Tension Guardrail Terminal with Resistive Coupling
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Solution Overview
Problem
Existing guardrail end treatments are unsafe for certain collision conditions, sensitive to installation details, and costly, failing to maintain tension during both end-on and re-directive impacts, which can lead to vehicle instability and excessive deceleration.
Innovation Solution
A guardrail terminal system with a resistive, tensile coupling that maintains tension during end-on or re-directive impacts by securing the W-beam guardrail element to a terminal support post, which releases tension during reverse-direction impacts to prevent instability and excessive deceleration, using a flattening structure to dissipate impact energy by compressing the guardrail into a flat plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a cable is used to connect the guardrail beam to the post to provide tension for redirective impacts, then the guardrail can redirect vehicles along the length-of-need portion, but the system cannot maintain tension during end-on and reverse-direction impacts
Solution Approach 1:
The connection between the terminal support post and guardrail beam is made dynamic through a breakaway mechanism. The post remains rigid and tensioned during normal operation and redirective impacts, but is designed to break away or release during end-on impacts. This dynamic behavior allows the system to adapt its structural response based on impact direction, maintaining reliability for its intended function while safely accommodating unexpected impact types.
2Loss of energy
If the guardrail terminal is designed to absorb energy by flattening the W-beam into a flat plate, then impact energy is dissipated, but the system may not maintain proper tension for redirective impacts
Solution Approach 1:
The guardrail system is segmented into distinct functional zones: the terminal support post section designed for energy absorption through controlled failure, and the length-of-need portion maintained in tension for vehicle redirection. The terminal portion includes the flattening structure and breakaway post, while the extended guardrail maintains its structural integrity and tension. This segmentation allows each segment to perform its specific function without compromising the other.
3Object-affected harmful factors
If traditional end treatments are used to eliminate spearing effects, then vehicle penetration is prevented, but the treatments operate in a ramp-like fashion that may induce vehicle launching and rollover
Solution Approach 1:
The terminal support post is designed to fail in a controlled manner during end-on impacts, converting the harmful impact energy into a beneficial controlled deformation process. The post breaks away or releases tension, allowing the guardrail beam to flatten and absorb energy progressively. This controlled failure mode prevents the harmful ramp-like launching effect while still providing energy dissipation and preventing vehicle penetration, effectively turning a potential hazard into a safety feature.
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 provides a higher level of safety performance across a wider range of collision conditions, reduces injuries and deaths, and maintains the guardrail in tension during critical impacts while preventing vehicle instability by releasing tension during reverse-direction impacts.
Implementation Method 1
a flattening structure to dissipate impact energy by compressing the guardrail into a flat plate
Implementation Method 2
A terminal support post couples to an upstream end of the terminal portion of the guardrail beam by a resistive, tensile coupling that maintains tension in the terminal portion of the guardrail beam
Data Source
AI summary
A terminal portion of a guardrail safety system includes a terminal portion of a guardrail beam having a downstream end and upstream end. The terminal portion of the guardrail beam slopes from a height appropriate for redirecting an errant vehicle to a height proximate the surface of the ground at an upstream end of the terminal portion.Support posts are installed adjacent a roadway in spaced apart relation to one another and are coupled to the terminal portion of the guardrail beam. A terminal support post is installed adjacent the roadway at an upstream end of the terminal portion of the guardrail beam. The terminal support post couples to an upstream end of the terminal portion of the guardrail beam by a resistive, tensile coupling that maintains tension in the terminal portion of the guardrail beam. The resistive, tensile coupling is maintained between the terminal support post and the guardrail beam during an end-on or re-directive impact by a vehicle. However, the resistive, tensile coupling between the terminal support post and the guardrail beam is released during a reverse-direction impact.