The shape and connection structure of high-strength bolts are basically the same as those of ordinary bolts. The working principle of high-strength bolt connection is to deliberately apply a large pre-tension to the bolt, so that the extrusion pressure between the contact surfaces is generated, so the friction force perpendicular to the direction of the screw is large, and the connection shear force is transmitted by this friction force. The pre-tension of the high-strength bolt is realized by tightening the nut. The torque method and the Angle method are generally used for ordinary high-strength bolts. Torque The tail of the high-strength bolt is used to control the pre-tension.
The bolts connecting the high-strength bolts are 10.9S or 8.8S high-quality alloy structural steel made of heat treatment, and the holes of the high-strength bolts should be drilled. The aperture of the friction-connected high-strength bolt is larger than the nominal diameter d of the bolt by 1.5 ~ 2.0mm; The aperture of the high-strength bolt is greater than the nominal diameter of the bolt d by 1.0 ~ 1.5 mm.
According to the stress state divided into friction type and pressure type
In fact, there are differences in design and calculation methods. Friction type high-strength bolts take the sliding between plates as the limit state of bearing capacity. The sliding between plates is regarded as the limit state of normal use, and the connection damage is regarded as the limit state of bearing capacity. Friction type high strength bolts can not give full play to the potential of bolts. In practical applications, friction type high-strength bolts are used in very important structures or structures that bear dynamic loads, especially when the load causes the bolt potential to be used as a safety reserve. In addition, pressure type high-strength bolt connections should be used to reduce costs.
According to the construction technology, it is divided into torsional high-strength bolts and large hexagonal high-strength bolts
In order to better construction, the large hexagon high-strength bolt belongs to the high strength level of the ordinary screw, and the torsional high-strength bolt is the improved type of the large hexagon high-strength bolt.
The construction of high-strength bolts must be screwed first and then screwed, and high-strength bolts need impact electric wrench or torque adjustable electric wrench; The final tightening of high-strength bolts is strictly required. The final tightening of high-strength bolts must use a torque electric wrench.
The large hexagon bolt consists of one bolt, one nut, and two washers. A torsional shear high strength bolt consists of a bolt, a nut and a washer.