Checking a footing for a steel tower
Checking a footing for a steel tower
(OP)
A 160 ft self supporting tower with three legs is shown in the attached sketch. The unfactored forces are due to wind and ice. A 16'x16'x24" footing was provided with #8 bars at 12-1/2" O.C each way bottom only. Don't you think this pad needs top reinforcing?






RE: Checking a footing for a steel tower
RE: Checking a footing for a steel tower
RE: Checking a footing for a steel tower
RE: Checking a footing for a steel tower
Mike McCann
MMC Engineering
RE: Checking a footing for a steel tower
RE: Checking a footing for a steel tower
BA
RE: Checking a footing for a steel tower
This is a good example of why it is necessary to have another engineer review the initial work. It's basic Quality Assurance.
RE: Checking a footing for a steel tower
DaveAtkins
RE: Checking a footing for a steel tower
The Canadian concrete standard A23.3-04 doesn't allow using the concrete tensile strength to resist bending. However, I checked to see if Factored Bending moment is smaller than (Mcr/1.2), in which case I would be comfortable without top rebars, but it wasn't the case.
RE: Checking a footing for a steel tower
A general rule:
If the footing mainly resists wind overturning then top and bottom reo.
If the footing mainly resists downward load from gravity then bottom reo should be okay.
By the way, you have not shown the horizontal reaction, those pedestals over the footing will be cantilevers in bending.
RE: Checking a footing for a steel tower
Yes, Thanks you. There is 6.7 K horizontal reaction at each pier.