Chance Technical Design Manual

DESIGN EXAMPLE 19: MONOPOLE FOUNDATION WITH STEEL GRILLAGE AND RS5500 HELICAL PILES

Provided Design Loads (on entire grillage) Fx = 34.06 kip (axial) Fy = 49.41 kip (shear) Mz = -35574 kip∙in (moment) Reveal Height: 5.33 feet

that the helices behave independently. The 5-degree angle also provides a better response to shear load. The first stage is an iterative solution using the design loads from the mono pole with the quantity and coordinates of helical piles with Ensoft’s GROUP software. Experience provides best practices to determine the number and coordinates of the helical piles. With these inputs, GROUP software will determine the actual loads on each pile. A model of the grillage can then be devel oped and analyzed with finite-element analysis (FEA) software to help size structural members within the grillage. With the loads applied to each pile obtained from the GROUP software, Chance® HeliCAP® software is used to design the helical piles. The following information is by no means a complete tutorial on the use of GROUP or HeliCAP software but is provided as an example of this type of solution.

These loads require a moment foundation that incorporates multiple helical piles into a steel grillage. Grillages that are mostly moment foundations will be limited in size by what can be transported to the job site. Moment foundations will also have helical piles installed at 5 degrees from vertical. This angle allows the piles to be spaced far enough apart at depth

DESIGN EXAMPLES

GROUP SOFTWARE INPUTS

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