DEVELOPMENT OF A PLASTICITY BOND MODEL FOR STEEL REINFORCEMENT

The development of an interface, non-associative, plasticity model for bond between ribbed, steel bars and concrete is discussed. The model relates average local slip and radial dilation to average bond shear s tress and radial confinement stress. The model partially accounts for the response of the damaged, finite-thickness region around the bar-th e bond zone. The model is developed for standard steel bars that are i nitially unstrained. With simplifying assumptions, data for the compon ents of a plasticity law are extracted from a key set of experimental results. In this paper, we emphasize the development of an expression for the yield surface for monotonic loading. While the forms of the mo del's components are empirically derived, they qualitatively reflect t he mechanics of the mechanical interaction of ribbed bars with the adj acent concrete. A characteristic length, related to the rib pattern, h elps quantify this interaction. The mechanics of the bond are difficul t to characterize in a simple form, but the calibrated model only requ ires four physical properties and reproduces with acceptable accuracy experimental results with various levels of radial confinement stress. Model refinements are suggested for future work. (C) 1998 John Wiley & Sons, Ltd.