Pole Guy and Anchor Design

[ThePunisher]

Hi all,

We have worked on a power line extension design at 34.5 kV only. Our power line engineer designed the extension using PLS-CADD and PLS Pole. He provided both sag and tension and pole layout (with hardwares modelled correctly as per Utility Code and IEEE and as oer our client's transmission standards). The pole guys are located including their leads, angles and forces based on the vertical and horizontal loading forces based on PLS-CADD calculations. In one of the diagrams the guy is shown up to the grade level only with the forces and angles shown.

I have given this to our structural person to specify and guy anchors based on the vertical and horizontal forces shown UP TO THE GRADE LEVEL as indicated in PLS-CADD report so he can size the anchor and specify the depth based on soil properties.

To my surprise he wants to validate the sag and tensions and validate the forces calculated by the software c/o our power line engineer who is currently on leave. I was thinking what for should he validate the forces reported at the guy limit at the grade level?

Am I missing anything and my structural person does not know what he is doing and he might be asking too much or crossing over into our electrical world. Appreciate some advise, thank you.

 

[bacon4life]

It would certainly prudent for the structural person to do an approximate hand calculation for one of the anchors. Using just a printed report from any computer program is dangerous without verifying the assumptions that went into the report.

PLS-CADD can do designs based on either using load factors per NESC table 253, or be using strength reduction factors. Although load factors work reasonably well for linearized hand calculations, the don't work when modeling real equipment using finite element analysis program such as PLS-CADD. For example, applying 4.0 wind load factor may result in 16x defection at the top of a pole in a FE analysis. For a realistic model, PLS-CADD would instead apply realistic loads to calculate the realistic pole deflection, then check that the pole is using no more than 25% of the strength. Depending upon exactly how the PLS-CADD report was generated, it could include either Actual loads or Factored load.

Additionally the structural engineer may want to verify whether the report contains loads calculated for the expected geometry, or whether the report is based on expected geometry plus allowable field tolerances. Our civil designer usually verifies that the as-built strength & clearance will be adequate even if the pole is set +/- 1ft in height and the pole/anchor are up to 3ft from the design location.