In this paper basic concept, brief history, state-of-the-art and future research and development items about high strength bolted connections in steel structures are mentioned.
High strength bolted connections are generally used as site connections of steel building and bridge structures. Most predominant high strength bolted connections are high strength bolted grip joints, where high preload in bolts and high slip coefficient at connection surface are required. Tension type connections, where high preload in bolts are generally required, are also used in various type of structures.
Tensile strength of usual high strength bolt (which are called F 10T) is 1, 000 N/mm2, and that of hot dip galvanized high strength bolt (F8T) is 800 N/mm2. But recently super high strength bolts, whose tensile strength is larger than 1, 400 N/mm2, were developed and already used in actual bulding structures. Nearly 150, 000 ton high strength bolts are yearly used in building strutuers and 15, 000 ton in bridge structures.
Research and development items about high strength bolted connections expected in near future are strengthening of tensile strength such as 2, 000 N/mm2, size up of bolt daimeter, improvement of corrosion resistance and fire resistance efficiency, chemical treatment of nuts, heightening of slip coefficient of connection surface, improvement of tightening methods of bolts and so on.