Flexible PavementFlexible pavement structure is assumed to behave elastically under the dynamic loads exerted byvehicular traffic. Linear elastic theory for layered system is adopted to calculate the stress/straindistribution within a pavement structure in response to traffic load. Although a flexible pavementstructure is typically constructed in several layers, it is modelled as a three-layered system fordesign purposes as presented in Figure 2. All the bituminous layers, including wearing course,base course and roadbase, are combined into one layer. The materials are assumed ashomogeneous and isotropic and are characterized by the modulus of elasticity (E) and Poisson’sratio (n). A constant value of 0.35 is assumed for the Poisson’s ratios of all the layersRigid pavement consists of concrete slab and sub-base on top of the subgrade. Modulus ofelasticity of concrete slab is normally much greater than that of granular sub-base and in-situsubgrade, resulting in most of the load bearing capacity of a pavement being attributed to thestrength of the concrete slab. Stresses in rigid pavements are induced by traffic loads and cyclictemperature changes of concrete slab, with their magnitudes also depending on the in-situsubgrade support.For design purposes, longitudinally and transversely jointed concrete slabs are modelled as asystem of hinged connected slabs on an elastic foundation that comprises the subgrade and theoverlying sub-base. The elastic foundation is simulated by a series of springs of constantstiffness, which are characterized by the modulus of subgrade reaction. Only one slab isconsidered in the structural design, and the adjacent slabs are modelled to allow a reduction ofthe imposed loads along the edge of this slab. The pavement model is shown in Figure 3 forcalculating the traffic-induced stresses across the slab.