Using Polymer Composites to Maximize Span with Longer Beams

Architecturally speaking, the term span refers to the distance between two intermediate support structures such as the abutments at either end of a bridge. It is a key engineering factor as span not only determines the length of elements that close the distance (i.e. beams) but also their strength. This is because the various load-bearing qualities of structural elements—bending moment, deflection, and so on—depend upon the distribution of forces across its length.

The maximum moment of bending or deflection in a horizontal beam occurs halfway between two supports. This means a longer beam is more prone to sagging and even failure than a shorter one. However, some applications demand longer beams to cross a given span. Bridge building, for instance.

Introducing Polymer Composite Bridge Components

Bridge builders have developed multiple ingenious solutions to the problem posed by span. The most common is perhaps the installation of multiple bearings as part of a complex substructure, which break-up the distance between supporting structures. Another is to use multiple smaller beams in a complex truss. But a novel solution is to change the underlying structural material used in bridge decks to something with inherently greater strength-to-weight characteristics than structural steel: Polymer composites.

Polymer composites have emerged relatively recently as a contending structural material in bridge building applications. They are advantageous in structural design throughout bridge superstructures and decks for various reasons, but here we will focus on the ability to pultrude high-strength polymer composite beams that enable bridge designers to maximize spans without relying on lateral bracing.

Our EXTREN DWB® polymer composite solution is a double-web beam structural element designed in cooperation with the U.S. Department of Commerce’s Advanced Technology Program (ATP), with the express goal of developing an optimal reinforced polymer for heavy structural applications.


We developed a hybrid polymer reinforced with a combination of both carbon and glass, yielding an excellent combination of stiffness and elasticity. The material was pultruded into a unique double web shape with greater torsional stability which is an important metric in resistance to bending stress—and is subsequently a good measure of overall beam stability.

Our long EXTREN DWB® polymer composite beams are available in sizes of up to 36” x 18”, and they have been tested extensively in laboratory conditions while proving their strengths in real-world applications. Additionally, we offer GRIDFORM™,  a prefabricated fiber reinforced polymer (FRP) double-layer grating grid system with an FRP plate bonded to the bottom grating layer as an integral stay-in-place (SIP) form.

Polymer Composite Beams from Strongwell

At Strongwell, we engineer pultruded fiberglass structural elements for a wide range of application areas. Our polymer composite beams have been proven in a range of pedestrian and municipal bridge building applications alike. Interested in using FRP in your next bridge? Why not contact one of the experts today?