multi-ply wood constructed columns
multi-ply wood constructed columns
(OP)
I have constructed twenty eight 5-ply built up wood columns made with 2" x 8" treated lumber. Each column is embedded in concrete(two foot diameter footing, four foot deep). These columns extend 13.5' above ground and support a cabin approximately 7 tons.
My question is what would an appropriate bolt pattern be using 1/2" diameter galvanized bolts. The cabin is located in a river flood plain and at present height is considered above the 100 year flood mark.
It has been suggested two bolts parallel to each other every 8". This seems excessive.
Also, is there any other approved method of bonding the 2"x8" lumber together other than bolting that can be used in this application(lag screws ect...). No glue has been used in the construction of the columns only various lengths of screws.
Thanks for your response.
My question is what would an appropriate bolt pattern be using 1/2" diameter galvanized bolts. The cabin is located in a river flood plain and at present height is considered above the 100 year flood mark.
It has been suggested two bolts parallel to each other every 8". This seems excessive.
Also, is there any other approved method of bonding the 2"x8" lumber together other than bolting that can be used in this application(lag screws ect...). No glue has been used in the construction of the columns only various lengths of screws.
Thanks for your response.






RE: multi-ply wood constructed columns
I'll also assume that you have put diagonal or X bracing in to handle horizontal loads like wind or water borne debris.
RE: multi-ply wood constructed columns
The NDS will provide you with minimum fastenings you need for built-up columns and guidelines on whether to use nails, lags, or bolts.
Two bolts at 8" o.c. does seem excessive but I am not experienced with the requirements so don't take my word for it. At the same time, three bolts seems too light. IMHO of course
RE: multi-ply wood constructed columns
1. What type of pressure treated wood was used? Is it the new stuff? If yes, you almost have to use stainless steel for fasteners.
2. What is the maximum vertical load on any column?
3. What is the maximum horizontal load on any column due to: wind on the cabin, water force on the columns, static and dynamic loadings on the columns due to stream debris and/or trees?
4. What is the maximum moment on the columns due to the cabin?
5. What are the columns founded upon? Rock?
6. Is all the lateral bracing provided by the columns embedded in the concrete footings? Any diagonals?
7. Any kind of wood in direct contact with concrete and some water will "rot" or deteriorate with time.
8. What is the stream velocity during flooding?
9. How high does the water get on the exposed columns during flooding?
10. Is there the potential of stream scour around the column footings during the flood event?
You need to get the professional recommendations from a knowledgeable structural engineer.