Wood beam reinforcement, mixed sections LVL with built-up
Wood beam reinforcement, mixed sections LVL with built-up
(OP)
Hi,
I have a wood beam built-up 4[2x10] (SPF), with 3 supports, the mid support is at 10 ft, and the total lenght of the beam is 17 ft. I want to remove the support in the middle. I would like to add an additional section for reinforcement (I guess it will be a ply of LVL) on each side. How do you determine the final resistance of the beam. How to determine the LVL depth needed, and when it is mixed with the 4[2x10] in sandwich, what will be the equivalent ?
Or, is it more common to determine the LVL needed and not to care of the 4[2x10] ?
thank you
I have a wood beam built-up 4[2x10] (SPF), with 3 supports, the mid support is at 10 ft, and the total lenght of the beam is 17 ft. I want to remove the support in the middle. I would like to add an additional section for reinforcement (I guess it will be a ply of LVL) on each side. How do you determine the final resistance of the beam. How to determine the LVL depth needed, and when it is mixed with the 4[2x10] in sandwich, what will be the equivalent ?
Or, is it more common to determine the LVL needed and not to care of the 4[2x10] ?
thank you






RE: Wood beam reinforcement, mixed sections LVL with built-up
RE: Wood beam reinforcement, mixed sections LVL with built-up
If the added members are stiffer they will take more load than just the amount that you are short. LVL's have a higher modulus of elasticity and thus will take a higher amount of load than the "softer" 2x10's.
To design these, you must first determine the applied loads on the beam and then determine your shear and moment values based on the longer span.
With that, most would simply "try" a couple of LVL members. Say two 1 3/4" x 14" members sistered onto the sides. These have a set stiffness (EI) that would be compared with the EI value of the (3)2x10 beam.
The beams will take their share of the load in proportion to the relative EI values.
For (3) 2x10's compared to (2) 1 3/4" x 14" the LVL takes about 80% of the load.
So you'd design the combined beam to share the load in that manner. Both should deflect the exact same amount by calculation (relative EI's create proportioned loads to result in the same deflections). This is also ensured by fastening them together.
RE: Wood beam reinforcement, mixed sections LVL with built-up
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Wood beam reinforcement, mixed sections LVL with built-up
RE: Wood beam reinforcement, mixed sections LVL with built-up
RE: Wood beam reinforcement, mixed sections LVL with built-up
RE: Wood beam reinforcement, mixed sections LVL with built-up
Personally, I would design the LVL's to support the total loading.
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.
RE: Wood beam reinforcement, mixed sections LVL with built-up
Then, I'd jack the existing column say 1/2 of the anticipated dead load deflection as if the LVL's were carrying full load, then install the LVLs.
RE: Wood beam reinforcement, mixed sections LVL with built-up
RE: Wood beam reinforcement, mixed sections LVL with built-up
RE: Wood beam reinforcement, mixed sections LVL with built-up
RE: Wood beam reinforcement, mixed sections LVL with built-up
RE: Wood beam reinforcement, mixed sections LVL with built-up
Great spirits have always encountered violent opposition from mediocre minds - Albert Einstein
RE: Wood beam reinforcement, mixed sections LVL with built-up
RE: Wood beam reinforcement, mixed sections LVL with built-up
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Wood beam reinforcement, mixed sections LVL with built-up
"IK do not get why an LVL, a with a higher allowed stress and section, would have a greater depth than the original joists. Makes no sense to me."
The original joists are 4 times 1.5" and the new LVLs are only 2 times 1.75", AND the new span is 17' vs old span = 10'
RE: Wood beam reinforcement, mixed sections LVL with built-up
I have often used C-Channels as you figured. Just make sure you have enough good bearing at each end!!
RE: Wood beam reinforcement, mixed sections LVL with built-up
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com