9 th International LS-DYNA Users Conference Simulation Technology (2) 8-53 Application of Dynamic Relaxation in Thermo-Elastic Structural Analysis of Highway Pavement Structures Samir N. Shoukry, Gergis W. William, Mourad Riad West Virginia University Morgantown, WV 26506-6103, USA Abstract This paper describes the application of the dynamic relaxation technique implemented in LS-DYNA in analyzing large transportation structures as dowel jointed concrete pavements under the effect of temperature variations. The main feature of the pavement model is the detailed modeling of dowel bars and their interfaces with the surrounding concrete using extremely fine mesh of solid elements, while in the bridge structure, it is the detailed modeling of the girder-deck interface as well as the bracing members between the girders. The 3DFE results were found to be in a good agreement with experimentally measured data obtained from instrumented pavements sections constructed in West Virginia. Thus, such a technique provides a good tool for analyzing the response of large structures to static loads in a fraction of the time required by traditional implicit finite element methods. Introduction Modeling concrete structures is very difficult because of the material and geometrical nonlinearity involved in such structures. For example, when modeling a concrete slab of a highway section, the interface between consecutive slabs must be modeled. If the adjacent slabs are joined using steel dowel bars embedded within the slab, this will create nonlinearity within the concrete slab. The same is true for a concrete bridge deck including steel rebar reinforcements or the interfaces with the steel girders. In general, when modeling concrete structures, their nonlinearity creates a situation that must be accounted for when choosing a modeling technique. A type of modeling focused on in this study involves the analysis of the interface between two connected concrete slabs joined by steel dowel bars, which has been modeled previously by various other researchers [1, 2]. Previous studies have made simplifications or assumptions by idealizing dowel bars as spring or beam elements. This approach ignores the dowel-concrete contact that leads to triaxial stresses near the edges of the slab [3]. Also, the contact interface introduces the axial dowel forces that will resist the concretes expansion and contraction due to temperature change that cause stresses to develop at the mid-slab [4]. In order to accurately model the stresses caused by the change in temperature, the contact interface between the concrete and the dowel must be accurately modeled. Accurately modeling the concrete-dowel interface requires a fine mesh around the dowel bar to accurately simulate the circular shape of the dowel. In the model demonstrated in this paper, a mesh of approximately 273,000 elements is used. Solving this problem using traditional implicit techniques is not practical because the calculation and recalculation of the stiffness matrix alone would be too expensive in terms of computing time. However, when looking at the literature and