Seismic Cable Restraint Clip Asymmetric Bolt Load Path
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Solution Overview
Problem
Seismic bracing systems experience premature failure due to the prying effect on anchoring bolts caused by the combination of shear and tension forces applied at angles relative to the bolt axis, leading to increased tension loads that can pry the restraint clip loose during earthquakes.
Innovation Solution
A restraint clip design with a rigid connection portion and terminal points located on one side of a plane perpendicular to the attachment flange, eliminating the prying effect by ensuring that forces applied from the bracing component are transmitted without multiplication, thus reducing tension on the anchoring bolt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional restraint clip with ears bent at 90 degrees is used to attach seismic cables to the building structure, then the cable can be secured to the structure, but the prying effect multiplies the tension force on the bolt causing premature failure
Solution Approach 1:
The restraint clip uses an asymmetric geometry where the cable connection point is positioned directly in line with the bolt axis, creating a symmetric load path that eliminates the prying moment. The clip body extends beyond the bolt on the opposite side from the cable attachment, preventing the clip from rotating or prying loose while maintaining direct axial loading on the bolt.
Solution Approach 2:
Instead of having the cable attach to ears that bend upward from the bolt (creating a lever arm), the invention inverts the geometry by positioning the cable connection point directly on the bolt axis. This reverses the traditional configuration and eliminates the mechanical advantage that causes prying forces.
2Adaptability or versatility
If the seismic brace pulls at an angle relative to the bolt axis, then the brace can accommodate various brace angles, but the tension component of the combined shear and tension loading increases due to the prying effect
Solution Approach 1:
The asymmetric positioning of the cable connection point directly on the bolt axis creates a load path that is independent of the brace angle. This allows the brace to accommodate various angles while maintaining direct axial loading on the bolt, as the connection geometry does not create additional moment arms that would amplify tension forces.
3Ease of operation
If a restraint clip design with ears bent upwards from the horizontal is used, then the cable can be attached using a loop formed with oval sleeves, but the clip acts as a second class lever multiplying the tension force to pry the bolt out
Solution Approach 1:
The invention extracts the problematic lever arm geometry from the traditional restraint clip design. By removing the bent ears that create the second-class lever mechanism and replacing them with a direct axial connection point, the design eliminates the force multiplication effect while retaining the cable attachment functionality.
Data Source
AI summary
A seismic cable restraint clip attaches a seismic brace component, such as a cable, to a building structure. A bolt is typically used to attach the clip to the building structure. The restraint clip is constructed to reduce or eliminate multiplication of force applied from the cable to the bolt through the restraint clip.