Transmission And Substation Foundations - Technical Design Manual

SECTION 7: DESIGN EXAMPLES

Design Example 5

Guyed Transmission Structure Design

Soils Profile • Layers

• 0-10 ft: 200 psf clay • 10-30 ft: 1000 psf clay • >30ft: 2000 psf clay • Water Table: Surface (0 ft)

Purpose This design example is intended to assist with the design of Guyed Transmission Structure foundation. This example will show how to design using L-pile® and a pinned head condition grillage. This type of structure will generally have tension, compression, and shear loads that will need to be calculated or provided by the tower manufacturer. After the loads for the structure have been determined, it is possible to design the piles. For this example the working loading and soil profile is as follows:

Pile Capacity: The first step in the design is to determine the pipe shaft diameter or Micropile required to resist the lateral load. To do this, the pile properties, soil properties, and loads are put into LPILE. The pipe properties can be calculated for all pipe products with the information found in the Drawings and Ratings section of this manual. Generally working loads will be input into LPILE so that failure criteria of x lateral deflection at working loads can be used. In this example, RS8625,188 Pipe Piles will be used. The results are plotted in Figure 7-20 and Figure 7-21.

Loads • Center Base

• Compression: 100 kip • Shear: 1 kip

• Guyes: 30 kip

Lateral Deflection (in)

-0.01

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

25 20 15 10 5 0

14

case 1*

Depth (ft)

Lateral Deflection vs Depth Figure 7-20

www.hubbell.com/hubbellpowersystems | 7-23