This study compares and calibrates the design outcomes of load and res
istance factor design (LRFD) to allowable stress design (ASD) procedur
es for hardwood glued-laminated (glulam) timber bridges. Three hardwoo
d species were considered: northern red oak, red maple and yellow pol.
,lar: The percent change between the LRFD and ASD outcomes was found f
or bending moment, shear stress and bearing stress, then a calibration
was performed which placed the LRFD outcomes to within +/-5% of the A
SD outcomes. The absolute magnitude of the difference in design outcom
e by method, when based on 10-year load duration, increased with span
length, with the LRFD outcomes being less conservative than the ASD ou
tcomes. A less conservative design results in a smaller beam section.
The LRFD outcomes were calibrated using a format conversion factor tha
t converted 10-year dry-use ASD allowable strength values to 10-year;
wet-use LRFD base resistance values. Changing to a 2-month load durati
on front a 10-year load duration reduced cross sectional beam and pane
l section requirements in the LRFD designs.