Pushover static analysis error

hr_park
Posts: 20
Joined: Tue Mar 31, 2020 7:44 am

Pushover static analysis error

Post by hr_park » Thu Apr 09, 2020 7:21 am

Dear Team STKO
Hi I have another question about analysis :!:

I've been working on 2 span bridge analysis and thank you for your help I can finish modeling
I referred to Opensees gravity example and pusfover eample for analysis options
gravity.png
gravity.png (21.56 KiB) Viewed 1281 times
pushover.png
pushover.png (61.7 KiB) Viewed 1281 times
But I have new problem in analysis
This is the screen shot when I run analysis and as you can in the lower left there is list of analysis steps which have gravity and pushover analysis.
Anal_Error.png
Anal_Error.png (237.51 KiB) Viewed 1279 times
m.png
m.png (33.7 KiB) Viewed 1276 times
To be honest, I am confused that it's right to post a analysis question because ths problem is also connected to Opensees program. So if you think it had better I ask this post to Openssees Homepage, let me know!
Last edited by hr_park on Thu Apr 09, 2020 9:29 am, edited 3 times in total.

STKO Team
Posts: 321
Joined: Tue Oct 29, 2019 8:45 am

Re: Pushover static analysis error

Post by STKO Team » Thu Apr 09, 2020 9:14 am

Dear User,
I don't see what the error is... could you be more specific?

hr_park
Posts: 20
Joined: Tue Mar 31, 2020 7:44 am

Re: Pushover static analysis error

Post by hr_park » Thu Apr 09, 2020 9:23 am

Sorry! May be you can see now :D

STKO Team
Posts: 321
Joined: Tue Oct 29, 2019 8:45 am

Re: Pushover static analysis error

Post by STKO Team » Thu Apr 09, 2020 10:26 am

It is fine if you ask OpenSees question here, no problem.
Now your matrix is singular, however there might be many sources of error.
Could you post the *.SCD file here? so we can have a look.

hr_park
Posts: 20
Joined: Tue Mar 31, 2020 7:44 am

Re: Pushover static analysis error

Post by hr_park » Fri Apr 10, 2020 12:59 am

Dear Team STKO

I send scd file to "info@asdeasoft.net"!

STKO Team
Posts: 321
Joined: Tue Oct 29, 2019 8:45 am

Re: Pushover static analysis error

Post by STKO Team » Fri Apr 10, 2020 10:55 am

Dear User,

I just downloaded your file and had a look. Your model is not running because it is singular. However it is singular because all geometries in your model are disconnected from one another.

Looking at your file I understood that you are trying to model using a "orphane mesh" approach, i.e. the typical procedure used in softwares like SAP2000 or MidasGEN, where you draw nodes, and then elements connecting those nodes....
This is not the way you should use in STKO.

STKO is a geometry-based modeler, like Abaqus, where you draw and work on CAD geometries, and at the end you do the mesh, thus discretizing that continuous geometry into a set of nodes/elements.

I give you a small example. Let's say you want to create a simple model with 2 nodes and 1 element connecting those nodes.
You followed this wrong approach:
  • create vertex 1 at position (X1, Y1, Z1)
  • create vertex 2 at position (X2, Y2, Z2)
  • create a line from vertex 1 to vertex 2.
  • mesh with option "uniform by divisions". This will create 1 element per edge
  • At this point you think the line is connected to vertex 1 and vertex 2, but this is not true, you just used the previous 2 vertices as O-Snap points... but they are not connected to the line. In fact, following this procedure you have 3 geometries, 2 vertices + 1 line. Then when you mesh the model you will have 4 nodes (1 for each vertex and 2 from the line) + 1 element.
You should follow instead this correct approach:
  • create a line from position (X1, Y1, Z1) to position (X2, Y2, Z2)
  • mesh with option "uniform by divisions". This will create 1 element per edge
  • at this points you have only 1 geometry, that generated a mesh with 2 nodes and 1 element connecting those nodes.
So keep in mind this rule:
If you have N geometries in the worktree, they will generate N disconnected meshes. Sometimes this make sense, because for example you want to create separated geometries and then use an interaction to define a kinematic constraint between them. But if you want 2 meshes to shared the same nodes, you shoule make just 1 geometry.

I could try to change your file to explain you how it should look like, however I do not know what you really wanted to achieve.
Try to follow the notes I gave you above, and have a look at our webinars. If you still have problems, send us a sketch of the porblem you want to model, so that I can modify your file accordingly

hr_park
Posts: 20
Joined: Tue Mar 31, 2020 7:44 am

Re: Pushover static analysis error

Post by hr_park » Fri Apr 10, 2020 1:22 pm

Dear Team STKO

Wow this is whole new things! Thank you very much. :)
As advised, I did a new modeling and thanks to you now singular error was fixed!
But still there are other errors. I attach the picture this post and send new scd file to your email.
1.png
1.png (142.88 KiB) Viewed 1256 times
2.png
2.png (31.76 KiB) Viewed 1256 times

hr_park
Posts: 20
Joined: Tue Mar 31, 2020 7:44 am

Re: Pushover static analysis error

Post by hr_park » Fri Apr 10, 2020 1:50 pm

+I would like to get mpco files from pre-processor in STKO and compare with mpco file which is extracted from my 2 span bridge tcl script. ( I already have mpco file from tcl script )
And I am interested to do know how similarly tcl scrpt can be embodied in STKO.
The final goal is visualizing seisimic analysis because I think STKO is one of the best software which has user friendly interface for modeling, accurate analysis and visualizing,.

STKO Team
Posts: 321
Joined: Tue Oct 29, 2019 8:45 am

Re: Pushover static analysis error

Post by STKO Team » Fri Apr 10, 2020 2:10 pm

Your model is still singular, you see it from the error (some elements on the diagonal of the stiffness matrix is 0).

This is because you still have disconnected geometries. Same as I explained before, If you have 2 lines in 2 different geometries, even if one of their nodes share the same position in space, they will still be disconnected (4 nodes, 2 elements). Instead if you want 3 nodes and 2 elments (i.e. one node shared by both element) you should create 1 polyline with 2 lines, instead of 2 separated lines.

Here is an axample of how to convert some separated lines in your model, into a sigle WIRE (in CAD a wire is a polyline).

These lines are independent geometries, even if their end nodes share the same location, they are separated nodes:
disc_01.png
disc_01.png (137.66 KiB) Viewed 1253 times

You can select them all, and use the "Make Wire" command (works only for lines) or the more generale "Merge" command (works for everything):
disc_02.png
disc_02.png (48.48 KiB) Viewed 1253 times

Now the previously selected geometries will desappear, and you will see a new "merged" geometry. This new geometry is the same as the input ones. The main difference is that now all the nodes that were sharing the same position, are now actually a single entity, thuse shared by multiple lines:
disc_03.png
disc_03.png (162.52 KiB) Viewed 1253 times

hr_park
Posts: 20
Joined: Tue Mar 31, 2020 7:44 am

Re: Pushover static analysis error

Post by hr_park » Fri Apr 10, 2020 3:52 pm

Dear Team STKO
Thank you for you help sincerely
Now I understand what you mean.

I have another question about other element merge like the abutment parts which are located at both ends.
The left and right ends of bridge are symmtrical structures.
This is how it look like when left part is spread.
Red part is belong to deck and rest part is belong to abutment.
9CD008CD-BDD1-40BD-9042-74465FDBB574.png
9CD008CD-BDD1-40BD-9042-74465FDBB574.png (155.73 KiB) Viewed 1249 times
---:zeroLengthBeamColumn
| :ElasticBeamColumn

I understand deck part is merged by wire but when I run Anlysis I have still same errors.
So I run analysis after merged deck part and abutment part seperately because there zerolengthelement between two part, but it still has same errors.

I am so sorry to bother you again :(

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