How to check whether a given structural support or frame can support a given machine 4

[mechanicaljw]

Dear all,

I wanted to find out if structurally, there is a rule for finding out if a given support or frame can support a given machine?

We have a current frame that supports a single machine but we need to connect or build an additional machine on top of this first machine and to support it with the same frame used for the single machine. How do i check if this is possible?

Thanks!
James

 

[hokie66]

Not "a rule", but this is the realm of structural engineering.

 

[thaidavid40]

If you do not know how to approach this problem, you should be working under the direction of a qualified PE, who will direct and review your work, or else you should hire a qualified PE to accomplish the analysis for you.

Thaidavid

 

[mechanicaljw]

Hi hokie66 & Thaidavid40,

Thanks for your response. Don't you know of any citation or literature that can be of some help to me?

Thanks!

 

[JStructsteel]

The rule is if the load exceeds the capacity, then it will not support it. The load you know, the capacity is a unknown, but easily calculated.

 

[mechanicaljw]

Hi Jrisebo,

Thanks for the response. By load, do you mean the static load (weight) of the machine(s)? What about the capacity? Can you please throw more light on this, eg how is it computed?

Thanks again for support.

Jimmy

 

[Lomarandil]

The load might be the static weight, it may be the static weight plus some dynamic effect, it may be those two components plus a lateral load.

You really need to consult a local structural engineer.

 

[JStructsteel]

The load is the weight of the machine. Capacity can be calculated by checking each member for strength per the load. That all depends on what the material is. Steel, concrete, wood, etc.

Then there is the case of other load cases, seismic, wind, etc. That could change the capacity.

 

[BAretired]

What kind of machine is it? Are there dynamic considerations such as impact, vibration, natural frequency etc.?

What kind of frame is it? For a static load, the capacity of the frame can be calculated using principles of statics, frame analysis and strength of materials. The calculations will depend on the type and material properties of the frame.

Your question is too general to get any kind of sensible response.

BA

 

[mechanicaljw]

Hello everyone,

Thanks for your input.

@ Jrisebo: I intend doing the following. We have two parallel beams & two cross beams at the ends of the parallel beams. The parallel or longitudinal beams are U-shaped. I want to determine the total weight of the machine and divide by 2 to be the weight taken by each longitudinal beam. Then i will set up an FEM Simulation with the beam fixed at both ends and the weight applied in the middle and determine the maximum bending stress including safety factor and compare it to the compressive strength (and not the tensile strength since beam is in compression between the machine weight and the floor) of steel, since the material is steel. If the computed value is less than that of the material i will judge the support to be safe.

Do you think the reaction forces at the fixed joints of the beam play a critical role due to the screws used in doing the fixing? I am thinking that they should be added to the FEA model?

Thanks as usual for your support.

Jimmy

 

[kingnero]

are those longitudinal beams resting on the floor over their whole length?
How are they fastened to the two "end" beams?
What exactly is the load path? Can you provide a sketch?

and what would you say is the difference between compression and tensile (yield) strength of steel?

 

[GregLocock]

thaidavid40, in mechanicaljw's jurisdiction there are no PEs, so he won't be able to rely on their wisdom, or gaze upon their beauty.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[racookpe1978]

And, with the information given, the system (building and frame) will likely fail.

It's why you hire engineers.

 

[thaidavid40]

"... in mechanicaljw's jurisdiction there are no PEs, so he won't be able to rely on their wisdom, or gaze upon their beauty."
This forum is worldwide. And much structural engineering is done through outsourcing these days. A qualified PE can be found, and retained, with just a little bit of effort. Living in a jurisdiction without structural PEs is no longer the absolute handicap it once was. This sounds like he needs a qualified person to look at his situation.

Thaidavid

 

[mechanicaljw]

Hi Kingnero,
Thanks for your Input. Appreciated.

I will try to answer your questions. The longitudinal beams are resting on the floor over their whole length as you suggested. They are fastened using a bolt and a nut (single at each point) and so four in total. I'm not sure about the next since i am yet to determine the load path. The sketch is attached in the screen shot attached. The rectangle in black is showing how the machine is mounted on the Support.

For the compressive yield and tensile yield strengths of steel, i got the following values from a text: 160N/mm^2 and 360 N/mm^2, respectively. Are you suggesting they should be the same? The exact steel material is S235JR.

Thanks again for your Support.

Jimmy

 

[kingnero]

European steel denominations for structural steel have their yield strength for thickness <= 16mm in their name.
S235 means fy = ReH = RP0.2 = 235 MPA. This is both tensile and compression.
you want to design for a certain % of that.

Your suggestion of approach doesn't add up, as the end connection of both beams don't have anything to do with how those beams react their force(s).
I'd model a uniform distributed load at the bottom, representing the floor, and two point loads on the top flange, as that's were the machine will make contact with the beams.
You'll want something that braces both beams, as they'll want to fall towards each other.

I don't know the dangers of this situation, either overbuild it or have it checked out by a competent person/firm.

 

[JStructsteel]

Based on what I see, I doubt it will support any additional weight.

 

[hokie66]

thaidavid40, where is your sense of humour? Greg was just pointing out that this is indeed an international forum, and "PE" is not used in most of the world to designate a qualified engineer.

 

[thaidavid40]

@hokie66 -
Why have you turned a considered suggestion for soliciting qualified help into a personal attack regarding my sense of humor? Is this your usual mode of operation? You know nothing about me, or my sense of humor, or else you wouldn't have made such an ill-considered statement. However, that didn't seem to slow you down from commenting on me personally, instead of keeping this forum focused on the poster, and his questions. @GregLoCock's contribution may have been offered in humor, but it also contained an assumption - regarding the availability of qualified help - which failed to address the options which I mentioned by follow up. That's all I said: that there are options available to the poster which were not mentioned in his post. None of this was offered by me in any way condescending or biased. It was a simple exhortation to let someone qualified assist with the design. There was nothing personal from me in any of that. And no need for anything personal from you in return. I would request that you forego your personal attacks, and keep this forum focused on helping each other.

Thaidavid

 

[BAretired]

It wasn't a personal attack. I read it as friendly kidding. If you have been around this site for as long as your profile says, you should realize that hokie66 is not in the habit of making personal attacks, even when they are warranted. Get over it!

BA