Guyed Stack Design

Dear jprashant31,

Your problem is not mechanical but structural and it is not enough to have a spreadsheet to solve it. Excuse me for being obnoxious, but your question sounds like this: "I need to design a rocket and build it in my garage; could somebody send me a simple 'do-it-yourself' manual or 'guide for dummies' how to do it?"

As usual with structural designs, you should start with two parallel workflows:

1. Loads (based an preliminary geometry, weights of non-structural components and climatic/seismic region where you design will be built) Most important here is to determine the wind load and pre-tension of the guy wires. If Seismic is not negligible in your region, you should think how to allocate masses along your stack for seismic analysis.

2. Geometry (including exact diameter and wall thickness of the stack pipe, metallic area of the guy wires and conditions of attachment i.e. spring or simple pin-connections)

By the way, you didn't tell how large a circle your stack is allowed to occupy in plan, what's the required diameter of the stack pipe, does it have platforms and other attachments, what's the linear weight of liners or any other non-structural materials, and what Building Code (what country) you should use.

All this information should be systematized (and that's were an Excel spreadsheet is handy) and input into a Structural Analysis Program and the analysis is run repeatedly for various load combinations.

If seismic is in effect, an additional analysis should be done to determine natural frequencies for quantitation of the Static Equivalent Force (this force is going to be distributed on the stack and applied as static for the Seismic Load case)

If you'd like to get more detailed explanations, you're welcome to ask.

Cheers,

Len

Dear BoqdanovL,

Your comments are precise.I think the area required for safe anchoring of stack will be substantially large.Installation appears to be unsafe.It is best to go for self supported design.

which structural analysis program you are referring ?

Ratnagiri

Dear Ratnadiri,

My understanding is that your structure has become a triangular tower with a stack in the center of the triangle. To make this tower tapered like a pyramid or a simple (but heavier) triangle prismatic shape - it's up to you.

Your next task is to define preliminary the typical cross-sections for the cords (or columns if you will) and bracing of this truss system.

There are many programs for structural engineering that handle modeling linear members very well: STAAD.Pro, SAP2000 & ETABS, GT-STRUDL, S-Frame, STRAP, NISA, LIRA, RISA, Robot-Millennium and so on. I could continue this list but it wouldn't make sense.

Cheers,

Len