Jim,
I can not argue with much at all regarding your statements. Except the
engineering costs at 20 hours @ $100 per hour would be abotu 45% the cost of
the tower.
I will probable have a hard time finding a local engineer that understands
all that is needed for a tower. Being an electrical engineer myself (NOT
EIT certified) and taking a few structural classes and with todays computer
programs I really can't understand why it would take anyone 10-20 hours to
spit out specs. You obviously do this and I don't so your knowledge
defintly superseeds mine and I bow down to your experience. That being
said here is my thought of tower analysis?
1. I get a soil boring and have it examined by our local founddation soil
sample people.
2. I send that to engineer which plugs in numbers of soil. Takes tower
structure and plugs that in.
3. engineer plugs in numbers for piers.
4. computer spits outs numbers for various wind loads.
5. If too small wind load engineer "beefs" up piers and goes to step 3.
Now if I took that to someone who has done towers in past they will have
most of this done and all they really will have to do it change the soil
numbers. That would cut time drastically. Yes thier experience level will
proable be double that of the $100/hour engineer but they will solve it in
just a few hours and cost less.
Again I appreciate your insight and remarks and wish not to take away from
them from above.
terry
----- Original Message -----
From: "Jim Lux" <jimlux@earthlink.net>
To: <isp@bnjcomp.com>; "towertalk" <towertalk@contesting.com>
Sent: Saturday, July 09, 2005 10:24 AM
Subject: Re: [TowerTalk] Pad and Pier for ROHN SSV. Pad and Pier Foundations
> At 07:42 AM 7/9/2005, isp@bnjcomp.com wrote:
>
>>Of couse like everyone else here on this list that puts up thier own tower
>>I am trying to save money. But also trying to stay safe. The property I
>>am putting this on was originally part of a piece of land that was hopeful
>>that the city would get a large business to be on. So for that reason
>>they did core samples of the property. So I am going to try to acquire a
>>copy of the results of those core samples to see what they say. So my
>>question is I don't see in Rohn's book a spot for "if XXX sandy conditions
>>then modify piers by doing this or that" or "if XXX compactness with clay
>>then modify piers by doing this or that".
>
> In general, the mfr won't provide this level of detail. If you're going
> to modify the "standard" installation, especially for a tower costing tens
> of thousands of dollars, they're going to expect that you have an engineer
> who can do the calculations for your local situation. You have to take
> into account not only the bearing strength of the soil, the details of the
> excavation/compaction method, and local regulatory stuff. Rohn can't be
> expected to know all the idiosyncracies of every building department and
> soil type.
>
> On the other hand, a local engineer can probably crank this sort of thing
> out, along with all the other structural calculations in 10-20 hours at a
> $100/hr or so, and an engineer's report would probably be required by the
> building department anyway. That's probably <10% of the cost of the
> overall job, considering the new cost of the tower, the excavation, the
> permitting, etc., especially if you treat it like a business, and you
> actully figure in the cost of labor for digging the holes, etc.
>
>
>
>> Once I get that where do I look for those modifications. Also I tried
>> when I bought this tower to get engineering drawings from ROHN but after
>> MANY calls was unsuccessful. Does anyone have any new experience with
>> new radian / rohn and think my ability to get those drawings would be
>> better? Better question is it seems all the information is in the
>> Rohn Catalog and I am wondering what I will get off of those drawings
>> that is not in the catalog (since the drawings will probable be for the
>> original owners Soil conditions).?
>
> You're talking about engineering drawings prepared for a specific
> installation? I'm not surprised that you couldn't get a copy. In some
> cases, the drawings remain the property of the engineer/architect who
> prepared them. In others, they are owned by the person who paid for the
> analysis.
>
> In any case, the drawings may not be of much use to you in a practical
> sense. As you say, they would be for a different installation, so you
> couldn't use them for your installation. They might be interesting to
> look at in an "understanding how the engineering analysis is done" sense,
> but you certainly couldn't just plug in your numbers and hope to trust the
> results. A lot of times, there's a goodly element of professional
> judgement in the analysis and drawings, and most engineers don't put ALL
> the gotchas into the analysis. Example: Engineers in San Diego probably
> don't even bother doing the ice loading calculations, or even mentioning
> that they didn't do them. The local building department isn't looking for
> them, the odds of icing occurring are so small that the engineer can be
> comfortable (in a professional responsibility sense) not mentioning them,
> etc.
>
> I am certainly leery of people who ask me for copies of drawings I've
> done, and want to know a WHOLE lot about why they want them. The last
> thing I'd want is someone to photocopy some drawings I've done (without my
> knowing and approving), submit them for their permit, have the counter
> person not worry about it not having an original wetstamp, have a
> disaster, and find out about it when the legal summons shows up in my
> mailbox. I'd prevail in the long run, but it would be expensive and time
> consuming.
>
>
>
>
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