AEWC Awarded Patent for Stronger Beam
Contact: Habib Dagher, (207) 581-2138 or hd@umit.maine.edu
The University of Maine’s AEWC Advanced Structures and Composites Center has been issued a patent (US Patent #7,862,675) for a method of prestressing glued-laminated timber beams that significantly increases the strength of the wood for use in bridges and other structures.
Associate Professor of civil engineering Mac Gray and Habib Dagher, director of the Advanced Structures and Composites Center, are the lead inventors on the patent.
Although not named in the patent, Olivia Sanchez, a research engineer at the center who has a master’s degree in civil engineering from UMaine, has been involved in research for the project. Former UMaine graduate student Rodrigo Silva-Henriquez added research several years ago.
The patent addresses a common problem of conventional glued-laminated (glulam) beams, which is they often fail in bending-induced tension. The Advanced Structures and Composites Center has found that adding small amounts of reinforcement to the tension side of the beam significantly increases its strength.
AEWC researchers used a fiberglass tendon as reinforcement. The fiberglass is bonded to the wood, but before the adhesive can cure, the force on the tendon is released, building up tension in the middle of the bottom of the beam. This strengthens the area of the beam that is required to carry loads, and the now-patented method increases the beam’s strength by 38%.
“What we found is we can tremendously strengthen wood by reinforcing it with a relatively small amount of fiberglass or other materials like that,” Gray says. “The bottom line is we’re seeing an increase in strength of a prestressed beam over a reinforced but not prestressed beam. You’re gaining strength without using any more material.”