Frequently asked questions.
What about durability, fire and UV performance of arches?
The original patent-pending 'Bridge-in-a-Backpack' technology was developed by the University of Maine and extensive testing was performed on environmental durability including freeze thaw, abrasion, fire, and UV.
Our composite materials are designed to protect against both UV and fire. The special resin we use to infuse the arch composite layers includes an advanced fire retarder. Its the same resin the Navy uses for their ships.
Abrasion may be a concern if the arches are exposed to flowing water. Most of our designs elevate the base of the arch above the mean or high-water mark. Arches exposed to flowing water include additional layers of protective material.
How much does an arch element cost?
Arch pricing is based on the unique design requirements of each bridge project. Our composite bridge system generates savings by reducing the total cost of the project. For example, because the arches are light-weight, transportation and heavy equipment costs may be lowered significantly. Furthermore, arches do not require the time and cost of rebar and extensive form-work.
In our experience the total cost of a project with our system is competitive or lower than conventional designs. In cases we generate savings of 20% or more.
Find out if we can lower costs for your bridge project.
Can the system build on a skew?
Yes, bridges can be designed and built on a skew. Similar to a slab-on-girder bridge, footings can be skewed while keeping the arches and head-walls parallel to the roadway, keeping the overall dimensions of the structure to the minimum required. In contrast to slab-on-girder structures, skews do not cause issues like reflective cracking, because of the load distribution provided by the soil overburden. We have designed bridges with skews up to 45°.
How much maintenance is required?
Composite bridges are low maintenance. The composite arches completely encase the concrete, providing critical protection from environmental degradation. Our composite bridge system eliminates rebar (steel) from the primary weight bearing members - and the encased concrete is protected from the spalling or cracking that affects reinforced concrete.
Composite bridges are designed for up to 100 years of lifespan, that's 2x conventional lifespan.
Are straight superstructure elements an option?
We can incorporate straight elements into the design. Standard designs use arches due to their efficient load carrying characteristics.
What is the minimum rise of an arch?
A minimum rise to span of 25% usually results in the most economical designs. In cases we can design structures down to 10% rise to span.
Is there a maximum arch height?
No.
What spans are available?
We currently offer single spans up to 70 ft. Multi-span bridges can extend to 800 ft. and more.
What is the diameter of a single composite arch element?
Standard designs include 6”, 12”, and 15” diameter composite arch elements.
What is the minimum and maximum amount of cover?
Normally the system requires at least 2 ft. of soil cover below the roadway paving. For projects that require a deep fill, we have designs for up to 45 ft. of cover. For even deeper structures that require greater soil cover, please contact us for options.
What information is needed before design can begin?
Before preliminary design, we require the following basic site geometries:
Rise measurements, width measurements, number of travel lanes, shoulder width, buried utilities, and basic soil conditions.
See if we can lower the cost of your bridge project.
How is the composite bridge system installed?
Watch a video of the McGee Bridge construction in Anson, ME.
What load requirements do you design for?
Our standard loadings are the AASHTO HL-93 or HS-25, but our designs accommodate nearly any loading requirements, including those well beyond AASHTO specifications. If your bridge project has special loading requirements, contact us.