination with conventional reinforcement. However, methods used to predict in-service crack widths incorporate performance parameters for fiber-reinforced concrete (FRC) measured at much wider crack widths than those that occur in service. This may result in a discrepancy between tests and inservice behavior, especially for FRC mixtures exhibiting rapidly changing performance immediately after cracking. This investigation has examined whether the crack width at which FRC performance is measured in standard beam tests has an influence on the accuracy of crack width predictions using Model Code 2010, and whether these predictions are realistic for a wide range of fiber types. The results indicate that predictions based on post-crack residual strength appear reasonable for a wide range of fiber types, but that accuracy is improved if post-crack performance is assessed at a crack width that more closely approximates the narrow widths that occur in service.