Below are some of the most frequently asked questions by our customers.
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(1) What is Comcore? (answer)
(2) What are the primary characteristics of Comcore? (answer)
(3) What is meant by dynamic load? (answer)
(4) How do you calculate a dynamic load? (answer)
(5) What is meant by "Fatigue Life"? (answer)
(6) What causes a composite to fatigue? (answer)
(7) What is the relationship of service life to fatigue loading? (answer)
(8) How do you evaluate a composite product, such as Comcore, for a given application? (answer)
(9) What are Comcore’s credentials as a load bearing material? (answer)
(10) What is the service load for a Comcore Cover or RoadPlate? (answer)
(11) What is meant by H20 loading? (answer)
(12) Why do most people use a 32,000lb. axle load and a 16,000 lb. tandem wheel load when referring to the H20 standard? (answer)
(13) What happens when a Comcore cover or RoadPlate reaches the end of its service life? (answer)
(14) What are the primary advantages of a Comcore Cover as opposed to cast iron covers? (answer)
(15) Can Comcore covers be used to replace iron covers in existing installations? (answer)
(16) How many different size manhole covers are there? What determines the size of a manhole cover, and are all of these different sizes necessary? (answer)
Comcore is a material system that combines a number of different materials so that they function as if they were a single material. Comcore was designed with those characteristics that will allow it to withstand the continued and repeated loading of highway vehicles when necessary.
(2) What are the unique characteristics of Comcore?
Comcore is a unique material with unique characteristics.
- It has a very high strength to weight relationship
- Comcore responds to impact shock like a solid material
- Comcore has excellent fatigue lifer
- Comcore is not affected by extreme temperature, weather or UV rays
- Comcore is transparent to Radio Waves
- Comcore is a good insulator of heat and noise.
(3) What is meant by dynamic load?
A dynamic load is one that is applied when a vehicle is moving. There is a difference in result between a vehicle moving faster than 10 mph and one moving less than 10 mph.
(4) How do you calculate a dynamic load?
The surcharge that AASHTO has attributed to dynamic loading is the result of the "lift" and "drop" of a vehicle when entering or leaving a bridge. According to ASSHTO this surcharge should be 130% of the static load that would be conveyed by a vehicle. It is questionable as to whether Non-bridge applications require this surcharge.
(5) What is meant by "Fatigue Life"?
Fatigue life is the length of time a material will safely support a service load without developing a significant loss of stiffness or deformation. Fatigue life and service life are, therefore, the same.
(6) What causes a composite to fatigue?
Like any other material Comcore fatigues in proportion to the number of times that it is deflected and the extent of that deflection.
(7) What is the relationship of service life to fatigue loading?
Comcore panels of the same thickness will carry the same service load, but the service life of each panel will depend upon the number of times that the panel experiences that load.
(8) How do you evaluate a composite product, such as Comcore, for a given application?
You must first know how you want the product to perform when it is in service. Next are the matters of laboratory testing and use history to verify that the product will perform according to requirements. Then there are references from known, reliable people in the field, and finally, there is actual field evaluation.
(9) What are Comcore’s credentials as a load bearing material?
The combination of testing and anecdotal history have shown that Comcore is a highly consistent and predictable material in its response to vehicular loading, and that it has excellent fatigue life. These characteristics give it significant credentials for such uses as road plates, utility covers and Trench Shoring.
(10) What is the service load for a Comcore Cover?
Comcore utility covers and RoadPlate’s are designed and built to carry an H20 service load.
(11) What organization established H20 loading?
The American Association of Safety Highway Traffic Officials (AASHTO) established a standard for bridge loading that they refer to as "HS20 or H20 Bridge Loading".
H20 loading refers to a maximum front axle load of 8,000 pounds. Rear axles are limited to a maximum axle load of 24,000 lbs. for a single back axle and 16,000 lbs. for 2 rear axles spaced no more than 4 ft. apart. (See AASHTO document "Highway Bridge Loading", #3.8.2.2, page 20.). H20 axle loading converts to a tandem wheel load for 24,000 lb., single axles of 12,000 lbs. and a tandem wheel load of 8,000 lbs. for 2-16,000 lb. axles (as seen on tractor trailers) spaced 4 ft. apart.
(13) Why do most people use a 32,000lb. axle load and a 16,000 lb. tandem wheel load when referring to the H20 standard?
In the AASHTO document for bridge loading (#3.8.2.2, page 20) a truck is shown with a single back axle. This is known as a mega-axle and is commonly used in bridge design instead of 2-16,000 lb. axles spaced 4 ft. apart. Immediately below the mega-axle there is a title showing a 32,000 lb. weight. In the footnotes at the bottom of the page it says "…for H-20 loading, one axle load of 24,000 pounds or two axle loads of 16,000 pounds each spaced 4 ft. apart may be used, whichever produces the greater stress, instead of the 32,000 pound axle load shown. It appears that not many people read the footnote.
(14) What happens when a Comcore cover reaches the end of its service life?
When it deflects it won’t come back to its original state developing a depression in the center. If the cover develops any type of deformation it should be removed from service.
(15) What are the primary advantages of a Comcore Cover as opposed to cast iron covers?
- A Comcore cover significantly reduces back injuries, smashed fingers and toes.
- A Comcore cover is non-metallic so that it won’t spark gases are present.
- A Comcore cover is LIGHTWIGHT - anyone, male or female, can lift a Comcore cover without help or equipment.
- A Comcore cover has no scrap value eliminating the incentive to steel covers.
- Comcore covers are RF transparent allowing radio and cellular transmission to underground equipment.
- Comcore covers are quiet eliminating the primary cause of replacing cover and frame.
- Comcore covers don’t bend, buckle crack or corrode.
- Comcore covers can be fit to already installed frames
(16) Can Comcore covers be used to replace iron covers in existing installations?
Yes, Comcore covers can be made to fit into frames already installed, although a custom cover might be required.
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