Bearing strength of cold-formed steel bolted connections with a gap

The existing design provision in North American Specification for Cold- Formed Steel Structural Member (AISI S100 2007) for the bearing strength of bolted connections were developed from tests on bolted connected sheets which were restrained by bolt nut and head with or without washers. However, for bolted connections used in the cold-formed assemblies, particularly in trusses, the connected sheets on the inside of the section (the gap) are usually unrestrained due to the limited space for installing nuts or washers. The warping of the unrestrained sheets may reduce the bearing strength of the bolted connection. This paper presents an experimental research to study the bearing strength of bolted connections with a gap. It was found that the AISI S100 works well for relatively thick connections but provides unconservative predictions for relatively thin materials. Based on the experimental results, a modified bearing strength method is proposed. The proposed method can be generally used for cold-formed steel bolted connections with a gap.