Transmission And Substation Foundations - Technical Design Manual

SECTION 7: DESIGN EXAMPLES

Design Example 4

Moment = Load*perpindicular distance

Therefore, the piles can resist the moment and axial loads in both directions. With the axial design completed, it is time to ensure the piles can take the shear loads. It is assumed that the piles will have a pinned pile head condition and the shear load is distributed to each pile evenly.

EQUATION 7-5

Along the grid, the summation of moments would look like this (positive is resistance and negative is load):

Shear

Shear Force

40 kip

∑ Moments=7.25ft*50kip*3piles+7.25ft*50kip*3piles-2000kip ft=175 kip ft

=

=

= 4.44 kip/pile

Pile

Number of Piles

9 Piles

Therefore, the piles can resist an additional 175 kip-ft of moment with a FS of 2.0. For the corner to corner analysis, the summation of moments looks like this:

This shear load as well as an axial load of 50 kips are input into LPILE along with the pile properties for RS4500.337 (found in the Drawings and Ratings section of this manual) and soil properties. See the Design Methodology section for assistance as well as the LPILE manual for assistance in using LPILE. The resulting deflection curve is included in Figure 7-18 and the moment curve is included in Figure 7-19.

∑ Moments=(10.3ft*50kip*1 pile+5.1ft*50kip*2pile)*2-2000kip ft=50 kip ft

Lateral Deflection (in)

Depth (ft) 16 14 12 10 8 6 4 2 0 -0.1

-0.05

0

0.05

0.1

0.1.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.65

0.7

0.75

0.8

0.85

0.9

case 1*

Lateral Deflection vs Depth Figure 7-18

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