Developing a Next-Generation Concrete Pavement Analysis Tool

Improving the structural analysis of pavement systems is crucial for advancing mechanistic-empirical design procedures. In the past, several finite element programs, such as KenSLAB, ILLISLAB, ILSL2, ISLAB2000, and EverFE, have been developed to compute the structural responses (stresses, strains, and displacements) of concrete pavements under various combinations of axle loading and temperature curling. These programs primarily utilize the generalized Westergaard model, treating the concrete pavement as a multi-layered plate resting on a Winkler foundation. The integration of ISLAB2000 based surrogate models into the design process of Pavement ME exemplifies the interdependence between structural analysis methods and mechanistic-empirical design procedures. However, with the rapid advancement of modern computing, the existing codebase of ISLAB2000 has become obsolete, lacking the flexibility to address emerging issues or incorporate more advanced models. The paper discusses the development of a next-generation program, incorporating modern software engineering tools such as git-based version control and automated testing, as the successor to ISLAB, called PITTSLAB. Aside from being rigorously tested against ISLAB, PITTSLAB includes several novel new features, such as explicit modeling of slab expansion and contraction, efficient modeling of multiple bonded concrete layers for multi-lift paving, and consideration of early-age effects. The latter is essential for accurate mechanistic modeling of built-in curling and offers an opportunity to significantly improve Pavement ME's modeling of rigid pavements. The paper will present the advanced features introduced in PITTSLAB, and highlight the importance of early-age characterization of slabs for improved modeling accuracy.