Transmission And Substation Foundations - Technical Design Manual

SECTION 7: DESIGN EXAMPLES

Design Example 4

EDGE SECTION

50 KIP COMP

2000 FT-KIP MOMENT

50 KIP SHEAR

ARROWS ON CAP ARE 100 KIP ULTIMATE PILES

CORNER TO CORNER SECTION

50 KIP COMP

2000 FT-KIP MOMENT

ARROWS ON CAP ARE 100 KIP ULTIMATE PILES

50 KIP SHEAR

5.1

5.1

5.1

5.1

Load Scenarios Figure 7-17

With the two layouts determined, it is now possible to analyze and ensure that the piles have the required capacity with the intended spacing. Because the pile cap will not be truly rigid and the fact that the piles can continue to deflect and resist load beyond the point they reach ultimate capacity, it will be assumed the capacity of each pile is 100 kips ultimate (50 kip working). To ensure the FS=2 kip will be used as the capacity of each of the 9 piles.

Because there are 3 piles that will not be taking any axial load from the moment in both cases, it is assumed that that axial load will be transferred through these piles and not through the other piles in the concrete cap. It is now possible to calculate the amount of moment that can be resisted by the layout. This can be conducted by using a summation of moments about the center of the cap (location where load is applied).

7-20 | www.hubbell.com/hubbellpowersystems