How have I not answered the original question? I have provided a perfectly satisfactory method of finding the maximum bending moments for design purposes. I presume that was the intent of the original question. If it wasn't, what was it?
You insist that FEA is the only method of solving the problem.
No, I haven't insisted that. I haven't even said or implied that. I said that was how I would do it, and it is a simple way to do it, that can be made as rigorous as the application requires.
Tell that to the many engineers who have been solving similar problems for many years without the advantage of FEA.
No I won't tell them that. But neither will I insist that there is something wrong with using a finite element analysis for problems that can be solved other ways, or that the older methods are inherently superior.
Yes, I'm still using Strand7 and pretty happy with it. The cost of the "big name" systems is a bit much for a sole practitioner, and I reaaly don't know how much extra benefit they give anyway.
Quite a few of top notch firms are using Strand7 in the US primarily for optimization. I can think of SOM and Halvorson Partners who are using it quite a bit for their tall buildings.
I am pretty fascinated by the program as well. Looks like it has a lot of API capability.
Doug:
Anything you want to share on the advantages of the program compared to the commercial ones such as SAP2000 or ETABS etc?
I think BAretired has a good point that straight-up FEA for slab wouldn't give you an perfectly accurate answer for the point-load-at-end-of-cantilever problem.
But I have to say, after designing with concrete for many years, that an FEA solution would at the very least be a good tool to use to get a handle on general slab behavior with a point load. You don't necessarily need a perfect solution.
I would tend to be a bit more conservative with the results as the full spread of the load using finite elements might not be as wide as the output would suggest.
I also think IDS's response to BA above is entirely fair. Let's keep the posts on point and be respectful everyone? OK?
Slickdeals - I'm afraid I can't comment on how Strand7 compares with the other programs, because I don't use them.
The things I like about Strand7 are:
- Reasonable price (about Aus$6000 in Australia)
- Includes everything in one package, at least it did when I bought it. They have started introducing add-on modules, but the "basic" package is still far more comprehensive than for many of the competitors; i.e. includes full 3D analyses, dynamic analysis, all available element types, non-linear analysis, heat flow, buckling, etc.
- I find the interface easy to use.
- Excellent support (at least in Australia)
- I find the Application Programming Interface (API) very useful. Allows easy and rapid transfer of data (both input and output) between Strand7 and Excel via VBA, and automated control of complex staged analyses. Also has modules for c++, Pascal, Fortran and Matlab. Quite a steep learning curve, but well worth the effort. Cost is Aus$1300
The only downsides I can think of relate to it being a small company, so probably not the first in the market with new developments. Also not so widely used outside Australia, so Strand7 skills may not be such a great asset in the job market. Also there's always the possibility that they'll be taken over and the product buried.
I think for simple the problem stated it is a tad silly to break out the computer program to get answers more accurately then we know actual loading/behavior/material properties/construction tolerances/etc. Just take the 45 with a reasonable upper bound on width as mentioned by others. Even better if the edge can be stiffened, just good practice. FEM has its place, but I think it tends to get overused.
I am not familiar with Strand7, went the website and it looks pretty nice. I am going to have to look into it more. SAP2000 is a overrated pain in the ass that doesn't work well IMO. For 90% of what I do on a regular basis RISA is cheap, quick, and works just fine.
I think for simple the problem stated it is a tad silly to break out the computer program to get answers more accurately then we know actual loading/behavior/material properties/construction tolerances/etc. Just take the 45 with a reasonable upper bound on width as mentioned by others. Even better if the edge can be stiffened, just good practice. FEM has its place, but I think it tends to get overused.
It's a matter of personal preference, and I don't have a problem with people using hand calculations if they prefer that, but if you are sitting in front of a computer with an appropriate program installed then it's not at all silly to use it to solve simple problems as well as complex ones. From my perspective FEA is underused rather than overused.
Just out of interest, if you use the 45 degree method, how do you design the reinforcement and stiffener in the other direction, i.e. along the length of the cantilever?
