Hi,
Does anyone have experience in using the CIM to model soil-structure interaction of shallow foundations?
Have you obtained reasonable results? Many thanks!
I tried to regenerate Figure 4.12 in PEER Report 2007/04 using their attached input file on Page 116-118 with minor necessary corrections.
However, the output shear-sliding relationship of CIM looks far away from those in Figure 4.12.
The CIM is defined as follows in OpenSees (PEER Report 2007/04 :
# linear coordinate transformation
geomTransf Linear 1
# define CIM – implemented as soilFootingSection2d in OpenSees
# section SFS2d Tag FS Vult L Kv Kh Rv deltaL
section soilFootingSection2d 1 2.6 1.81e+7 14.63 8.14e+8 7.5e+8 0.1 0.01
# SFS2d material must be used with a zeroLengthSection (ZLS) element
# element ZLS eleID iNode jNode matID <orientation vectors>
element zeroLengthSection 1 1 2 1 -orient 0 -1 0 1 0 0
SSI: Contact Interface Model (CIM)
Moderator: Moderators
-
Thomas_Tang
- Posts: 9
- Joined: Fri Oct 05, 2007 11:46 am
- Location: Simpson Gumpertz & Heger
Thomas,
It has worked fine for me. It looks like you have made the correct modifications to the input parameter order, but make sure your FS (Vult/V) value is consistent with the existing vertical load (V). You are using FS=2.6. while that example defines the model for the shorter benchmark structure with FS=3.1.
You say "... the output shear-sliding relationship of CIM looks far away from those in Figure 4.12. "
First, to replicate the figure 4.12 exactly you need to recompile opensees with the newer soilfootingsection2D source code which contains the elastic rotation input parameter. Contact Prof. Gajan (s.gajan@ndsu.edu) for that.
I can't imagine the Shear-sliding being effected much by the slightly different FS you are using or not having the elastic rotation introduced in the newer version. Double check your post-processing procedures to make sure you are plotting the correct data.
Once you correct the FS the output should be the same as figure 4.12 with the exception of more settlement during lower levels of shaking (beginning and end of the motion) due to the absence of the elastic rotation in the version you are using.
Jose
It has worked fine for me. It looks like you have made the correct modifications to the input parameter order, but make sure your FS (Vult/V) value is consistent with the existing vertical load (V). You are using FS=2.6. while that example defines the model for the shorter benchmark structure with FS=3.1.
You say "... the output shear-sliding relationship of CIM looks far away from those in Figure 4.12. "
First, to replicate the figure 4.12 exactly you need to recompile opensees with the newer soilfootingsection2D source code which contains the elastic rotation input parameter. Contact Prof. Gajan (s.gajan@ndsu.edu) for that.
I can't imagine the Shear-sliding being effected much by the slightly different FS you are using or not having the elastic rotation introduced in the newer version. Double check your post-processing procedures to make sure you are plotting the correct data.
Once you correct the FS the output should be the same as figure 4.12 with the exception of more settlement during lower levels of shaking (beginning and end of the motion) due to the absence of the elastic rotation in the version you are using.
Jose
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Thomas_Tang
- Posts: 9
- Joined: Fri Oct 05, 2007 11:46 am
- Location: Simpson Gumpertz & Heger
Many Thanks!
Dear Jose,
I appreciate your quick reply!
What you typed is very helpful and encourages me to use the model.
I did contact Dr. Gajan to know the exact input arguments for CIM in current version of OpenSees.
I will double check my codes and postprocess of the output.
I will let you know if I overcome this trouble.
Best,
Thomas
I appreciate your quick reply!
What you typed is very helpful and encourages me to use the model.
I did contact Dr. Gajan to know the exact input arguments for CIM in current version of OpenSees.
I will double check my codes and postprocess of the output.
I will let you know if I overcome this trouble.
Best,
Thomas
-
Thomas_Tang
- Posts: 9
- Joined: Fri Oct 05, 2007 11:46 am
- Location: Simpson Gumpertz & Heger
Dear Jose,
I am sorry that I still cannot get results comparable to those in Fig.4.12(b).
Firstly, can you please confirm some details in the input Tcl file on Page 116-118 in PEER Report 2007/04?
1) I changed the last line on Page 116 to be
set wFloor -7.8e+4
I think "hFloor" should be a typo.
2) Are the values wFooting=-2.67e+5 N, wFloor=-7.8e+4 N correct for the 4-story building?
Base on Figure 4.2, the weight of the footing can be estimated as
(unit weight of RC: 24500N/m^3)*(14.63m*4.57m*1.83m)=3.00e+6 N, which is way larger than 2.67e+5 N.
On the other hand, I cannot see the relationship between wFloor=-7.8e+4 N and the data in Table 4.1 on Page 38.
BTW: is the weight of one wall shown in Table 4.1 resulted from the unit weight of RC,
~24500N/m^3, and the dimensions shown in Figure 4.2 on Page 36 ?
3) I added "set n 1" before the first line on Page 117. Otherwise there would be error when running OpenSees.
4) I added "integrator LoadControl 0.1" to the analysis objects for gravity loading on Page 117. Otherwise, there would be error.
5) Is the Rayleigh damping specified on Page 118, "rayleigh 0.05 0 0.05 0", correct?
Does that mean to reach 5% damping ratio?
Does Rayleigh damping apply to CIM model as well?
Does CIM model take into account radiation damping in soil half-space?
With the changes (1), (3), (4) above and also the modification of the input arguments of soilFootingSection2d, running of the Tcl script on Page 116-118 in the report
with unscaled WVC270 earthquake record yields unreasonable high-frequency oscillation
in the horizontal sliding behavior (i.e. shear force and horizontal displacement) of the CIM element.
It would be greatly appreciated if you can answer my questions
or just post your input file that gives correct results!
Regards,
Thomas
I am sorry that I still cannot get results comparable to those in Fig.4.12(b).
Firstly, can you please confirm some details in the input Tcl file on Page 116-118 in PEER Report 2007/04?
1) I changed the last line on Page 116 to be
set wFloor -7.8e+4
I think "hFloor" should be a typo.
2) Are the values wFooting=-2.67e+5 N, wFloor=-7.8e+4 N correct for the 4-story building?
Base on Figure 4.2, the weight of the footing can be estimated as
(unit weight of RC: 24500N/m^3)*(14.63m*4.57m*1.83m)=3.00e+6 N, which is way larger than 2.67e+5 N.
On the other hand, I cannot see the relationship between wFloor=-7.8e+4 N and the data in Table 4.1 on Page 38.
BTW: is the weight of one wall shown in Table 4.1 resulted from the unit weight of RC,
~24500N/m^3, and the dimensions shown in Figure 4.2 on Page 36 ?
3) I added "set n 1" before the first line on Page 117. Otherwise there would be error when running OpenSees.
4) I added "integrator LoadControl 0.1" to the analysis objects for gravity loading on Page 117. Otherwise, there would be error.
5) Is the Rayleigh damping specified on Page 118, "rayleigh 0.05 0 0.05 0", correct?
Does that mean to reach 5% damping ratio?
Does Rayleigh damping apply to CIM model as well?
Does CIM model take into account radiation damping in soil half-space?
With the changes (1), (3), (4) above and also the modification of the input arguments of soilFootingSection2d, running of the Tcl script on Page 116-118 in the report
with unscaled WVC270 earthquake record yields unreasonable high-frequency oscillation
in the horizontal sliding behavior (i.e. shear force and horizontal displacement) of the CIM element.
It would be greatly appreciated if you can answer my questions
or just post your input file that gives correct results!
Regards,
Thomas
1) +2).. It seems like a typo. You could compare with the BNWF input file and the description in the chapter.
3) + 4) What you did looks reasonable.
5) This is not 5% damping, check the rayleigh command in the manual. I believe the rayleigh damping should apply to every element in the model. There is no radiation damping internally modeled in soilfootingsection2D.
I didn't make the input file you refer to so I don't have a working file, but I hope you figure it out.
Regarding numerical stability, I have seen sudden/sharp hardening in the moment and shear. Try making $deltaL (the internal footing node spacing) a bit smaller, this should help. You will find this is the biggest factor in computation time, don't make it too small. Also the file you are looking at uses $dtmin=dt/10, I commonly use $dtmin much smaller (e.g <dt/100). This should help you converge at the smaller tolerances in the for loop where the analyze command is given and hopefully avoid the sharp oscillations in response you see now.
Good Luck!
3) + 4) What you did looks reasonable.
5) This is not 5% damping, check the rayleigh command in the manual. I believe the rayleigh damping should apply to every element in the model. There is no radiation damping internally modeled in soilfootingsection2D.
I didn't make the input file you refer to so I don't have a working file, but I hope you figure it out.
Regarding numerical stability, I have seen sudden/sharp hardening in the moment and shear. Try making $deltaL (the internal footing node spacing) a bit smaller, this should help. You will find this is the biggest factor in computation time, don't make it too small. Also the file you are looking at uses $dtmin=dt/10, I commonly use $dtmin much smaller (e.g <dt/100). This should help you converge at the smaller tolerances in the for loop where the analyze command is given and hopefully avoid the sharp oscillations in response you see now.
Good Luck!
-
Thomas_Tang
- Posts: 9
- Joined: Fri Oct 05, 2007 11:46 am
- Location: Simpson Gumpertz & Heger
-
gavindegraw1
- Posts: 1
- Joined: Mon Nov 28, 2011 12:15 am
Re: SSI: Contact Interface Model (CIM)
I guess that kinda decent information, that's really impressive & I wish to hear from you next time soon !
Re:
jaugalde wrote:
> 1) +2).. It seems like a typo. You could compare with the BNWF input file
> and the description in the chapter.
>
> 3) + 4) What you did looks reasonable.
>
> 5) This is not 5% damping, check the rayleigh command in the manual. I
> believe the rayleigh damping should apply to every element in the model.
> There is no radiation damping internally modeled in soilfootingsection2D.
>
> I didn't make the input file you refer to so I don't have a working file,
> but I hope you figure it out.
>
> Regarding numerical stability, I have seen sudden/sharp hardening in the
> moment and shear. Try making $deltaL (the internal footing node spacing) a
> bit smaller, this should help. You will find this is the biggest factor in
> computation time, don't make it too small. Also the file you are looking
> at uses $dtmin=dt/10, I commonly use $dtmin much smaller (e.g <dt/100).
> This should help you converge at the smaller tolerances in the for loop
> where the analyze command is given and hopefully avoid the sharp
> oscillations in response you see now.
>
> Good Luck!
Thank you a lot for sharing your experience!
> 1) +2).. It seems like a typo. You could compare with the BNWF input file
> and the description in the chapter.
>
> 3) + 4) What you did looks reasonable.
>
> 5) This is not 5% damping, check the rayleigh command in the manual. I
> believe the rayleigh damping should apply to every element in the model.
> There is no radiation damping internally modeled in soilfootingsection2D.
>
> I didn't make the input file you refer to so I don't have a working file,
> but I hope you figure it out.
>
> Regarding numerical stability, I have seen sudden/sharp hardening in the
> moment and shear. Try making $deltaL (the internal footing node spacing) a
> bit smaller, this should help. You will find this is the biggest factor in
> computation time, don't make it too small. Also the file you are looking
> at uses $dtmin=dt/10, I commonly use $dtmin much smaller (e.g <dt/100).
> This should help you converge at the smaller tolerances in the for loop
> where the analyze command is given and hopefully avoid the sharp
> oscillations in response you see now.
>
> Good Luck!
Thank you a lot for sharing your experience!