Splice in Wood Beam

[ajk1]

Is there any way to make a splice in a wood beam that is too long to bring into the building in one piece? The span is 8 m and the beam depth is 400 mm.

Is it generally better to try to splice at mid-span or at the quarter point?

 

[msquared48]

A splice would be hard to say thecleast. I would rethink the solution and consider the possibility of using a new transverse flush beam to support the beam in question at the cut point.

Mike McCann, PE, SE (WA)

 

[Brad805]

Splices in a large wood beam are a last resort. The connection plates, lag screws (split rings or glulam rivets) and sources for field error are a problem. If I had too, I would look at the end 1/3 assuming that was short enough. Shear is not quite as bad to deal with, but the axial forces at mid span can be a problem if the beam is stressed.

I assume you have some corners to go around or stairs to go up. No windows or doors that can be removed to get the beam in one piece?

 

[woodman88]

Do as msquared48 states or cut a hole in the building and slip the whole beam in that way. The only way I would splice a wood beam is with steel channels to each face.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[KootK]

If you can stomach the extra material cost, you could use a multi-ply beam with staggered splice joints. As we've discussed here before, that scheme has some interesting nuances as well.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[TehMightyEngineer]

The only time I've ever spliced a beam was in a continuous beam where I could suffer a non-moment connected splice. Essentially there are very few situations where these are worth the trouble. Often the only reason you're splicing the beam is because it's very large. Large beams require large splices. These large splices cause lots of cracking issues, very difficult to detail it correctly. Often easier to just redesign the beam or cut a hole in the wall in my opinion. Alternative materials like steel or wood trusses (which can be spliced a lot easier) make more sense as well.

Maine Professional and Structural Engineer.
(Just passed the 16-hour SE exam, woohoo!)

 

[jfmann]

Splicing 26-foot long x 16-inch deep wood beam should be feasible with steel plates, but it is difficult to imagine there is not a more cost effective solution......such as sky hook, whoa! (chuckles).

Back in the "day" (further back than I dare realize).......I designed 21-foot long steel beam to allow for removal of interior bearing wall at center of 2-story house. After handing over plans, I queried owner as to whether contractor had figured out how to install........ahhhh!! Months later, pleased-as-punch owner sent photos showing final result.....so I had to ask......how did that large I-beam get in there?.......owner says crew of eleven "linebackers" working for steel fabricator hauled 'er in sliding door in back wall.......reminded me of brief tour of duty on railroad, moving steel rails........so perhaps you just need to call in the troops........or look for sky hook!

John F Mann, PE

http://www.structural101.com

 

[ajk1]

The responses are pretty well what I told our engineer but came on the forum just to be sure.

To Kootk - you have a good memory -- I had forgotten about the multi-ply beam that we discussed in connection with another project! - maybe worth having a look at that possibility...thanks.

 

[ajk1]

To Kootk - apparently this is only a single span beam so I don't think the multi-ply beam will work if it is only one span. Multi-ply requires continuity of plies. Also the engineer says that the longest piece of wood they can get in is 4 m; the beam length is 8 m

 

[KootK]

Think of the plies on either side of the main spliced beam as simply really long side plates. In your case, the "beam" is two one ply by 4m pieces connected end to end. The splice plates would be two 4m lengths on either side of the beam and centered on the splice.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[jfmann]

Where is this location that length of wood is limited to 4 meters (13 feet)?.........are you in some desolate desert area without wood?........or Katmandu? ;-)

It is essential to correctly address forces involved with splice design.

For LVL, 5-1/4" thick by 16" deep (Fb = 2900 psi)....capacity of flange splice (top & bottom) would have to be about 40,000 lbs to fully develop design bending capacity of this beam. Steel plate (A36) would have to be at least 1/4-inch thick by 5-1/4 inch wide.
To connect splice plate to beam requires (90) 1/2-inch diameter lag screws on each side of joint....or 180 lag screws for tension splice at bottom (and probably same for compression splice at top unless you want to try to use compression of wood bearing at joint). Even if 3 rows are used......with spacing of 2 inches.....length of splice on each side of joint is then 60 inches which almost reaches end of beam at support!

Consideration of the magnitude of forces involved may temper enthusiasm for any multi-splice arrangement using staggered joints.......especially without any members that are full-length. At the very least, such design should be tested (perhaps at the SRE Test Labs).



John F Mann, PE

http://www.structural101.com

 

[ajk1]

Thanks for the latest comments. I have to think about Kootk's comment overnight.

jfmann - the problem is not getting 8 m long wood beam; the problem is getting it into the basement of a old narrow building in downtown Toronto.

 

[racookpe1978]

It will be far, far easier to remove two, three, or four of the stair treads, then lower the beam down through the hole where the stair treads used to be, than it will be to splice the main brace (er, beam).

 

[racookpe1978]

Now, another way is to leave the wooden beam "unlaminated" and bend the individual laminate plies down and through the "bendy" stairway and doors, then glue the laminates together in place in the basement with 14,000 clamps. A 1/8 thick laminate is practically paper as far as stiffness goes. 1/4 laminates can bend a lot if the bend radius is gentle and handled with care.

Basement in Toronto, right? Is it dry enough, warm enough to let the glue set and dry for 2-3 days without being in an oven or steam heated vessel?