Transmission And Substation Foundations - Technical Design Manual (TD06088E)

Table C-C-2.2 - from AISC 360-05

HELICAL PILES AND ANCHORS

The strength of the concrete will also factor into the axial compressive strength of helical piles. Higher strength concrete results in higher bearing pressure with both embedded new construction pile caps (P1) and foundation repair brackets (P1). Helical piles can be one-piece foundation elements, but are more commonly produced in sections that are coupled together during installation. Therefore, the strength of the coupling must be considered in the design as part of the shaft (P2). CHANCE helical pile couplings are designed to meet or exceed the torque correlated geotechnical capacity [Method 2] . They are also designed to meet or exceed the bend- ing strength of the shaft itself. Structurally, the couplings limit both the tension and compression strength. For CHANCE Type SS helical piles, the coupling bolt is the limiting factor for tension strength. Load direction is an important consideration and strongly affects the shaft type and size required. This was discussed previously under P4. The Application (new construction, foundation repair, earth retention, etc.) also affects the shaft type and size required. For example, it is not practical to use large diameter shaft helical piles for underpinning existing building structures.

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