Beam and pile anchor foundation for towers

Abstract

A foundation system for a tower, such as a wind turbine, includes a central hub assembly, a plurality of post-tensioned concrete beams, and an anchoring system associated with each beam. In use the foundation system is arranged so that the bottom surfaces of the concrete beams bear on soil and the anchoring is disposed within the soil. The beams can be inverted bulb-T beams having post-tensioning cables inserted there-through and cooperating with an oppositely disposed related beam. The central hub assembly can include a plurality of stacked disk elements or steel frame elements that are post-tensioned together to form a single hub structure.

1 - 15 . (canceled) 
     
     
         16 . A tower foundation system, comprising:
 a central hub assembly;   a plurality of post-tensioned concrete beams projecting radially outward from the central hub assembly at equal circumferential intervals, each post-tensioned concrete beam having a proximal end adjacent to the central hub assembly, a distal end spaced from the proximal end, a longitudinal axis extending from the proximal end to the distal end, an upper surface, and an on grade bottom surface;   each post-tensioned concrete beam includes a plurality of post tensioning cables therein that extend through the proximal end and that post-tension the respective beam;   for each post-tensioned concrete beam the distal end thereof is not directly connected to the distal end of an adjacent one of the post-tensioned concrete beams;   a gap is provided between the on grade bottom surfaces of each adjacent pair of the post-tensioned concrete beams; and   each post-tensioned concrete beam includes an anchoring system connected to the distal end thereof, each anchoring system includes a pile cap disposed below the on grade bottom surface and the pile caps are disposed within the soil.   
     
     
         17 . The tower foundation system of  claim 16 , comprising an even number of the post-tensioned concrete beams. 
     
     
         18 . The tower foundation system of  claim 17 , comprising six or eight of the post-tensioned concrete beams. 
     
     
         19 . The tower foundation system of  claim 17 , wherein the post-tensioned concrete beams are arranged such that each post-tensioned concrete beam is disposed diametrically opposite another one of the post-tensioned concrete beams, and for each of the post-tensioned concrete beams the plurality of post tensioning cables thereof extend through the central hub assembly and into the post-tensioned concrete beam positioned diametrically opposite thereof. 
     
     
         20 . The tower foundation system of  claim 16 , wherein each concrete beam includes a substantially horizontal top flange that forms the upper surface and a substantially horizontal bottom flange that forms the on grade bottom surface, a vertical web that interconnects the top flange and the bottom flange, and the gap is provided between the bottom flanges of the adjacent pairs of the post-tensioned concrete beams. 
     
     
         21 . The tower foundation system of  claim 20 , wherein for each inverted bulb-T concrete beam the plurality of post tensioning cables extend through the top flange and the bottom flange longitudinally from the proximal end to the distal end. 
     
     
         22 . The tower foundation system of  claim 16 , wherein the central hub assembly comprises:
 a steel frame or a plurality of precast concrete disk elements coupled by a post-tensioning system.   
     
     
         23 . A method of supporting a tower of a wind turbine, comprising:
 installing a foundation system at a location where the wind turbine is to be installed, the foundation system includes: a central hub assembly; a plurality of post-tensioned concrete beams projecting radially outward from the central hub assembly at equal circumferential intervals, each post-tensioned concrete beam having a proximal end adjacent to the central hub assembly, a distal end spaced from the proximal end, a longitudinal axis extending from the proximal end to the distal end, an upper surface, and an on grade bottom surface; each post-tensioned concrete beam includes a plurality of post tensioning cables therein that extend through the proximal end and that post-tension the respective beam; for each post-tensioned concrete beam the distal end thereof is not directly connected to the distal end of an adjacent one of the post-tensioned concrete beams; each post-tensioned concrete beam includes an anchoring system connected to the distal end thereof, each anchoring system includes a pile cap disposed below the on grade bottom surface; and   wherein installing the foundation system includes arranging the foundation system so that the on grade bottom surfaces of the post-tensioned concrete beams bear on soil and the pile caps are disposed within the soil, and a gap is provided between the on grade bottom surfaces of each adjacent pair of the post-tensioned concrete beams.   
     
     
         24 . The method of  claim 23 , further comprising mounting the tower of the wind turbine to the central hub assembly.