Laboratory Evaluation of Alignment Tolerances for Dowel Bars and their Effect on Joint Opening Behavior

This report presents an experimental and analytical investigation on the fundamental pullout behavior and joint opening behavior of misaligned dowel bars in concrete pavement joints. Experimental investigations were conducted to determine the fundamental joint opening behavior of concrete pavements, and to evaluate the effects of dowel misalignment on joint opening behavior. The parameters included in the experimental investigations were the number of dowel bars (1, 2, 3, or 5) at the joint, the dowel misalignment type (horizontal, vertical, and combined), misalignment magnitude (0, 1/36, 1/18, 1/12, 1/9 radians.), and uniformity across the joint. The effects of these parameters were evaluated on the joint opening behavior and structural distresses observed in the specimens. Numerous instrumented laboratory-scale specimens of pavement slabs with doweled joints were tested. The second task focused on the development of 3D finite element models for computing the complex stress states and resulting damage in concrete pavement joints with misaligned dowels, and their validation using experimental results. The concrete pavement is modeled using a damage-plasticity material model, which uses concepts of damaged plasticity formulation in compression and cracking combined with damage elasticity in tension. The longitudinal bond between the steel dowel and the concrete is modeled in two parts. (i) The longitudinal bond resulting from chemical adhesion, mechanical interlock, and static friction (in the aligned state) is modeled using spring elements. (ii) The longitudinal bond resulting from transverse interaction between steel dowels and the concrete pavement is modeled using surface-to-surface contact-interaction elements and associated friction models. The 3D finite element models are validated using results from the experimental investigations. These validated models provide significant insight into the 3D stress states and principal stresses that develop in concrete pavement joints with misaligned dowels. They are used to evaluate analytically the effects of misalignment type, magnitude, uniformity, and distribution on the 3D stress states and resulting damage in concrete pavements. The analytical results (3D stresses and strains) from the finite element analyses were considered to identify significant limit states and distresses in the concrete pavement joints. Parametric studies were conducted and recommendations on misalignment tolerances based on these parametric studies have been made. A preliminary investigation to capture the effects of misaligned dowel bars combined with wheel loads has also been carried out in this research study.