Methods for constructing tensionless concrete pier foundations and foundations constructed thereby
A tensionless concrete pier foundation for supporting a tower and a method of constructing the same is provided, the foundation having an outer CMP and an inner CMP with an annular space therebetween in which a plurality of sleeved tower anchor bolts are embedded, at least the outer CMP having an upper edge that is flush with the top of the foundation after the tower has been installed. A method of plumbing a tower anchor bolt cage using a bolt alignment ring is also provided that includes coupling the upper ends of the CMPs together with lateral spacing bolts that extend across the annular space. The tower anchor bolt cage is suspended from the lateral spacing bolts by the bolt alignment ring, and the lateral spacing bolts are shimmed on a low side as necessary for leveling the alignment ring and plumbing the bolt cage, before concrete pour.
1. A tensionless concrete foundation for supporting a tower, the tensionless concrete foundation comprising:
a concrete pier in an excavation, said concrete pier including an outer corrugated metal pipe (CMP) and an inner CMP having a smaller diameter than the outer CMP to define an annular space between the inner CMP and the outer CMP, said annular space being filled with concrete, a bottom end of said outer CMP being positioned at a bottom of said excavation;
a plurality of lateral reinforcing and spacing bolts separately nutted adjacent both inside the inner CMP and outside the outer CMP, respectively, and extending horizontally across said annular space; and
a plurality of sleeved anchor bolts each having a lower end and an upper end, said plurality of sleeved anchor bolts being suspended from the lateral reinforcing and spacing bolts and embedded in the concrete in said annular space, the lower end of each sleeved anchor bolt being secured to an embedment ring adjacent a bottom end of the concrete pier, the upper ends of said plurality of sleeved anchor bolts extending upwardly to above a top of the tensionless concrete foundation, the top of the tensionless concrete foundation being defined as an upper surface of the concrete in the annular space when fully grouted to be level with an upper edge of said outer CMP, said upper edge of said outer CMP thereby being flush with the top of the tensionless concrete foundation.
2. The tensionless concrete foundation as set forth in claim 1 , wherein said inner CMP also has an upper edge that is flush with the top of the tensionless concrete foundation.
3. The tensionless concrete foundation as set forth in claim 1 , wherein said plurality of lateral reinforcing and spacing members include an upper set of lateral spacer bolts adjacent a top of the inner CMP and a top of the outer CMP and a lower set of lateral spacer bolts adjacent a bottom of the inner CMP and a bottom of the outer CMP.
4. The tensionless concrete foundation as set forth in claim 1 , further comprising a floor made of a material selected from the group consisting of steel mesh, rubber mat, diamond plate, and plastic sheet.
5. The tensionless concrete foundation as set forth in claim 1 , further comprising a safety protection element covering the upper edge of the outer CMP.
6. The tensionless concrete foundation as set forth in claim 1 , wherein the concrete is the annular space includes an upper layer that is poured with higher compressive strength concrete than the concrete filling the annular space below said upper layer.
7. A tensionless concrete foundation for supporting a tower comprising:
a concrete pier in an excavation, said concrete pier including an outer corrugated metal pipe (CMP) and an inner CMP having a smaller diameter than the outer CMP to define an annular space between the inner CMP and the outer CMP, said annular space being filled with concrete, a bottom end of said outer CMP being positioned at a bottom of the excavation;
a plurality of sleeved anchor bolts each having a lower end and an upper end, said plurality of sleeved anchor bolts being embedded in the concrete in said annular space and the lower ends of said sleeved anchor bolts being secured to an embedment ring adjacent a bottom end of the concrete pier, the upper ends of the plurality of sleeved anchor bolts extending upwardly to above a top of the tensionless concrete foundation, the top of the tensionless concrete foundation being defined as an upper surface of the concrete in the annular space when fully grouted to be level with an upper edge of said outer CMP, said upper edge of said outer CMP thereby being flush with the top of the tensionless concrete foundation; and
a plurality of lateral reinforcing and spacing bolts extending horizontally across said annular space and separately nutted adjacent both inside the inner CMP and outside the outer CMP, respectively, from which lateral reinforcing and spacing bolts the sleeved anchor bolts are suspended.
8. The tensionless concrete foundation as set forth in claim 7 , wherein said plurality of lateral reinforcing and spacing members include an upper set of lateral spacer bolts adjacent a top of the outer CMP and a top of the inner CMP and a lower set of lateral spacer bolts adjacent a bottom of the outer CMP and a bottom of the inner CMP.