Transmission And Substation Foundations - Technical Design Manual

SECTION 6: PRODUCT DRAWINGS AND RATINGS

Type RS2875.276 Helical Piles per ICC-ES AC358 for Building Code Evaluation

RS2875.276 Lateral Deflection Analysis FOR Seismic Design Categories D, E, & F: The free-headed pile lateral movements at allowable loads (lateral only – no vertical) of Chance® Type RS2875.276 helical piles can be determined from the following table.

∆ = y t Δ= t

P h = Allowable lateral load L = Pile length y t = Δ = Lateral drift of pile head H = Length from pile head to groundline D o = Depth along pile shaft to point of first zero-deflection point (y t = 0), a.k.a. the flexural length of pile h = Depth along pile shaft to point of zero slope (St = 0) M = Bending moment in pile shaft

P h H GROUND FIRST ZERO DEFLECTION POINT (y t =0) ZERO SLOPE POINT (S t = 0) (LOWER) GROUND FIRST ZERO DEFLECTION POINT (y t =0) ZERO SLOPE POINT (S t

D o 0

h

L

For lateral resistance in non-seismic areas, special analysis and tests of RS2875.276 helical piles indicate allowable lateral load with less than 1/2” lateral deflection in stiff, firm, and soft soils. Test and analysis data are listed in the table. Per AC358 1.4.7, the Shaft Flexural Length (Do) is measured from the top of the pile down to the first point of zero lateral deflection in the soil. AC358 1.4.8 defines the Shaft Seismic Flexural Length (Seismic Do) as 120% of the Shaft Flexural Length, which for RS2875.276 helical piles embedded in stiff, firm, and soft soils is 4.8 ft, 5.0 ft, and 7.6 ft respectively.

Non-Seismic Lateral Loading (Seismic Design Categories A, B, and C)

Seismic Lateral Loading (Seismic Design Categories D, E, and F)

Soil Type

Allowable Lateral Load (Ph) (Kip)

Drift At Pile Head (Yt) (In) Depth To

Soil (H) (Ft)

Depth To

Yt = 0 (Do) (Ft)

Depth To St = 0 (H) (Ft)

Allowable Story

Drift (Δ) At Pile Head

Bending Moment In Pile (Kip∙In)

Allowable Lateral Load (Ph) (Kip)

Drift At Pile Head (Yt) (In)

Depth To Soil (H) (Ft)

Depth To Yt = 0 (Do) (Ft)

Depth To St = 0 (H) (Ft)

Allowable Story

Drift (Δ) At Pile Head

Bending Moment In Pile (Kip∙In)

Stiff Soil:

1.85 0.54 0

4.0 4.8 0.009h 27.6 1.85 1.17

0.8

4.8

5.6 0.017h 42.0

N = 9 to 20 Firm Soil: N = 5 to 8 Soft Soil: N = 1 to 4

1.48 0.54 0

4.2

5.3

0.008h 24.0 1.5

1.14 0.8

5.0 6.2 0.015h 36.0

0.47 0.54 0

6.3

7.8

0.006h 10.8 0.50 1.29 1.3

7.6

9.2 0.012h 18.0

All shaft, coupler, and bracket-tube shapes and materials have been checked for adequate ductility per AC358 3.14.3; AISC 341 Table D1.1 (including applicable footnotes); and IBC 1810.3.6.1. Lateral deflections during seismic loading should be checked against the ASCE-7 Table 12.12-1 (reproduced below) showing Allowable Story Drift values for various structure lateral load resistance system types that are presented as ratios of the story height in Seismic Design Categories D, E, and F. The story height (h) assumed for the helical pile is the depth from the pile top down to the point of zero pile slope-from-vertical in the soil (St). The Allowable Story Drift in the seismic loading table above must be less than or equal to the Allowable Story Drift in Table 12.12.1 in order to determine if RS2875.276 helical piles can be used in that Structure Type and Risk Category.

Table 12.12.1 Allowable Story Drift, Δ Structure

Risk Category I or II III

IV

Structures, other than masonry shear walls, four stories or less above the base as defined in Section 11.2, with interior walls, partitions, ceilings, and exterior wall systems that have been designed to accommodate the story drifts

0.025h

0.020h

0.015h

Masonry cantilever shear wall structures

0.010h

0.010h

0.010h

0.007h 0.010h

Other masonry shear wall structures

0.007h

0.007h

All other structures

0.020h

0.015h

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