Live load distribution on longitudinal glued-laminated timber deck bridges

Over the past few years the United States Department of Agriculture (USDA), Forest Products Laboratory (FPL), and the Federal Highway Administration (FHWA) have supported several research programs. This paper is a result of a study sponsored by FPL, with the objective of determining how truckloads are distributed to the deck panels of a longitudinal glued-laminated timber deck bridge. Currently, the American Association of State Highway and Transportation Officials (AASHTO) LRFD (load and resistance factor design) Bridge Design Specification provides live load distribution provisions for longitudinal glued-laminated timber deck-panel bridges. The AASHTO LRFD live load distribution provisions for longitudinal glued-laminated timber deck bridges were based on the assumption that the bridge deck behaves as one slab and ignores the discontinuity of the bridge deck panels. This study investigated this assumption by using analytical models that validated field test data from several in-service bridges and data from a full-scale laboratory test bridge. The analytical models accounted for the effects of the interface between the deck panels as well as the effects of the transverse stiffener beams on the distribution of the live- load. The analytical live load distribution results above were compared with both the AASHTO LRFD and AASHTO Standard Specifications.