Bolt Connections

 

Considerations

1. number of shear planes

• single
• double
• etc

Multiply value for weakest plane by the number of planes.

 

2. types of structural members connected

• wood-to-wood
• wood-to-metal
• wood-to-concrete
• wood-to-masonry

Photo Journal of Home Construction - see STRUCTURE categories

 

Washers

1. loads both shear and axial loads 2. locations head-to-wood, nut-to-wood 3. shape bearing stress < F'c⊥  4. purpose protect wood  5. installation do not embed washer retighten as wood dries 6. quality plastic hinges predictable Fyb		source
		source

 

A307 bolts

NDS tables based on Fyb = 45 ksi ASTM A307 Standard Specification for Carbon Steel Bolts, Studs, and Threaded Rod 60,000 PSI Tensile Strength grade alloys hardness ultimate tensile strength Fu no minimum yield strength Fy historically okay  SAE J429 Mechanical and Material Requirements for Externally Threaded Fasteners proof, yield, ultimate curve NDS appendix I		source

 

 

Drilled Holes

proper hole diameter + good alignment = light tapping

• hole 1/32" to 1/16" larger than  bolt
• holes too small → splitting
• holes too large → nonuniform bearing

source

source

 

 cut vs tear wood

smooth surface = increased bearing capacity + less deformation		Wood Handbook
sharp bits higher drill speed lower feed rate		source

 A307 bolts

full-body vs reduced-shank/body

source

link link purpose

• body 9% smaller than major-thread diameter
• doubles gap

 

 

Bolt Sizes

NDS only has dowel bearing strengths F_e for ≤ 1-in. diameter

small-diameters flexible enough to redistribute stresses and create more uniform loading