Module 4: Pavement Design

Lecture 29 Rigid pavement design

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Critical load positions

Since the pavement slab has finite length and width, either the character or the intensity of maximum stress induced by the application of a given traffic load is dependent on the location of the load on the pavement surface. There are three typical locations namely the interior, edge and corner, where differing conditions of slab continuity exist. These locations are termed as critical load positions.

Equivalent radius of resisting section

When the interior point is loaded, only a small area of the pavement is resisting the bending moment of the plate. Westergaard's gives a relation for equivalent radius of the resisting section in cm in the equation 1.

$$b=\left\{\begin{array}{ll}\sqrt{1.6a^2+h^2}-0.675~h&\mathrm{if}~a<1.724~h\\ a&\mathrm{otherwise}\end{array}\right.$$ (1)

where $a$ is the radius of the wheel load distribution in cm and $h$ is the slab thickness in cm.