Vehicle Crash Attenuator Friction Cable System
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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 vehicle can pass through the terminal end, 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 creates a tortuous path to exert frictional forces, combined with movable guardrail sections and a backstop mechanism to absorb and distribute impact forces, preventing gating and redirecting vehicles safely.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional guardrail terminal ends are used with cable assembly arrangements, then the structure provides anchoring and tensile load transfer, but the terminal ends gate during angled impacts allowing vehicles to pass through unsafely
Solution Approach 1:
The impact head is divided into multiple segments (first impact head portion, second impact head portion) that can move independently relative to each other and the guardrail sections. This segmentation allows each portion to absorb energy through controlled movement while preventing the entire structure from gating during angled impacts.
Solution Approach 2:
The patent employs dynamic elements including movable impact head portions that can translate along the guardrail sections, and a cable system with turnbuckles that allows controlled deformation during impact. This dynamic behavior enables the structure to adapt to different impact angles and absorb energy without gating.
2Strength
If the impact head is designed to be stiff to prevent vehicle penetration, then structural strength is improved, but the structure becomes too rigid causing vaulting or jumping over during impact
Solution Approach 1:
The impact head portions are designed to move dynamically during impact rather than remaining completely rigid. The first and second impact head portions can translate along the guardrail sections, allowing controlled deformation that absorbs impact energy while maintaining sufficient strength to guide vehicles safely.
Solution Approach 2:
The structural parameters of the impact head are optimized to balance strength and flexibility. The use of multiple guardrail sections with specific thicknesses (e.g., 3/16 inch to 1/2 inch) and the cable tensioning system allows the structure to exhibit appropriate rigidity under normal conditions while becoming more compliant during impact to prevent vaulting.
3Force
If the cable assembly is made taut to prevent movement during impact, then lateral resistance is improved, but friction is insufficient to slow down impact head movement
Solution Approach 1:
The cable system incorporates turnbuckles and routing arrangements that create a tortuous path for the cable between the impact head portions and the anchor. This curved configuration increases the frictional engagement between the cable and pulleys/turnbuckles, enhancing energy dissipation through friction while maintaining lateral resistance.
Solution Approach 2:
The cable system acts as an intermediary element between the impact head portions and the ground anchor. The turnbuckles and cable routing mechanisms serve as intermediate components that increase frictional contact, allowing the system to dissipate impact energy through friction while maintaining the necessary lateral resistance to control impact head movement.
4Loss of energy
If the guardrail terminal end is designed to absorb energy through post breaking, then energy absorption is improved, but the structure allows uncontrolled penetration and gating
Solution Approach 1:
The energy absorption function is distributed across multiple components: the first and second impact head portions, the guardrail sections, and the cable system. Each segment absorbs a portion of the impact energy through controlled movement or deformation, preventing uncontrolled penetration while maintaining reliable vehicle guidance.
Solution Approach 2:
The system employs dynamic energy absorption mechanisms where the impact head portions move along the guardrail sections and the cable system deform under tension. This dynamic energy absorption provides controlled penetration behavior, allowing the structure to yield in a predictable manner during impact while preventing gating and maintaining vehicle control.
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 vehicular impact forces, preventing gating and redirecting vehicles away from roadside hazards, significantly reducing damage to vehicles and their occupants compared to conventional guardrail systems.
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
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.