Difference between friction type and pressure type connection of high strength bolt

High strength bolt connection is to clamp the plate of the connecting plate through the large tightening pre tension in the bolt rod, which is enough to generate great friction force, so as to improve the integrity and stiffness of the connection. When the shear force is applied, according to the different design and stress requirements, it can be divided into two types: high strength bolt friction type connection and high strength bolt pressure bearing type connection. The essential difference between the two is that the limit state is different, Although it is the same

However, there are great differences in calculation methods, requirements and application scope. In the shear design, the ultimate state of high strength bolt friction type connection is that the external shear force reaches the maximum friction force provided by the bolt tightening force between the contact surfaces of the plate as the limit state, that is to ensure that the internal and external shear force does not exceed the maximum friction force during the whole service life. The plates will not slide relative to each other

The displacement deformation (the original gap between the screw and the hole wall is always maintained), and the connected plate is subjected to elastic overall stress. In the shear design, the external shear force is allowed to exceed the maximum friction force in the bearing type connection of high-strength bolts. At this time, the relative slip deformation occurs between the connected plates until the bolt rod contacts the hole wall, and then the connection depends on the shear of the bolt body, the bearing of the hole wall and the contact surface of the plate

The simultaneous interpreting of friction forces is the ultimate state of shear connection. In short, the friction type high strength bolt and the pressure bearing high strength bolt are actually the same kind of bolt, but whether the design considers the slip. Friction type high-strength bolts must not slide, the bolt does not bear shear force, once sliding, the design is considered to reach the failure state

The ultimate failure is equivalent to the common bolt failure (bolt shear or steel plate crush).

From the perspective of usage method:

In general, high strength bolts are used to connect the main components of building structure. Ordinary bolts can be reused, but high strength bolts can not be reused. High strength bolts are generally used for permanent connections.

High strength bolt is prestressed bolt, friction type uses torque wrench to apply specified prestress, pressure bearing type screw off plum head. The common bolt has poor shear performance and can be used in secondary structure. Ordinary bolts need only to be tightened.