Dowel bars are subject to large cycles of fatigue loading as the bars transmit loads from one portion to another of a concrete pavement, bridge, or other structural components. As the continued cycling occurs, the bearing of the contact from the bar on the concrete can cause an "oblonging" of the hole surrounding the bar for a typical circular bar. Thus, a need exists to reduce the bearing stresses between the dowel bar and the concrete. The combination of the corrosion and bearing fatigue problems for dowel bars leads to the need to consider alternative shapes and materials for dowel bars. Research has been on-going at Iowa State University (ISU) on both the alternative shapes and the alternative materials for dowel bars. Several types of structural tests and analyses have been conducted at ISU. Recently, an extensive study was made of the gaps of knowledge that exists for design and research for all types of dowel bars and the associated parameters. The structural laboratory work at ISU has focused on many different potential dowel bars of various shapes and materials, including elliptically-shaped fiber reinforced polymer (FRP) and steel dowels. The goal of the elliptically-shaped dowel bars was to reduce the maximum contact bearing stress between the bar and the concrete. This paper will present some of the key results of earlier laboratory tests that have been conducted over a period of approximately 15 years, including a brief summary of the theory, as background. Key sections of the paper include knowledge gaps and needed research for FRP in concrete.
Samenvatting