crane loads

[Commandant]

We have a client that wants us to make a last minute change and add a 40 ton crane with a 40’-0” span to a building that has foundations being poured next week. Does anyone know where I can get the loading information?

 

[trainguy]

A drawing of the crane installation from the crane manufacturer, which the client or architect should provide, would be a good start.

But better yet, convince the client not to do it, at the risk of severely delaying construction.

It's likely that just about every major structural component could require modification, including the foundations.

tg

 

[JAE]

You need to get a proposed set of data from a crane manufacturer regarding bridge weight, hoist weight, etc.

Check out AISC for crane impact factors vertically and horizontally.

 

[dhengr]

From the crane manufacturer?

 

[csd72]

commandant,

Your job as a consultant is not only to crunch the numbers but to also make the client aware of the implications of their decisions.

That said, is is pretty easy to estimate the maximum reaction from a 40 ton gantry crane, it will be somewhere in the realm of ... 40 ton. maybe add 20% for contingencies and redesign the foundations accordingly (if necessary).

The problem will be with the anchor bolts as you may need additional ones for the crane supports.

throughout the whole process keep the client informed of what you are doing and the implications so they dont come pointing the finger at you later when changes are required.

 

[steellion]

A moving load of 40 ton (+30% overload for testing) must have the structure be acceptable anywhere on the crane rail. Plus the self-weight of the crane itself, which you'll have to get from the mfr. Information like maximum deflection (which is likely to be much more stringent than normal), height requirements, etc, also must be gathered from the manufacturer. This is a major change.

 

[Commandant]

I would love to get the crane manufacturer to tell me the loads. There is only one problem. The crane manufacturer will not provide the design information until there is an order and the client will not place the order until a later date in order to avoid having to cough up the down payment now. Sure I can throw something at it but since I want to maintain a good relationship with the client I don’t want to be too conservative.

 

[CTW]

The owner needs to find another crane manufacturer. Crane manufacturers normally provide basic load information up front with their bid such as estimated crane weight, wheel loads and bumper forces. Without this information, as well as a lot of other particulars about the cranes components, an owner cannot make an informed decision about which crane to purchase. This is standard information for crane bids. Any crane manufacturer who refuses to provide this should not be considered by the owner.

 

[boo1]

The building design must include the vertical and lateral-load-resisting systems (both directions). Lateral loads can arise from wind, seismic or inertia forces.

very late for adding major elements. Stop the foundation placement till loading and design changes are known.

 

[hawkaz]

If they won't stop the pour and can't get you info- Be very conservative in your assumptions. Put a fluff factor of 2X or 3X on it and let them know that you are doing this so they can maintain the schedule.

If you guess wrong, the fix will be a nightmare.

 

[a2mfk]

Wow, I can see forgetting maybe a 3 ton crane that would be useful down the road for some light industrial facility.... But forgetting that you may need a 40 ton crane until the last second!? How can owners be smart enough to acquire the amount of money to buy buildings but then on the other hand be so ignorant (sometimes, wait, a lot of the time...)

Having done crane runway and frame design, let me tell you there is a lot more than meets the eye. And I agree with others, any crane mfr worth their wait in salt can give you lots of safe, conservative prelim numbers. A lot of them have software for this and actually pretend to do engineering, so beware of that. Probably little harm like others suggested in adding a 25%-50% or more safety factor to their numbers.

40 ton may have a large impact on your lateral loading from start/stop forces, and obvious effects on your gravity loading if you plan on using the building structure and not using separate runway columns...

 

[engphila]

hawkaz is correct: be very conservative with your estimate of additional loading - and there's no need to be apologetic for perceived overconservatism, it's unreasonable to expect refinement with poor data and an overaggressive schedule. Years ago, an experienced engineer and former coworker would often lament "...no partial credit if building fall down!".

engphila

 

[hokie66]

You don't design a building and then put a 40 ton crane in it. You design a building to support a 40 ton crane.

 

[paddingtongreen]

I'm with hokie on this. When you put a big crane in a building, the support of that crane becomes the focus, other considerations are ordinary. But, if you must go ahead....

Unless you want to make a conservative adjustment, the best way is to retrofit the crane structure within the building. Provide additional columns between the building columns. use a horizontal truss between the building columns to provide lateral support for the crane columns. The building framing then has to handle the horizontal loads which, are easily estimated.

"Conservative" adjustments are difficult when you don't know the details, how much moment to put into the column? should double columns be used? etc.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[Zambo]

A gantry crane with 40' (12m) span. But does it run on rails cast into the slab or is it going to be supported on runway beam running between columns?

Let's assume the gantry crane spans between steel columns (no rails). Then for a 40T crane I think best not to use the building structure columns but instead to provide separate columns for the crane. The crane columns may be tied back to the building columns. This means that you need foundations for the crane columns at perhaps 6m spacing, if you are going to tie back to the building coulumns those foundations will need to be enlarged to take both columns.

On a previous project we provided a gantry crane (this was a box beam girder type) with 1 x 30T hook and 1 x 10T hook. So I think we can assume equivalent to 40T. The span however was 25m.

The gantry carriages (one at each end of the gantry girder) had 2 wheels each. So total 4 wheels each with a max reaction of 225KN approx total =90T. But for the columne and foundation loads you also have to add the runway beams.

The runway beams have to be designed to fairly stringent deflection requirements. Depending on the code it could be span/500 or span/600, so large sections.

 

[Zambo]

Why about draw up your design assumptions and a brief description of how the crane will be supported and the maximum allowable foundation loads. Then later it will be your client's responsibility to procure a crane that complies with your design brief. It may even be possible to send this to the gantry crane manufacturer to confirm it is suitable before you cast the foundations.

 

[ToadJones]

Where is this Gantry talk coming from?
The OP didn't mention a Gantry did he?

Was the building designed for other cranes and they just want to add another 40 Ton crane?

If so, this might not be as bad as you would think.
Sometimes it is only a matter of adding bumper extensions between cranes to keep the cranes from loading the same areas.

Information on crane weights and wheel loads can be found in the Whiting Crane Handbook.