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11.1 Problem Statement Dowels are used in jointed portland cement concrete (PCC) pavements to provide load transfer, reduce faulting, and improve performance. These dowels are placed either manu- ally before concrete placement or during construction by automatic dowel bar inserters to expedite construction and reduce cost. Inspection of pavements in several states revealed that misalignment of dowels generally occurs regardless of the placement method. These inspections also revealed that slab cracking and other forms of distress may not always occur as a result of such misalignment. However, limited research has been performed to determine the extent of dowel misalignment in pavement construction and its effect on performance. This report presents the research conducted under NCHRP Project 10-69 to address the issues associated with dowel alignment and develop approaches for estimating the effects of different levels and types of misalignment on performance, thus improving the analysis and design of concrete pavements. The objective of this research is to develop guidelines for dowel alignment in concrete pavements. The research addresses all forms and combinations of dowel misalignment (i.e., vertical and lateral skew and displacement). 1.2 Scope of Study The research was conducted to develop guidelines con- cerning dowel alignment in concrete pavements. The effects of dowel misalignment on pavement performance were eval- uated through a literature review; laboratory tests of indi- vidual dowels; field measurements of misalignment levels, distresses, and joint performance; and finite element modeling of pavements with different types and levels of misalignment. The laboratory tests dealt with dowel-concrete interaction of individual dowels to evaluate the effects of specific types and levels of misalignment in a controlled environment. Pullout testing was conducted on individual dowels to iden- tify the misalignmentâs effect on expansion and contraction of the concrete due to shrinkage and thermal effects. Indi- vidual shear-pull testing was conducted to determine the effect of different types and levels of misalignment on ultimate shear strength and stiffness. Finite element modeling was used to augment the results of the laboratory study. An equiv- alent dowel diameter concept was developed to facilitate quantifying the effects of dowel misalignment on pavement performance. C H A P T E R 1 Background
