Prediction of Dowel Action against Concrete Core without Consideration of Transverse Reinforcement

Abstract

In this study, reinforcing bars acting as dowels were investigated. Direct shear tests on specimens with a wide range of strengths for concrete (30 and 60 MPa) and steel (400 and 600 MPa) were conducted. Furthermore, finite-element (FE) models with selected concrete and steel material models, such as damage plasticity and ductile damage models, were developed. The existing predictive equations tended to show either larger or smaller maximum dowel forces depending on the size of the dowel. Such results were obtained because consideration of the effect of dowel action in design equations for interface shear transfer were originally based on the bending resistance of the reinforcement rather than splitting failure of the concrete body. This is justifiable, because in many practical situations splitting failure is prevented by the presence of confining reinforcement or by sufficient edge distance. The different results between the predictive equations and test data for maximum dowel force were minimized by calibrating the weight factor of the dowel bars. Accordingly, new equations are proposed to improve the accuracy of maximum dowel force and the corresponding slip; the new equations use data from the tests, analytical results for the current model, and from the literature. To estimate the maximum dowel forces, different coefficients were proposed depending on the failure mode and yield strength of the dowel bar. The average absolute difference ratios for the maximum dowel force and slip from a 400-MPa dowel bar were improved from 29% to 13% and 49% to 21%, respectively. The newly developed model successfully predicted the overall behavior of dowel action in a concrete structure without transverse reinforcement.