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Send me the questions & numbers ...

 

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I might be the only civil engineer here lol. I'm only just graduating but I'm pretty good with concrete -ok with steel. I'll be very busy these next two days and then leaving for France for 2 weeks but Ill take a look at it if I have some free time
 

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Discussion Starter #5 (Edited)
for stuff like bracing (FSTB, RSTB, LECB, etc), which models should I predominantly be looking at to calculate stresses and deflections? At first I looked at Column Buckling due to an applicable slenderness ratio, but I also saw beams with fixed ends under a uniformly distributed load. So yea that's what I'm wondering.

EDIT: I know it's no where near as simple as those models, but I just want to wet my beak with the formal understanding of it. :)
 

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Less bracing more 4v long tunes GM!
 

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That's a different direction than I thought this was going. :eek:

Basically most bracing would be under the combined stresses of compression/tension and torsion. The ends would/should be considered fixed in most cases. You will be better served with symmetrical sections such as square or round cross sections.

In general, I prefer high carbon chromoly steel due to strength vs weight. In basic stress calculations, you can get twice the strength in the same dimensional section or half the weight for the same strength. It is available in common tubing sizes (round or square) as well as solid round sections. But you probably already knew that. ;)

Modeling the loads would be difficult to quantify in my opinion and I prefer to use a simulation software such as SolidWorks Simulation to ascertain critical stress/strain points and visualize deflections. You can fix the ends as required and apply tension or compression combined with torsional loads.

For general bracing, you usually want the largest girth that will fit in the required space to give you higher strength properties. For example, under the same stress, a 2" cross section would be better than a heavier 1" cross section. In practice you will be limited by physical space and commonly available sections so the possible combinations won't be an extended exercise.

I hope this helps or at least gets you started in the right direction. :)
 

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Discussion Starter #8 (Edited)
Less bracing more 4v long tunes GM!
I'm working on it! Work has been killer this year, way more so than I could have imagined.:(

That's a different direction than I thought this was going. :eek:

Basically most bracing would be under the combined stresses of compression/tension and torsion. The ends would/should be considered fixed in most cases. You will be better served with symmetrical sections such as square or round cross sections.

In general, I prefer high carbon chromoly steel due to strength vs weight. In basic stress calculations, you can get twice the strength in the same dimensional section or half the weight for the same strength. It is available in common tubing sizes (round or square) as well as solid round sections. But you probably already knew that. ;)

Modeling the loads would be difficult to quantify in my opinion and I prefer to use a simulation software such as SolidWorks Simulation to ascertain critical stress/strain points and visualize deflections. You can fix the ends as required and apply tension or compression combined with torsional loads.

For general bracing, you usually want the largest girth that will fit in the required space to give you higher strength properties. For example, under the same stress, a 2" cross section would be better than a heavier 1" cross section. In practice you will be limited by physical space and commonly available sections so the possible combinations won't be an extended exercise.

I hope this helps or at least gets you started in the right direction. :)
No Solidworks here, unless you want to send me a fully-functional "evaluation" copy. :D What you mention is what I've seen using basic beam stress/deflection for a beam of constant cross-section, under a uniformly distributed load. Basically what I was looking at was to slightly "overbuild" with a safety-factor included to account for the fact that there will be stresses I cannot account for without simulation software.

Just tinkering around.....Values don't represent any particular design, just plugged some stuff in....
https://docs.google.com/spreadsheets/d/1g3mZXGguxxVBmBg2v_BY8lftq-aUarGEH6T0h90cVms/edit?usp=sharing

using Machinery's Handbook as reference material.
 

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It's been over a year since I've had steel but off the top of my head for calculating slenderness you have to check your kL/r value and compare it to your f critical. Your k value is a constant depending on type of beam or column. Obviously cantilever is worse like a 2.0 were as a fixed at both ends is like a .8. L is length. R is radius of gyration about the bending axis or the strong axis. Buckling will generally only control with heavily loaded tall columns. Beams are almost always moment with little axial forces which I'm sure you already know. In my steel manual there are a lot of great formulas for calculating deflection based on load, moment of interia, length, etc for 99% of beams you will work with. You could probably find them all online.

I'm not as good with software yet. But there are some good simple free/cheap programs like skyciv that will model all sorts of frames and trusses. I used it a bunch for my senior design project for determining moments, shear, etc. I did the structural analysis of a 34' double barrel slab culvert. It acted more like a bridge than a culvert
 

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What you mention is what I've seen using basic beam stress/deflection for a beam of constant cross-section, under a uniformly distributed load. Basically what I was looking at was to slightly "overbuild" with a safety-factor included to account for the fact that there will be stresses I cannot account for without simulation software.

Just tinkering around.....Values don't represent any particular design, just plugged some stuff in....
https://docs.google.com/spreadsheets/d/1g3mZXGguxxVBmBg2v_BY8lftq-aUarGEH6T0h90cVms/edit?usp=sharing

using Machinery's Handbook as reference material.
A uniformly distributed load is not applicable in the case of bracing but will yield insight to comparable strengths between materials and sections (as depicted in your spreadsheet).

If you think of the case with a FSTB, you will have fixed ends with torsional loading combined with an end moment similar to a cantilever load. I would play with the numbers on different sections looking at torsional strain and cantilever strain. The tradeoff is a section that will resist torsional load better is not what will give better results for a cantilever load. Likewise, the best section to resist cantilever loads is not the best section to resist torsional loads. Think of the loading differences between a 2" round tube vs. a 2" square tube.
 
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