Tower crane peer review

SM89 · Jul 9, 2017

I am new to doing peer review on tower cranes. The tower crane stands 260ft tall with a massive foundation. I see the designer has used crane dead load & weight of crane footing in arriving at reactions and overturning moment. In my opinion wind loads should be included to obtain base reactions, i could be wrong. Please share your valuable input.. If i am supposed to check for wind loads what would be a quick way to get the reactions without having to do the entire calculations myself, because this is only peer review. I just want to get a feel for structural capacity of footing with wind loads on tower crane.

Thanks,
SKM

SM89 · Jul 17, 2017

Thanks Slideruleera,
I believe that 15t is allowable uplift capacity of pile and it may have reserve capacity for ultimate. The crane will be used for about an year. Based on RISA model maximum uplift in pile is 26k. Am concerned that by multiplying the 26k with 1.5 overturning safety it exceeds the allowable uplift capacity. And the crane is already in job site. Don't know if I should hit the panic button!!.
But even with 1.5 safety factor it is still within ultimate capacity which Twice the allowable. So 30t or 60k.

Any suggestion is welcome.

Thanks.

SlideRuleEra · Jul 17, 2017

SM89 - Suggest concentrating on the highest priority subjects:

Number One is getting that rebar spacing increased, especially the bottom rebar mat. One way would be to use two complete bottom mats stacked on top of each other. That is (#11 @ 8" O.C. Each Way) x 2. Another way is use larger rebar (#14). IMHO, the foundation is not really constructible as shown. Getting 6000 psi concrete under and around the bottom mat (#11 @4" Each Way) without serious honeycomb is doubtful.

Number Two is getting more piling. For a heavily loaded 27'x 32' mat I would expect to see maybe 30+ driven piling. With more piling, required bearing value and uplift capacity per pile go down.

What safety factor to use is pretty far down the priority list. But, for now let's accept the proposed 30 ton ultimate uplift capacity per pile. That is the value (30 tons) to be verified by an uplift field pile test... this is one reason, of several, why more piling (lower loading) is the way to go. Of course test for the 150 tons bearing, too. These tests are not of the steel piling themselves, they will be fine, it for the soil/pile interaction.

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