38% Stronger Reinforced Glulam Construction Beams

PROBLEM: Builders prefer reinforced glulam beams for applications benefiting from thier beauty or shape versatility.  But glulam beams have a tendency to weaken (delaminate, or peel) on the ends when the center of the beam is bent or stressed.

SOLUTION: UMaine offers reinforced glulam beams that withstand end delamination under 38% more bending stress compared to other reinforced beams, and 95% more stress compared to non-reinforced beams.

HOW IT WORKS: Bending stress is applied mechanically to the beam before the glue is applied.  When glue is then applied and allowed to set, the laminated layers are locked into the stressed position they will experience in the final construction.  This is called pre-stressing, and it is the first time this method has been successfully demonstrated on reinforced beams.  Examples of reinforcing material include glass fiber, polymer, carbon fibers or any combination of materials.

The 38% and 95% strength improvement of our beams v. other beams were observed under experiments comparing glulam beams of similar length and layup 1) 15 glass fiber reinforced pre-stressed using our method, 2) 15 glass fiber reinforced, not pre-stressed, 3) 15 unreinforced, not pre-stressed.


– AEWC Advanced Structures and Composites Center has designed and monitored over 25 demonstration FRP-glulam bridges and piers (see link below).  Pre-stressed FRP-glulam beams are ready for incorporation into demonstration projects.

– Companies interested in evaluating feasibility of these new pre-stressed beams, or in exploring the use of the pre-stressing process for other applications are encouraged to contact any team member below.

Sponsored by the State of Maine Department of Transportation.

TECH REF: 2009-15.

PATENTS: US Patent 7,862,675


Mac Gray, Inventor

Habib Dagher, Inventor

Kris A. Burton, Technology Commercialization


Research papers and Bridge Demonstrations

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