Multi Ply LVL beams framing into another multi ply LVL beam - side loading, not top loaded

[Said the Sky]

So where I am from the base building engineer for a multi storey regular stickframe building may or may not specify engineered wood beams (LVL, PSL etc), for the most part we "try" to coordinate with the supplier designer with them providing us their shop drawings and we take care of the total building stability in terms of how the gravity loading affects our lateral design. The supplier designer usually provides engineered joist sizes and spacing and usually the engineered beam plies (depth usually governed by architect), they sometimes get to choose the layout themselves, then when we recieve their drawings we see if we can make our lateral work based on that.

per the simpson strongtie hangers - as an alternative to nails they may use longer SD screws that penetrate into multiple plies. Who specifies when to use the longer screws and when to use nails? is it the supplier designer? and per the circled comment in the picture, who supplies the extra fastner requirements at the location of the connection? is this the supplier also? I know for typical uniform loading for multiply beams there fastener tables from the supplier which I doubt the contractor never reads.. and I doubt they would be able to read the charts anyways as it requires calculation of the uniform loading to find the nail requirements. I believe whats more critical is the beam to beam connections where there is a large concentrated load and may require additional fasteners.

I guess my question is, when we have a multi ply beam framing into another multi ply beam, who designs the fastener requirements at the location where the two beams meet. Since in side loaded wood beams we have to ensure there is enough lateral resistance of the fasteners to carry the load to all beams and not overload the one beam.

tia

 

[JStructsteel]

In my world, whoever sizes the beam should size and specify the connection. Who ever stamps is responsible too.

What you are describing is a simple proposition.

 

[DoubleStud]

The engineer for sure. The spec usually specify how to nail multi-ply beam together. If that standard spec nailing isn’t enough, then it is the designer’s responsibility to say so.

 

[XR250]

You

 

[gte447f]

It sounds like you are delegating the design of the floor framing to a "specialty engineer" retained by the contractor? Is that the case? If so, then I could see an argument that the engineer responsible for the delegated design (not you) should be responsible for the connections between floor framing members, similar to how the engineer responsible for the delegated design of metal plate connected wood trusses is responsible for truss to truss connections.

Whether or not the design of simple floor framing members, whether engineered wood products or not, should be delegated to a "specialty engineer" is another story. I personally think the practice of delegated design is getting out of control, and this seems like a prime example of how ridiculous it is getting. Why shouldn't the EOR design these simple floor framing members?

 

[Said the Sky]

where I am from the supplier has engineers/designers on staff that design the roof trusses and also the floor framing such as engineered joists, engineered beams. They will provide shop drawings to the EOR for review so we know where to place column supports for their beams, and size our foundations based on which way their joists are running etc etc. In these shop drawings they provide all connections from beam to beam and joist to beam etc. However in these shop drawings I don't see any specifications with respect to the nailing requirement between plies.

We do specify basic nailing patterns based on uniform loading situation, but the beam to beam connection I believe should be scope of the supplier design engineer if the uniform loading nailing pattern between plies is not sufficient.

 

[structSU10]

So mark up the submittal and ask for more information? Or give them a call and talk it through?

Your job is to make sure what they provide meets the design intent. It is surprising the column layout and such is also up to them but if that is the case as long as they meet your performance requirements on your drawings and specs and are stamping everything all you need to do is ensure it works within the prescribed system you show.

 

[gte447f]

Said the Sky, in the delegated design scenario that you have described, I agree that the delegated design engineer (not you) should be responsible for the design of the beam-to-beam connection, including any additional/supplemental fasteners required between various plies of the multi-ply supporting beam.

P.s. These types of things (e.g., loop holes, gray areas, and things falling through the cracks of coordination between parties) are precisely the reasons why I generally don't think the practice of delegated design is good for the profession of engineering, especially for simple things like floor framing members of dimensional or engineered lumber.

 

[Said the Sky]

thanks GTE

I believe the delegated design is common in my area is because of cost savings, its better to pay the suppler designer (not a full fledged engineer) to design it in their proprietary software, than have an engineer size the beams.

but I have also worked on projects where we sized the beams (more complicated layout) and we provide the loads to the supplier to design connections. I have also noticed that when we do provide the beam layouts they run their own calculations anyways. (I see it in their calculation package).

I agree- all the delegated design has muddied the waters a bit and took some scope away from the EOR. I feel the same with steel buildings where we send our beam and layout to the supplier and they design the connections. At my previous firm I would have liked to design the connections, it makes for a more well rounded engineer.

 

[phamENG]

Said the Sky - there should be essentially zero cost savings doing it that way. Because the EOR should be reviewing the supplier's calcs and layouts in detail. And you still have to do the load chasedowns to spec columns, studs, and footings anyway. So the cost savings only comes at the expense of the EOR doing his/her job. For items that are true specialties - connection design (beyond basic shear/moment/brace connections), proprietary systems, MPC trusses, etc. - delegated design makes sense. But for standard beam sizes...it's inexcusable.

I delegate floor systems using engineered wood products and trusses. There are too many possible manufacturers to choose from, so I spec APA Performance Rated I-Joist categories for pricing, and have the supplier submit detailed calcs of the actual product to be installed.

For LVLs, I just spec sizes based on Weyerhauser since they're the weakest around - if they substitute anything else it'll be at least as strong/stiff.

At the end of the day, every structural member in a building is the responsibility of the Engineer of Record, delegated or not.