James K. Cable
About the research
Joints are always a concern in the construction and long-term performance of concrete pavements. Research has shown that we need some type of positive load transfer across transverse joints. The same research has directed pavement designers to use round dowels spaced at regular intervals across the transverse joint to distribute the vehicle loads both longitudinally and transversely across the joint. The goal is to reduce bearing stresses on the dowels and the two pavement slab edges and erosion of the underlying surface, hence improved long-term joint and pavement structure performance.
Road salts cause metal corrosion in doweled joints, excessive bearing stresses hollow dowel ends, and construction processes are associated with cracking pavement at the end of dowels. Dowels are also a cost factor in the pavement costs when joint spacing is reduced to control curling and warping distress in pavements. Designers desire to place adequate numbers of dowels spaced at the proper locations to handle the anticipated loads and bearing stresses for the design life of the pavement.
This report is the third report on the evaluation of elliptical steel dowels. This report consists of a graphical analysis of the performance data regarding dowel material, shape, size, configuration, and location in the test pavement. These results provide the engineer with options in the use of the elliptical-shaped steel dowels at alternative spacings and configurations in the joints to provide equal or better performance than the traditional 1.5 in. (31.8 mm) diameter bars. The data indicates that the medium-sized elliptical steel dowels do provide the same or better performance than the standard 1.5 in. traditional round steel dowels in terms of ride, faulting, and load transfer values. With the elliptical shape, the spacing of the medium bars can be extended to 15 in. and possibly 18 inches in. Wheel path only elliptical bars at 12 inch in. spacings are an alternative.
About the research
The objectives of this research were as follows: investigate the static behavior of steel elliptical and round epoxy-coated dowel bars; investigate the failure modes of steel elliptical and round epoxy-coated dowel bars; evaluate the benefits and drawbacks of elliptically shaped dowels bars for load transfer; determine the effect of dowel bar spacing and projected load transfer efficiency; and evaluate if variable spacing in combination with shape factor and bar size can optimize costs and constructability.