The difference between high-strength bolt friction type and pressure bearing type connections
The difference between high-strength bolt friction type and pressure bearing type connections
High strength bolt connection is achieved by clamping the plates of the connecting plate with a large tightening pre tension force inside the bolt rod, which is sufficient to generate a large amount of friction force, thereby improving the integrity and stiffness of the connection. When subjected to shear force, according to different design and force 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
There are various types of bolts, but there are significant differences in calculation methods, requirements, and scope of application. In shear design, the high-strength bolt friction type connection is the ultimate state where the external shear force reaches the maximum possible frictional force provided by the bolt tightening force between the contact surfaces of the plate, which ensures that the internal and external shear forces of the connection do not exceed the maximum frictional force throughout its entire service life. The board will not experience relative slip
Displacement deformation (the original gap between the screw and the hole wall is always maintained), and the connected plate is subjected to elastic overall force. In shear design, the external shear force is allowed to exceed the maximum friction force in high-strength bolt compression type connections. At this time, relative sliding deformation occurs between the connected plates until the bolt rod contacts the hole wall. Afterwards, the connection relies on the shear force of the bolt rod body, the pressure on the hole wall, and the contact surface between the plates
Finally, the shear failure of the rod body or the bearing failure of the hole wall is taken as the ultimate shear state of the connection. In short, friction type high-strength bolts and pressure type high-strength bolts are actually the same type of bolt, but it is only about whether sliding is considered in the design. Friction type high-strength bolts must not slide and do not bear shear force. Once they slip, the design considers them to have reached a state of failure, which is technically superior to
More mature; Pressure bearing high-strength bolts can slide, and the bolts also bear shear force, resulting in failure equivalent to ordinary bolt failure (bolt shear failure or steel plate compression failure).
From the perspective of usage:
The bolted connections of the main components of building structures are generally made with high-strength bolts. Ordinary bolts can be reused, while high-strength bolts cannot be reused. High strength bolts are generally used for permanent connections.
High strength bolts are pre-stressed bolts. Friction type bolts use a torque wrench to apply the specified pre-stress, while pressure type bolts unscrew the torx head. Ordinary bolts have poor shear resistance and can be used in secondary structural parts. Ordinary bolts only need to be tightened.
