Segmented EMAS Anchors Mitigate Jet Blast Uplift
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Solution Overview
Problem
Existing aircraft arresting systems, such as EMAS, face challenges with uplift forces from jet blast, reduced effectiveness for smaller aircraft due to insufficient weight and tire loading, and increased arresting loads at higher exit speeds, which can compromise system integrity and performance.
Innovation Solution
A vehicle arresting system comprising a base layer of crushable aggregate and a cover layer of cementitious material with a density of 100 lb/ft³ or less, along with a plurality of anchors featuring a support rod and puck configuration that includes a shear linkage to break at a predetermined load, enhancing energy dissipation and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous geogrid walls are embedded within the bed of compactible material to counter uplift forces, then the integrity of the EMAS is improved, but the installation process becomes more difficult and time-consuming
Solution Approach 1:
The continuous geogrid wall is divided into discrete segmental blocks that are individually placed and connected. This segmentation allows for easier handling and installation while maintaining the structural integrity needed to resist uplift forces. The segments can be independently positioned and connected through interlocking mechanisms or bonding agents.
Solution Approach 2:
The geogrid structure transitions from a rigid continuous wall to a flexible segmented system that can adapt during installation. The segments can be maneuvered into position more easily and connected flexibly, allowing the installation process to adapt to varying site conditions and improving overall installation efficiency.
2Strength
If continuous geogrid walls are embedded within the bed of compactible material, then uplift resistance is improved, but grading and installation become more difficult
Solution Approach 1:
Dividing the geogrid into segmental blocks creates discrete units with defined geometries that are easier to grade and level during installation. Each segment can be independently positioned and graded, eliminating the difficulty of grading a continuous flexible wall while maintaining sufficient uplift resistance through the cumulative effect of multiple connected segments.
Solution Approach 2:
The segmental geogrid provides sufficient uplift resistance through the collective action of multiple segments rather than requiring a fully continuous wall. This partial continuity approach maintains adequate strength while significantly improving ease of installation and grading operations.
3Loss of energy
If the EMAS material is designed to compact and give way to aircraft tires, then energy dissipation is improved, but the system becomes less effective against smaller lightweight aircraft
Solution Approach 1:
The EMAS system incorporates localized reinforcement elements such as geogrid segments positioned at specific depths and orientations within the compactible material. These localized reinforcements provide additional resistance for lightweight aircraft that lack sufficient weight to effectively engage the compactible material, while allowing the material to maintain its energy-dissipating compaction characteristics for heavier aircraft.
Solution Approach 2:
The EMAS system combines compactible material with geogrid reinforcement to create a composite structure. The compactible material provides energy dissipation through compaction for heavy aircraft, while the geogrid reinforcement provides additional mechanical resistance for lightweight aircraft, creating a multi-functional system that addresses the full range of aircraft weights.
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 effectively mitigates uplift forces, improves engagement with smaller aircraft, and maintains consistent arresting performance across varying exit speeds, ensuring the integrity and effectiveness of the arresting bed.
Implementation Method 1
each support rod is coupled to its associated puck via a shear linkage designed to break at a predetermined load
Implementation Method 2
The material in the EMAS is designed to compact and give way to the aircraft tires during an overrun event
Implementation Method 3
an energy dissipating, deformable, crushable, and/or compactible material that engages the aircraft wheels and slows the aircraft by dissipating its kinetic energy
Data Source
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AI summary
A vehicle arresting system includes a base layer comprising a crushable aggregate (54) and a cover layer comprising a cementitious material having an oven-dry density of 1602 kg/m3 (100 Ib/ft3) or less. The system also may include an arrestor bed and a plurality of anchors (60). Each anchor (60) includes a support rod (64) coupled to an associated puck (62), each support rod (64) being secured to a foundation that supports the arrestor bed, and each puck (62) being embedded in the cover layer slab of the arrestor bed. Additionally, each support rod (64) is coupled to its associated puck (62) via a shear link breakable at a predetermined load. A method for arresting a vehicle includes depositing a base layer on a region where the vehicle is to be arrested, the base layer comprising an aggregate (54), and depositing a cover layer over the base layer, the cover layer including a cementitious material having an oven-dry density of 1602 kg/m3 (100 Ib/ft3) or less.