Too much camber! 3

[jerseyshore]

Came across a new one. A local registered design professional sized a EDIT: W18x175 to span 32 ft clear across a new house. The problem was they also specificed an additional camber of 1/2".

Well, guess what, they put it up and it was bad. Not sure if the 1/2" camber was in addition to any natural beam camber (I'm not camber expert,very very rarely do I specify it), but it was humped pretty badly in the middle.

Normally we get called in to reduce deflection, not increase it. They framed the 2nd and 3rd floors and that thing didn't budge. Yes not all of the dead load was on it, but even with the full 15 or 20 PSF at each floor I don't think that's going to make a difference.

Any creative thoughts on how to get this thing close to level?

 

[BridgeSmith]

Something's not adding up. A 50ksi wide flange beam that's 18" deep and 187 lb/ft could carry a uniform load of about 12,000 lb/ft. That seems ridiculously high for a house. Also, As JLNJ pointed out, nobody rolls W18x187 in the US.

 

[dik]

Bridge... it's only A36, so it's not so bad...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[BridgeSmith]

Ok, so only 8000 lbs per ft...

Even supporting a 20 psf roof dead load, a 40 psf snow load, a 50 psf dead + live floor load, that's a tributary width of 72'. Is the house 140' wide?

 

[dik]

you forgot to add an LOL...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dvd]

Heat straightening - maybe get a structural fabrication shop to send a couple of experienced hands out for a couple of hours. Routinely done in conveyor fabrication - fabrication folks seem to read the shapes and do a good job. Worst that could happen is that the house burns down, and then a properly cambered beam could be used ...

see attached article

 

[gte447f]

As others have pointed out, something doesn't sound right about this situation. Sounds like a whole lot of stupidity (I will refrain from saying incompetence) on the part of the "registered design professional", the steel fabricator, and the construction contractor. Otherwise, we aren't getting the full story.

Jersey, why are they pulling you into this mess? Why aren't they taking it up with the registered design professional that designed it? You should be reaching out to them before wading into this.

 

[driftLimiter]

I checked out the software you said was used and saw this image which makes me feel that this could be easy for someone to mess up.

 

[gte447f]

What is a "non-engineer registered design professional"? Architect, Interior Designer, Surveyor?

 

[jerseyshore]

Sorry, W18x175*

 

[BridgeSmith]

Still seems way too big for what it's being used for, unless there's something substantial I'm missing. Who stamped the structural design/plans?

 

[SE2607]

I haven't been on this forum very long, but I must say if nothing else, this forum is entertaining! LOL

The first thing I would say to the "non-engineer registered design professional" is to stay in their own lane. I would then tell the owner that he got what he paid for. I would then tell the contractor "Hey, I f*cked up. Deal with it."

Alternatively, they could eliminate the camber by hanging a chunk of concrete from the center of the beam. It would only have to be 6'-8" cubed! Call it an "architectural feature".

Seriously, 1/2" in 32 feet is hardly visible. It might be difficult to frame around, but I'm sure it's better than the alternatives.

 

[jerseyshore]

I'm out right now, but I didn't see all of the calcs beforehand. This thing is supporting a pretty big house. Some W10x88s and W10x54s frame into it, but still, I've rarely seen this type of beam used in bigger steel buildings let alone in a house. That beam could probably hold up 10 of my entire houses.

And yes non-engineer RDP is just a snarky way of me saying Architect. Architects probably do their own structure on 95% of houses in NJ. Most are pretty straightforward, but obviously this is not something that should've been done.

That beanchek program is something nearly every architect around here uses. Mostly for flitch beams, but it's cheap and as you can tell not a great program.

 

[jerseyshore]

And the architect is the one who called me. I looked at something totally separate from this (garage floor), but you know how these things go, once you consult for one aspect of a project they call you in for all of the other issues.

They do have gyp on the floors, but their biggest issue was just the precut studs below are too short so they'll have to lengthen things as needed.

Does anyone know how much natural camber would even be on a beam like this? And is cambering a small amount difficult? I truly have no idea. Don't think I've called for camber in a steel beam ever. Seems reckless that a program like BeachChek can even recommend camber like that. DL posted the screenshot above and it shows for wood beams too.

 

[gte447f]

I think natural mill camber tolerance is limited to 1/8" per 10' of length. I believe the tolerance for induced camber is -0",+1/2" plus 1/8" per 10' over 50'.

 

[gte447f]

Rules of thumb for camber.

Only spec camber of 3/4" or more. Camber less than 3/4" is difficult to induce.

Don't camber beams shorter than 24'.

Don't camber beams with web thickness less than or equal to 1/4"

Don't camber beams less than 14" deep.

These are just rules of thumb. Some of them are based on common fabricator capabilities, so individual fabricators may have different guidelines or recommendations.

There is a April 2009 Structure Magazine article that includes the above information. You can look it up yourself if interested.

 

[gte447f]

AISC has a Design Guide 36: Design Considerations for Camber. I have not read the document.

 

[dik]

and we do some good serious stuff here, too... more than just entertaining...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[TLHS]

How often are you guys actually cambering things? I have done it maximum twice in the last ten years, but I work in a lot of industrial types of things where dead loads that you'd consider cambering out are a very small part of the overall load generally, and you can normally size members to reasonably optimal depths.

 

[driftLimiter]

We've done three tiltups this year and they wanted WF beams instead of OWSJ. To get the 52' spans we end up with deflection controlled 'joists'. Here we specified camber as a means to reduce weight. At these spans I get camber between 1" - 2". On these buildings you have 100s of joists so if you can save some weight on camber its well worth it.

 

[BridgeSmith]

For bridge girders, we've decided that heat cambering is not cost-effective compared to fabricating welded plate girders. Cold cambering isn't an option for most of the rolled beams we use (w24's and up).