Minimum number of bolts
Minimum number of bolts
(OP)
Many design codes and specifications (e.g. AASHTO & AISC) require that bolted connections for structurally significant components contain a minimum of two bolts, regardless of the strength required.
Today I was working with the NDS Timber design spec and noticed that this requirement doesn't seem to be included. Did I miss it, or is one connector all that is required for bolted/lagged timber connections?
Thanks!
Today I was working with the NDS Timber design spec and noticed that this requirement doesn't seem to be included. Did I miss it, or is one connector all that is required for bolted/lagged timber connections?
Thanks!






RE: Minimum number of bolts
RE: Minimum number of bolts
RE: Minimum number of bolts
Try the same with two pencil holes.
I always liked this analogy with bolts.
RE: Minimum number of bolts
RE: Minimum number of bolts
I can see situations that could arise where one bolt has way more capacity than the connection requires. Off the cuff (remember I am not an authority on wood design), I would probably be OK with a single bolt if the calculations show I have more than twice the capacity I need. This philosophy is consistent with ACI that requires you to provide stirrups when the shear demand exceeds half the capacity of the concrete alone.
RE: Minimum number of bolts
Applying this to the design of wood connections the rule of thumb I follow is the fewer the number of fastners the better. Don't use eight bolts if only four will carry the load.
Because of wood shrinkage and distribution of load in connections the use of more fasteners then you need often times produces poorer results. To get a feel for this look at the geometry factor and the reduction required for eight bolts or eight shear plates in a row.
In practice I seen connections that by leaving out every other bolt, you could increase the calculated compression capacity.
Returning to your orginal question, I am not aware of any code provision that requires the use of a minimum of two bolts. In practice I see a lot of single bolt connections.
Personally I like to use a minimum of two bolts for several reasons. As stated above for the prevention of rotation and for redundancy. I also think it is good detailing practice .
RE: Minimum number of bolts
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Chapter 5 has a good summary with some interesting conclusions. If I read it correctly, the "optimum" number of bolts per connection (for the loading tested) may be three.
My own experiences indicate that a reasonable compromise, in many cases, is one bolt (sized to take the loads) AND a small number of appropriately sized nails for partial redundancy and to improve joint rigidity.
www.SlideRuleEra.net
RE: Minimum number of bolts
Regards,
Lutfi
RE: Minimum number of bolts