InTrans / Aug 14, 2018

Field performance of timber bridges: 17. Ciphers stress-laminated deck bridge

In September 1989, the Ciphers bridge was constructed
within the Beltrami Island State Forest in Roseau County,
Minnesota. The bridge superstructure is a two-span continuous
stress-laminated deck that is approximately 12.19 m long, 5.49 m wide, and 305 mm deep (40 ft long, 18 ft wide, and 12 in. deep). The bridge is one of the first to utilize red pine sawn lumber for a stress-laminated deck application. The performance of the bridge was monitored continuously for 24 months beginning July 1993, approximately 46 months after installation. Performance monitoring involved evaluating data relative to the moisture content of the wood deck, the force level of stressing bars, and the behavior of the bridge under static load conditions. In addition, temperatures were collected from the bridge superstructure and ambient air. Based on field evaluations, the Ciphers bridge is performing satisfactorily with no structural or serviceability deficiencies.