Jump to content
I Forge Iron

Help! Metal fabricators advise


Recommended Posts

After having searched on many structural steel related forums, so many formulas and terms got me more confused than anything else. All I need to know is: what`s the max vertical load a 2.5 mt long 120 x 120 x 4mm square structural tube can withstand ? Ignoring the especifications of steel, I would assume for safety reasons, the one I have on hand is the lowest resist hot processed. Any input will be appreciated. Thanks. Nelson.

Edited by nelson
Link to comment
Share on other sites

Please give more information please. Direct vertical load is one thing, adding a meter sq plate to the top of the tube/post and loading the plate is another as you now have not only a center load but also some load at least 1/2 meter from the center. Wind, earth shake, the kid leaning against the tube/post, and a whole list of other stuff must be factored into the answer.

Link to comment
Share on other sites

A quick review of engineering involved shows that the answer is not definable in the form you have asked it.

The alloy is the first question. Who's specs. Loading and anchoring.

There are books that give the typical bending load for BEAMS. The failure of columns is a whole lot more complicated. It depends in large part on the length and modulus of elastisity of the steel.

It would be irresponsible to give you advice with out understanding the application in detail.

Link to comment
Share on other sites

Glenn and Charlotte,
I understand a few basic principles of construction, but obviously not enough to even ask appropiately a question regarding my building at home. Certainly, safety issues are of paramount importance, so that`s one of the reasons I`m here asking `cause I don`t want the roof falling down on anyone. Anyway, I was able to search and find some specs on the 120x120x4mm structural square tube:

Cold formed Steel Structural Square Tube ASTM A500 Grade C

Recomended use as column for big axial loads, moderate momentums and large KL

Static Properties:
I = 397.30 cm4
S= 66.22 cm3
r= 4.70 cm

Fy = 3.515 Kg/cm2
Fb = 0.69 x Fy

e = 4mm
r = 6mm

A (section) = 18.01 cm2
Weight = 14.14 Kg/mt

*QUESTION: given those specs above, what would be the max vertical load 4 sections of that tube spaced 6 ft apart from one another in a square pattern, if they are joint (welded) together at a 2.5 mt height, using another 4 pieces of the same material? Let`s assume the foundations are fine, and there`s no threat of wind, earthquake or a heavy guy leaning on them. LOL, just a big tank for water on top. Thanks so much for help. Nelson.

Link to comment
Share on other sites

Ok here is an answer. I am not, repeat, I am not an engineer.
Years ago I majored in math and physics and have maintained in intrest in those fields.

The answer that I give is based on using a free online calculation session using the information you gave us, and comparing it some hand calculation's all based on Euler's buckling formula.

Given the circumstances you described 18,000 Kg would be a reasonable expectation. This answer is for a load on the column top. One column one load.

The more firmly fixed( "clamped is the engineering expression" ) the column ends are the higher the buckling resistance. Filling the column with concrete would obviouslly increase the bucking resistance.

I strongly advise you to get advice from professionals before you commit any money or risk anyones life.

Edited by Charlotte
add material
Link to comment
Share on other sites

Thanks for introducing Euler`s formula. Very interesting, but I will take your advice, because what I`m building is a hut, where the roof will roughly weigh about 160 thousand # over the columns, and that`s no weight to play with. Thank you.nelson.

Link to comment
Share on other sites

I woulld not get under that much water without more shoring than four posts. And if there were sufficient posts for that weight I am not sure about the wind, or tremors. A tank that big is also a sail in the wind. And in any case only a certified welder should be used but I am not sure of how much experience you have at that or what your area would require for certification. For me I would want someone that works in that area to seek councel from. These folks have looked pretty hard for you and someone else must may confirm what they came up with.

Link to comment
Share on other sites

Iron and Rich, when I talked about a tank over 4 columns, that was just a simplified way not to trouble too much, to find out the max load that a 2.5 mt high column of a structural square tube 120x120x4mm could support when welded to nearby columns. I didn`t want to complicate matters but for a tech advice and engineering calculations, all details must be provided for a sound construction so that`s the reason I`m submiting all info required to an arquitect, following Charlotte`s advice. I`ve done some construction as heavy as that one, but not with the shape, slope and height that the images show, and all that complicates matters. Wind and quakes are no worries at all. The plan view shows the 21 columns all around the square hut, plus two more at the entrance. Then there are 4 lengthwise across the center. These 4 columns are of critical importance due to heavier loads and increased height they must comply with safely. There`s a seroius termite problem in the area, so no wood. The roof will be a 2 " concrete pour resting over arched prefabricated beams to achieve that typical hut shape. I`ve been doing some iron-cement work and feel confident the work will be fine with some sound advice. The small scale hut work is of basically the style for this big hut, except that it`ll be open, and only the kitchen and bathrooms areas will have walls. This no high tech construction, no problem with regulations, but it got to be SAFE! The whole problem will be solved switching to larger structural columns at the center. 200x200x 6mm should be more than necessary and ad more safety to this artisian hut. Those giants at the center will not only look good, but let the sorrounding columns at rest with little load stress to handle. The hut sholud be near 6 mt high for ventilation and design look. Comments are welcomed. Nelson.




Link to comment
Share on other sites

Forgot to include these pics of the roof style of the big hut 24x8mt, similar to the small scale hut made for a carnival parade. Well, there`s my sister, me, one of my 4 beloved pits, and two of the three macaws in the place. Sorry if all deviated from Iron work to structural, to cement, to macaws...lol. Nelson.

Edited by nelson
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...