×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Tower Analysis Program
2

Tower Analysis Program

Tower Analysis Program

(OP)
Currently we use TnxTower for tower analysis/design projects, but it does not do a seismic analysis as required by TIA 222-G-05 now, and will not for at least six months.

There is another program we have found out there, TSTower, that does do seismic, but we hare having a real problem communicating with the company to get even a demo program, hence our frustration and need to post here.

Is there another analysis/design program out there that does seismic and anyone recommends for monopole, trussed and guyed tower projects?

Any insight would be appreciated. Thanks.

Mike McCann
MMC Engineering

RE: Tower Analysis Program

Mike...when I was doing tower analysis, we used STAAD, STAAD-Pro, and mTab-Stress. I haven't done one is a few years, but wouldn't RISA-3D handle that? Maybe JoshPlum will weigh in on it.

RE: Tower Analysis Program

STAAD has their STAAD(X) Tower program, but I doubt that it's any more advanced than tnxTower. From the very small bit I know about the tower industry, tnxTower is the recognized standard.

Good luck.

RE: Tower Analysis Program

(OP)
Ron:

RISA sold their tower program, RISA Tower, two or three years ago, and it is now TnxTower.

Mike McCann
MMC Engineering

RE: Tower Analysis Program

Thanks, Mike....see...I'm always behind!

RE: Tower Analysis Program

Actually, it's more like TnxTower split off from RISA. Our main RISATower developer opted to buy the program from us. So, it's the same basic people involved with writing and supporting the program as it was when it was RISATower. We still have a pretty tight relationship with them. And, we even handle most tech support related to the license protection.

Regarding Seismic and Towers (either monopoles or trussed), I started a nice write-up a couple of year ago on the RISA-3D / TnxTower integration awhile back. Originally intended for inclusion in the TnxTower Training class. And, there is a lot in there about seismic. I'll try to locate it and post a link in a follow up.

For the seismic portion, I basically started with the standard example model (Falcon 120 G)that TnxTower uses for self supported / trussed towers and brought it into RISA-3D. Then I used the three different methods from the TIA / EIA G standard for doing seismic and compared the results to the wind load results.

Note:
I located the tower in the one of the highest seismic regions of the US, but was eventually able to demonstrate that the seismic base shears were less than 50% of the wind base shears. Therefore, per an exception in the G standard, seismic could be ignored for the tower.

RE: Tower Analysis Program

This should link to a Zip file on our FTP site which has the draft version of the training manual listed above. Note: it is a draft version because Peter / Tower Numerics purchased the program before we could put the finishing touches on it.

RISA-3D / TnxTower Integration

Note:
  • Our FTP site gets cleared out periodically, so I cannot promise how long that link will be valid.
  • There are both RT3 and R3D files in that zipped file. Normally files that get exported from TnxTower will always be an RT3 file. But, I created the R3D files as well... just because I wanted to be able to give these out to RISA-3D users who did not own TnxTower.

RE: Tower Analysis Program

(OP)
Josh:

Ok on the genesis of TnxTower and Risa. Sorry. I guess that I misunderstood Peter.

However, under the new TIA 222G-05, it is now required that a seismic analysis be performed, as well as wind and ice. I agree that seismic will seldom, if ever, control, but it is no longer a wash based on experience. A sharp reviewer, and client, will want to see it on paper. For my own edification when I was getting into this a couple of years ago, I ran a few towers by hand, using the seismic methodology of TIA 222-G, and found similar results as you.

Mike McCann
MMC Engineering

RE: Tower Analysis Program

Mike -

It is required.... But, there are a number of outs in the G standard. I'm looking at the G standard Rev 2, which should be 2008, and seismic can be ignored for the following cases:

1) Structure class 1 with an Ss equal to 1.0 or less.
2) Regular structures of any class where the seismic base shear is less than 50% of the wind load base shear.

The frustrating caveat with the 2nd exception above is that you have to actually demonstrate that the base shear is less than 50% of the wind load. And, that's the extra work some plan checkers / jurisdictions may be looking for.

In my examples, when I used Method 1 and 2 I didn't come up with a lower base shear. I was using just about the worst case location for seismic, so that shouldn't have been too much of a surprise. Even so, when I used method 3, the seismic base shear was low enough I could justify relying solely on the TnxTower analysis (which did not include seismic).

It's not difficult for someone like me (who is experienced with Response Spectra Analysis) to run a Method 3 analysis in RISA-3D. So, it should be relatively easy (for someone like me) to demonstrate that just about any Tower doesn't need seismic to be considered in the design.

Obviously, not as easy for your typical tower engineer who doesn't have my background with analysis and dynamics. But, that's one of the reasons why I put together that manual.... because I wanted to alleviate some of the fear / concern folks had about the new seismic "requirements" in the G standard. Both by giving an example calc and by demonstrating that even for that high seismic case, it was not likely to control.

RE: Tower Analysis Program

(OP)
Josh:

We should make new code a recommendation that all towers need to be anchored in place by guys and supported by balloons so that there would be no seismic to consider. Things would be so much simpler... bomb

Mike McCann
MMC Engineering

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources