Transmission And Substation Foundations - Technical Design Manual (TD06088E)

DESIGN EXAMPLE 3 H-FRAME STRUCTURE DESIGN WITH CONCRETE CAP AND MICROPILE DESIGN SYMBOLS USED IN THIS DESIGN EXAMPLE

T-Z CURVE.......................AXIAL DISPLACEMENT VS LOAD PLOT 7-17 Mp................................................................................. PLASTIC MOMENT 7-19 FS..............................................................................FACTOR OF SAFETY 7-20 K t ........................................................... TORQUE TO CAPACITY RATIO 7-21

Purpose This design example is intended to assist with the design of H-Frame Structure foundations. This example will show how to design using GROUP® and a concrete cap. A grillage can be used for an H-frame structure, and an example of how to design for a grillage is given in Design Example 2 Each leg of the H-Frame Structure will be supported by a concrete pile cap. This type of structure will generally have tension, compression, shear, and moment 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 loading soil is as follows: Loads • Compression: 100 kip • Tension: 80 kip • Shear:

DESIGN EXAMPLES

• Transverse: 9.5 kip • Longitudinal: 1 kip

• Moment

• Longitudinal: 150 kip-ft

Soil Profile:

• Layers • 0-10 ft: 28° Friction Angle Sand • 10-30 ft: 30° Friction Angle Sand • >30ft: 35° Friction Angle Sand • Water Table: Surface (0 ft)

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