Institute for Transportation

This paper presents results of timber plank tests, for planks used in highway bridge decks. Tests were carried out to determine the flat-wise use factor, which is represented by the ratio of modulus of rupture (MOR) for flat-wise loading to MOR for edge-wise loading. Four sizes were tested. The tests confirmed that MOR for flat-wise loading is considerably larger than for edge-wise loading for the larger planks tested and that flat-wise use factor increases for larger plank width. The flat-wise use factor in the current bridge design code is overly conservative for typical plank sizes. New flat-wise use factors are recommended for the design of wood plank decks for highway bridges. The recommended values vary from 1.10 to 1.6.