Structural Repair of Heavy Timber with Epoxy

Described here is one of the first major repair projects on heavy timber trusses where the epoxy repair method was exclusively utilized. This project was preceded by 3 years of research at Mississippi State University and Georgia Institute of Technology to evaluate the structural and economical feasibility of the method. Six buildings with heavy timber trusses were repaired at Robins Air Force Base in central Georgia. Members ranged from 2 by 6’s to 3 by 12’s with bolt and split ring connectors. The damage was primarily at tension chord joints and typically consisted of: longitudinal end splits through connectors, cracked splice plates, and longitudinal splits throughout the entire length. The repair method consisted of 1) cleaning the damaged area, 2) sealing the joint with epoxy gel and placing injection ports, and 3) injecting a low viscosity epoxy into the damaged joint until completely filled with epoxy. A total of 641 joints were repaired with a cost per joint of $136. Based on conventional repair on several of the same buildings a few years earlier, the epoxy repair method resulted in 30 to 50 percent cost savings. Quality control measures consisted of taking shear block specimens periodically for laboratory testing. Such tests insured that the epoxy mix was of a consistent quality for proper strength development. The successful completion of this repair project has illustrated the effectiveness of the epoxy repair method. Applications for the technique are steadily expanding and the repair of timber structures by such methods is rapidly coming of age.

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