Guy Tower analysis-Linear and Non-Linear
Guy Tower analysis-Linear and Non-Linear
(OP)
I’ve been tasked to do a structural analysis check on an existing guy mast, standing for 12years. A communications company wants to put up extra dishes. Using a frame anlysis programme (PROKON-South Africa), I did a linear analysis first and checked all the members under axial stress, all checked OK. Then I did a non-linear analysis and the programme tells me it can’t analyse because it is unstable due to long slender elements. Now I assume the tower will buckle under my design windspeed (1:50 year storm) which I followed according to our codes. Now how do I go about writing my report stating ,” the tower you build which has been standing for 12 years is unstable”. I’ve ran the frame anlysis under smaller winds and it stands but as soon it starts getting higher the structure is unstable.
Any advice on how to approach my report.
Any advice on how to approach my report.






RE: Guy Tower analysis-Linear and Non-Linear
RE: Guy Tower analysis-Linear and Non-Linear
Castigliano
RE: Guy Tower analysis-Linear and Non-Linear
what i mean is the guy on the down-wind side is probably going to buckle (the imposed compression from the wind load exceeds the pre-tension in the cable. but can the cable on the up-wind side carry the required load ? in which case the down-wind cable sags, and the tension in the up-wind cable increases.
if it can't work then you do indeed have a problem. was the original tower designed for the same loads ? maybe the required load now is higher than it was, maybe the original analysis leaves something to be desired. if these are the loads required today, i think you should make the owners aware of your findings. however they react to this information, i think you still have a duty to the general public (who live around the tower).
RE: Guy Tower analysis-Linear and Non-Linear
Guyed tower analysis cannot be handled by a frame program. There are specific analysis engines for these types of structures. Contact an engineer experienced in these types of structures.
VOD
RE: Guy Tower analysis-Linear and Non-Linear
The anlysis program allows for catenary cables and takes the stiffness into account. If a member buckles it removes that member from the structure and anlyses without it, but still finds the structure unstable(second order anlysis). This is what the support centre of the the program tells me and they get the same results with the model as i do so i am confident in my model.
What hand calculation stabilty checks can be done?
RE: Guy Tower analysis-Linear and Non-Linear
But isn't the program just telling you that you need more elements in the structure for it to assess it correctly, and not that the structure fails?
corus
RE: Guy Tower analysis-Linear and Non-Linear
i would look at your linear and NL results to see if you can see either (or both) of these things happening.
2nd, can't you reinforce the tower ... increase the pre-load, add cables, add struts (as both of these increase the compression load in the tower core) ?
3rd, charity or not, if this was in the US and something undesirable happened in the future, it'd be your a$$ on the line.