Thank you for detailed explanation for SOLID65 model, I have been working on ANSYS for past 1 year, but your video has cleared so many doubts I had encountered in my analysis.
That was so prefect. Not only the explanation and the voice, but also learning apdl part. Thanks slot Could you please teaching some non linear compression test including crack and fracture?
This is a great tutorial! Thanks! But I have a question, how about using Command APDL for Reinforced Concrete Beam? Is there any command that will be executed since the concrete has a reinforcement? Or is there another command for the reinforcement itself?
Have you tried using the Reinforcement type for line bodies in Ansys 2020? I think it is easier like that. I´m trying to model a bending test for a RC pole for electric lines by applying displacement to the top. Do you know how could I determine cracks or at least the first crack? For the concrete I use Menetrey-Willam model
The new reinforcement feature is robust, but Menetrey Willam is not as good as ANSYS trying to promote, also Drucker Prager concrete and Micro-Plane model. The research paper using those model only demonstrate the model under a very small scope. There is a very high chance that we will get significant erroneous results without SOLID65. It is very easy to notice what I'm trying to say by just replace the concrete model with MW or DP or MP in my tutorials and compare to the experimental results.
Hi Thanapon, thank you for the video. I have a question. I'm trying to model the creep of concrete in my model on Ansys Workbench but on the program are present only experimental formulation for the creep (e.g. Strain Hardening, Time Hardening, Generalized Exponential, Norton, ...). However I need to model creep using the model which is reported in the European Codes (Model Code 1990 and Model Code 2010). This is the equation reported in the European Code where the strain is given by the sum of the initial strain at the moment of the application of the load (sigmact0) and the strain due to the creep. εcσ(t,t0)=σc(t0)[(1/Eci(t0))+(ϕ(t,t0)/Eci)]. Is there in Ansys the possibility of use this method for the creep of concrete? Thanks for your advice.
In practice, the problems that require long-term properties of concrete (creep and shrinkage) involve prestressed loss, long-term deflection, or long-term column shortening in the tall building. All those problems will be calculated using Midas, ADAPT, CSI-ETABS, CSI-SAP which are more suitable than ANSYS. CEB-FIP 90 and fib-MC2010 also included in ETABS for example.
I watched and followed the video. It was very specific to help me better understand the usage of ADPL Commands. However, when I try changing the input condition instead of the displacement I assign with the pressure value, all other declarations stay the same, but the result is an error. The same happens when changing the boundary conditions. Please tell me why?
Either providing the nodal displacement as input in order to obtain the member forces or providing the external forces in order to obtain nodal displacement are identical as long as the FE model is numerically stable. (Also refer to the numerical method in finite element analysis for further information.) The finite element method used in the computer software is based on matrix analysis. The matrix itself doesn't recognize whether nodal displacement or nodal forces as input. The results will always be the same as long as the matrix is mathematically the same (static equilibrium). If you still have trouble with a solid element of how the above explanation works, try testing with simpler elements such as line element (truss element is the easiest to test and verify), then plane element, then solid for the last. And try to begin with linear elastic analysis, then nonlinear analysis. In short, understanding how the matrix works will help overcome much trouble when using computer software.
In addition, there is some situation when trying to obtain structural displacement while applying nodal forces in such a way that the structural stiffness degraded (due to the nonlinearity effect) to the point that it is tough for numerical solution to be converged because of numerical stability is so bad. In this same situation, applying nodal displacement instead of nodal forces improve and in many cases prevent numerical instability and help the solution to be converged easier than using nodal loads, some reference called this method a displacement control. Although in theory, applying nodal loads or nodal displacement are considered equivalent but the numerical convergence is significantly different, especially for the highly nonlinear problem.
For the rebar that explicitly modeled with the LINK element, ANSYS workbench now able to directly support both input and output data. There is no longer a need to prepare APDL command for rebar that has been explicitly modeled. For smeared rebar, use Real Constant menu in Mechanical APDL. The APDL command for smeared rebar will look like this. tb_rebarratio_x = 0.0 tb_rebarratio_y = 0.0018 tb_rebarratio_z = 0.0018 meaning that there is no smeared rebar along the global X-axis and there are smeared rebar of 0.0018 (volume ratio) along the global Y/Z-axis. And followed with these: !* Smeared rebar in VR1 direction (0,0) degree, VR2 (90,0) degree and VR3 (90,90) degree R,solid65_matid,steel_matid,tb_rebarratio_x,0,0,steel_matid,tb_rebarratio_y, RMORE,90,0,steel_matid,tb_rebarratio_z,90,90, RMORE, ,
I tried to solve a little bit more complex structure (simply supported beam) with the same way, but I couldn't solve the structure. ANSYS gives an error massage "an unknown error occurred during solution". I would be grateful if you help. Thank you very much for your kind interest.
The tutorial in the following playlist includes various structural elements from basic such beam/column to more complicated such as heavily reinforced one. ua-cam.com/play/PLYX5ua4SRf6zibnuG3WM43gLJkUVBUgkx.html I also put some guides for people who got stuck with errors in the comments down below each video. Hopefully, it would help you get past the errors.
@@ThanaponBuamongkolChannel Thank you for your quick response. I have already watched the videos you recommend. I modeled simply supported beam without rebars and, I wanted to replace solid 185 with solid 65 using APDL commands like in this video. When I activate the command the solution fails. I will be trying to fix the errors. Thank you very much again.
SOLID65 is naturally not suitable for plain concrete models as a structural element due to meshing dependent problems (different mesh cause different numerical problems) and convergence issues after cracking. The simply supported beam without rebars will certainly cause numerical issues, no surprise. Numerical issues will appear soon after the first crack. You'd better leave the plain concrete beam model alone for a while until you learn CPT215 which is better than SOLID65 when dealing with plain concrete. CPT215 supports tensile strain-softening, therefore, better numerical stability. The reason that the SOLID65 concrete cube in this tutorial works just fine without any numerical difficulty even with post-cracking behavior because of the way boundary condition applied. It is displacement controlled that reduce the number of degree of freedom that need to be solved in the matrix, hence, numerical issues have been suppressed this way. If SOLID65 is not good when concrete cracking, why it is performing well in the reinforced concrete model? The answer is, the rebars will be immediately activated right after the first crack and stabilize the numerical in the stiffness matrix, hence, the solution could be converged this way.
@@ThanaponBuamongkolChannel I see. Actually, I am interested in masonry structures rather than the concrete ones. But as far as I know, Solid65 is a suitable finite element for masonry. I want to analyze a historical structure under seismic loads and check for cracks. Actually, there are studies performed using Solid65 for masonry. I don't know whether the CPT215 is suitable for masonry or not. Besides this, the solution is terminated with error messages even if non-linear parameters are not assigned to the material model. Thanks a lot again.
Try to suppress the APDL command (right-click at the item and choose to suppress), the model will now become linear elastic, the solution supposes to be a success. If not, the problem may be laid somewhere from geometry, meshing, boundary conditions, and loading. Try to fix them. Once success with the linear elastic model without APDL, gradually add APDL command by starting with linear elastic material, then add a non-linear property, then cracking (concrete). Normally, it is cracking that cause issue. Since your problem involves brittle material behavior, try to google search something like "ANSYS restart analysis". With the restarts feature, you will be able to adjust the substep size every time your solution fails to converge. Every time you restart, the analysis will continue right after where the solution just fails.
SOLID65 suffers from meshing dependent and convergence issues. Disable crushing mode by putting -1 and replace with a manual crushing check (the 0.003 strain) will help the solution converge easier. With cracking alone, it already creates enough challenge in numerical convergence. The better element for concrete strength degradation (the negative slope in the stress-strain curve) and strain softening after cracking is CPT215. The downside of CPT215 is its parameters are quite skeptical and hard to verify at the moment. It requires some more time for CPT215 to be fully explored. For the time being, SOLID65 is the most reliable just because its model is the most explored.
@@g30923 ANSYS will not recognize 0.003 on its own, the user has to manually interpret the analysis results. By trial and error until there is a suitable range of results.
Hello Thank you for your tutorial video. I have a question here on my mind. At the beginning of the video, you have entered Isotropic Elasticity data using the Engineering data section. At the same time, you have created another Isotropic Elasticity data as a command block (the same Isotropic Elasticity data you created before) in the Mechanical APDL section. Is there a need for such a situation? When we create the data we enter into Engineering Data, as an instruction block do we need to re-enter the data? Or can Ansys detect this automatically and solve it? Could you please share your e-mail address? Thank you for taking the time to read my message and for your help.
Actually, there is more than one way to set up the workflow. The recommended workflow for a beginner is as shown in the video which the APDL command will overwrite the data previously defined from engineering data. Therefore, whatever defined in the engineering data will be never be used later on. The structural analysis will always follow the APDL command. No, you do not need to always follow the exact steps as shown in the video.
When I am trying to provide element property to my concrete and rebar its not working on them . no change in elements. Can you please make a tutorial step by step if possible to write apdl command u used in other analysis? Other than not working it also shows error and my rebar is not deforming.
There is only a concrete model in this video. You only need the APDL command for the concrete model. For other materials such as steel, you can directly assign the material using Workbench. This video already shows the step by step of how to achieve the APDL command for the concrete model. Regarding another video that involves both concrete and rebars, please kindly post the comment/question on that video's comments section so that I could figure out which part you probably get stuck with.
Thank you for detailed explanation for SOLID65 model, I have been working on ANSYS for past 1 year, but your video has cleared so many doubts I had encountered in my analysis.
That was so prefect. Not only the explanation and the voice, but also learning apdl part. Thanks slot
Could you please teaching some non linear compression test including crack and fracture?
This is a great tutorial! Thanks! But I have a question, how about using Command APDL for Reinforced Concrete Beam? Is there any command that will be executed since the concrete has a reinforcement? Or is there another command for the reinforcement itself?
Check out the playlist in the description.
Have you tried using the Reinforcement type for line bodies in Ansys 2020? I think it is easier like that. I´m trying to model a bending test for a RC pole for electric lines by applying displacement to the top. Do you know how could I determine cracks or at least the first crack?
For the concrete I use Menetrey-Willam model
The new reinforcement feature is robust, but Menetrey Willam is not as good as ANSYS trying to promote, also Drucker Prager concrete and Micro-Plane model.
The research paper using those model only demonstrate the model under a very small scope.
There is a very high chance that we will get significant erroneous results without SOLID65. It is very easy to notice what I'm trying to say by just replace the concrete model with MW or DP or MP in my tutorials and compare to the experimental results.
Hi Thanapon, thank you for the video. I have a question. I'm trying to model the creep of concrete in my model on Ansys Workbench but on the program are present only experimental formulation for the creep (e.g. Strain Hardening, Time Hardening, Generalized Exponential, Norton, ...). However I need to model creep using the model which is reported in the European Codes (Model Code 1990 and Model Code 2010). This is the equation reported in the European Code where the strain is given by the sum of the initial strain at the moment of the application of the load (sigmact0) and the strain due to the creep.
εcσ(t,t0)=σc(t0)[(1/Eci(t0))+(ϕ(t,t0)/Eci)].
Is there in Ansys the possibility of use this method for the creep of concrete?
Thanks for your advice.
In practice, the problems that require long-term properties of concrete (creep and shrinkage) involve prestressed loss, long-term deflection, or long-term column shortening in the tall building. All those problems will be calculated using Midas, ADAPT, CSI-ETABS, CSI-SAP which are more suitable than ANSYS.
CEB-FIP 90 and fib-MC2010 also included in ETABS for example.
Thanks a lot. It ıs great! It would be more useful if the tutorial includes crack plotting.
@NOOR AZIM BIN MOHD RADZI did you find out how to exclude steel?
I watched and followed the video. It was very specific to help me better understand the usage of ADPL Commands. However, when I try changing the input condition instead of the displacement I assign with the pressure value, all other declarations stay the same, but the result is an error. The same happens when changing the boundary conditions. Please tell me why?
Either providing the nodal displacement as input in order to obtain the member forces or providing the external forces in order to obtain nodal displacement are identical as long as the FE model is numerically stable. (Also refer to the numerical method in finite element analysis for further information.)
The finite element method used in the computer software is based on matrix analysis. The matrix itself doesn't recognize whether nodal displacement or nodal forces as input. The results will always be the same as long as the matrix is mathematically the same (static equilibrium).
If you still have trouble with a solid element of how the above explanation works, try testing with simpler elements such as line element (truss element is the easiest to test and verify), then plane element, then solid for the last. And try to begin with linear elastic analysis, then nonlinear analysis.
In short, understanding how the matrix works will help overcome much trouble when using computer software.
In addition, there is some situation when trying to obtain structural displacement while applying nodal forces in such a way that the structural stiffness degraded (due to the nonlinearity effect) to the point that it is tough for numerical solution to be converged because of numerical stability is so bad.
In this same situation, applying nodal displacement instead of nodal forces improve and in many cases prevent numerical instability and help the solution to be converged easier than using nodal loads, some reference called this method a displacement control.
Although in theory, applying nodal loads or nodal displacement are considered equivalent but the numerical convergence is significantly different, especially for the highly nonlinear problem.
thank you so much.Is there a way to solve steel in line and in solid part
For the rebar that explicitly modeled with the LINK element, ANSYS workbench now able to directly support both input and output data. There is no longer a need to prepare APDL command for rebar that has been explicitly modeled.
For smeared rebar, use Real Constant menu in Mechanical APDL.
The APDL command for smeared rebar will look like this.
tb_rebarratio_x = 0.0
tb_rebarratio_y = 0.0018
tb_rebarratio_z = 0.0018
meaning that there is no smeared rebar along the global X-axis and there are smeared rebar of 0.0018 (volume ratio) along the global Y/Z-axis.
And followed with these:
!* Smeared rebar in VR1 direction (0,0) degree, VR2 (90,0) degree and VR3 (90,90) degree
R,solid65_matid,steel_matid,tb_rebarratio_x,0,0,steel_matid,tb_rebarratio_y,
RMORE,90,0,steel_matid,tb_rebarratio_z,90,90,
RMORE, ,
to model the soil, which type of finite element is suitable in Ansys?
Plaxis or GTS-NX are better tools for the FEM soil model than ANSYS.
I tried to solve a little bit more complex structure (simply supported beam) with the same way, but I couldn't solve the structure. ANSYS gives an error massage "an unknown error occurred during solution". I would be grateful if you help. Thank you very much for your kind interest.
The tutorial in the following playlist includes various structural elements from basic such beam/column to more complicated such as heavily reinforced one.
ua-cam.com/play/PLYX5ua4SRf6zibnuG3WM43gLJkUVBUgkx.html
I also put some guides for people who got stuck with errors in the comments down below each video. Hopefully, it would help you get past the errors.
@@ThanaponBuamongkolChannel Thank you for your quick response. I have already watched the videos you recommend. I modeled simply supported beam without rebars and, I wanted to replace solid 185 with solid 65 using APDL commands like in this video. When I activate the command the solution fails. I will be trying to fix the errors. Thank you very much again.
SOLID65 is naturally not suitable for plain concrete models as a structural element due to meshing dependent problems (different mesh cause different numerical problems) and convergence issues after cracking.
The simply supported beam without rebars will certainly cause numerical issues, no surprise.
Numerical issues will appear soon after the first crack.
You'd better leave the plain concrete beam model alone for a while until you learn CPT215 which is better than SOLID65 when dealing with plain concrete. CPT215 supports tensile strain-softening, therefore, better numerical stability.
The reason that the SOLID65 concrete cube in this tutorial works just fine without any numerical difficulty even with post-cracking behavior because of the way boundary condition applied. It is displacement controlled that reduce the number of degree of freedom that need to be solved in the matrix, hence, numerical issues have been suppressed this way.
If SOLID65 is not good when concrete cracking, why it is performing well in the reinforced concrete model? The answer is, the rebars will be immediately activated right after the first crack and stabilize the numerical in the stiffness matrix, hence, the solution could be converged this way.
@@ThanaponBuamongkolChannel I see. Actually, I am interested in masonry structures rather than the concrete ones. But as far as I know, Solid65 is a suitable finite element for masonry. I want to analyze a historical structure under seismic loads and check for cracks. Actually, there are studies performed using Solid65 for masonry.
I don't know whether the CPT215 is suitable for masonry or not. Besides this, the solution is terminated with error messages even if non-linear parameters are not assigned to the material model.
Thanks a lot again.
Try to suppress the APDL command (right-click at the item and choose to suppress), the model will now become linear elastic, the solution supposes to be a success. If not, the problem may be laid somewhere from geometry, meshing, boundary conditions, and loading. Try to fix them.
Once success with the linear elastic model without APDL, gradually add APDL command by starting with linear elastic material, then add a non-linear property, then cracking (concrete). Normally, it is cracking that cause issue.
Since your problem involves brittle material behavior, try to google search something like "ANSYS restart analysis". With the restarts feature, you will be able to adjust the substep size every time your solution fails to converge. Every time you restart, the analysis will continue right after where the solution just fails.
I'm new to ansys ... why the crushing stress -1?
SOLID65 suffers from meshing dependent and convergence issues. Disable crushing mode by putting -1 and replace with a manual crushing check (the 0.003 strain) will help the solution converge easier.
With cracking alone, it already creates enough challenge in numerical convergence.
The better element for concrete strength degradation (the negative slope in the stress-strain curve) and strain softening after cracking is CPT215. The downside of CPT215 is its parameters are quite skeptical and hard to verify at the moment. It requires some more time for CPT215 to be fully explored. For the time being, SOLID65 is the most reliable just because its model is the most explored.
@@ThanaponBuamongkolChannel How does Ansys know that the rupture criterion is at 0.003 strain? in the video the last point was at 0.00243
@@g30923 ANSYS will not recognize 0.003 on its own, the user has to manually interpret the analysis results. By trial and error until there is a suitable range of results.
Hello
Thank you for your tutorial video.
I have a question here on my mind. At the beginning of the video, you have entered Isotropic Elasticity data using the Engineering data section. At the same time, you have created another Isotropic Elasticity data as a command block (the same Isotropic Elasticity data you created before) in the Mechanical APDL section.
Is there a need for such a situation?
When we create the data we enter into Engineering Data, as an instruction block do we need to re-enter the data?
Or can Ansys detect this automatically and solve it?
Could you please share your e-mail address?
Thank you for taking the time to read my message and for your help.
Actually, there is more than one way to set up the workflow. The recommended workflow for a beginner is as shown in the video which the APDL command will overwrite the data previously defined from engineering data. Therefore, whatever defined in the engineering data will be never be used later on. The structural analysis will always follow the APDL command.
No, you do not need to always follow the exact steps as shown in the video.
Sir this method is not working for me
Which part is not working? Inside the Mechanical APDL or in Workbench?
When I am trying to provide element property to my concrete and rebar its not working on them . no change in elements. Can you please make a tutorial step by step if possible to write apdl command u used in other analysis?
Other than not working it also shows error and my rebar is not deforming.
There is only a concrete model in this video. You only need the APDL command for the concrete model. For other materials such as steel, you can directly assign the material using Workbench.
This video already shows the step by step of how to achieve the APDL command for the concrete model.
Regarding another video that involves both concrete and rebars, please kindly post the comment/question on that video's comments section so that I could figure out which part you probably get stuck with.
Im working in a RC beam model, if i can contact you it would be really helpfull