Reactions of Tower crane.

[dgkhan]

Please see attached file. It provides moment of 1620 k-ft. How he came up with vertical reactions on foundation and also when crane is climbing in building? I divided with moment arm and took care of vertical load but answers ! ! !
I know I should design on this basis and not to worry but still it should be simple statistics to find out.
I am ignoring slew moments etc. for now

 

[hokie66]

The tower crane will be freestanding until after the first two suspended floors are built.

 

[BAretired]

Using your calculation of 1620/5.91666 = 273.8k assumes the moment is directed in an orthogonal direction to the baseplate. This amounts to 127k per bolt. If you consider other directions, you will find a maximum and a minimum force in each anchor bolt. Check it out and see if you agree with a range of 126 to 160 kips. I don't feel like going through all of the calculations myself, but I firmly believe it would be a good exercise for you.

BA

 

[msquared48]

"The tower crane will be free, standing until after the first two suspended floors are built."

Isn't punctuation and the English language great?

My only question regarding the OTM is, is this the worst case of wind and payload, assuming the crane will probably be operating in winds up to 20 or 25 mph?

Mike McCann
MMC Engineering

 

[hokie66]

Mike,
Are you saying that freestanding is not a good word?

BA,
273.8/2 = 137. But I agree, the diagonal would control.

dgkhan,
You don't need statistics, you need statics.

That's enough pedantry for today. Cheers.

 

[msquared48]

No... Just playing with ya...

Mike McCann
MMC Engineering

 

[dgkhan]

hokie,
u got me right. I do this though, In 1986 when I started engineering school, took me while before I can call moment and not momentum. U were not there right?
any way, i am trying all possibilites and not getting the same results.

 

[MaddEngineer]

I think he is looking at the worst case when to crane is slewed at 45, 135, 225 & 315 Degrees and assuming a base moment arm of 8'. He then subtracted Vmin/4 to get U and then added Vmax/4 to get C.

When I checked R = 1620/8 = 202.5k, U = 202.5-126/4 = 171k

However, for C I get 242.5k a little off from 250k noted. But it is in the ballpark, maybe round off error or typo?.