| The general bearing mode of failure often controls the capacity of cold-formed steel bolted connections loaded in shear. Previous research has shown that the absence of washers can significantly lower the bearing resistance of these connections. Experimental studies have also revealed that the bearing capacity can be formulated with a gradated bearing coefficient that is governed by the ratio of fastener diameter to sheet thickness.;A gradated bearing coefficient method, which was based on an investigation of bolted connections composed of mild steel as well as thin high strength steel, has recently been proposed to cold-formed steel design code committees in North America, Australia and New Zealand. However, the new bearing method does not include provisions for the design of washerless bolted connections. For this reason a total of 168 bolted connection shear tests designed to fail by bearing were performed. The test program included connections with and without washers, which were divided into single and double shear, as well as high strength steel (Grade 550) and mild sheet steel (Grade 230) categories. The thickness of the sheet steel material ranged between 0.43 mm and 1.53 mm. In addition, data for 381 washerless bolted connection specimens from previous experimental investigations was included in an evaluation of current cold-formed steel design standards and specifications. Modifications to the connection design procedure contained in the 2001 North American Specification were proposed. |
