Re: Lattice Tower Erection Issue 1

[greece22]

Hello Gents,

New to the forum and here is my first post. Need some opinions here. Basically we are installing a triangular lattice tower (100ft) and the civil technician on site has indicated a minor error in the alignment/spacing of the tower foundations (three (3) piles, one (1) to support each leg). As a result the angle members are out of alignment by about 1/8" - 1/4" on two of the legs in that the angles do not fall flush against the cleats as they should.

My question is that is this small deviation a cause for concern or can we reasonably proceed with stacking the upper sections? If it is cause for concern what is the recommended path forward?

I have attached a picture which shows how the angle falls against the cleats. Your input here would be greatly appreciated.

Regards,

 

[desertfox]

Hi greece22

First let me say I know nothing about transmission towers but I would be concerned about a bolted joint as shown in the picture.
The reason for my concern would be the additional loadings placed on the bolt eg:- prying, I see it as a sure fired way to fail the bolt in service.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[msquared48]

In that this tower probably has five 20 foot sections, the problem is just going to get worse as you proceed up the tower.

The problem should have been corrected at the foundation before the erection process began.

You need to contact the tower manufacturer (Valmont, or whomever) and ask them what to do as they designed the tower. Probably not the foundation...

Mike McCann, PE, SE (WA)

 

[transmissiontowers]

I think Mike is right. Contact the tower vendor and take more pictures (it's hard to tell why the gap is happening in your one picture).

For Desertfox, these towers transfer loads from lacing to leg through bolt shear and bolt bearing and the bolts don't really need to be that tight because they do not transfer the load through friction. The bolts just need to be in the hole.

Are the legs round pipe with plates welded at 60° or are the legs closed 60° angles? It is hard for me to see in your picture.

If it is a foundation rotation problem that is causing the twist, you may check with the vendor and slightly slot the base plate holes so you can rotate the leg so the lacing lays flat as it should. As a disclaimer, I do T-Line towers and am only a little familiar with these triangular microwave towers. I have analyzed a few of them that we own for antenna loads.

One other question, is the tower guyed or free standing?

_____________________________________
I have been called "A storehouse of worthless information" many times.

 

[greece22]

Hello Gents,

Really appreciate your comments.

The tower is free standing and we have identified the source of the problem.

The spacing of the tower legs is accurate. However the orientations of the two rear legs of the tower are not in alignment with the center of the tower.

As such we needed to twist these legs slightly. The course of action we took on recommendation from our engineer (time critical installation so we could not wait on maufacturer's response) was to drill new holes in the splice plate (1" plate thickness) provided the spacing for this alignment was not smaller than the existing edge distance. Coincidentally the spacing and edge distance are the same i.e. 3/4". Note: See attached tower drawing and pics.

The tower is now in perfect alignment (angles now lay flat on the cleats) and we will proceed with the stacking of the upper sections tomorrow.

Any thoughts on if these additional holes, or their spacing, can affect the structural integrity of the plate/connection. Would value a second opinion here for my own knowledge and understanding.

Regards,

 

[transmissiontowers]

The bending planes of the base plate will not intersect with the old holes so you should be fine.

_____________________________________
I have been called "A storehouse of worthless information" many times.