Ted: See my comments below. There has been a lot of discussion lately on the strength of concrete When you order your concrete from the redi-mix plant just tell them you want 3000 psi or 4000 psi con
Ted: See my comments below. This is second try with better format so you can see my comments vs Ted's Sorry about the original. Hank When you order your concrete from the redi-mix plant just tell the
John: Actually as someone mentioned previously, OHSA and most states require shoring for excavations more than 4 feet deep if someone is to be in the excavation. My previous discussion does not condo
I agree if only the existing soil has a well drained structure and is above the natural water table. Hank Hank, I'll give you 50% on the garden hose answer. You can compact SAND very well with a gard
Bill: I agree with your observations concerning the guyed tower and potential failure scenarios... The freestanding tower if engineered and installed correctly and with a constant cross section will
Dave: Doing some quick calculations based on 9.7 sf of antenna lumped at 60 feet and 45g tower section with 55-15=40 foot of cantilever and 110mph design wind. This generates over 50,000 lb-ft of mom
Dave: My anaylsis basis comes from the 1997 UBC Building Code Wind Design criteria. For a design wind of 110mph 9.7 sf of antenna at 60 feet has a wind load of 408 pounds. The cantilever moment due t
Wes: Remember though the exterior walls are designed to take the load spread out over their full area, that is how the wind load is actually applies. The problem with bracket loads is that they are a
Mel: Actually tube, if you are refering round sections, shapes are a little more expensive than angle. The round section has full symmetry and is a more efficient shape in compression loading than an
List readers: Actually you can put the guys where you want within reason. You just have to account for the increased force developed in the guy as you move the anchor point closer to the tower base.
Gerald: Actually I don't think any of it is attributed to the fact it is 4-way guyed. A design condition would be with the wind load in line with one of the guys. In this case one guy is taking all t
Gary: Actually the wind pressure varies from the ground up due to the "boundary layer effect" of the fluid (air) and the friction of the ground surface. The building code wind pressure design factors
Bill: Yes you can do this. It involves drilling and grouting (expoxy) reinforcing dowels into the existing footing and incorporating the old foundation into the new foundation design. In most cases,
Kelly: The accepted practice is to pour concrete either on undistrubed native soil or compacted engineered backfill. Typically engineered backfill is crushed rock or similar that is designed to compa
Hello out there in towerland: I've been reading with interest the latest thread on rebar and concrete. I thought I would try to explain some of the questions. I am doing this in the light of helping
Mike: I'm not sure what the corner bars are. I don't have the diagram or drawing. However it is common to use 2 layers of bars say at 12"c/c each direction in the bottom of the footing and also in th
Fred: The safety factor is typically stated as the value used in the design as a ratio of the breaking strength of the guy. Sometimes it is a ratio of the allowable strength but not often. Therefore
Kurt and reflector: I think the issue of safety factors and allowable stress and ultimate stress gets somewhat confusing. In regards to the Guy safety factor; the EIA/TIA-222-F spec in paragraph 8.1.
Bill: The equation used in TIA/EIA 222-F which is the latest revision and the UBC defines the basic wind speed stagnation pressure (a datum) value as: Qs = 0.00256V*V This is base on Bernoulli's equa