ASSESSMENT OF COMPUTER PROGRAMS FOR ANALYSIS OF FLEXIBLE PAVEMENT STRUCTURE

Five computer programs were reviewed and evaluated to establish the most appropriate one for routine pavement structural analysis, including two 2-D axisymmetric finite-element programs (ILLI-PAVE and MICH-PAVE), one 3-D finite-element program (ABAQUS), and two multilayered elastic-based programs (DAMA and KENLAYER). The most commonly used criteria for pavement design--the maximum surface deflection, tensile (radial) strain at the bottom of the asphalt concrete (AC) layer, and compressive strain at the top of subgrade--were used as the basis for selection. The effects due to treatment of dual-wheel and single-wheel loading and idealization of linear and nonlinear on pavement structure responses were also investigated. For linear and nonlinear analyses, only DAMA and MICH-PAVE satisfy the natural boundary conditions in which the vertical stresses equal the imposed contact pressure of 689 kPa (100 psi). For linear analysis, MICH-PAVE gives the intermediate maximum surface deflection, compressive strain, and tensile strain; for nonlinear analysis, DAMA yields the intermediate maximum surface deflection, compressive strain, and tensile strain. The natural boundary condition is also satisfied in DAMA, and dual-wheel loading can also be considered in computations. The results from ABAQUS yield the lowest tensile strain compared with other programs. The stress-dependent behavior of the material within each layer can be represented using MICH-PAVE and DAMA only when the thickness of the AC layer (h1) is about 22.86 cm (9 in.) or more. The difference between dual-wheel and single-wheel loading is more prominent when h1 is thin (with a maximum difference of 40.5% when h1 is 7.62 cm). This suggests that DAMA is probably the most appropriate computer program, among the five computer programs investigated, to use for routine structural analyses of flexible pavements.