RISA 3D - Plates Problem 1

[tchaudry]

I am building a model in RISA 3D using beams elements for the steel tower and plate elements for the concrete pad underneath the tower. The concrete pad will be supported on HP piles. I can select beams and nodes using the cursor in the GUI but I cannot select plate elements? Can I select a plate and delete it rather than finding out the plate number and deleting the plate in the spreadsheet? Moreover, some of my plates are triangular and some are rectangular and as a result, the local coordinate system of the plates differ. My objective is to analyze and design the concrete pad and the tower members. Will this have any effect on the final design moments? What about Mx and My?

 

[JoshPlumSE]

Probably too many questions to answer easily... in one post!

Regarding the GUI:
It sounds like you're just an inexperienced user who doesn't yet understand how to use the program. I would really suggest going through the tutorial / User's Guide. I'm not sure that any of them are going to address the exact interface issues you're talking about, but it should get your more comfortable working in the program. In the RISA interface, plate elements should behave the same way as beams and joints. You can double click them to bring up properties, you can select or unselect them by clicking. You can use the graphical delete tool to delete them.

Regarding the Orientation of plates:
This will not adversely affect any individual analysis results. The joint deflections will be the same, the member forces will be the same. The individual plate forces will still be accurate. However, the graphical CONTOUR of the plate results will have discontinuities. If the program is plotting the Mx moment based on the local x axes of the plates, but some plates have a local x axis pointed in a totally different direction, then the contour becomes less meaningful. The spreadsheet plate force results are still accurate for that plate, but the program can't contour them very well because that requires that Mx mean the same thing for adjacent plates.

You can use the Modify Plates tool to try and rotate your local axes so that they approximately line up. Also, you can use the internal force summation tool to come up with design forces that are NOT dependent on local axes.

 

[medeek]

I'm having the same issue. I can't seem to use the gui to click on the plates and access their individual properties. Maybe I'm clicking in the wrong place.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[jayrod12]

Correct me if I'm wrong josh, but I think You need to click on the centre of the plate

 

[JoshPlumSE]

Jayrod -

Yes, you should click on the center of the plates rather than the edges. That certainly could be the source of his frustration. However, there are plenty of times where other elements are 'in front' of the element someone is trying to click on and they don't realize it. So, it could be something else as well. It's tough to tell without seeing what they're doing.

 

[dozer]

I'm test driving RISA right now and this post is about to push me off the fence about how I feel about entity selection in RISA. In STAAD you tell it what type of entity you want to pick so there is no confusion. The downside is, of course, unless you are already in the mode you want, you have to tell it what type of entity to pick. I haven't played with RISA enough to know if I like their method better, but, as I alluded to, I'm about to decide I don't.

If you want to pick something that is behind something else is there a way to ensure you pick the desired entity? (Without gyrating the view so that it is now in front.)

 

[appot]

dozer, i always rotated the view to accomplish what you are asking. Once you get used to the limitations of the line selection tool and the box selection tools it makes things easier (granted it is still time consuming). I never used the "criteria selection." My models were never that large. From what I have seen, RISA does't give much input on how to create your model to best use the criteria selection tool. Maybe Josh or someone else has some input not his matter.

In RISA's defense, all of the FEA programs have some deficiencies when it comes to their GUI. If you are using one program regularly, you will learn its strengths and weaknesses. You will also learn how to 'exploit' those strengths to your benefit when you are post-processing.

 

[JoshPlumSE]

I've been on vacation for the last week or so, and didn't see your guy's posts until today.

Dozer - There are numerous ways to select elements in RISA.
[ol 1]
[li]You can directly click on an element in the graphics view. This is the most straight forward (and is what we were talking about) and involves no additional guidance by the user. All you do is point your cursor at something and click the mouse. Being so simple, it can be a little tricky when there are multiple elements in line with each other. I'm thinking about a rectangular tank in a 3D view where you are looking at multiple levels of plates at once. How do you ensure that you click on Plate A, rather than plate B? This is not always obvious[/li]
[li]You can use the "selection toolbar" to box select, line select, et cetera. This is very flexible and robust.You can use the box select to select ONLY one particular elevation, then "Lock" the view so that the rest of the model cannot be accidentally selected. There is a criteria select option allows you to select based on other criteria (material, element type, orientation, et cetera).[/li]
[li]You can also use the spreadsheets and select or unselect elements in the graphics view based on which lines are highlighted in the spreadsheets.[/li]
[/ol]

In Medeek's case, I'm not sure what his issue was. But, based on his description, I'm guessing he probably wasn't clicking on the center-ish of the plate. But rather on the edge or corners of the plate. Though I would have to watch him do it to understand exactly what he was doing wrong.

I'm not that familiar with what STAAD does (at least not anymore). But, we don't really get users complaining about selection in RISA compared to STAAD, so that probably says something. In fact, I'd guess that this is an area where we're complemented by users more than normal. They may be comparing us to SAP or RAM more than STAAD, so that's not definitive. If there are ways to improve selection in RISA, we're always open to hearing them. So, if you test drive it and see something that you really don't like, or something that you you think should work better, let us know.