Crane Tower Foundation 5

[steelbeam]

If you have any experience with this Subject please read on.
I am reviewing calculations for the design of a temporary crane tower foundation. In the initial review I asked for the breakdown of the loads (DL,LL,W,ect) from the crane manufacturer. With this info I thought the foundation designer should use ASCE/SEI-7 load combinations to design his foundation. In the responses back to me the crane manufacturer told the foundation designer that "splitting the loads out is not done in the tower crane industry". The table of loads at the base of the crane from the crane people to the foundation guy are still given as service moment, horizontal & vertical forces. I think the crane people should be able to give the breakdown so the foundation can be evaluated using ASCE/SEI-7 or ACI 318, 9.2. The other problem is that the crane is designed by a German code(DIN). Lastly I asked for a check when the crane was out of operation and could have wind & icing of the members per Chapter 10 of ASCE-7. The manufactuer's response, "no ice build up is permitted on the crane. If ice is starting to build up the contractor must have a means of removing it. Snow build up of 4" or greater should also be removed". How does he do this when the tower is 246 ft. tall and boom extends out 123 ft.?

 

[chicopee]

Crane tower foundation is covered in Shapiro's Cranes and Derricks. Buy a copy as it is a valuable reference.

 

[Agent666]

We have the same issue in New Zealand, you get one set of loads that don't include all of the constituent loads.

We actually have a pretty good crane code with the loadcases you could ever want and specific loadcases for the design of the foundations for tower cranes.

So we just treat it by considering the manufacturers loads by a live load factor of 1.5 multiplied by another load factor of 1.25 for dynamic factors. The resulting load factor is considerably higher than the crane code max load factors for individual loads. We've tried getting the individual loads out of the manufacturer, but it's like getting blood out of a stone!

We usually only take a load factor of 1 on the slewing moment because that's all our code requires and it's the only load that is separated (and it's usually quite hard to deal with otherwise)

 

[CANPRO]

I've designed many crane bases for many different manufacturers. They almost all provide in/out of service reactions lumped together. If you really wanted to, you could probably work backwards from the different scenarios in the tables to determine the breakdown of the loads. In my experience this isn't necessary.

If you proportion the footing to satisfy bearing - with the lumped together service loads provided - the footing ends up so deep that you could factor the lumped reactions by 1.5 (conservative) and still probably only need a nominal amount of steel (or at least not an unreasonable amount of steel).

Regarding the snow/ice build-up: I practice in Eastern Canada and I've never seen or heard of an excessive amount of snow/ice on the crane. Not saying it can't happen, but probably unlikely. It might be worth having a talk with the contractor to see if they do have a reasonable means of removing snow and ice if required.

 

[MotorCity]

This seems like the complete opposite of what you get for loads in the PEB industry where they give you hundreds of load combinations and you are left to sort them out yourself.

Anyway, what is your responsibility or the purpose of your review? Are you doing a peer review, the EOR, checking shop drawings, etc.?

If you are assuming responsibility, I would insist that a breakdown of the loads be given to you if they are service loads. Otherwise, how do you know what load factors to use for foundation design? If the loads were given as factored LRFD loads, I would be inclined to assume the same for foundation design (even though there may be subtle differences in the LRFD load combinations for steel and concrete).

For what its worth, I agree that requiring snow and ice to be removed is a ridiculous requirement.

 

[MrHershey]

Have designed several. They won't split it up. Just use the highest load factor and be done with it.

Usually loads are at service levels. If they don't specifically say that then ask. I know Morrow typically has it in their notes.