Comparative Analysis of Design Codes for Timber Bridges in Canada, the United States, and Europe

The United States recently completed its transition from the allowable stress design code to the load and resistance factor design (LRFD) reliability-based code for the design of most highway bridges. For an international perspective on the LRFD-based bridge codes, a comparative analysis is presented: a study addressed national codes of the United States, Canada, and Europe. The study focused on codes related to timber bridges and involved the following parameters: organization format, superstructure types, loads, materials, design for bending, design for shear, deflection criteria, and durability requirements. The investigation found many similarities and some distinctive differences between the three bridge codes. Although the United States and Canada have different design load configurations, these result in similar bending moments and shear effects over a typical span range. However, the design load configuration in the European code produces bending moment and shear effects that are two to three times greater than the U.S. and Canadian levels. The comparative design of a glulam girder bridge revealed that the smallest beam size was required by the Canadian code and the largest was required by the European code.