Laboratory evaluation of alternative dowel bars for use in Portland cement concrete pavement construction

Dowel bars are a useful tool for transferring loads from one highway concrete slab to another across joints. Although dowels are used to increase load transfer capabilities across joints, they introduce problems, including stress concentrations and corrosion. Most dowel bars have circular cross sections. The regions of stress concentration for circular dowels are at the top and bottom of the cross section. However, alternative materials and shapes may perform better. Study results showed that elliptically shaped dowels reduced bearing stresses at the dowel-concrete interface. Much research has been conducted at Iowa State University and nationally to study parameter changes and performance of dowels. Parameters including dowel material, dowel shape, joint width, and dowel spacing have been used to evaluate bearing stress performance. Laboratory testing, field testing, and finite element analysis have all been performed to study these parameters. Six highway dowel types representing a variety of material and shape parameters were studied at Iowa State University. All dowels were found adequate to transfer normal highway loads. The deflections measured for all dowels were well within the recommended maximum deflection to ensure rider comfort. The calculations and evaluation of six dowel types showed that none of the specimens failed (dowel yield or concrete failure) before the American Concrete Institute Committee 325 allowable stress was achieved. All six dowels could transfer loads of at least 5,000 lb without exceeding the allowable stresses. Some of the significant findings from this most recent study of dowel parameters are addressed.