Steel Beam supporting 5 Ton Crane

I had this project where a 10 metre I-beam (UB 762x267X197 kg/m) was designed to carry a 5Ton crane girder. I have designed the I-beam based on BS5950. I have factored the load to account for the dynamic effect, includes transverse load effect, moving load effect and a unrestraint length of 10 metres. However soon after the installation of the crane, when the crane moves, it creates loud noises. The crane supplier have blame it on the underdesign of the I-beam. And now the owner is going to sue us. Can someone advice if the I-beam is adequate for the intended usage or has it been underdesigned. Appreciate your response.

 

[IJR]

I guess that if the beam is well designed, and if you observe no vibration or significant deflections in the beam, then one reason could be bad rail/wheel alignment.

Think about that. I have never heard of a crane girder making noise.

 

[butelja]

Did you check to see what style of wheels the crane trolley is using? They are typically available in either tapered or non-tapered versions. The tapered wheels work well on a standard S section I-beam due to the tapered flange, but the non-tapered will tend to have the trolley run off center and scrape on the beam. I hope this helps.

 

[ADT]

I agree with the others re. the rail/wheel thing. Also if your beam was under-designed it wouldn't make noises it would deflect, deform etc.

But the main point to make is that you must get up there while the crane is operating and find out what is making this noise. Take photographs, check deflections along the beam; by stringline is probably enough to indicate a problem; observe the motion of the crane; is it skewing etc. Have a close look at the wheel to beam actions.

Anything else is guesswork and finger-pointing and as Engineers we're not supposed to guess, except where still uncertain but based on the very best information collected about the problem.

In conclusion I would say the beam you quote should do the job over a 10m span. However the flanges which are carrying the crane trolleys (am I right here?) could be too slender and require some form of stiffening. Also the centre-centre distance of trolley wheels as measured perpendicular to the beam span, if excessive, can cause increased flange bending and local flange deformation.

Anthony Tugwell
Project Director & Consulting Engineer - now in Australia

 

[Gourile]

Hi!
The crane manufacturer claim of making noise because of underdesign is just a nonsense. Give your calculations to a third party for approval. If your design calculation is ok, the crane manufacturer can not carry out the claim. Just don't give up to their hastle and think scientifically! Crane girder never cries! if under-designed, just fails or deflects outer allowable range, as other fellows mentioned!
Have luck.

 

[Riz]

Skysky,

It seems u have a crane mounted on a single gantry girder. BS 5950 covers all aspects of design.

Effect of crabbing action may be happening to the system u have designed.

If your crane is electric operated than the dynamic impact force need to be increased by 25%. (ie increase in static wheel loads)I have a feeling that your surge deflection is almost approaching the limiting deflection.

Have u checked web buckling under the wheels?

Riz

 

[JAE]

Just a few thoughts on the situation, from an ethics/professionalism view. If you get in a situation where your client speaks of suing, the best thing is to immediately respond to the situation by coming alongside the client and insisting that you assist in determining the source of the problem in a professional way. The worst thing an engineer can do is become defensive.

Gourile, I appreciate the comment about getting your calcs to a third party for a peer review, but this should be a step later in the process. As an engineer, you were hired to provide a service to the client and ensure that the design is adequate and serviceable. Why get defensive immediately about a problem when you don't yet know what the problem is?

An owner will only get more angry and frustrated if his/her engineer does not seem responsive or interested in assisting in solving the problem. Extra time and cost is incurred but this is preferable to getting sued.

Some engineers have claimed that you should only provide additional services in solving problems on your projects if you insist on compensation for the time and effort involved. This, they claim, allows you to maintain a position where you are not assuming any liability for the problem. This may be true when a client calls you long after the project is completed, but with an immediate issue during or soon after construction it may not be wise.

Do what ADT stated and get up there and be a hero to your client. Even with them being angry you can maintain your professionalism and verify exactly what is happening. Once the cause is known, the solution (or blame) will most likely fall into place

 

[ehcet]

Have 33 years experience in crane design. Contact me at 905-712-2373 or ehcet@idirect.com
Regards, Ernie

 

[LPPE]

I don't know about banging noises from a crane, but I have heard loud bangs in buildings. It has to do with the connections. The bolts weren't designed as slip-critical, but when they are tightened, they are tightened to a certain tension. After the building was constructed and the conc. floor slabs placed, in early mornings when the sun was coming up and the air was being heated, sometimes there would be an unsettling BANG!. After discussion, it was determined that some bolts were going from slip to bearing.
In summary, perhaps your banging noise is coming from the connections?

 

[ishvaaag]

Yes the bangs in a steel buiilding I lived 5 years I have heard myself. I assume it was welded structure but main beams were simply continuous over 2 columns, and one cantilever at each end. The beam slipped in its column mounts whichever they were clearly upon day/night thermal cycles and whole building heard.

I also have experienced shrieks in slender steel buildings about 14 stories tall under windstorm, simply dynamically coming unto bearing. Tese things quite likely here in old steel buiuldings where much mere isostatic joints were present.

In any case I think the complaint must be clearly related to the movement of the crane...other assumption would be too strange.

 

[ehcet]

The banging noise, if the crane is moving, comes from
the misalignment of the crane. It does not run smooth,
the misalignment causes to "skew" and the wheel flange is
hitting the crane rail also transferring this lateral
force to the supporting structure.
The crane beam itself (where the trolley running) does not
make noise except again if the trolley is not aligned
properly.