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Bracing of Piles 1

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visitor

visitor

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Mar 28, 2002
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In NYC Building Code, it requires all piles to be laterally braced.

One of the provision states :
Single-pile or two pile groups or a single line of piles may be considered to be adequately braced if connected to, and braced by, a self supporting floor system provided : (1.) that the details and dimensions of the floor and the wall or pier are of adequate strength to resist lateral displacement of the pile cap under conditions of maximum eccentricity of the applied load; (2) that the wall or pier is braced until connection of the floor framing is made and the flooring (or slab) is in place.

Can someone help me to interprete the above? What is a self supporting floor system? If I have a pile supported structural slab, what am I supposed to check/calculate to make sure that all my single pile and two pile groups are adequately braced?

Also, I have a retaining wall which is to be pile supported too. What should I do to ensure that it is laterally braced?

Thanks for your help.
 
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I don't know about the slab but retaining walls are usually constructed at or below grade to retain fill. As such the pile are usually entirely below grade and bracing is not only unecessary it is impractical.

As for the floor slab, the same would be true if the slab were placed on grade yet supported on pile. Something that's been referred to as a "Land Pier".

It appears that the code is addressing stability both globally and local. However if your pile are not unbraced for some height above ground, then the soil will act to brace each pile. [sig][/sig]
 
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I agree with Qshake, but your Geotechnical engineer should review the soil for potential liquefaction. Under some seimic conditions the jello we call soil could lose some stiffness. This could pose a problem, requiring grade beams or the like to connect the pile caps. [sig][/sig]
 
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Regarding liquefaction, concerns for this type of soil failure really need to extend beyond the structure. Soil remediation (dynamic compaction, stone columns etc) would be an effective and likely solution but not bracing pile. Remember the photos of the japanese buildings leaning over in the 1964 Niigata earthquake; If those buildings were founded on piling, bracing would not have improved the performance of the building. In fact the buildings were relatively undamaged although they were unusable.

Qshake. [sig][/sig]
 
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The bracing of the pile caps is done using tie beams if not braced by a floor diaphragm. Most seismic codes require tie beams.
 
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