Wire Initial Tension in Guyed Stack

[J1D]

Can someone advise the typical initial tension of the wires? Some structural design guide suggests a 1/8 breaking strength of the wire (IWRC).

The stack (foundation) I’m designing is about 300ft tall, two sets of guys. The vendor’s information is not quite available yet.

Thanks in advance.

 

[civilperson]

Depends on the angle with the vertical. The compressive, (vertical), component is the limiting factor. The total downward force from all oriented guys will have to be less than the safe compressive strength of the mast/chimney/stack. I use an upper limit of 50% of yield for horizontal guys and proportionally less for lesser angles from vertical.

 

[apsix]

Try looking through this thread

http://www.eng-tips.com/viewthread.cfm?qid=182955&page=12

 

[dbuzz]

The CICIND code for steel chimneys recommends that the pretension should be between 15 and 30 percent of the maximum tension due to design wind under the hot condition.

 

[csd72]

You also need to look at deflection of the cables as well as the stack.

The higher the initial tension the less the cables will sag.

Also the higher the tension the less the lateral deflection of the stack.

so there is a trade off between strength and deflection in this case.

 

[VoyageofDiscovery]

J1D,

These are things I have had to deal with, with respect to bottom pinned guyed stacks approximately 300 ft.

Vibrations
Guy galloping
Fatigue cracking in the lower region of the stack

I have found the typical guy tensions are not really applicable in my experience and may require monitoring by the Owner.

HTH

VOD

 

[J1D]

Thanks very much for the information.

I'm waiting for the vendor's data for the initial tension, which determines directly the deadmans.

On the other hand, the amount of initial tension doesn't seem to affect the shaft deflection too much, while the upper guy's elevation does. From the preliminary diagram, the free-standing section of the stack above the upper guys is about 85ft, this not only causes big bending at the guyed location, also introduces a huge vortex shedding of wind gust on the cantilever portion.