Vehicle Crash Attenuator Cable Routing and Friction Control
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Solution Overview
Problem
Existing highway guardrail end treatment systems face issues with energy absorption and lateral resistance during vehicle impacts, leading to undesirable outcomes such as gating, where the guardrail allows the vehicle to pass through, potentially causing unsafe results.
Innovation Solution
A crash attenuator apparatus with an impact head structure attached to the ground, a backstop structure, and a cable system that engages with guardrail supports to create a tortuous path for the cable, providing frictional resistance and distributing impact forces across interconnected guardrail sections, which are slidably movable to absorb and redirect vehicle impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a cable assembly arrangement is used to anchor the terminal end to the ground, then tensile load is transferred to the ground anchor, but the terminal end may gate and allow the vehicle to pass through
Solution Approach 1:
The terminal end is divided into multiple functional segments: impact head, guardrail sections, cable assembly, and support posts. Each segment performs a specific function - the impact head absorbs initial impact energy, the guardrail sections provide lateral resistance, the cable assembly transfers tensile load to the ground anchor, and the support posts provide structural stability. This segmentation prevents gating by ensuring that multiple segments work together to stop the vehicle rather than allowing it to pass through a single weak point.
Solution Approach 2:
The patent combines multiple energy absorption and resistance mechanisms into a single integrated terminal end structure. The impact head, guardrail sections, cable assembly, and support posts are merged into a cohesive system that collectively absorbs impact energy, provides lateral resistance, and prevents gating. The cable assembly is routed through the impact head and guardrail sections to create a unified structure that distributes forces across multiple components.
2Force
If the cable follows a tortuous path through the impact head, then friction is increased to slow cable movement, but the structure becomes more complex
Solution Approach 1:
The cable is routed through a tortuous path with multiple curves and bends within the impact head structure. This curved routing increases the cable's contact length with the impact head components, thereby increasing frictional resistance. The cable passes through guides and channels that create a convoluted path, allowing the cable to engage multiple surfaces and generate sufficient friction to control the impact head's movement during vehicle impact.
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 apparatus effectively absorbs and distributes forces from both head-on and side impacts, preventing gating and redirecting vehicles away from the attenuator, thereby reducing damage to vehicles and their occupants.
Implementation Method 1
cable engagement structure in frictional engagement with the cable and in operative association with the impact head to exert frictional forces on the cable to control and resist movement of the impact head toward the backstop structure
Implementation Method 2
cable routing means adapted to form a tortuous or convoluted path through which a cable is threaded. The convoluted path that the cable must follow through the impact head of the invention restricts movement of the cable through the head, thereby providing sufficient friction
Implementation Method 3
impact head that slides down the W-shaped guardrails and breaks away the support posts as it travels down the rails
Implementation Method 4
designed to spread or absorb some of the impact energy
Implementation Method 5
breaks away the support posts as it travels down the rails
Implementation Method 6
controlled release terminal (CRT) or frangible posts
Data Source
AI summary
Crash attenuator guardrail apparatus includes an impact head and a backstop having a cable and guardrails supported by guardrail supports located between the impact head and the backstop. Frictional forces are applied to the cable to control and resist movement of the impact head toward the backstop and provide lateral resistance. The guardrail supports include a base having break away structure and brace members having bends and which shorten or lengthen to absorb energy resulting from vehicle impact.