Tower Crane erection and structural stability 1

[perfectaccess]

Hi

I would like to know the process of erection of tower crane and how every step is structural stable
I would appreciate any reference

 

[KootK]

For a tall building, you'll often be tying the crane back to the building slabs at intervals. Reference: Link

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[jayrod12]

And as far as erection goes, Most times the cranes are self erecting once the base has been built. It inserts sections below and then continues to climb up.

For what it's worth, currently directly across the street from our office is a free-standing tower crane (construction of a 22 storey building) that is on a 2m thick pilecap that is supported by a dozen or so driven steel H-piles. And I'm watching it in 30km/hr gust 55 km/hr winds and it's not noticeably swaying.

 

[bookowski]

Doesn't always work

http://www.nydailynews.com/new-york/crane-collapse-manhattan-article-1.1194790

 

[dhengr]

Bookowski:
I think that crane needs some viagra.

Perfectaccess :
Normally the crane supplier worries about the crane stability. In looking at the fl. slab elevations, they will pick floors at which they want the crane laterally supported and tied into the building slab edge or spandrel beams or columns. They will give you loads at the support brackets, caused by their crane, and then you should design and check that these connections are done properly, clear rebars, don’t overload any parts of the structure, etc. I think that if you goggle around a bit you could find some videos of this crane erection process.

 

[MrHershey]

Typically the crane will jump itself and put new pieces in the middle as others have noted. There may be periods of relative instability during that jumping process but my guess is you'd never jump during high (and perhaps even moderate) winds in order to safeguard against any issues.

Also usually they'll tie to the building and piggyback off of the building lateral system every 80-100 ft. Obviously if your building's shorter than this they won't. They'll tie back to shear wall core if it's close enough or to slab if it's not. Then someone has to engineer the connection for them. Tends to be a collaborative process between building EOR and then whoever's designing the tieback shoe and anchorage. Tieback designer would be responsible for the shoe (crane attaches to shoe, shoe attaches to slab), which is usually made of structural steel. My firm will usually take care of the anchorage to concrete as well, not sure if other firms do. Loads are huge, usually over 100 kips. So lots of anchors, usually throughbolted to preclude anchor pryout, and usually have supplemental rebar to resist breakout as we're typically within a couple feet of the edge of slab. Then EOR will need to take a look at reactions to slab and see if they need any extra rebar/PT for in-plane shear (usually not an issue), in-plane moment (occasionally an issue, depends on how you look at it), and out-of-plane moment (usually an issue, since crane typically ties in 6-12" above top of slab with a reaction of 100+ kips).

Will also be supported at base. We usually try for deep foundations but sometimes get pushed into mats. Have seen a couple crane types that spread their load out a lot better (not just one reaction) and are ballasted, so you can get away with spread footings.

 

[perfectaccess]

Thank you all guys
I have couple of basic questions about stability of the tower crane (regarding concept)

We have tower crane, the loads applied neglecting wind load will be
1. Counter weight load
2. Boom own weight
3. Loads carried by the boom
4. Mast own weight

For overturning calculations, if we assume that overturning will occur in the center of mast, then (with case of loads exist)
A. The maximum allowed loads to be carried Boom load(own weight) will oppose the counter weight load(and if any balance moment will be resisted by foundation)
B. But in case no load is carried, only the boom load (own weight), will resist counterweight load (it will be safe???)

In both case mast weight will base through center of foundation,and center of overturning, so it was not considered

Thus we can see different in moment amount between case A,B , so the foundation will carry differently on those two case


Secondly,

Regarding my situation, we have 30 floor tower, and the contractor submit shop drawings of fixing tower crane, and he asks for openings, but the senior engineer respond is to load the crane load only on core and columns, and not on beams, since beams are not design to this, thus I have the following questions

1. Why the contractor want to load beams or columns vertically, since I believe it could be stable vertically and only he need to put support laterally on columns for lateral stability when he needs.
2. We have 30 floor tower, so I think the contractor will use the hydraulic jump to assemble and raise the crane up, and here I have seen many videos, showing ,while he assemble the new piece ,he is carrying small load near the mast, so any interpretation for this(it is definitely overturning ,buy can’t get it??)

 

[racookpe1978]

Have you talked to the crane company specifically, and not just to us?

 

[perfectaccess]

I am trying to learn,if you don't mind please

 

[MrHershey]

On the first part, all of these loads are provided by the crane company. You shouldn't be trying to figure this out yourself. You'll miss something. Almost all tower crane reactions (both base and tieback) that I've seen are governed by wind when crane is not in operation, so looking at all those loads and neglecting wind probably isn't going to give you the answer you're looking for.

As for the second question, the senior engineer wants to connect tower crane to columns? Does this tower crane have a foundation? Does it go all the way to the ground or is it supported vertically off of your structure? I have not seen this done in our area though I have seen it done on super tall skyscrapers. Wouldn't seem worth it for a 30 floor tower, but obviously don't know the particulars.