Bolt-type Tension Clamp Fatigue-resistant Design: Stress Control At The Conductor Exit

During long-term operation, overhead transmission lines are subjected to cyclic loads such as wind vibration and tension fluctuations, making the contact area with the clamp highly susceptible to fatigue damage due to stress concentration. This is the fundamental reason why the industry continues to demand higher fatigue resistance from the bolted type strain clamp wire clamp.

Conductor Exit Curvature Radius: The Structural Basis of Fatigue-Resistant Design

According to the relevant technical conditions of GB/T 2314-2008, the radius of curvature at the exit of the bending extension of a non-compression tension clamp must not be less than eight times the diameter of the installed conductor. This parameter directly determines the magnitude of the additional bending stress on the conductor at the clamp exit—the smaller the radius of curvature, the more concentrated the additional stress on the conductor, and the higher the risk of fatigue breakage.

In the structural design of dead end strain clamp, we use the exit curvature radius as the core control indicator for fatigue resistance performance, combining it with conductor stiffness and cross-sectional parameters for targeted matching, thereby reducing the dynamic stress amplitude of the conductor in the contact area from a structural perspective.

U-bolt clamping force distribution and gripping force uniformity

Bolt-type tension clamps utilize the vertical pressure of the U-bolt to create a frictional clamping force on the conductor through the combined action of the clamping block and the cable groove. In fatigue-resistant design, the uniformity of clamping force distribution is equally crucial:

• Bolt tightening sequence: Clamping forces must be applied sequentially to prevent localized cold deformation of the aluminum strands due to single-point overload;

• Arc surface compressive stress balance: By rationally designing the arc angle of the cable groove, the large-arc friction force and the U-bolt clamping force work synergistically, ensuring a uniform gripping force distribution across the conductor cross-section;

• Material selection and matching: The clamp body uses an aluminum alloy similar in material to the conductor, reducing the risk of combined electrochemical corrosion and contact fatigue.

The goal of this design logic is to maintain the dynamic gripping force stability of the bolted dead end clamp clamp within a strength benchmark of over 105% of the conductor's calculated breaking force, ensuring reliable constraint on the conductor even under conditions such as light wind vibration and conductor galloping, thus extending the overall service life of the line hardware.