Load sharing effects in light-frame wood-truss assemblies

Load sharing among repetitive wood members interconnected by structural she athing strengthens light-frame assemblies beyond that assumed in designing a single member. A repetitive member factor of 1.15 applied to bending resi stance has been traditionally included in wood design standards to account for this effect. The focus of this study was to quantify load-sharing effec ts on members in metal-plate-connected wood trusses. This was accomplished using a detailed structural analysis model and statistical characterization s of lumber stiffness and strength properties. Monte Carlo simulations were conducted on six common truss configurations and one dimension lumber jois t Boor where wood member properties were randomly selected from distributio ns representing properties of the lumber grade. The assemblies were analyze d with and without attached sheathing to directly quantify the load-sharing effects in the system. The computed mean load-sharing factors ranged from 1.06 to 1.24 in the truss assemblies and from 1.17 to 1.19 for the joist as sembly. The load-sharing factors were found to be applicable to wood truss members subject to tensile or compressive forces in addition to bending for ces.