Institute for Transportation

This report describes the design, modeling, and testing of two portable timber bridges, each consisting of two non-interconnected longitudinal glued-laminated timber (glulam) deck panel modules 1.8 m (6 ft) wide. One bridge is 12.2 m (40 ft) long while the other bridge is 10.7 m (35 ft) long. The modules are fabricated in a double-tee cross section. Before fabrication of the modules, researchers collected information on modulus of elasticity of each lumber lamination. After the bridge modules were fabricated, static bending
tests were conducted at the laminating plant. During those static bending tests, the bridge modules exhibited linear elastic behavior. When actual lumber property data were used in transformed section and finite element models, the models overpredicted the stiffness of the bridge panels. The transformed section results provided the best agreement with test results. During a subsequent monitoring program, the bridges performed well overall; although some damage occurred to the bridge modules during their removal. The
bridges appear to be cost effective alternatives for temporary stream crossing applications. Further work may be needed to determine if this design concept is applicable for permanent bridge applications.