Disagree with the plan reviewer... does this mean I'm wrong... forever..

[CBlaker114]

Hello all,

I've got an interesting situation where I've had plan reviewers in Miami Dade as well as Broward County (Florida) reject analysis' our firm has performed on telecom structures(cell phone towers) and site that Miami Dade requires 175mph (Vult) wind speeds for all class II structures and Broward requires 170 mph. These requirements come from the Florida Building Code Section 1620.2 which was added into the code during it's initial inception to incorporate requirements as found in the previously governing South Florida Building Code. This code no longer exists and the FBC governs statewide. Miami-Dade does not have an established county code which would add further restrictions to the FBC.

I have provided the information above so that I can point your attention to Section 1609.1.1 Exception 5 which defers to TIA-EIA-222- Revision G for wind speed on communication tower and steel antenna support structures. TIA-222-Rev G bases it's wind speeds on ASCE7-05. I have a slightly overstressed tower and my tower is located about 10 miles inland so going strictly by ASCE7-05 iso-lines, I should be able to drop the wind speed about 5 mph which will bring the stresses into the acceptable range.

Question 1) Do I have ground to stand on if I design per the wind found in Rev G (or ASCE7-05) to push back on the permit reviewer when they tell me I HAVE to use 175mph(or the Vasd equivalent). This has happened before and we usually acquiesce their request, but this slight overstress will cost the owner a lot in modifications so I'm trying to do what I can here.

Question 2) Is this my problem? Should I use the reduced wind speed(at the tower owners request) though I KNOW this is going to be a pain getting through permitting. Just tell the owner.. it's designed to code as you've request... getting it through permitting is your bag....?

...again... Miami Dade does not have a published building code so I'm not sure of the legalities of them just saying "we require this... see it's on this box I need to check."

Any thoughts are appreciated. I've dealt with this quite a bit but I've never gone to the mattresses with the municipality so I'm just wondering about others' experiences with this sort of thing.

 

[Celt83]

your fighting an uphill battle regardless of the governing code essentially "The authority having jurisdiction" has indicated to you what the design wind velocity should be. That part in quotes is plastered all over all of the respective codes to note that "hey unless "The authority having jurisdiction" tells you otherwise a panel of industry professionals, technical advisers, etc. recommends using x as minimum under the following conditions."

That said have you tried having a conversation with the reviewer/s to work thru where their requirement is coming from and why you feel it's no longer applicable?

Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

 

[GC_Hopi]

This would be be a tough battle. These two counties are defined as high velocity hurricane zones by FBC and the wind speed for HVHZ are given in FBC 1620.2 As you can imagine and as it should be hurricanes are taken very seriously so getting any exception would be difficult. As far as the second question that would be between you and the owner. If you explain the circumstances they should understand and hopefully be reasonable and not blame you for designing to code.

 

[CBlaker114]

Celt83 - That's a really good point. The "the authority having jurisdiction" verbiage is essentially that same as your mom's "because I said so!" irrefutable, unyielding, absolute...haha

And no. I've not had a conversation with the reviewer. The specific project I'm referring to is in the due diligence process for my client so there's no active installation in the near future. My client is trying to get an idea of any additional future revenue if they're to purchase this asset.

GC Hopi... totally agree with you about the seriousness of hurricane winds, however the falloff in wind loads as you move inland is very real so I think there would be a big argument for being able to reduce the wind load. Those wind maps really do show this pretty accurately..

Thanks for the thoughts..

 

[JLNJ]

"Your Honor, I used an older code to 'make it work'..." does not sound like a strong opening statement.

 

[CBlaker114]

JLNJ... FBC 2017 references TIA Rev-G which References ASCE7-05... so under that exemption it would be the currently adopted source of wind loading for telecom supporting structures... Also.. I'm not arguing to use previous wind loads... especially since ASCE7-16 typically reduces the wind loads(though in SFlo,they're pretty much the same as ASCE7-10). My question had nothing to do with using an outdated lower wind speed but the ability to use the wind speed as shown in the ASCE7 as deferred to in the current code via the previously mentioned exemption.

 

[rb1957]

do you win arguments with your wife/spouse/... ?

I live in a similar world ... in the face of all rational argument what the authority says trumps (no pun intended) the interpretation of the rule.

another day in paradise, or is paradise one day closer ?

 

[jgailla]

Miami-Dade is very political and cliquey. You will have to make friends regardless of the final outcome. Developers usually hire local pretty girls to walk plans through.

 

[azcats]

Is there anything in the link below that might help your argument?

http://www.floridabuilding.org/fbc/commission/FBC_1016/DEC_Statements/Staff_Analysis_DS2016-058.pdf

FWIW, I think you're correct to use TIA loading and winds, but you're up a creek if you can't convince the AHJ's representative. My guess is he wants to check a box and doesn't really understand the issue at hand...just like JLNJ.

 

[TLHS]

I personally feel like it's a stretch to chase references for information that is specified in the original document. I get that there's maybe an exception listed, but if you're going to go from a document that's based on the IBC and has local wind requirements that were intended to take precedence over the ASCE maps, then go to a structure specific code, then chase that back to ASCE and use their maps you might not be meeting the intent.

I also don't really think the exception means what you think it does. To me that reads as though they are saying you can use the methodology of TIA rather than the methodology of ASCE-7. It doesn't exclude you from the windspeed requirements later on. The people using ASCE-7 methodology, which is what you are given an exception from, don't get to use the ASCE-7 maps so why would you get to? They use the windspeeds provided further down in the flordia building code section. You don't have an exception to 1609.03, which is where the design wind speeds are.