Rational and economic design of reinforced concret pavements based on finite element analysis

Abstract

In this research the behavior of a conventional concrete pavement of uniform thickness and a thickened edge box type pavement with holes for utility services have been investigated under traffic wheel loads using finite element technique. The effects of thickness, width and length of a conventional pavement, thickness of subbase (of CBR 20) and the subgrade CBR on the pavement deflection, tensile stress and subgrade pressure were studied. For the box type pavement the variables included are the end and midslab thickness, the width and length of slab, the thickness of the subbase and the CBR of subbase and subgrade. Eight noded isoparametric brick element has been used for the analysis. The study shows that for a conventional pavement, the maximum values of pavement deflection, tensile stress and subgrade pressure are reduced with an increase in slab thickness. The presence of a subbase further reduces the above values among which the most significant reduction takes place in the subgrade contact pressure value. An increase in pavement width and length of slab also reduces the tensile stress and deflection. When a better quality subbase is used, the deflection and tensile stress are reduced. Similar effects are noticed for a better quality (higher CBR) subgrade. But the most significant benefit is observed for change in CBR from 1 to 4. The pavement deflections of a box-type pavement, particularly with an equivalent subbase are much lower than the corresponding values for a conventional pavement. The subbase also substantially reduces the tensile stress in the pavement. The type of pavement, whether conventional or box-type, is much more important in reducing pavement deflection and stresses than the quality of the subbase expressed in terms of CBR value. Based on the findings of the present study, a new design rationale has been suggested for both box and conventional type of pavements, which will help to make the design of concrete pavements more economic and rational.