Structural steel load/stress limit

da.bees

Well-known Member
I'm aware that between engineers and lawyers,there's no numbers available from mfgrs or distrubitors but I'm wondering if there's any kind of unofficial comparions availabe. Something where dead loads were put on various members supported at various points until they failed. Still the possability of being sued but thought someone might have done it then wrote the results. Saying "I don't know how much it will support but I can tell you it DIDN'T support xxxx pounds when we tried it."
 
Build it twice as heavy as you think will hold and call it a day..
If the sky falls we're all gonna be dead anyway :lol:

Engineers never take responsibility if their design fails anyway.They always find someone else to blame but never them.
 
When I was working some of the bigger machines that we built had hydraulic presures over 4000psi. The engineers had a 4 times policy. The first time I ever saw pipe with 5/8 to 3/4 sidewalls. Did not have to worry about burning a hole thru that
 
Structural steel is tested for its yield and tensile strengths.We always called for certified test results on the grade steal we specified. there are many many types and grades of steel
in the old days we usually called for grade 36 steel--it had 36KSI as its yield strength and we use the code value of 20KSI for design for bridges---buildings used up to 24KSI for design--there are many steels with much higher values nowadays--=-for prestress concrete design we used steel cables that had steel with 180KSI yield strengths.
tensile strengths are quite a bit higher than yield strengths but the elongation is so great that its generally not used in design.
 
I have to take exception with that statement--many bridge failures have been caused by errors in design and have been documented.Lots of failures also caused by fabrication errors that should have been caught by the engineering inspector
there are many cables in the Brooklyn Bridge that were rejected by the engineers but midnight swaps by the Boss Tweed gang got away with the fraud---Roebling found out about this and added extra cables to compensate.
 
You mean like: "Don't drive into the door post when there is three feet of wet snow sitting on the roof"?
 
The type of testing you described and completed goes on all the time Typical R&D research and development. This would involve stressing PARTS of the complete units until they break toward the ultimate goal of a complete unit failure. For instance shooting a chicken out of a cannon to test windshield's This would go on until the windshield held and the surrounding structure failed Then beefing up the surrounding structure. Or testing cargo nets pulling on the attachment points until they failed then beefing up the area until you pulled the sides of the aircraft in. The biggest issue I think these days on a home build for instance a tractor is structural steel coming from a source that is known to build junk. Quote(I'm wondering if there's any kind of unofficial comparisons available. Something where dead loads were put on various members supported at various points until they failed) You can find most all of the information online. However why complicate it build it till it holds twice the limit you require.
Best of luck Byron.
 
When I doubled as company service manager, I was the guy that had to go to the customer and fix the engineer's design. That sure kept me busy, but I got it done!
 
I've had more than one engineer that when I told him his design would not work per the blueprint. He told me to re-fabricate the parts and give him the dimensions and he would draw it that way. For the most part this was typical in a first production installation or modification. I don't know if your using bolts but it always safer to use tension bolts because they have the same shear strength but more tension strength these would typically have a larger head diameter and the tension nuts as well would have a larger diameter and in some cases more threads inside the nut. These would also be fine thread.
 
My statment about lawyers and engineers wasn't intended to start a rant. Wherther we like it or not there is not a little book with information many of us would like to buy if it existed. Steel is rare amomg things used daily by so many that doesn't have published guidlines in chart format. There are some math formuals to figure it out,unfornatuly they are greek to me. I'm talking about,3"x 4"x 1/4tr cold rolled angle will support *** lbs on a '''' span or **** lbs on a '' span or ****** lbs on a ' span.
Yeees,I know as someone pointed out "that kind of testing gos on every day" but I also know they don't publish the results for public use.
Why do some people answer questions like this by saying they always overbuild everything they do when we know good and well they didn't use 2x8 white oak studs on 12" centers,fastened with stainless nails in their houses. I'll try something different, thanks guys.
 
I don't know of anything that will do exactly what your asking. However, a Bing search for steel beam load rating calculator turned up several hits. One of them is linked below. I didn't try it, but it might be what you need.
Steel beam calculator
 
The most common source for steel structures is the AISC. They have 2 different methods for the calculation, ASD or Allowable Stress Design and LRFD or Load Reduction Factor Design. Any structural shape that is not a free space member, basically unsupported is reliant on the position and type of connection it has to the supporting structure. What you are wanting would not be possible to provide with any accuracy.
 
Sorry no harm meant that was never my intension. I have to agree with Bill in IN. You haven't given enough information I think from what you just posted now you have a piece of angle Iron or steel 3 inch's x 4 inch's x 1/4 inch thick.. I was thinking you were on the right track by testing it nothing more! L angle is inherently unstable and susceptible to twisting. If the angle was 48 inch long bolted to a wall with 5/8 bolts every 4 inch's then you should be able calculate the limit across the span .But there's no book that will give you the limits without knowing the number, diameter and spacing of fasteners & were or how the load will be carried. I beams and channels or box beams are better chooses. An L angle with unequaled sides is more complex to calculate. I think if you can clarify what it is your building maybe a sketch someone could help.
 
I know what you mean. Any steel supplier I've ever bought from wouldn't guaranty a 12" I beam would hold the weight of a butterfly if it landed on it.
 
if you can't find the specs you need,
ask a steelworker. Not the company engineer, ask one of the long employed big guys.
Tell them, or show them the job and the steel.
Most will tell you just by looking.
"Ya ain't gonna hurt that setup"
or
"Yer gonna be dead"
 
Ask the ironworker to perform analysis, provide a stamped set of calculations for the span, determine the safe working load in pounds, safety margin or redundancy.

Everyone wants to trash the engineer, but none will be able to give you those answers. This is not sound advice or strategy, given the potential.
 
Its a great question, and it true, there is no handbook that I know of that a layperson can use to safely design a steel structure, there's a reason for that. The question you seek an answer to is best derived by a licensed professional engineer. AISC is reference material, its a guide, materials are selected for design based on strengths and statistics. If you need to know about one component, its a simple task for an engineer to determine this.

Sure, I can reference a W shape, say a W10x22, beam with a 10" web, that weighs 22lbs a foot, that's in a framing plan of a building on the structural drawings for a 100lb per sq ft floor, that and say the load chart on the engineering toolbox states its good for 30,900 lbs on a 12' span, should I just accept what I read, install based on that or should the specific details of the entire structure be analyzed to insure all aspects are considered have been reviewed, moment forces, the weight of the member, connections, columns, footings, soil conditions, its all related.

We don't build structures based on conjecture, we build them based on designs provided by qualified professionals that detail, analyze and calculate what is to be built. Why is it that people get the idea that one can arbitrarily design a load bearing structure or member without any technical analysis to insure it meets the loading requirements? If I did this on commercial buildings, there would be widespread failure, with injury and loss of life, not to mention the lawsuits and claims.
 
I have processed many submissions of the certified test results, it was a required submittal on all state jobs designed by OGS, that and the steel's origin was to be U.S, with rare exceptions, like south african steel when there was shortages. It was stacks of paper for record, and its clear why this is done.
 
I have as well, dealt with some arrogance with one over a foundation projection of a very old brownstone building in Manhattan, that was an encroachment into the foundation of a high rise building I was constructing. I looked at the field conditions, surveyed the condition and detailed it, suggesting a jog in the foundation wall be made and that reinforced concrete by utilized as the shop drawings for the precast plank deck were already approved and the plank in production. Unforseen condition, below grade, could not disturb the existing, solution presented for review, analysis, calculation, he was unresponsive for awhile, but he was also the engineer on record, having provided the stamped and perforated structural drawings approved by the city of new york, it had to come from him. I demanded the review of the condition and that a solution be provided, he dragged his behind with it and held up the progress of the job until he was cornered. Same engineer specified 6000 psi high strength block, 5000 psi was all I could get certified test results on, as beyond that, you could not, at the time get any certifications for higher strength, the engineer was put on notice and the building constructed with 5000psi high strength CMU. (block)

I've worked daily with engineering firms on difficult jobs, field tolerances, details blown, literally putting me in a position to create new details that would work, but had to be be calculated. This one job was loaded with these problems and progress was halted. We performed a mock up of our work, it was a job we took over and was assigned to us by a bonding company after a default of contract by the previous contractor. It was a total mess. We were to install this curtainwall from existing materials and terrible shop drawings. I had to inventory and detail huge piles of material on site, re-engineer most connections and the curtainwall system itself, which showed a rotational failure in our testing laboratory mock up of the system. The mock up was key, had that occurred in the field.... 600lb pieces of glass would have fell from 5 stories to the sidewalk.

Even with all the defects, the faulty material which was received on site by the previous contractor, we scrapped it, and ordered new materials once everything was laid out. We could not have succeeded without the engineering required, it would have been a complete disaster. I was on the phone several times a day and was faxing field sketches daily, of as-built conditions and suggested details to resolve the problems. It resulted in a thick calculation booklet provided by the engineer, that was approved and on record for the building.
 
(quoted from post at 07:59:51 04/28/15) Ask the ironworker to perform analysis, provide a stamped set of calculations for the span, determine the safe working load in pounds, safety margin or redundancy.
Everyone wants to trash the engineer, but none will be able to give you those answers. This is not sound advice or strategy, given the potential.

A machinist gets a drawing marked "MILTFD-41". After searching his recources, he calls the engineer to ask him what that specification is. The engineer replies, " make it like the F'n drawing, for once !".

Quite often, making performance parts for vintage race cars, I would call the engineer and tell him that a minor change would cost much less to make, or that a certain feature would require a new machine or tooling to build.
No matter what you make, there is a balance of cost, weight, speed, and strength to be decided.
 
Absolutely, of course there is a wide spectrum involved, manufacture, machine shop, fabricators, construction etc. Sure it works on paper, looks good on paper too LOL, but I'm the guy who has to build it ;) ! LOL ! I've never had much trouble working with designers, most want to work with you, ones that don't are certainly problematic, the one I cite below would have never been selected as an engineer of record at design time, you just can't have that kind of arrogance involved with these matters, even the architect of record who I often went through to get to him was appalled, being they provided complete set of documents for the job. It was funny when I bypassed them and hammered this guy. He directly stalled my progress, not to mention it was a cost add for both design and construction, all of that reflects directly on me as a manager, not so much the unforseen condition, mostly the delay. Most if not all project managers have zero tolerance for nonsense such as a schedule impact caused by a cavalier designer not fulfilling his contract for engineering services specific to the project. That in itself is unacceptable, there are other things that you can't control and have to adapt, this was not one of them.
 
Thanks Wayne,that link is formated more "user friendly" than waht I've seen in the past. I'll feel comfortable asking my pharmacist grandson for help with those math formulas rather than asking engineers for stamped drawings if I need to build a livestock loading ramp or bale mover wagon. Since what gos on around our farm shop isn't comparible to hi-rise construction,I believe we can put togeather a wall chart that will be a lot of help with material lists in the future. Might even save a few dollars on steel and filler,not to mention the ability to move projects around without a crane. Once again,thank you for taking time to find that exelent site for me.
 
I agree with you--the first priority is to design it safe,second for it to be long lasting, and third to be cost effective. When i took my professional engineers exam for my license there were mandatory questions on economics that you had to answer correctly and they were a significant portion of your grade--other questions on engineering were able to choose from in various fields. As a designer we constantly got suggestions from contractors to use different materials and methods--sometime as substantial savings to the taxpayers--( I worked in structural design for a county DPW)
 
The AISC "Steel Construction Manual" has tables that can be read by a structural engineer for quick comparison and design of beams. Most shapes are standardized so the strength "should" be the same regardless of the mill/supplier. Once you get to more than a simple beam problem (single load; simple shape) there several things that need to be checked to assure integrity of the beam (multiple tables/ equations). So do the tables exist: YES; do you need to be an engineer to understand them properly: YES!

bjb
PE Civil Structural
 

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