Jib Crane Foundation

[InDetail]

I am working on a project on which the Geotech. engineer has recommended use of piles for a Post type Jib Crane foundation. The Structural engineer is however responsible for the structural design of the piles (which I personally find atypical but needs to be done). We are proposing a 36" dia. single caisson under the jib crane.

Anyone have any experience of using this foundation type for a jib crane. Any input will be truly appreciated.

 

[PSlem]

What is capacity and length of beam?

 

[msucog]

the geotech provides design parameters and allowable capacities related to the soils but the structural more often than not designs the actual piles/caissons. and only 1 36" caisson?

 

[jdonville]

Indetail,

I would think that you would want a raft or mat supported by a pile group. The bearing pressure at the tracks will also depend on the geometry of the load (slew angle) relative to the tracks. If the tracks are going to be in a fixed position, then the piles should be located below the points that will exert the most ground pressure. If the tracks may be oriented in any direction, then you may need to spread more piles to cover the uncertainty in where the maximum bearing load will be exerted on the soil by the tracks.

J

 

[civilperson]

The maximum moment from the jib crane can be resisted by the caisson depending on the horizontal soil modulus and the depth. I would model the caisson as a rigid structure with a pivot location approximately a third up from the bottom of the caisson. This is usually the most economical design if the auger can get access to the site.

 

[weab]

Without doing a soil-pile interaction analysis (perhaps with software), this might be complicated. I'm guessing that the soil report doesn't address how to handle a concentrated moment at the top of the caisson. However, theoretically this could work.

I would generally expect a footing with 3 or 4 12" piles or so, could be steel or timber with tension connectors. The loads resolve into point loads which should be easily addressed by the axial capacity of the piles based on driven depth, some in compression, some in tension.

 

[hokie66]

InDetail,

Since you didn't give much information about the reach and capacity of the jib, you got a variety of answers. But civilperson is correct, a 36" bored pile will support a significant jib, depending on the soil characteristics. The geotech should give you advice as to the lateral resistance of the soil.

 

[csd72]

This is a good book on it:

http://www.constructionbooksdirect.com/Product.asp?PID=5479

It is written in the UK.