DEMO 5: Equivalent-Static and Dynamic Structural Analysis Using ACS SASSI-ANSYS Integration Capability
This demo shows the Option A capability for structural stress analysis using ANSYS structural model based on the ACS SASSI analysis results. The demo problem illustrates a deeply embedded concrete pool structure subjected to seismic loading. It is assumed that the user already performed a complete ACS SASSI SSI analysis with full post-processing for computing acceleration and relative displacement time frames, as described in the Demo 1 problem.
This demo will take the user through the process of applying the seismic analysis results from ACS SASSI v300 to an ANSYS model via the ACS SASSI-ANSYS integration tools. This problem will demonstrate both the static and dynamic capabilities of the ACS SASSI-ANSYS integration tools.
This demo assumes that that the user is working in the following directory:
C:\ACSV300\DEMO_PROBLEMS\DEMO5\
All path names in this demo are shortened to the relative path in that directory i.e.
C:\ACSV300\DEMO_PROBLEMS\DEMO5\ACSSASSI_Model_Database will be written as .\ACSSASSI_Model_Database. The full path should still be used when performing the steps in this demo problem.
1 Overview the entire demo process 1.1 Perform the full SSI analysis
The equivalent static and dynamic analyses in ANSYS will uses results from the SSI analysis performed in ACS SASSI, therefore The first step is to complete the ACS SASSI SSI analysis including full post-processing to generate acceleration and relative displacement frames for the concrete pool structure. The concrete pool structure SSI model is defined in the Demo5.pre file.
For this problem, it is assumed that the SSI analysis was performed in the
“.\ACSSASSI_Model_Database” folder. All the necessary input files to complete the SSI analysis in ACS SASSI are included in the .\Demo_Problem\Demo5\
ACSSASSI_Model_Database folder on the installation disc. The batch run command file for the full SSI analysis, Demo5.bat, is also provided. The user can launch this file to complete the ACS SASSI SSI analysis including the full post-processing.
If user wishes to skip the full SSI analysis, a compressed archive named DEMO5_SSI_Data.zip is also provided. This archive contains all the SSI analysis results. If the user wishes to skip the SSI analysis, the archive should be extracted to the .\ACSSASSI_Model_Database folder for later use, otherwise these files will be created there during the SSI analysis.
After the SSI analysis is complete, or the results have been extracted from the archive, all the necessary SSI results can be found in the .\ACSSASSI_Model_Database directory. The folder
.\ACSSASSI_Model_Database\ACC will contain the translational acceleration frames and the folder .\ACSSASSI_Model_Database\THD will contain the translational displacement frames
1.2 Prepare the folders to generate the ANSYS analysis loading
Before the user starts using the ACS SASSI-ANSYS integration tools, two folders will be created to use as working directories for the static load conversion and ANSYS analysis and the dynamic load conversion and ANSYS analysis. These steps will be detailed in section 2
1.3 Generate nodal mass data of the SSI structure model
Nodal masses of the SSI structure model are needed to generate the equivalent static loading and dynamic loading. The ACS SASSI-ANSYS integration tool has a function to generate this nodal mass data. Please see the “ACS SASSI-ANSYS Integration” user manual for the details on how to generate nodal mass data.
1.4 Generate seismic loading file for the refined ANSYS model
After the mass data is generated, The ACS SASSI-ANSYS integration tool can generate the boundary conditions for the ANSYS model using the "Displacement and Acceleration” option.
Please see the “ACS SASSI-ANSYS Integration” user manual for details.
NOTE: The user will be able to find all the input files for the load conversion process in the Demo5 folder on the installation disk. These files may be useful for comparison if the user is experiencing difficulties understanding any of the file formats.
The following sections demonstrate a general procedure for performing equivalent static and dynamic analyses in ANSYS.
2 EQUIVALENT-STATIC SSI STRESS ANALYSIS (FOR THE COARSE MODEL, DEMO5.DB)
This section will demonstrate the procedure used to generate seismic loading for equivalent static analysis in ANSYS using ACS SASSI results.
2.1 Prepare selected acceleration and/or displacement frames for critical time steps:
1. Using Windows Explorer run the .\ACSSASSI_Model_Database\Demo5.bat file to start the SSI analysis run, or extract the
.\ACSSASSI_Model_Database\DEMO5_SSI_Data.zip archive in the same folder to skip the SSI analysis run.
2. Create a new folder called .\ACSSASSI_Results_for_Static_Analysis. There should now be two folders in the C:\ACSV300\DEMO_PROBLEMS\DEMO5 folder;
.\ACSSASSI_Model_Database
.\ACSSASSI_Results_for_Static_Analysis
3. Copy the following files to the .\ACSSASSI_Results_for_Static_Analysis folder:
ACC_04.510_00903 and THD_04.510_00903. These files are found in the
.\ACSSASSI_Model_Database\ACC folder and the
.\ACSSASSI_Model_Database\THD folders, respectively. These files are the frames that are considered as critical time steps in this demo.
4. Copy Demo5.hou from the .\ACSSASSI_Model_Database folder to the .\ACSSASSI_Results_for_Static_Analysis folder.
2.2 Prepare required data for seismic loading generation:
1. Start the ACS SASSI UI
2. Define the model name and path with the
mdl,demo5,C:\ACSV300\DEMO_PROBLEMS\DEMO5\ACS_SASSI_Model_Database command.
5. In the ACS SASSI UI, select Model Input.
6. A new dialog window will open for inputting the .pre input file. Select the file named Demo5.pre and click Open.
7. The Demo5.pre file (containing ACS SASSI UI commands) is read. When done, type SAVE in the command line.
8. Under the Model menu, select Export to ANSYS. This action will create a file named
“demo5.inp” is an ANSYS APDL commands file, and contains the converted ANSYS finite element model from the ACS SASSI model.
9. Create a folder named .\ANSYS_Static_Analysis in the demo5 directory. This will be the ANSYS working directory for the equivalent static analysis. There should now be three folders in the C:\ACSV300\DEMO_PROBLEMS\DEMO5 folder;
.\ACSSASSI_Model_Database
.\ACSSASSI_Results_for_Static_Analysis .\ANSYS_Static_Analysis
10. Copy the Demo5.inp file that was created in Step 8 to the .\ANSYS_Static_Analysis folder.
2.3 Generate the node mass of the structure
11. From the Modules menu in the ACS SASSI UI, select the ANSYS Eq. Static Loading option. This will open a new input window for the ANSYS equivalent-static loading generator (the LOADGEN module).
12. Check the box for Generate Mass Data in the Mass Data for Inertial Load section.
Make sure the radio button for Lumped Mass is selected. The SASSI Model and Results Input section will become inactive.
13. In the text box next to the Lumped Mass Data, enter mass.dat. This will be the name of the mass data file that will be created and used when the equivalent-static seismic forces are computed.
14. In the Path box, enter
C:\ACSV300\DEMO_PROBLEMS\DEMO5\ANSYS_Static_Analysis. This is the default path, and my be different if the demo is not run in the default directory.
15. In the bottom text box for the APDL File, type mass_gen.inp. This is the input file that will be used in ANSYS to write the necessary nodal mass files.
16. Click OK. This will create the mass_gen.inp file.
17. Launch ANSYS in the
C:\ACSV300\DEMO_PROBLEMS\DEMO5\ANSYS_Static_Analysis folder.
18. In ANSYS, load the Demo5.inp file that was copied to the .\ANSYS_Static_Analysis folder in Step 10 using the following command: /INPUT, demo5, inp (This model will be referred to as the Coarse Model in the user manual for the ACS SASSI-ANSYS
integration tool). Save the model, and ANSYS will create the model database called demo5.db in this folder.
19. Delete any existing boundary conditions with the DDELE,ALL command (make sure you are in /PREP7 or you will see and error that DDELE is not a recognized BEGIN
command)
20. Load the mass_gen.inp file using the /INPUT, mass_gen, inp command. ANSYS will perform a modal analysis and write the nodal masses to mass.dat.
2.4 Generate the seismic loading file for ANSYS model
21. From the Modules menu in the ACS SASSI UI, select the ANSYS Eq. Static Loading option. This will open a new window for the ANSYS equivalent-static load generator input (the LOADGEN module).
22. Select the "Displacement and Acceleration” option at the top of the load generator window.
23. Click on the arrow button to the right of the HOUSE Module Input box. Browse to the location of the Demo5.hou file (this should have been copied to
“.\ACSSASSI_Results_for_Static_Analysis” folder by the user in step 4). Select the Demo5.hou file and click OK. The Path name box above the HOUSE Module Input box will be filled in automatically based on the selection of the Demo5.hou file.
24. In the Displacement Results text box, browse to select the THD_04.510_00903 file from the .\ ACSSASSI_Results_for_Static_Analysis folder. In the Trans.
Acceleration Results text box, enter ACC_04.510_00903 which is assumed to be in the same directory as the displacement frame.
25. In the Path box in the ANSYS Model and Data Input section, enter
C:\ACSV300\DEMO_PROBLEMS\DEMO5\ANSYS_Static_Analysis. This is the default path, and my be different if the demo is not run in the default directory.
26. Enter mass.dat into the Lumped Mass Data box.
27. Enter ANSYS_Static_Loads.inp into the APDL File box in the ANSYS Output File Section.
28. Click OK. An ANSYS APDL file containing the displacement loads is now created in the .\ANSYS_Static_Analysis folder with the name specified in Step 35.
2.5 Apply the seismic loading to the ANSYS model and Perform static analysis
29. Return to ANSYS. Open your model that will be applied the seismic loading (This is refered to as the refined model in the user manual for the ACS SASSI-ANSYS
integration tool). In this demo, the same Demo5.db is used as refined model. So, user should open Demo5.db if it is not already open from the mass generation phase. First,
all the node boundary conditions must be deleted. This can be done using the command DDELE,ALL (make sure you are in /PREP7 or you will see and error that DDELE is not a recognized BEGIN command)
30. Load the APDL file created in step 28 using the /INP, ANSYS_Static_Loads, inp command. This will apply the seismic loads to the ANSYS model.
31. Under the Solution section in ANSYS, select Analysis Type New Analysis. Select Static in the window that opens, and click OK.
32. Select Solve Current LS. This will start the solution process.
33. Use the ANSYS postprocessor to view the SSI results from the ANSYS static run.
The equivalent-static analysis at the critical time is complete. In the following section, the procedure for performing a dynamic analysis with seismic loading will be demonstrated.
3 DYNAMIC SSI STRESS ANALYSIS (FOR THE COARSE MODEL, DEMO5.DB)
This section will demonstrate the procedure for performing a dynamic analysis of the structure model in ANSYS using the seismic loading from ACS SASSI results. This section assumes that the user has completed all the steps in section 2, and therefore all the SSI results, nodal mass, active node files and ANSYS inputs are available.
3.1 Prepare data for generating seismic load for dynamic analysis in ANSYS
1. Create a new folder called .\ACSSASSI_Results_for_Dynamic_Analysis using Windows Explorer for save the SSI results and related data files. There should now be four folders in the C:\ACSV300\DEMO_PROBLEMS\DEMO5 folder;
.\ACSSASSI_Model_Database
.\ACSSASSI_Results_for_Static_Analysis .\ACSSASSI_Results_for_Dynamic_Analysis.
.\ANSYS_Static_Analysis
2. Copy the Demo5.hou file from the .\ACSSASSI_Model_Database folder to the .\ACSSASSI_Results_for_Dynamic_Analysis folder.
3. The user will need to prepare the Ground Acceleration File. The format of this file is outlined in the ACS SASSI-ANSYS integration documentation. For this demo, the file is called ground_acce.txt and is provided to the user in the
.\ACSSASSI_Results_for_Dynamic_Analysis folder on the installation disc. Copy this file to the .\ACSSASSI_Results_for_Dynamic_Analysis folder created in Step 1.
4. Copy all the relative displacement frame files from the SSI analysis in the .\ACSSASSI_Model_Database\THD folder to the .\
ACSSASSI_Results_for_Dynamic_Analysis folder.
5. Create a new folder called .\ANSYS_Dynamic_Analysis. This will be the ANSYS working directory for the dynamic ANSYS analysis. There should now be five folders in the C:\ACSV300\DEMO_PROBLEMS\DEMO5 folder;
.\ACSSASSI_Model_Database
.\ACSSASSI_Results_for_Static_Analysis .\ACSSASSI_Results_for_Dynamic_Analysis .\ANSYS_Static_Analysis
.\ANSYS_Dynamic_Analysis
6. Copy the Demo5.inp file from the “.\ACSSASSI_Model_Database” folder to the .\ANSYS_Dynamic_Analysis folder.
3.2 Generate the seismic dynamic load for ANSYS dynamic analysis
1. In the ACS SASSI UI, select Modules ANSYS Dynamic Load. A new window is opened for the ANSYS dynamic load generator input (the LOADGEN module).
2. Click the arrow button next to the House Module Input box, and browse to the
Demo5.hou file that was copied to the .\ACSSASSI_Results_for_Dynamic_Analysis folder in Step 2. The Path box will automatically be filled in.
3. Click the arrow button next to the Ground Acceleration File box, and browse to the provided ground acceleration file in the .\ACSSASSI_Results_for_Dynamic_Analysis folder (copied there in Step 3). Select it and click OK. In this demo, the acceleration file is “ground_acce.txt”.
4. In the Path box in the ANSYS Model and Data Input section, enter .\ANSYS_Dynamic_Analysis
5. In the Raleigh Damping Coef. section, enter 0.45473e-3 for Alpha and 0.2154 for Beta in this demo. These values correspond to an approximate 5% viscous damping ratio at in the low-middle frequency range.
6. Enter ANSYS_Dynamic_Loads.inp into the APDL box. This is the name of the file that will be input to run the ANSYS dynamic analysis.
7. Click the OK button to write the seismic load file for the ANSYS dynamic SSI analysis using APDL commands.
3.3 Run ANSYS to perform dynamic analysis under seismic load
8. Launch ANSYS in the .\ANSYS_Dynamic_Analysis folder, to create an ANSYS model database called demo5.db.
9. Load the Demo5 .inp file In ANSYS using the command: /INPUT, demo5, inp, which was copied to the .\ANSYS_Dynamic_Analysis folder in step 6. Click “Save DB” to save this ANSYS model database as demo5.db.
10. Load the ANSYS_Dynamic_Loads.inp file in ANSYS using the command /INPUT, ANSYS_Dynamic_Loads, inp; The dynamic analysis starts automatically.
11. Use the ANSYS postprocessor to view the SSI results after ANSYS dynamic analysis is done.
The dynamic analysis with ANSYS now complete.
