I would think for wood it would be relatively additive. I would be providing the largest spacing between the unlike fasteners (likely governed by bolts).

here was one study for steel-to-timber joints with nails and bolts

http://www.researchgate.net/publication/257476094_...

By CWC they are additive. The controlling failure for nails in anything softer than D.F. is usually lateral deformation of the nail, while in bolts it is usually yielding of the wood itself.

I would think a prudent design would to find the maximum capacity of your nails first, and then size an appropriate bolting connection to take up the rest as the nails will usually fail first.

Thanks for the info, and yes wood connections.

EIT
www.HowToEngineer.com

Is there a section reference for the CWC that you might be able to provide?

EIT
www.HowToEngineer.com

I'm living up to this one... I may have lied - I was thinking of a Simpson whitepaper on multiple fasteners but it was not CWC or CSA approved - truly sorry about that. Will fact check more thoroughly before I post in the future.

OS86 - 10.2.2.3.1 & 10.2.2.3.2: "... fastenings of the same type and size arranged symmetrically..."

I would not use both unless the bolts could be installed first, then loaded to take up the hole slop, then the nails installed. (Like that's going to happen). Otherwise the nails could take all the load until they fail if there is too much play in the bolt holes.

Mike McCann, PE, SE (WA)

@Signious - no worries.

@msquared - Good points.

This is evaluating an existing condition that has been there for a long while. If designing new I would not combine them. For my situation even combining the nails and bolts did not meet the required strength, so I will need to reinforce the connection ("but at has stood for years!" they will shout I'm sure). I was curious for future reference.

EIT
www.HowToEngineer.com