Breakaway Bolt Head for Signpost Connector Installation
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Solution Overview
Problem
Existing signpost designs for roadways are either costly and time-consuming to install due to the need for precise torque verification of threaded fasteners, and they may not adequately meet safety criteria for impact resistance, as they can be vulnerable to wind loads and require frequent replacement after collisions.
Innovation Solution
A signpost connector system using slip bolts with bolt heads that break away at a pre-determined torque load, allowing for secure coupling and separation of the sign support from the anchor, reducing installation complexity and cost, and meeting impact resistance standards by separating upon collision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If threaded fasteners are used to couple the anchor to the sign support with pre-determined torque, then the coupling strength is improved, but the installation complexity and time increase due to torque verification requirements
Solution Approach 1:
The bolt head is designed to automatically break away at the pre-determined torque load, making the bolt self-servicing by eliminating the need for external torque verification tools and procedures. The bolt itself performs the torque verification function through its breakaway mechanism.
Solution Approach 2:
The bolt head is designed as a disposable component that breaks away after serving its purpose of securing the connection at the correct torque. This allows the main bolt body to be reused while the head is discarded, simplifying future installations.
2Reliability
If threaded fasteners are used with torque verification, then the coupling reliability is improved, but the installation time increases
Solution Approach 1:
The breakaway torque mechanism is pre-configured into the bolt head design during manufacturing. This preliminary action ensures that the correct torque is automatically achieved during installation without requiring time-consuming verification steps on-site.
Solution Approach 2:
The bolt head automatically verifies and enforces the correct torque through its breakaway mechanism, eliminating the need for separate torque verification procedures and reducing installation time while maintaining reliability.
3Ease of repair
If shear bolts with pre-determined break points are used to separate the sign support from the anchor upon impact, then the anchor reuseability is improved, but the vulnerability to wind load shearing increases
Solution Approach 1:
The bolt head is designed with localized breakaway points at specific geometric features (corners or edges) rather than a general weakness throughout the bolt. This localized quality allows the breakaway to occur predictably at the head while the main bolt body remains strong enough to resist wind loads.
Solution Approach 2:
The bolt is segmented into a reusable main body and a disposable head portion. The head is designed to break away at controlled points, separating the sacrificial element from the valuable anchor component, enabling anchor reuse while maintaining connection integrity.
4Loss of substance
If the sign support is designed to shear from the anchor upon impact, then the cost of anchor replacement is reduced, but the connection strength is weakened
Solution Approach 1:
The connection system is segmented into a permanent anchor and a removable bolt assembly. The bolt head is designed as a sacrificial element that breaks away upon impact, allowing the anchor to remain in place and be reused, thereby reducing material costs while maintaining adequate connection strength during normal operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system simplifies installation by eliminating the need for torque wrenches, reduces costs, and ensures reliable separation during impacts, aligning with FHWA yield criteria for roadside structures, while being less prone to premature failure from wind vibrations.
Implementation Method 1
at least one of the plurality of bolt heads is configured to break away from the bolt when a pre-determined torque load is induced to the at least one bolt head during installation of the sign support
Implementation Method 2
the first head breaks away from the bolt to thereby tighten the bolt to a pre-determined torque
Data Source
AI summary
A signpost connector for use in coupling a sign support to an anchor includes at least one bolt having a plurality of bolt heads, wherein at least one of the plurality of bolt heads is configured to break away from the bolt when a pre-determined torque load is induced to the one bolt head.