Bolts and nuts form the most fundamental and essential fastener combination in steel structure connections. Used together, they tightly secure connected components through threaded engagement. A bolt is typically a cylindrical rod with external threads, featuring a hexagonal or square head at one end; a nut is a ring-shaped component with internal threads that, when tightened onto the bolt, applies pre-tension force, creating either friction-type or bearing-type connections between members. In steel structure engineering, high-strength bolted connections are the primary connection method, second only to welding, and are widely used in critical applications such as beam-to-column joints in steel frames, truss splices, bracing connections, and anchor bolt fixings for equipment foundations.
