Parametric Study on Behavior of Stress-Laminated Southern Pine Bridge Decks

Stress-laminated timber bridge decks have gained popularity in the United States in recent years. As with all wood exposed to the environment, wood for these decks must be treated with preservatives. There has been reluctance to build chromated copper arsenate (CCA)-treated wood bridges because of concerns about dimensional stability. Because no research has been undertaken to investigate the use of CCA-treated southern pine stress-laminated bridge decks, a good resource for economical rural bridges has remained untapped. The objective of the present study was to evaluate the performance of various wood preservatives on stress-laminated southern pine bridge decks. A total of nine decks with seven different preservatives were built and exposed to the environment for more than 2 years. Force levels in prestressing rods and wood moisture contents from each deck were continuously monitored. It was found that the short-term variations in the rod stress levels are less for decks with oil-type preservatives than for decks with CCA preservatives. The long-term performances of decks with both preservative types were found to be similar. The anchorage effect on deck performance was found to be negligible.