Structural framing, or the skeleton that supports a building, is critical for stability as it supports all other components, from drywall to windows and roofs. Traditionally, construction framing has been made from wood or steel. But researchers at the University of Notre Dame, working in collaboration with the structural design firm Frost Engineering and Consulting, have developed novel pultruded FRP framing configurations to expand the use of composites within the construction industry.

Based on input from Frost’s clients, which include manufacturers, fabricators and installers of pultruded products, the team identified framing connections as a primary hindrance to widespread adoption of FRP. They pinpointed a need for semi-rigid, lapped joint connections.

“Semi-rigid connections have been used in various other materials, such as steel and reinforced concrete, to solve one of the most fundamental challenges of structural framing, which is to provide lateral stability while avoiding clashes with access paths, utilities and architectural features,” says Kevin Walsh, assistant teaching professor in the Department of Civil and Environmental Engineering and Earth Sciences at Notre Dame. “By designing and testing lapped connections specifically, we are avoiding the issue of flange connection plates clashing with decking used for walking surfaces, as well as improving the efficiency of fabrication and installation.”

The team developed, tested and analyzed a variety of rotationally semi-rigid, beam-column joint connections to ascertain the rotational strength and stiffness of laminated pultruded FRP surface materials under different surface preparation conditions and framing configurations, as well as how these unique stress conditions alter the performance needs of adhesives currently available. The corresponding construction project for this novel FRP structural framing was two low-rise, generator access platforms in a data center campus in Arizona, each measuring 52 x 167 feet and constructed in September 2021. Pultruded FRP profiles used for the installation included W columns, I beams, L angles for beam web connections and miscellaneous C channel shapes with adhesives and steel bolt hardware for transverse beam connections.

Prior to the installation, the team tested 15 specimens to ensure they adhered to the American Society of Civil Engineers’ Load Resistance Factor Design Standard for Pultruded Fiber Reinforced Polymer Composite Structures, commissioned by ACMA. “While some fabricated items could be improved for future tests and similar projects, we validated that the configurations would have more than enough capacity for the design basis criteria for this particular project in Arizona,” says Walsh.

The team plans to design and test specimens prior to the installation of similar framing configurations across the U.S. in the next year. Walsh believes the FRP lapped, semi-rigid connections will initially attract end users in sectors that require low-rise, personnel access platforms and utility support systems, such as industrial manufacturing, data centers and water and wastewater treatment facilities. But he envisions a broader market for composites in construction and is consulting with collaborators at Frost on approximately 40 other design needs the company’s engineers have identified.