Relaxation in High-Strength Bolted Connections Using Galvanized Steel

Abstract

In recent bridge construction in Connecticut involving heavy sections, galvanized coating thicknesses were in excess of 12 mils. The current American Association of State Highway and Transportation Officials specification is based on research conducted with coating thicknesses not greater than 6 mils. Since thicker coatings on steel can reduce shear capacity in high-strength bolted connections, there was concern that the thick galvanized coating could compromise the performance. In this research, tests were conducted to study the relaxation and the shear capacity of high-strength bolted connections with galvanized coating thicknesses up to 20 mils. Both normal and oversize holes were studied. The research shows that the shear capacity of connections with thick galvanized coatings is reduced due to the loss in the clamping force. The test results have been used to develop design guidelines.