Glulam Beam Lateral Stability Over Supports - Wood Design Expert

[Sofish]

Hi All,

I'm designing a simply supported glulam for a pile cap soffit form. Glulam size is 10.75"x18" 24F-V8 1.8E, balanced layup. Each end is supported by a HSS4x4x0.375 with 3/4" dia coil rod hanger, (1) coil rod on either side of the glulam. This glulam hanger only provides vertical support and does not provide lateral support or rotational support.

Approach 1)
Since the d/b <2 for this glulam, no lateral stability support is required along the length plus rotation does not need to be prevented at these hanger supports. This approach assumes that you can apply stability requirements from 2018 NDS section 3.3.3.2 that allows use of alternative guidelines from section 4.4.1 (d/b <2 = no lateral bracing required). Section 3.3.3.2 states that it applies only to "sawn lumber", but article TT-085B by APA states that section 3.3.3.2 and 4.4.1 is applicable to glulams.

Approach 2)
On the other hand, going strictly by the language of section 3.3.3.2, you would not be able to use 4.4.1, since our circumstance is for a glulam and by section 3.3.4 --> d/b >1, therefore rotational prevention blocking is required over supports.

Can anyone speak from experience on if d/b <2 is applicable to glulams in eliminating the need for any kind of lateral or rotational bracing?

Thanks

 

[phamENG]

Is this temporary form work for concrete? If so, I wouldn't worry too much. A sketch would help to make sure I'm seeing it right, but I think you're probably okay.

In general, you don't need to meet detailing requirements for a permanent structure in temporary forms that will only be loaded for a few days. Especially those where you know exactly what loading to expect.

 

[Agent666]

I'd say wood is wood, whether sawn lumber or Glulam or LVL. It all buckles the same.

The only difference I see is that maybe Glulam is stronger therefore the code writers envisaged higher restraint forces or something and altered the rules accordingly. But in this part of the world (NZ) there is no distinction between the buckling of sawn lumber and any engineered wood product. There are some differences in determining capacities, but the same buckling behaviour applies.