Influence of moving load, structure, temperature gradient, and wheel configuration on load transfer efficiency

An airport pavement consists of one or more paving materials over the natural subgrade. Pavement design involves the interaction of pavement with vehicular loads and climatic conditions. The Federal Aviation Administration (FAA) uses a mechanistic design procedure, FAARFIELD, for the design of rigid airport pavements. The FAARFIELD (FAA Rigid and Flexible Iterative Elastic Layer Design) procedure is based on layered elastic and three-dimensional finite element-based structural analysis developed to calculate design thicknesses for airfield pavements. The design procedure assumes constant stress-based load transfer efficiency (LTE (S)), of 25% at the joints. Variations in environmental conditions, loading characteristics, type of joint and pavement material properties can affect load transfer efficiency. FAARFIELD does not consider curling stresses in determining the Portland Cement Concrete (PCC) layer thickness. The curling stresses, induced due to the temperature differentials at the top and bottom of the PCC slab can lead to higher combined stresses (loading plus curling) in pavements and can affect the load transfer efficiency at the joint. This study analyzes the effect of pavement layer properties, loading characteristics and temperature curling on stress-based load transfer efficiency. This study is carried out for static loading conditions using FEAFAA (Finite Element Analysis - FAA) program. Results of this research indicate that LTE (S) is insensitive to modulus of PCC and base material. However, LTE (S) increases at negative temperature gradients (temperature at top of PCC surface \u3e temperature at bottom of PCC) and when number of loaded areas (tire footprints) increase. It is observed that LTE (S) is highly sensitive to the joint stiffness including spacing of the dowel bars. The airport pavement design procedure uses finite element models that are developed based on static analysis assuming that the speed of the vehicle is zero. However, most of the time, load transfer takes place under moving vehicles. Recently completed studies have shown that LTE (S) values under moving aircraft loads can be significantly higher than 0.25. This research documents a study of dynamic mechanical responses of rigid pavement at the joint under moving aircraft loads. The MRC (pavement constructed on conventional base) section of CC-2 (Construction Cycle-2) test pavement at the Federal Aviation Administration\u27s (FAA) National Airport Pavement Test Facility (NAPTF) is modeled using 3D finite element software, ABAQUS. The model is calibrated by determining pavement damping parameters and joint stiffness values using heavy weight deflectometer (HWD) data and the strain profiles captured from the dynamic sensors installed within the pavement at various locations. The effect of moving aircraft at varying speeds on tensile strains at the bottom of PCC at the joint (epsilon-critical) and dynamic LTE (S) at the joint is studied. Results of this research indicate that epsilon-critical at the joint decreases with increasing speed. The dynamic LTE (S) at the joint is enhanced at higher speeds. Sensitivity of dynamic LTE (S) to pavement damping showed that the dynamic LTE (S) at the joint increases with pavement damping