Guardrail Feeder Chute Shield Plate Wedging Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing energy absorbing guardrail systems face issues with vehicle wedging into feeder chutes during angled impacts, potential buckling of W-beam rails, and inadequate anchor cable release mechanisms, leading to snagging and excessive deceleration of vehicles.
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, and a supplemental anchor cable system to maintain tension in the W-beam rail, along with an enhanced Post 1 design for better lateral strength during side impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the feeder chute is left open on the traffic-side to allow vehicle passage, then vehicle redirection is enabled, but vehicles can wedge into the chute causing snagging and potential rollover
Solution Approach 1:
A shield plate is introduced as an intermediary element between the vehicle and the feeder chute opening. The shield plate prevents direct contact between the vehicle and the chute, eliminating the wedging hazard while still allowing the vehicle to be redirected along the rail by the impact force.
Solution Approach 2:
The feeder chute is segmented into an open downstream end for vehicle passage and a shielded upstream portion. The shield plate is positioned at the upstream end where wedging would occur, allowing the downstream end to remain open for redirection while protecting the critical upstream area.
2Use of energy by moving object
If the W-beam rail is allowed to move freely during impact, then energy absorption occurs, but the rail may buckle out of the chute causing the energy absorption process to stop
Solution Approach 1:
The shield plate is installed in advance to prevent the buckling phenomenon before it can occur. By blocking the traffic-side opening, the shield plate eliminates the path along which the rail could buckle during impact, ensuring continuous energy absorption throughout the impact process.
3Ease of repair
If the anchor cable release mechanism relies on Post 1 breakaway, then cable release is achieved, but under certain impact conditions Post 1 may not break away properly causing snagging and excessive deceleration
Solution Approach 1:
The upper post section is designed with modified geometric parameters - specifically reduced thickness and optimized dimensions - to ensure it breaks away at the intended location under impact loads. This parameter optimization ensures reliable cable release across various impact conditions while maintaining lateral strength when needed.
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. An improved upper section of Post 1 has an anchor bearing plate with a cooperating stabilizing bolt engaging with the upstream face of the upper post section. The downstream side of the upper post section is provided with split, spaced-apart strut sections which do not obstruct the rear cable pass through notch.