I want to run a simulation on a 60 foot aluminum walkway where the beams are only welded on the side faces and not all around. I split the model up into "parts" thinking this would help I want to select these faces to define contact but its not letting me or i just dont know what i am doing. i cant seem to find the answers in any forums so any help would be great
thanky you
Dave
Hi Ryan
not sure what i am doing then. do i treat each body as a truss?
i go thru the simulation advisor and get to the part of selecting faces to weld and i get the run around of questions and always end up at the start. It seams to default the walkway as a beam? the faces i want to will are the inner and outer faces of the walkway post which are 3x3 sq tube. not all around
Dave
Dave,
First off, I should have asked if you are using a full version of Simulation or just Express. I have never used the advisor before so I am not sure what you are referring to exactly when you say you are selecting faces to weld.
If you built this structure as a weldment and used structural members than by default SW will treat all the bodies as Beams. For your purpose this does makes sense plus it will solve much quicker. You could treat all the bodies as solids and then you could choose faces to constrain. What are you trying to determine with this analysis? That might help pinpoint the issue you are having.
Ryan W.
I am using a full version of simulation, i did build it as a weldment using structural members.
I am trying to detremine a factor of safety since people will be walking down this and it will be free spanning 60 feet.
im joining all the 3x3x1/8 sq together with welds and i am not welding it all the way around at every joint only 2 welds per joint, opposite faces. im trying to attach a picture but i am not winning that one now either
Dave
Well I can maybe save you some time there then because a Beam analysis will not take into account how the ends are welded together. It just assumes they come together at a node. You can refine the connection at the node some but you cannot do any kind of weld analysis at the node. Beams is a very simplistic way to view a model and is more for gettingquick results over large truss like structures. If you want detailed weld analysis I know there is a feature in 2011 (and I assume 2012) that allows you to define a weld between two bodies and then do an analysis strictly on that connection, however, the pieces must be defined as shells I believe. I have not been able to use this feature since I am still stuck using 2010 thanks to corporate bureaucracy. Plus I am not sure how well it would work in a larger structure such as yours. If you want to look more closely at connections in particular you can treat all bodies as solids and add features to mimic your welds but that can be pretty time consuming. You can also choose one connection and model it separately and then run an analysis on it by itself using forces determined from an analysis of the structure as a whole. Hope some of this helps.
Ryan W.
i will try and treat as solid and see what i come up with, bit of a learning curve and not much in tutorials
thank you
Dave
No problem. I treat almost all of the weldments I work on as solids. One thing you will want to watch out for though is how fine of a mesh you need to get all the bodies to mesh properly. Since your model is 60ft you are going to get a lot of nodes and this will of course slow your analysis down. Make sure you use a relatively coarse global mesh and then refine your mesh using the Mech Controls on parts that are failing. Good luck.
Ryan W.
Hey Dave,
Ryan is on the ball. You use the beam analysis to get the loads at the joint. You should also know that SWX beam analysis is not their strongest suit by a long shot so ensure that you believe your analysis results. Many people have found many issues with this aspect of the code. Since it sounds like people could get hurt or killed be sure the analysis is good enough and you understand what's up. With that said, find the joint with the worst loading - these will be resolvable on beam center lines then make a free body diagram of the joint and figure out the loads in the welds and use a manual method to assess the welded joints. The welded joint function Ryan has mentioned has also had its share of issues - like bad results at non normal angles. No idea if it has been addressed yet or not. You could do a solid analysis on hte joint but again be judicous in asssessing the results though this aspect of the code tends to work pretty well. These analysis need to be done with some care in set up and interpretation.
No idea what you mean by "only on the side faces" but in general you want the welds loaded in shear and not in tension with throat depths and lengths sufficient to get the job done, Given this is aluminum - not sure which one but in the welded state it may have substantially reduced strengths in the as welded condition. And fatigue of welded Al joints is also something to pay attention to. You are going to want to aim for stress in the welds in the very low 1000's of psi or less depending on what the material is, how long it is supposed to last, what the load spectrum is and other things. You might want to consider a marine alloy in the 5000 series for corrsion and weldability . Good luck.
doing the whole structure as solid elements is going to be a challenge and assessing the joints this will be tough as well if you get the analysis to run. Remember you need the structure in the as welded state and not in the right before you weld it state, which is where most people design too. Good luck
not winning
think i might have to go back to the drawing board. it would be great if there was a you tube demo!
to much to know all at once for a new user. we do get them engineered by a proffesional. just trying to do our own research first
If you are not running anything later than SW2010 I would be willing to take a look at your model and see if I can get it to run.
Here is a zip of the file if your able to open it to see what i am up to
i treated all as solid bodies, tried to define contact sets with all items that bond due to welds ie the long upper rail with the upright posts and diaginal posts
got meshing errors?
Not sure how one know when they have done it right. practice i guess alot of room for errors
Sorry Dave, I cannot open it. It is a future version.
gotta love advancment in technology
is there a way for me to save in past formats?
No, but you can save it as a IGES and then I can open it. I can see what I can do with it but it won't be as helpful to you that way unfortunately.
heres the igs
to make it easy, untrim all the cuts at thh ends of the members and save as a parasolid. Then you need to a cavity op at the ends to get a good fit - but that may not work in all cases - the dreaded thin geometry error but at least he will have what he needs to fix in the hard way.
wish i new how to do all that
i will explore!
You could just go save as and pick the parasolid format - works way better than IGES. to untrim go into the strucutral memeber commands that you used to makethe various members and just take away all the trimming at the ends of the members. You do not need the trims to do a beam analysis, and the trimmed ends need to be well managed if you want to be able to mesh with solid elements. Did you take any training on simulation? Even if you did they don't much cover the subtleties but your instructor should have at least told you how hte solid mesher works. If not lookin hte appendix of the training manual for simulation essentials - otherwise try the help and the knowledge base.
sorry no training other than tutorials and persaverance
ive looked but ill carry on. thought this would have been a easy one
It is but you need to understand the rules of how these things work. Seems like hte beam analysis was pretty straight forward - as long as you put it together with structural members, beam analysis usually is. It is really easy if you do not trim anything - do it after the analysis.
Good afternoon Dave,
I have no experience in Walk Way design or simulation, however one thing popped out at me; Welded Aluminum?? I would think you have chosen Aluminum for weight, but do you realize how far the expansion and contraction is going to be with a temperature change of 80 degrees. Can't you use a clamp design rather than welding, aluminum welds tend to fracture at the weld root. With all the possible linear movement, even as a manufacturer I would shy away from this project, unless it is designed in a way that movement won't put undue stress in the assembly.
Just my two cents,
John
weve been and others having been building them for years. not concerned it cant been its just to what level of bracing to build to. other companies have been building lighter models than what we do for of course cheaper. they r all engineered so they say, it is just that some engineers over build and i am trying to use this tool for knowledge in the design proceess.
in the end it is the engineer who bears all with his stamp
i used beam analysis and i got result that worked. do i trust them? not sure
i believe beem analysis does not take into account that it is welded. this is what i am trying to accomplish on here is finding out how to specify a welded joint. not having much luck with contact sets or bonded faces. i get errors when i do it.
i will keep reading and researching
Dave
I have attached my model which contains a study using solid bodies and one showing beams. The solids study took about 5 min to mesh and another 5 to solve. I did not spend much time trying to get this number down with changes to the mesh. You might be able to but probably not significantly. Anyway, it is not too bad in my mind. Gives you a good chance to get up from your desk and go get a coffee.
The beams of course meshed and solved in seconds so there is no comparing the two that way. From the pictures of the results I have included you can see that the stresses are not even close which illustrates a downside to using the solid bodies which is that you will always get stress concentrations where your pieces meet that can make your results look very unappealing. Beams are great so long as you are sticking with just structural members, however, once you start adding things like plates and lugs that cannot be treated as beams you are opening a whole new can of worms. Much more difficult to get the bodies connected nicely.
I hope this model will be of some help to you.
Hi Dave,
From the picture it appears you are running this analysis using Beams. I am not totally clear what side faces you are referring to. Are you trying to constrain the ends of the model? Anyway, if you are running this model as a Beam analysis than you will not be able to constrain any faces, you are only able to constrain nodes in a Beam analysis so the first step is to get your nodes set up the way you want them. Then apply you constraints to them.
Ryan W.