Transmission And Substation Foundations - Technical Design Manual (TD06088E)

DESIGN EXAMPLE 1 HELICAL PILES/ANCHORS FOR TELECOMMUNICATION TOWERS SYMBOLS USED IN THIS DESIGN EXAMPLE SST.............................................................SELF SUPPORTING TOWER 7-4 T ug .............................................................. UPPER GUYWIRE TENSION 7-5 IA ug ................................. UPPER GUYWIRE INSTALLATION ANGLE 7-5 T lg ...............................................................LOWER GUYWIRE TENSION 7-5 IA lg .................................LOWER GUYWIRE INSTALLATION ANGLE 7-5 C........................................................................................... COMPRESSION 7-5 FS..............................................................................FACTOR OF SAFETY 7-5 kip..............................................................................................KILOPOUND 7-5 R uc ........................................... RECOMENDED ULTIMATE CAPACITY 7-5 K t ........................................................... TORQUE TO CAPACITY RATIO 7-6 T...................................................... MINIMUM INSTALATION TORQUE 7-7 DL................................................................... RESULTANT AXIAL LOAD 7-7

Purpose This design example provides an aid in the selection of appropriate helical guywire anchors and center mast helical piles for telecommunication towers. The guywire loads are to be resisted by a helical tension anchor. When the vertical and horizontal components are provided the resultant must be determined as well as the angle between the resultant load and the horizontal, (this is the angle the helical anchor should be installed at to properly resist the guywire load(s)). There may be one or more guywires that come to the ground to be restrained by one or more helical anchors depending on the magnitude of the load and/or the soil strength. Helical piles can be used to resist the loads from the structure mast. These loads will generally be composed of a vertical load and a lateral load at the base of the mast or pole. If the structure is a self supporting tower (SST), the loads from each leg of the tower must be resisted. These generally consist of vertical uplift and compression loads

DESIGN EXAMPLES

Tower Guy Anchor and Foundation Figure 7-1

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