Post on 13-Jan-2022
SCRAPER MESH SYSTEM FOR BRIDGE STAY CABLES
TOPOMACHINES
“Scraper Mesh System”: Schematic view & working principle
Traction Cable
Actuator
Scraper Ring
Actuator
Back & forth motion
Scraper Mesh System for Stay Cables: General layout
Scraper Mesh Termination
Scraper Mesh
Command Control System
Electric winch
Electric winch
Need Analysis: Snow removal
Snow Removal
Snow has low mechanical strength, but could have big accumulation.
In wet snow weather, slush bombs could form.
If not removed quickly, snow can freeze and generate ice.
Snow has to be removed from the entire surface of the stay pipe quickly
and frequently
Ice Removal
Ice adhesion strength is high.
During freezing rain, an ice layer can appear.
If not removed quickly, thick ice could form.
The more quickly ice is removed, the less energy is required.
o Scraper Mesh System removes snow mechanically.
o While it looks relatively easy to remove snow from a stay pipe, few solutions have been proposed.
o Mechanical solutions are the most appropriate, as thermal solutions require considerably more energy.
Need Analysis: Ice removal
Snow Removal
Snow has low mechanical strength, but could have big accumulation.
In wet snow weather, slush bombs could form.
If not removed quickly, snow can freeze and generate ice.
Snow has to be removed from the entire surface of the stay pipe quickly
and frequently
Ice Removal
Ice adhesion strength is high.
During freezing rain, an ice layer can appear.
If not removed quickly, thick ice could form.
The more quickly ice is removed, the less energy is required.
o Few systems are able to remove ice from a stay pipe.
o Important: a de-icing system is not necessarily able to remove snow from the stay pipe.
o An example for that is the Pulse Electro-Thermal De-icing System (PETD).
De-icing is difficult due to ice adhesion strength
o Ice is a brittle material.
o But its adhesion strength to underlying surfaces could be very high.
o For a stay pipe made of HDPE, breaking shear stress of ice could be of the order of 1 Mpa or even more.
More powerful design of the Scraper Mesh System is not the solution.
Stay pipes would have to resist unacceptable large forces.
Complementary Action - Thermal
o A Heating Skin melts the ice at the stay pipe interface.
o This action effectively cancels ice adhesion strength.
o As a result, the Scraper Mesh can remove very thick ice easily.
Dual strategy to remove ice
Principal Action - Mechanical:
o Adjusting Scraper Mesh motion frequency.
o As a result, the Scraper Mesh removes any ice accretion and prevents ice layer formation.
Overall Snow & Ice Removal System
Our Snow & Ice Removal System is composed of two sub-systems:
o Scraper Mesh;
o Heating Skin.
Snow & Ice Removal System
Scraper Mesh
Main Sub-System
Removes Snow & Thin ice
Heating Skin
Auxiliary Sub-System
Melts the ice at stay pipe interface.
Snow & Ice Removal System action
Melts the ice interface
Moves back & forth
Removes Snow & Ice
Heating Skin
Scraper Mesh
Scraper Mesh
(if necessary)
Fully Automatic Snow & Ice Removal System
• Snow removal: – Mechanical sweeping; – Regular iterative motion (e.g., @5-minute intervals); – Prevents snow accumulation.
• Ice removal: – Interface heating (if necessary) + Mechanical scraping; – Regular iterative motion (e.g., @5-minute intervals) – Prevents ice layer formation, removes ice accretion of any thickness.
• Fully automatic, high performance system: – Robust, modular design – Service life = 50 years – Reliable, Available, Maintainable, Safe – Low Operation & Maintenance Costs
Today, our system is the only available Fully Automatic Snow & Ice Removal System for Stay Cables.
Heating skin activated
Heating skin activated
Aerodynamics & aesthetics
Aerodynamics
Negligible additional drag due to Scraper Rings and Traction Cables.
No expected aerodynamics effect, as air is allowed to flow freely around Traction Cables.
Helical ribs can be included in the design of the Scraper Mesh in order to prevent galoping.
Aestethics
The Scraper Mesh would be barely visible, particularly if it is of the same color as the stay pipe.
Proposed prototype test bench
Scraper Mesh System: Advantages
• Off-the-shelf technology
• Automatic, push-button system
• Robust, high performance, cost-effective
• Ultra-lightweight
• Can be made almost invisible or otherwise decorative
• Architectural Mesh option available (polygonal or biological design)
www.topomachines.com
contact@topomachines.com