Steel structure bolts are key load-bearing connectors in steel skeleton systems such as buildings and bridges, and are mainly used to bear dynamic loads and shear stresses. Different from ordinary bolts, their strength grades are generally above grade 8.8. The tensile strength of M24 grade 10.9 high-strength bolts can reach 1040MPa, and the ultimate tensile force of a single bolt exceeds 30 tons, which is equivalent to lifting three off-road vehicles at the same time. This type of bolt generates friction between steel plates or directly bears shear force through pre-tightening force to form a rigid node.
According to the force mechanism, it can be divided into two categories: the friction type relies on the bolt pre-tightening force to press the steel plate, which is suitable for bridge nodes that bear alternating loads; the pressure type allows the steel plates to slide to the bolt rod to contact, and uses the bolt’s shear resistance (such as the flange connection of the wind power tower). In seismic design, the friction type is more common because it can effectively dissipate seismic energy.
Materials and processes determine performance boundaries. After quenching and tempering, the commonly used 35CrMo alloy steel has a hardness of HRC32-39, and the low-temperature impact energy of -40℃ remains above 54J, which meets the needs of severe cold areas. Surface protection needs to match the environment – hot-dip galvanizing is used in C5 corrosion environment, and the salt spray resistance time is greater than 1000 hours; chromium-free Dacromet coating is used in chemical industry zone, and the acid spray resistance performance is improved by 40%.
Intelligent hydraulic wrenches have been popularized in modern engineering, and the preload control error is reduced to ±3% through pressure sensors and angle encoders. Special attention should be paid: bolt hole deviations exceeding 2mm need to be expanded, and bolts contaminated by electric welding sputtering must be replaced – local high-temperature tempering will reduce the strength by 30%.
From 300-meter-class super-high-rise core tubes to suspension bridges with a span of kilometers, the amount of steel structure bolts can reach millions. The main project of the Hong Kong-Zhuhai-Macao Bridge consumed more than 2.5 million sets of high-strength bolts, all of which were tested by magnetic particle inspection and hardness gradient testing. Comprehensive considerations are required when selecting: the torsion shear type anti-loosening design is preferred for vibrating parts, while special scenes such as nuclear power plants require stainless steel materials and radiation resistance certification. With the development of modular buildings, maintenance-free weathering steel bolt systems are gradually being used in the field of prefabricated steel structures.
Dabang Fasteners is a professional fastener manufacturer and supplier. The company has passed ISO9001/ISO14001/ISO45001/SGS certification, and the company’s products have also passed the national testing. Relying on the product advantages, production advantages, cost advantages and rich export experience of the head office, our fastener products have been exported to more than 154 countries and regions, serving more than 1800 customers, and have received many praises.
Post time: May-29-2025