Wood Beams Prestressed with Bonded Tension Elements

A method has been developed whereby a strip of high-strength steel can be pretensioned and bonded to the face of a wood beam so that it will, on release, transfer force to the beam in the form of uniform shear in finite end zones. The method was used to prestress full-size beams laminated from grade L-3 Coast Region Douglas-fir. Their structural behavior was studied and compared to that of matched unprestressed beams. Test data show that the prestressed wood beams behave essentially as predicted by theory; that they exhibit greater stiffness, greater strength, lass variability of strength, far greater work to maximum load, and design loads that are predictable and far in excess of those for the matched unprestressed beams.