Adroit Construction of Ashland was hired to shore the massive 14.5” x 78” x 70’ Glulam. Once the shoring was in place, the roof was secure. OSF then hired two engineering firms, Marquess & Associates of Medford and KPFF of Portland, to study the problem and three emergency repair options were considered. In the end, a proposal from Western Wood Structures to design and implement a repair scheme was accepted. Our design was preferred because it did not add a significant amount of weight to the existing roof structure and because the work could be completed in a timely manner.
Our first task was to seal the outer surfaces of the beam with an epoxy paste to prevent epoxy leaking. After roofing was removed to allow access to the top of the beam, we then drilled 180 holes into the beam which measured 1-3/8” in diameter and approximately 66” in depth. One inch diameter rebars were placed in the holes and then filled with epoxy, 105 gallons total. Once the epoxy cured, the “shear dowels” had essentially “stitched” the beam back together.
Finally, the beam was post tensioned using steel cable anchors, a steel cable guide, and 15 high strength cables in order to increase its carrying capacity and to meet current code requirements. The cable anchors were installed to the soffit of the beam also using rebars set in epoxy-filled holes.
In our review, we determined that the cause of the failure was attributed to a connection detail on the original drawings. 9” x 32.5” Glulam purlins that measure framing in to one side of the failed beam were attached in hangers near the bottom of the main beam and below its neutral axis which can cause excessive tension perpendicular to grain stresses in the member. Current timber construction standards identify this as a connection detail to avoid.
Our work was completed on July 17th several days ahead of schedule. OSF has announced that the Bowmer will re-open on August 2nd. The owners and Shakespeare fans can rest assured knowing the next play will be performed beneath a main carrying beam that is stronger today than it was when originally manufactured in 1969.