Towertalk
[Top] [All Lists]

[TowerTalk] Fwd: *** - Television tower topples]

To: <towertalk@contesting.com>
Subject: [TowerTalk] Fwd: *** - Television tower topples]
From: n4kg@juno.com (n4kg@juno.com)
Date: Wed, 5 Dec 2001 08:44:08 -0600
N4KG response inserted below.

On Wed, 5 Dec 2001 "Joe Subich, K4IK" <w8ik@subich.com> writes:

        SNIP

> > For (relatively) short guyed amateur towers under 100 feet the  most
> > common failure mode is that of a broken guy support from excessive
> > horizontal forces. While the failure of a top guy of a multi-level
> > guyed tower might constrain the debris radius by allowing top 
> sections to fold around lower guy supports, this would still not be the

> classic downward crumple observed in the TV tower.

        Multiple guy points in each direction are the key to
        allowing a tower to 'fold' in the event of a *single*   
        guy failure.   N4KG
> 
> This would only happen if all they guys on a single side failed at 
> the  same time.  The *only* failure mode in which I could envision a 
> multiple 
> simultaneous guy failure is vandalism (the anchor rod is cut) or if 
> the anchor block were to fail and the anchor pull out of the soil. 

        One scarry scenario would be if the anchor rod were
        to RUST through, unseen by the owner.  Fortunately,
        this seems to be a rare occurance.   This is a STRONG
        argument for TWO anchors in each direction.  N4KG

> If an amateur tower were, for example, have a leg rust out I would 
> expect a crumple or crushing fall just like a commercial tower. 

        NOT exactly. Remember that for a guyed tower,
        almost ALL of the forces at the base are vertical.
        Fortunately and amazingly, even a single tower leg 
        seems sufficient to support a *short* tower but don't
        bet your LIFE on it.  N4KG

        Case in point:  I have two such towers, still standing.
        
        One, a 55 ft TV tower with horizontal braces (NO
        diagonal braces) and roughly 12 inch face width
        where ONE leg rusted through at the ground where
        I had left a string tied around the leg (who knows why).
        I placed a plate under the rusted through leg, drove
        3 ft pieces of angle iron half way into the ground
        on the outside of each leg.  Then I cross braced 
        the legs inside the tower using two pieces of 2X10
        rotated to engage all the legs and nailed together. 

        Two, an 80 ft TV tower of identical construction
        with TWO legs rusted through at the ground.
        (Scared the H*** out of me when I discovered it)
        Both towers were placed in the ground roughly
        30 inches with NO concrete 20 years ago.
        Again, I drove some heavy angle iron around
        each leg, and crossed braced the bottom 
        opening using 2X8's in an H configuration
        stacked on top of each other, up to the first
        step, bracing the bottom of the tower in
        all three axis'.  Both towers are STILL STANDING 
        after 2 years, having survived some quite
        high straight line wind events.  N4KG

        N4AR has a 200 ft Rohn 45 tower that SHEERED
        the legs at the top of his concrete base when
        a tornado twisted the tower with 4 stacked 4L20's.
        It is still standing with an additional concrete
        block poured around the bottom of the tower,
        on top of the original concrete base.  N4KG
        

> > I dare say if the TV tower had suffered the total loss of one of 
> its upwind guy supports, it, too, would have fallen like a giant tree.
> 
        SNIP
> 
> 73, 
> 
>    ... Joe, K4IK 
> 

________________________________________________________________
GET INTERNET ACCESS FROM JUNO!
Juno offers FREE or PREMIUM Internet access for less!
Join Juno today!  For your FREE software, visit:
http://dl.www.juno.com/get/web/.

List Sponsored by AN Wireless:  AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 100 feet for under $1500!!  http://www.anwireless.com

-----
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com


<Prev in Thread] Current Thread [Next in Thread>
  • [TowerTalk] Fwd: *** - Television tower topples], n4kg@juno.com <=