Methods for structural analysis of space frames

[george85]

My name is George, I am an architect from Serbia. When I finished my faculty of architecture, I realized how wrong I was in a choice of my life profession. I should choose civil engineering instead. At the end the civil engineering is real science, real creative force, the architecture is pure bullshit, based on nothing (based on something some people call art). Well enough of these heart breaking stories about my profession, this is what I wanted to ask you:

First of all, this forum is the best Civil Engineering encyclopedia and community on the web. Keep it that way. I am spending all of my free time reading the articles from your forum. Amazingly interesting!

Few months ago, I bought books related to Civil Engineering. Statics and Mechanics (Structural Analysis), Soil Mechanics, Materials in Civil Engineering. And started studying from them. But now, I am especially interested in Space frames, so interested that I am thinking of starting to attend a Civil Engineering faculty from october this year.

I wanted to ask about the Space frame (space trusses, this is what I mean:

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I am especialy interested in methods of calculation of these structures. I am using a local application called Tower

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It is probably not the best one, maybe not in the first few ranking applications for structural analysis, but it is on serbian language, and it is a lot easier for me to work with it, than with SAP. Although I am going to try to learn using SAP definitively.
Ok, back to the story, for now I know how to make the structural analysis of the space frame truss (I even did a two directions curved roof from space frame truss), involving analysis from the load of the structure itself, temperature changes, and displacement of the backbones (supporters). I have also managed to design the structure further into steel.
So the calculation of these structures is not a great problem to me (at least this is what I think, maybe I am doing something wrong, but nevermind ). The stability and dynamics is something that I do not know nothing about. But I am willing to learn, I am going to boy a book about Dynamics.

The main thing why I am contacting you is like I said: the theoretical part of the methodology for structural analysis of space frame trusses. What are the methods? Are there few of those? What are the equations? Are there some books or e-books about this?

I downloaded the "Structural Engineering Handbook by Wai-Fah Chen" and this book has a section with "Space frame structures by Tien T. Lan". I found a part where he mentions the discrete method, continuum analogy method and matrix methods for the structural analysis. But where are the equations for these methods?


Thank you for all the help and answers.

[denim]

I study civil engineering for 10 years (4 years undergraduate + 2 years Master + 4 years PhD), I like architecture better.

Your questions can be answered in a lot of books. Check this out:

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Good Luck!:sarcastic:

[struceng]

@george: I think a big percentage of architects have feelings like you but they don't confess it around. I appreciate you because of that. And you gone further also by educating yourself on Civil Engineering (appreciate^2). Just like denim, mine is 15 years (with PhD) and I prefer to be an Architect :sarcastic:

This book is purely just for your interest:

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[Haseeb Jamal]

Hello George Spasic

The problem is that the books that we see today about structural analysis are all similar to each other. I had the same problem as you have, in finding the related formulas. Most of the numerical problems in structural analysis books just finish up with determining rotation or displacement at nodes. I could find the following links to help you.

Analysis, Design and Construction of Steel Space Frames

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Matrix Structural Analysis

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Structural Analysis

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Matrix Structural Analysis

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Structural Equation Modelling

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Structural Equation Modelling

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[george85]

Thank you once again Mr. Haseeb Jamal both for email and this reply. Keep doing the good work, it is splendid.

About my civil engineering studying: unfortunately there is a problem with standards in my country (Serbia). We are still using the so called JUS standards for civil engineering (wich are in most cases copied german DIN standards). I heard that all of Europe is using the Eurocode one, and that germans are also planning to abandon their DIN, if they haven't done this already.
The problem is also the one that old professors at the Civil engineer faculties in my country, are not willing to teach the Eurocode principles. So the numerous students will still have to wait for a couple of years until this "dinosaurs" go the retirement, and then get a proper teaching of Eurocode at the faculty.
I supose that the structural analysis is the same at DIN and Eurocode (M,T,N diagrams). But the design (of steel, wood and concrete) is completely different. And all the books that I already bought about design of steel, wood and concrete are made by JUS standards.
So it seems that it is pointless of learning from them, I need to start learning from some of books from here. But it is quite difficult for me to learn from the ones at the english language, because there are a huge number of therms, that I do not understand. For example:

hinged joints
bearing strength
yield strength
shear strength
stress
slenderness ratio
deflections
threshold

I tried translating it using a dictionary, but it didn't help. I need to buy some kind of a English Civil engineer dictionary.

[PanosP]

@George85
I am afraid my friend that I will have to disagree with you as far as design codes are concerned. I mean that DIN1045-1 and DIN18800 are very similar to EN1991 and EN1993. At least in principle. If you go into details you will notice that DIN18800 has different material safety factors and PM and buckling interaction formulae. Nonetheless the principles are the same. And by principles I mean ways in which global and local verifications can be performed (see for example structural analysis methods including imperfections).
Regarding your professional concerns I would advise you not to be bothered with tags and titles. All construction related professions are dynamic professions. They are evolving with time. Hence an "internal" transfer is always possible. Not to mention that some of the greatest architects (eg Mies Van der Rohe) had sound knowledge of the structural behaviour. On the other hand civil engineers should also have knowledge of architectural issues. How many engineers know what the slope of an disabled persons' access ramp should be? HOw many engineers know what the size of a car parking bay area should be?
Regarding your engineering terms inquiry I would strongly recommend an index search inside "Structural and Stress Analysis" by Megson.
Good Luck

[seb3k]

PanosP
you are correct, newer DIN fachberichte 101-104 are quite similar to eurocode, based on probability and not maximimum stresses, and in some ways even more clearer(easier to interpret) than EC.
But JUS standard is based on older DINs.

George
Try to be more relaxed :) and learn as much as possible, because engineering principles are the same no matter what code you use


And a bit of help for you or someone in the future having similar problems :)


hinged joints - obicni zglob
bearing strength - nosivost
yield strength - granica popustanja
shear strength - posmicna otpornost
stress - naprezanje
slenderness ratio - vitkost
deflections - progib
threshold - prag necega?

[dvng]

PanosP

learnung structural analysis and design through Books is definitely not the way to go. Archtects and Engineers is the same. They first need to be practioner and learn through the peer review way. There is a lot of art in structural engineering especially conceptually and stability. If you can;t understand the true concept of structural behavior then by reading books is not going to get you very far. You need to practice engineering via the mentor route. This method is much more effective than reading books.

[ssi3k]

Dear George85,

Don't limit yourself to space frames which are in actual trusses, usually trusses composed of so many members. Truss members are traditionally solved by matrix analysis using stiffness method, displacement method, etc. With the advent of finite element method (FEM) which are broader in scope and can solve many types of problems than the traditional method, truss members can be modeled as beam elements or truss elements. Thats why, nowadays, structural analysis and design programs such as ETABS, SAP, SAFE, etc. are using finite element method (FEM) in their subroutines. That's why I advise you to study also FEM.

You don't need to study how to program the equations; all you need to do is understand the principles and used ETABS, SAP, etc to solve your problems.

FEM can be applied to any structures, of any size and shape, any complex space frames. Actually even into the field of medicine, meteorology, hydrology and other physical sciences FEM is being applied nowadays.

With regards to your profession, actually I also studied structural engineering for 7 years (5 in BS and 2 in my MS). However, I still like architecture more. You see, if you compare it to a lady, architecture is her physical look, the shape and the outside beauty; whereas structures are the skeletal system or the bones. We admire ladies for their beauty not for their bones! :w00t:

[elbarto_87]

If you are interested in space frames, then you will want to have a look at some references regarding the direct stiffness method which is what the majority of all frame analysis programs are using (users have already posted links). It may also be useful to look at the flexibility method as you work up to the direct stiffness method. The flexibility method is easier for myself to understand, however I have written programs for analysis of 3D space frames in the past and I have always used the stiffness method as it is much easier to code in my view.

My recommendation:

1) Look at the principles of virtual work
2) Try examples of flexibility method (start with truss)
3) Try examples with stiffness method (try a portal frame or something)

I studied these topics before I started using any software and it helps a lot. Any one who uses software like frame analysis packages without first having at least some exposure to these methods is being pretty "optimistic" I would say.

Good Luck