Retrofit reinforcing structure addition and method for wind turbine concrete gravity spread foundations and the like

A method of installing a retrofit spread foundation reinforcing structure addition onto an existing concrete gravity spread foundation having a concrete central pedestal and a concrete spread section, the existing concrete gravity spread foundation already supporting a tower or wind turbine and being a completed structure before the retrofit spread foundation reinforcing structure addition is installed on said existing concrete gravity spread foundation to extend the useful life thereof, the retrofit spread foundation reinforcing structure addition including a cementitious annular collar having an outer perimeter that includes a shape sustaining member, a plurality of radial bolts extending horizontally through the collar and into the concrete central pedestal, and a plurality of vertically oriented anchor bolts extending downwardly through the collar and the spread section of the foundation, the method comprising the steps of:

• identifying an existing concrete gravity spread foundation having a concrete central pedestal and a concrete spread section to be reinforced;
• drilling a plurality of horizontally extending core holes in the sides of the concrete central pedestal of the already existing concrete gravity spread foundation for the radial bolts of the retrofit spread foundation reinforcing structure addition;
• inserting the radial bolts into said horizontally extending core holes in the sides of the concrete central pedestal;
• encircling the concrete central pedestal of the already existing concrete gravity spread foundation with the shape-sustaining member of the retrofit spread foundation reinforcing structure addition to define a generally annular ring around the concrete central pedestal of the already existing concrete gravity spread foundation;
• placing a plurality of sleeve members in a vertical orientation in the generally annular ring for the anchor bolts of the retrofit spread foundation reinforcing structure addition to be drilled through and securing the sleeve members for concrete pour;
• pouring concrete into the generally annular ring between the shape-sustaining member of the retrofit spread foundation reinforcing structure addition and the concrete central pedestal of the already existing concrete gravity spread foundation to form the cementitious annular collar, said annular collar encircling the concrete central pedestal and pressing down upon the spread section of the already existing concrete gravity spread foundation;
• drilling and installing the anchor bolts, generally centralized in said sleeve members, lower ends of said anchor bolts extending vertically through the gravity spread section and into the underlying substrate constituted by at least one of soil and rock lying beneath the concrete spread section of the existing concrete gravity spread foundation;
• post-tensioning the radial bolts;
• and
• post-tensioning the anchor bolts.