SAP 2000 and Load Management / Display

[TLHS]

Hi all,

I'm evaluating a bunch of software at the moment, and since SAP 2000 is one of the few pieces of analysis software where you still get an actual perpetual license, and it takes the Canadian codes seriously, it has a step up on most other things.

That being said, I'm struggling on something here and I feel like I must be missing something.

I'm mostly coming from STAAD, so I'm used to awful and undocumented processes and can deal with that once I'm used to it.

Am I supposed to be using load patterns to manage things I'd be using a single load assign for in STAAD? I'm used to having a load assignment for something like a distributed load and assigning it to 20 beams, then maintaining it in the one place. SAP 2000's database system seems to have a load entry for every piece of geometry. So if I want to have something where I can track that one typical load, I think I should be making an individual load pattern for it. Then I can fill down on the interactive database editor to change the load if I want to later?

After that, is there an organized way to view and edit a whole load case or a whole load pattern at once?

I can graphically examine a load case, but that's not really that manageable in a lot of situations. I can look at all load assigns for joints, frames or areas in the interactive database editor, and filter by load pattern. That's a lot of clicks to get to something basic, and it's still only seeing part of the picture at once because I can't see the area, joints and beams all at once.

I feel like this must be something that there's a workflow for that people have figured out and makes sense or such a basic thing would have been changed.

This is pretty basic stuff, but tutorials and documentation tend to be examples showing someone making a perfect model from scratch without needing to do maintenance or modification on it. Realistically, most of the time being done on analysis tends to be in modifying and adjusting things once the skeleton is there. Having a usable model is 90% about organizing your inputs in a way that you can work with later, and I'm not quite aligned with the right mindset.

(Finding the copy assigns command a day or two ago answered a lot of questions for me)

 

[271828]

I don't know how loads work in STAAD, so I can't compare the approaches. I'm not sure how everybody uses load patterns, load cases, and load combinations, but I'll describe what I do, using a three-span continuous floor beam for example.

In the model, Define the following Load Patterns: dead load (D), superimposed dead (SDL), live on span 1 (L1), live on span 2 (L2), and live on span 3 (L3). Apply the unfactored loads to the members in these patterns. For example, select all members and go to Assign, Frame Loads, Distributed and specify the loads for the D pattern. When they're specified, they'll be shown on the screen in the current units (bottom-right of the window). If you want to stop seeing what was assigned, go to Assign, Clear Display of Assigns. If you want to turn the display of a load pattern on, then go to Display, Show Object Load Assigns.

The next step is to set up the load combinations. I typically use "Load Cases" for this. There are also "Load Combinations." I think those are used in the design modules, which I never use, so I can't offer much more on those.

For example:

To compute the maximum positive moment in the first span, define a Load Case called 1.2D + 1.2SDL + 1.6L1 + 1.6L3. Set the load combination factors to 1.2, 1.2, 1.6, and 1.6. Set the other particulars of this load case, such as linear or nonlinear.

To compute the maximum negative moment at the first interior support, define a load case called 1.2D + 1.2SDL + 1.6L1 + 1.6L2.

To compute the maximum total deflection in the first span, define a load case called D + SDL + L1 + L3.

And so on, until you have the various load cases you need for the design.

 

[ggcdn]

@TLHS, as far as workflow goes, I'm basically always working on the model visually for loads. If I have elements that are loaded the same, I sometimes assign them to groups for easy selection / modification

I set up patterns/cases/combos differently than 271828. I create a unique pattern for every different load that needs to be applied, and each pattern will also have its own case with a factor of 1. If you need response spectrum analysis then that has a case as well, but no corresponding pattern.

Then, I use combos for all combinations of loads. If you want to use any of the design features, you would need to make combos anyway or use the auto-generated ones.

On another note, @271828, you may want to check out the Range-add type of load combo if you are often manually creating live load patterns.

https://wiki.csiamerica.com/display/kb/Range-add+load+combination

-JA
try [link calcs.app]Calcs.app[/url] and let me know what you think

 

[271828]

I set up patterns/cases/combos differently than 271828. I create a unique pattern for every different load that needs to be applied, and each pattern will also have its own case with a factor of 1. If you need response spectrum analysis then that has a case as well, but no corresponding pattern.

Then, I use combos for all combinations of loads. If you want to use any of the design features, you would need to make combos anyway or use the auto-generated ones.

In my example, you would have load patterns called something like D1 for dead load on Span 1, D2, D3, SDL1, SDL2, and so on?

On another note, @271828, you may want to check out the Range-add type of load combo if you are often manually creating live load patterns.

https://wiki.csiamerica.com/display/kb/Range-add+l...

Thanks for that. I'll check it out. Somehow that feature got by me. LOL. I don't do a lot of continuous beams and was just using that as an example.

 

[ggcdn]

@271828, I wouldn't normally split out things like dead load since its not really patterned. There would just be 1 self wt case and 1 SDL case applied with different magnitude in different areas if needed

-JA
try [link calcs.app]Calcs.app[/url] and let me know what you think

 

[271828]

ggcdn, In that case, I don't see how our use of load patterns is different.

It sounds like the main difference in our approaches is that you're using load combinations, which is fine. I just haven't started doing that yet.

 

[Celt83]

Been awhile since I played around with SAP but if I recall correctly their load combinations were a linear sum of load case responses, so for any code load combinations that you wanted a p-delta analysis against you really needed to define that as a non-linear load case and not a combination in SAP.

 

[ggcdn]

@Celt I believe that is still correct - if you need any nonlinear-type analysis then the loads need to all be put into a single case.

-JA
try [link calcs.app]Calcs.app[/url] and let me know what you think

 

[271828]

That information might be old. I have v20 on my computer. I see a button that says "Create Nonlinear Load Case from Load Combo." That might allow one of these to be other than a simple linear combination.

 

[TLHS]

Thanks to both of you. Understanding how you guys are approaching it is helpful. I think my understanding of the available tools was right, so I've just got to adjust the way I think about managing things. Thinking about my own biases on the subject, STAAD was historically several extra clicks to display loads in a useful way graphically with numerical values. So I'm also just not practiced in working with load magnitudes that way.

We'll see what a little practice does.