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1-8 of 8 messages
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Tower Building Permits and Wind Loading
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by W1AN on April 4, 2009
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Putting zoning issues aside, what engineering documentation have members found acceptable to their local building departments for wind and ice loading for new tower installations? Most US states have or will adopt the new TIA-222-G standard which spells out design requirements for structures which include ice and wind loading with 3 second gust ratings. These wind ratings range from 70MPH to over 140MPH. In Connecticut they range between 90 and 120MPH. Since many towers specifically free standing "ham affordable" towers have advertised ratings much less than required for much of the country, how has this affected our ability to install new towers? And have local building departments accepted towers that crank down an alternative to meeting the strict wind loading requirements for the full extended height? What are your experiences?
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RE: Tower Building Permits and Wind Loading
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by WB2WIK on April 4, 2009
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I'm lucky to be in California, where all that stuff has little meaning. Here in L.A., to get a permit for a tower you only need the manufacturer's blueprints with a CA P.E. seal on them, and verify your excavation and foundation are what the manufacturer recommended. We don't have hurricanes here, so the gust ratings don't apply (at least not yet)!
I think it probably is becoming more challenging in many areas, especially Florida, to get a tower "certified" for installation. A lot of places require a P.E. seal on the design documentation verifying that by calculation the tower will meet the local standards, and that can cost from a few hundred to a few thousand dollars.
If you're in CT, you might consult with the League, who is local to you and probably has more expertise than most on this.
WB2WIK/6
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RE: Tower Building Permits and Wind Loading
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by K6AER on April 4, 2009
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Steve is right. Most locations have a few basic rules that are common across the USA.
Your tower if it falls must not fall across property lines. Most of the time this is not a problem unless you have a small lot.
Most building and planning commissions are fine with the supplied prints from the tower manufacture. A manufacture of towers has their towers signed off for all 50 states.
Occasionally a city will require a separate PE to sign off on the tower plans and they might require soil samples in addition.
You r biggest problem will be getting approval from the city after the neighbors within a 500 foot radius get notified. There might be hearings and in some locations this process can be quite expensive. Lawyers will be involved in depending on the level of hysteria on ham towers.
Get a copy of the local building ordinances regarding non commercial towers so you can have your ducks lined up and you have answers for questions for the planning commission.
Understand how PRB1 applies to your situation.
Don’t go into the community emergency aspect of ham radio…nobody cares.
Good Luck.
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RE: Tower Building Permits and Wind Loading
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by KB9CRY on April 5, 2009
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"what engineering documentation have members found acceptable to their local building departments for wind and ice loading for new tower installations?"
All towers are built to withstand, on their own, most wind and ice scenarios. As winds increase or ice loads up, the tower manufacturers reduce the allowed antenna load. The tower is what is permitted, not the antennas. It is up to the responsible tower owner to understand what winds and ice loading can occur in their areas and only install the appropriate antenna(s).
"Since many towers specifically free standing "ham affordable" towers have advertised ratings much less than required for much of the country, how has this affected our ability to install new towers? "
No affect that I have witnessed.
"And have local building departments accepted towers that crank down an alternative to meeting the strict wind loading requirements for the full extended height?"
I do not think they allow this because how can assure it will be cranked down when it should be?
"Most locations have a few basic rules that are common across the USA.
Your tower if it falls must not fall across property lines. Most of the time this is not a problem unless you have a small lot."
This is not true. I have my big tower permitted no problem and it is closer to my property line than it is high. Most towers do not fall down like in the cartoons. They buckle and fall straight down towards the base.
Most building and planning commissions are fine with the supplied prints from the tower manufacture. A manufacture of towers has their towers signed off for all 50 states.
No, not true. The manufacturers prints are for a generic design using "typical soil conditions".
"Occasionally a city will require a separate PE to sign off on the tower plans and they might require soil samples in addition."
Or an SE and I've never heard about soil samples being required since the need for the local PE or SE means they are knowledgeable about the soil conditions in the area. They sign off and are liable in that regard.
"You r biggest problem will be getting approval from the city after the neighbors within a 500 foot radius get notified. There might be hearings and in some locations this process can be quite expensive. Lawyers will be involved in depending on the level of hysteria on ham towers."
Another not true. This may occur if you are requesting a variance from a published tower restriction. I did all my permitting by myself and no neighbors were involves.
"Get a copy of the local building ordinances regarding non commercial towers so you can have your ducks lined up and you have answers for questions for the planning commission."
Finally good advice. I don't mean to bash but many of the previous statements are NOT general rules across the country. I'd say these are the NON general rules across the country.
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RE: Tower Building Permits and Wind Loading
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by JIMPDX on April 7, 2009
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I have very timely information on this particular subject. Today my permit for installation of a MA-40/MARB-40 was rejected by the county building department. I had my foundation engineered under the current code which in Oregon is the International Building Code. The tower is certified under the Uniform Building Code which makes all of their documentation moot to the county. The problem rises out of the IBC requiring a wind loading calculation of 80 MPH where the UBC only required 70 MPG. Long story short, my foundation was approved but I cannot erect the MA-40 on it! Bottom line, do all your homework BEFORE you buy a tower. No matter how good a deal you get! I did not know that Oregon had adopted the IBC two years ago, as we were always the UBC in the past, hell I used to sit on one of the committees back when I was working.
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RE: Tower Building Permits and Wind Loading
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by K6AER on April 7, 2009
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KB9CRY,
“Finally good advice. I don't mean to bash but many of the previous statements are NOT general rules across the country. I'd say these are the NON general rules across the country.”
Philip,
I have put up well over 300 commercial and private towers in my 35 years of tower construction and tower climbing instruction. The last 15 years have been with a cell phone provider and believe me, general building requirements are very close no matter what city you are in. Basing tower advise on your single or limited tower building experience is a very narrow vision.
Putting up one tower at your home and getting lucky with a lax planning commission does not make the normal construction process.
A PE will sign off on the mechanical construction but very few have soil experience which is generally handles by a separate engineering corporation. Many will have soil engineer they refer to when soil density and stability is a question. A PE is not a Certified Civil Engineer
If your tower is taller than the distance from the tower base to the property line you will need to have a variance from the planning commission. These can be obtained but the process is much more difficult and will require a public hearing as a norm. Yes, I know guyed towers generally fall in a collapsed pile equal to +/- 20% of their height but free standing tower can fall in a linear line. I have blown many free standing towers in a fall line. It just takes a bit of a shape charge and a little wind. For a unplanned fall you only need a lot of wind.
As for neighbors getting notified, this is the norm with any permit process. If you city doesn’t do this, something is missing in the building department.
Remember getting lucky is not the same as proper planning.
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RE: Tower Building Permits and Wind Loading
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by KB9CRY on April 8, 2009
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Michael I will acknowledge your experience and will refrain from taking the bait you offer.....
"Basing tower advise on your single or limited tower building experience is a very narrow vision."
How towers do I have at my QTH? How many have I assisted in the planning and erection? How do you know how limited my vision is or my technical background?
"Putting up one tower at your home and getting lucky with a lax planning commission does not make the normal construction process."
Luck increases with hard work.
"A PE will sign off on the mechanical construction but very few have soil experience which is generally handles by a separate engineering corporation. Many will have soil engineer they refer to when soil density and stability is a question. A PE is not a Certified Civil Engineer"
And that is why my county required an SE and also a local SE that DOES have experience with local soil conditions.
"If your tower is taller than the distance from the tower base to the property line you will need to have a variance from the planning commission."
No No No Not in my county you don't. You can't make such a categorical statement. Maybe in your area, but not in mine.
"These can be obtained but the process is much more difficult and will require a public hearing as a norm."
Agreed
"Yes, I know guyed towers generally fall in a collapsed pile equal to +/- 20% of their height but free standing tower can fall in a linear line."
Maybe yes and maybe no. You can't make a distinction.
"I have blown many free standing towers in a fall line. It just takes a bit of a shape charge and a little wind. For a unplanned fall you only need a lot of wind."
I have never used explosives.
"As for neighbors getting notified, this is the norm with any permit process. If you city doesn’t do this, something is missing in the building department."
Maybe for your commercial towers yes, but not for other types of towers. The reg for commercial towers are totally different than non-commercial towers. And my city is better than yours I am sure!! (How's that for a shot back across the bow?)
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RE: Tower Building Permits and Wind Loading
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by WB2WIK on April 8, 2009
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The "local" stuff does vary quite a bit, at least for residential work. Commercial/industrial might have more broad commonality -- probably does.
Here in L.A. where I am, my telescoping tower is not set back from the property line far enough that the tower would fall on my property if it came down in a straight line from the base. In fact, it could actually hit my neighbor's house. However, I was granted a permit anyway because the engineer who reviewed the documents conceded that the way the tower was designed and installed, it would be virtually impossible for it to fall from the base; the 99.9% more likely scenario would be for the top section (smallest cross section), which has only about 1/3 the bending moment strength of the base section, would fold over -- and if that occurred, the resulting mess would all be on my property and not really close to anything.
They also reviewed the setback from the HT lines (7200V Delta 2-line power running across the tops of 50' tall wooden utility poles at the rear of the property) and under "worst case" conditions the tips of my 20m beam would miss those lines by only five feet if it fell -- and that was deemed sufficiently far away, after engineering review.
Then, here in L.A. for many decades they allowed people to install permanent (in ground) swimming pools under high tension lines...that ordinance changed recently for new construction, but all older construction is grandfathered in forever. Part of my pool is literally 50' beneath the power lines and it's been that way for 40 years.
We don't go swimming during violent windstorms. ;-)
WB2WIK/6
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