Torsion on LVL beam supporting brick 2

[structurebeton]

I recently did an inspection on an 18 ft span beam lintel, most likely made of an LVL beam (Drywall is still in place). The beam is supporting half of a 2nd story, roof and brick. The brick is supported on a steel angle which in turn is bolted to the LVL beam. The beam is currently at a deflection of L/300 and the brick facade has cracked. There is also slight twist of the steel angle.

The questions are:
1) Is it allowed by code to support brick with a Pre-engineered wood beam? (Despite the fact that the criteria of L/600 deflection is respected). I could not locate on IBC2006 were this is addressed.

2) Do you have a good reference on calculating strength of a wood beam due to excentric loading, such as brick?

3) In repairing the beam, should we simply replace the wood with a steel tube beam, which then would require steel columns...

Any comments would be appreciated. Thanks,

ST

 

[structurebeton]

The pattern of the cracking does not indicate a settlement problem.

 

[JAE]

structurebeton

If you are designing strictly under the IRC, then it does appear that the LVL is a code violation (i.e. supporting masonry veneer over an opening per R703.7.3.)

The IRC does allow masonry to be supported by wood such as cases where an exterior wall turns back over a roof (per IRC Figure R703.7.2.1). But it explicitly says no to wood beams supporting masonry over openings.

Since you have a wood beam supporting masonry in violation of the IRC, your next step would seem to be to go to the IBC in accordance with IRC R301.1.3 where it states that "Engineered design in accordance with the International Building Code is permitted for all buildings and stuctures, and parts thereof, included in the scope of this code."

So as an engineer, you can go to the IBC as structurebeton mentioned above. So that then raises the question of whether wood beams can support masonry veneer in the IBC.

In the IBC - section 1405.5 indicates that masonry veneer must meet ACI 530. Also, section 2304.12 states explicitly that no masonry may be supported by wood.

ACI 530, section 6.2.2.3.3 states the following: "Provide noncombustible lintes or supports attached to noncombustible framing over openings where anchored veneer is not self-supporting..."

So the wood beam is simply not code-compliant.

 

[DaveAtkins]

I just looked at the photos, and I think we all may be going down the wrong path here. I think these cracks have nothing to do with the deflection or torsional rotation of the lintel, but rather have to do with the fact that THERE ARE NO EXPANSION JOINTS IN ANY OF THE BRICK VENEER!!! The brick has all kinds of openings, corners, etc., with no allowance for brick expansion. Of course the hot Georgia sun is going to cause all of this veneer to expand, and it is cracking at openings and corners, where the brick is weakest.

I would recommend cutting in a vertical expansion joint on each side of the overhead door, filled with sealant and a backer rod. I would consider adding a vertical EJ where the veneer steps up over the projection, to the left of the overhead door. I wouldn't do anything with the lintel.

DaveAtkins

 

[structurebeton]

Even though the lack of control joint would have contributed to the cracking, the pattern of cracking (diagonal at the edges and vertical in the middle span) indicates to me a cracking due to excessive deflection.

What I am a bit concerned now is that apparently wood beam lintels are illegal. The contractor will have a fit, and generally speaking, because they haven't seen that on a house they will think that I am not a qualified engineer.

 

[diarmud]

What are the code provisions and are they are applied in your area? Check with the contractor (or others) to determine if it's common practice in your area to support masonry with an LVL.

If this required a building permit, go take a look at the approved plans and compare them to what you have - bigmig is right, drywall is cheap, you need to know the existing conditions.

The building code official will tell you if they allow it, you can ask their opinion about common practice and if they think it's acceptable. Be somewhat obtuse, dont' identify your client or the house yet.

Please let us know how it turns out.

 

[JAE]

I'd agree with diarmud on this. The first thing you should do is contact the building department with this generic question - certainly there are many houses in your area with a garage and brick over the door. Might be interesting to see what they say.

If they say LVL's are OK, then I'd also be interested in how they respond to the code logic I posted above. It may be that the local code, as adopted, had amendments to the IRC that allow it but I wouldn't bet that would be true.

 

[DaveAtkins]

I think there must be exceptions to the Code, because brick supported off wood lintels has been done here in Wisconsin, even on apartment buildings, which are governed by the IBC, not the UDC (Uniform Dwelling Code governs single family residences and duplexes here). Is it possible that an LVL or PSL protected by GWB can be considered "noncombustible"? I don't think so, but what the Code official thinks is what really matters.

I just find it hard to believe a steel lintel is required for your condition.

DaveAtkins

 

[kslee1000]

I agree that the beam has deflected and causing those cracks. Since this occurrance has been a slow process as you noted, I guess the wood beam has gradually weakened with time. I am not an expert on wood, only speaking from my own experience with wood beams in my garage, have you considered jack-up the beam and strengthen it by adding steel facial plates if there is adequate space?

 

[msquared48]

It's not that the wood has weakened with time, it's the process of increased humidity and drying throughout the year.

A piece of wood, when wet with high humdity as in Georgia - 90 to 95% extended at times, then drying out with a decrease in humidity, will develop a memory of the deflection it has seen and will not return to the original shape. This happens with varying load and varying humidity. The same phenomenon is used to advantage in the construction of wicker furniture.

This is not a problem that is going to go away on its own. It will continue long term. The installation of a steel beam would avoid this problem.

Mike McCann
MMC Engineering

 

[structurebeton]

Mike,
I believe they used an LVL or PSL to span 18 ft. However, I think it was not designed to suppport 1.5x dead load => Therefore, the beam has been subject to long term creep. I think LVLs are less subject to humidity conditions, don't they?
Anyway, when they uncover the beam header, I will see the real story behind...

 

[hokie66]

I agree with DaveAtkins that there should have been vertical control joints. But I think that the cracks are definitely due to deflection rather than temperature affects.

Some have said that it is common to have brick veneer over garage doors, but I think this instance is uncommon. You have a two car garage with one single door, a roof valley coming in over the door, varying height veneer, a lot of things to go wrong. The architectural design contributed a lot to this situation.

 

[JAE]

hokie66, in your area of the world do they use wood beams to support concrete or masonry? I know in some places there are very hard woods that may not be susceptible to the kinds of moisture concerns that compelled the IBC provisions here in the states.

 

[hokie66]

JAE, I am not really up with the current housing code provisions here, as I don't do any small scale residential work. I will post in the AS/NZS code issues forum and see if someone knows. If not, I will check out the BCA (Building Code of Australia) soon and let you know.

I don't think there are provisions preventing concrete or masonry support on timber structures. Certainly, there are a lot of existing examples, including lintels. There are a lot of old brick buildings here with hardwood footings. As long as the sapwood was removed and a durable species was used, they are generally still in good condition after 60 to 100 years. One species, called ironbark for good reason, was commonly used. Even the termites found it too hard. Most housing here was built with hardwoods until recent years, but now plantation pine is the preferred material with house builders. And now the termites are well fed.

Regardless of the supporting structure, it would be very uncommon here to use brick veneer over a double garage door. Lightweight cladding is used.

 

[msquared48]

I don't know how others feel here, but I'll throw this thought out for discussion/consideration...

Could it be the INTENT of the IBC/IRC is that wood members not support STRUCTURAL concrete/masonry, but that brick VENEER supported by wood is allowed? It seems to me that there is a difference.

True that falling brick veneer can kill, but that does not involve the structural failure of any main STRUCTURAL building component. If so, it needs to be clarified. If not, then maybe I'm reading more into the code than exists.

Mike McCann
MMC Engineering

 

[JAE]

Mike - the part in the IRC that denied masonry over openings was in a veneer section, I believe....I'm away from the office but I'll check on Monday.

 

[apsix]

"Regardless of the supporting structure, it would be very uncommon here to use brick veneer over a double garage door."
In my experience (Aus, UK) no one would use timber to support brick veneer in a typical suburban home, especially over an 18' door.
Obviously it is more common in other parts of the world.

 

[msquared48]

This is why I wonder if a structural engineer was involved in the original design of the residence...

Mike McCann
MMC Engineering

 

[structurebeton]

Because the beam is failing, I very doubt a structural engineer was involved. In fact, very seldom a Structural engineer is involved in residential structures...

 

[structurebeton]

Here is the conclusion of this issue. Since I had given and estimate of between $5,000 and $ 30,000 to do the repairs, the seller had seek another opinion and got this second opinion, AFTER the sheetrock was pulled out:

....The 18-foot garage door opening is framed with a 3-ply 18” LVL. The beam is supporting the second floor
bonus room, roof and brick loads. There are cracks in the brick directly above the center of the door, along
the right side, and above the door on the left. Our calculations indicate that the 3-ply beam is slightly
overstressed to meet the brick deflection requirements of L/600. Furthermore, it is our understanding once
the brick was removed to verify bolting of the steel angle, it was discovered that at some locations the
vertical leg of the angle was not in direct contact with the beam, but rather compressible material. We
recommend that the compressible material be removed from behind the angle and the angle be bolted
directly to the beam. In addition, we recommend installing a 2-ply 16” LVL directly under the floor joists
spanning past the existing door header king studs. The new beam will carry the second floor load,
removing the load from the garage header....


So, there was 2 issues: Undersized Beam, And Compressible material between the angle and the beam...

This still does not resolve whether or not it is legal to use wood as a lintel beam.

 

[weh]

The IRC (2006,703.7) allows the use of wood members to support brick veneer provided the brick weighs less than 40 psf and deflection is limited to L/600 for total load and and is located in seismic zone A,B or C.