McCall Engineering (ME) was retained by FPInnovations to conduct the study of non-forest industry loadings on forestry bridges and to prepare simplified Live Load Capacity Factors (LLCFs) for typical forestry bridge types that can be used to screen forestry bridges for an overload quickly. Since data for heavy off-highway non-forest industry vehicles were not readily available, ME proposed to represent overloads by three typical overweight permit vehicle configurations; a standard track width low bed vehicle, a wheeler axle (8-tire axle) low bed vehicle and a wheeler axle platform trailer vehicle. It was assumed that an overweight permit would be sought from the MOF when a non-forest industry equipment transporter plans to move a heavy load on exclusively off-highway routes that include a Forest Service Road (FSR). The live load factors for these configurations operating under single trip permits are well understood and summarized in CSA S6 (Canadian Hwy Design Bridge Code).
The objective of this study was to calculate simplified adjusted LLCFs for representative forestry bridge types, spans and design vehicles, and three reference permit vehicle types and to develop a tool to enable LLCFs to be extracted for spans ranging from 5 m to 70 m and considering four typical bridge cross sections, 13 bridge design vehicles and three reference permit vehicles. The LLCFs can then be used by experienced bridge evaluators to quickly screen-evaluate bridges for any overload vehicle with a similar (or wider) track width as one of the reference permit vehicles.