Transmission And Substation Foundations - Technical Design Manual

SECTION 7: DESIGN EXAMPLES

Design Example 4

-10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115

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

case 1*

Bending Moment vs Depth Figure 7-19

f. Axial FS=2.0 g. 1” of Lateral deflection acceptable at working loads

These results show that the piles will be able to carry the required shear capacity with 0.9” deflection and 114 kip-in of moment. This deflection is generally acceptable for transmission structures and the moment is less than the 0.6 Mp used in standard design. Recommendation: 1. Install 9-RS4500.337 Helical Piles a. Helix Configuration: 10/12/14/14/14/14 b. Installation torque: 16,700 ft-lbs c. Locate piles per attached Pile Layout (Figure 7-16)

3. Notes a. May reach installation torque before reaching minimum embedment. Adhere to minimum embedment requirement i. Ensure final torque is greater than installation torque b. Maximum torque for RS4500.337 is 21,000 ft-lbs. Do not overtorque!

d. Estimated Embedment: 50 ft e. Minimum embedment: 20 ft 2. Assumptions

a. Boring is representative of the location i. Water table depth is deeper than 50 ft b. Given loads are working (moment and shear can act in any direction)

i. Compression: 50 kip ii. Moment: 2000 kip-ft iii. Shear: 40 kip c. Piles are installed at ground level d. Torque to Capacity Ratio for RS4500 is 6:1 e. Pinned Head Condition

7-22 | www.hubbell.com/hubbellpowersystems