Guardrail Feeder Chute Shield Plate Wedging Prevention
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Solution Overview
Problem
Existing energy absorbing guardrail systems face issues with vehicle wedging into feeder chutes during angled impacts, leading to potential rollovers and buckling of the W-beam rail, which can disrupt the energy absorption process, and the breakaway post may not release the anchor cable properly under certain impact conditions, causing excessive deceleration.
Innovation Solution
The introduction of a shield plate along the traffic-side of the feeder chute to prevent wedging, an improved anchor cable release mechanism at the downstream end using a release arm and pivot bolt, and an enhanced Post 1 design with increased lateral strength to maintain rail tension and prevent buckling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the feeder chute is left open on the traffic-side, then vehicles can pass through smoothly during head-on impacts, but vehicles may wedge into the chute during angled impacts causing rollovers and the W-beam rail may buckle
Solution Approach 1:
A shield plate is introduced as an intermediary element on the traffic-side of the feeder chute. The shield plate prevents vehicles from wedging into the chute during angled impacts while still allowing smooth passage during head-on impacts. The shield acts as a mediator that filters harmful angled impact scenarios while permitting normal operational scenarios.
Solution Approach 2:
The shield plate adds a new dimensional element to the feeder chute structure. By extending the chute structure in the lateral dimension with a shield plate, the system gains the ability to prevent wedging without blocking the primary longitudinal passage path for valid impacts.
2Adaptability or versatility
If the breakaway post is designed to fail easily for head-on impacts, then the anchor cable can release properly, but the post may not break away under certain impact conditions causing excessive deceleration
Solution Approach 1:
The breakaway post is designed with non-uniform structural properties along its length. The post has varying wall thicknesses and structural characteristics at different locations, creating specific weak points that fail under certain impact conditions while maintaining strength under others. This local differentiation enables conditional response to different impact scenarios.
Solution Approach 2:
The breakaway post transitions from a static structural element to a dynamic one that changes its mechanical properties during impact. The post is designed to remain rigid under normal conditions but becomes compliant and fails at predetermined points when specific impact forces are applied, enabling adaptive response to varying impact conditions.
3Strength
If heavy straps or thicker chute walls are used to prevent cutting of the chute and W-beam railing, then cutting is prevented, but the device complexity and weight increase
Solution Approach 1:
The chute edges are formed with curved, rolled configurations instead of sharp straight edges. The inwardly rolled edges create a continuous curved surface that is inherently more resistant to cutting forces while distributing stresses more evenly. This curved geometry provides enhanced protection without requiring additional materials or complex structural modifications.
Data Source
AI summary
A highway crash attenuation system having W-beam rail elements attached to a plurality of vertical posts. An impact terminal with a feeder chute guides one or more of the W-beam rail elements through the impact terminal. The feeder chute has an impact shield extending along a traffic-facing side of the chute from an upstream-most end to a downstream-most end of the chute closing the traffic-facing side of the chute. The system also has an anchor cable release mechanism for releasing the cable downstream of the first vertical post and an improved first breakaway post.