DIPLOMAT: analysis program for bituminous and concrete pavements

Burmister's layered elastic theory is extended to accommodate an interior loading of a multilayered pavement system incorporating an arbitrary sequence of elastic plates and spring beds, in addition to isotropic layers. The formulation is coded into a new computer program, called DIPLOMAT, thereby allowing for the first time direct comparisons between the distinct analytical approaches conventionally used for so-called rigid and flexible pavements. The new program is as user friendly and computationally efficient as the widely used layered elastic analysis program BISAR. In addition to permitting multiple-wheel loads, DIPLOMAT may be used to investigate the effects of a variety of interface and boundary conditions, including that of a rigid base. When considering a plate on grade, DIPLOMAT reproduces the closed-form solutions by Westergaard (dense liquid foundation) and by Losberg (elastic solid foundation). On the other hand, for a pavement section consisting of up to five isotropic layers, the new program reproduces the BISAR solutions for bonded or unbonded layers. A number of applications of the program are presented, including an assessment of the structural contribution of compressible (granular or bituminous) bases under a concrete pavement slab, and determination of the interface spring stiffness that accounts for constructed layer compressibility. Some implications of program results to pavement design are also discussed.