Constrained Beam-in-Solid

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Somayeh Mollaei

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Apr 14, 2021, 1:37:27 PM4/14/21
to LS-DYNA2

Hi,
I urgently need an example of defining steel rebars bonded to concrete solid elements using Constrained_Beam_in_Solid keyword. 
I'm trying to model a reinforced concrete structure under blast loading with eigenvalue extraction; So  Constrained_Lagrange_in_Solid keyword does not work properly for me. 
   

James M. Kennedy

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Apr 14, 2021, 2:03:51 PM4/14/21
to Somayeh Mollaei, LS-DYNA2

Dear Somayeh,

 

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You might look at these features:

 

http://lsdyna-china.com/u/b1101b1e-707e-4983-9f64-894861bc37ab/file/637092603974782368.pdf

 

https://ftp.lstc.com/anonymous/outgoing/hao/cbis/manuals/CONSTRAINED_SOLID_IN_SOLID.pdf

 

https://ftp.lstc.com/anonymous/outgoing/hao/cbis/manuals/CONSTRAINED_BEAM_IN_SOLID.pdf

 

https://ftp.lstc.com/anonymous/outgoing/hao/cbis/

 

http://lsdyna.com.cn/2017conf/document/2017_Session_Chenhao02.pdf

 

Chen, H., “An Introduction to *CONSTRAINED_BEAM_IN_SOLID”, FEA Information Solutions, Vol. 5, Issue 10. pp. 79-83, October, 2016.

 

http://www.feaiej.com/2017/feaiej_q1_2017.pdf

 

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A short note that might be of interest:

 

Moharrami, M., Chen, H., and Koutromanos, Y., “Accounting for Bond-Slip Effect in

LS-DYNA using Constrained Beam in Solid Formulation”, June, 2016.

 

https://ftp.lstc.com/anonymous/outgoing/hao/cbis/tutorials/presentation-Hao-Bond_slip.pdf

 

The assumption of a perfect-bond between concrete and steel was the first bond interaction

system studied, utilizing the *CONSTRAINED_LAGRANGE_IN_SOLID formulation. 

Beam bond was another bond interaction system investigated using the *CONSTRAINED_

BEAM_IN_SOLID formulation in the program:

 

Iwalekar, A.A., "Finite Element Analysis and Experimental Validation of Reinforced Concrete

Single-Mat Slabs Subjected to Blast Loads", Master’s Thesis, Department of Civil and Mechanical

Engineering University of Missouri-Kansas City, Kansas City, Missouri, 2018.

 

https://mospace.umsystem.edu/xmlui/bitstream/handle/10355/67037/Thesis_2018_Iwalekar.pdf

 

The *CONSTRAINED_BEAM_IN_SOLID keyword addressed both perfect bond and

bond-slip interaction:

 

Lockhart, E., "Modelling the Failure of Reinforced Concrete Subjected to Dynamic

Loading Using CDPM2 in LS-DYNA", Senior Project, School of Engineering, University

of Glasgow, United Kingdom, January, 2017.

 

https://petergrassl.com/tempFiles/Loc17.pdf

 

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Examples of rebar coupled to concrete (*clis and *cbis) are given here:

http://ftp.lstc.com/anonymous/outgoing/support/FAQ_kw/concrete/coupling_by_clis.k.gz and

http://ftp.lstc.com/anonymous/outgoing/support/FAQ_kw/concrete/coupling_by_cbis.k.gz

 

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Sincerely,

James M. Kennedy

KBS2 Inc.

April 14, 2021

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axial_strain_rebar_cbis.jpg
axial_stress_rebar_cbis.jpg

Somayeh Mollaei

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Apr 15, 2021, 1:54:27 PM4/15/21
to LS-DYNA2
Dear  Jame,
Thank you very much on the wonderful references suggested above. They were really useful.

As I mentioned, I'm trying to model a RC structure under blast loading with eigenvalue extraction;
I was wondering if you have any examples of Eigenvalue extraction during an Explicit analysis (i.e.  explicit with intermittent eigenvalue extraction )

Thanks for your consideration

James M. Kennedy

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Apr 15, 2021, 2:20:14 PM4/15/21
to Somayeh Mollaei, LS-DYNA2

Dear Somayeh,

 

Please see if the intermittent eigenvalue analysis is of some help.

 

From the LS-DYNA User’s Manual:

 

http://ftp.lstc.com/anonymous/outgoing/jday/manuals/DRAFT_Vol_I.pdf

 

*CONTROL_IMPLICIT_EIGENVALUE

 

Remarks:

 

1. Performing Eigenvalue Analysis. To perform an eigenvalue analysis, activate

the implicit method by selecting IMFLAG = 1 on *CONTROL_IMPLICIT_-

GENERAL, and indicate a nonzero value for NEIG above. By default, the lowest

NEIG eigenvalues will be found. If a nonzero center frequency is specified, the

NEIG eigenvalues nearest to CENTER will be found.

 

When NEIG > 0, eigenvalues will be computed at time = 0 and LS-DYNA will

terminate.

 

When NEIG < 0, an intermittent eigenvalue analysis will be performed. This is a

transient simulation during which loads are applied, with eigenvalues computed

periodically during the simulation. Changes in geometry, stress, material, and

contact conditions will affect the eigenvalues. The transient simulation can be

either implicit or explicit according to IMFLAG = 1 or IMFLAG = 6, respectively,

on *CONTROL_IMPLICIT_GENERAL. The curve ID = -NEIG indicates when

to extract eigenvalues, and how many to extract. Define one curve point at each

desired extraction time, with a function value equal to the number of eigenvalues

desired at that time. A d3plot database will be produced for the transient solution

results. Consecutively numbered d3eigv and eigout databases will be produced

for each intermittent extraction. The extraction time is indicated in each database’s

analysis title.

 

Sincerely,

James M. Kennedy

KBS2 Inc.

April 15, 2021

James M. Kennedy

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Apr 15, 2021, 2:26:43 PM4/15/21
to Somayeh Mollaei, LS-DYNA2

Dear Somayeh,

 

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http://www.d3view.com/dynamic-solution-type-using-imflag-in-control_implicit_general/

 

3. Intermittent Eigenvalue Extration, IMFLAG = 6.

 

For IMFLAG=6, LS-DYNA uses Explicit and allows the extraction of eigenvalues

intermittently throughout the simulation. To define the times at which the eigenvalue

extraction is performed, the parameter NEIGV in *CONTROL_IMPLICIT_

EIGENVALUE must be set to a negative number. The absolute value of NEIGV

then refers to a load curve ID (see LCID in *DEFINE_CURVE) which allows the

user to define the number of eigenvalues as a function of simulation time. It should

be noted that the abscissa axis refers to time that can be either pseudo or transient

beginning in LS-DYNA version 971R3 allowing users to extract eigenvalues even

in the dynamic relaxation phase. Negative abscissa values correspond to pseudo time,

and positive values correspond to the transient portion of the simulation. It is also

important to note that a user can extract intermittent eigenvalues during the Implicit

solution by setting IMFLAG=1 and using a negative value for NEIGV. In versions

prior to 971R3, the abscissa points were not treated as key-points such that the

Implicit timestep is automatically adjusted to meet the time specified in NEIGV

curve. For example, if DT0=0.2 and the current converged step is at 1.0 seconds,

then an abscissa point in NEIGV of 1.1 will be skipped without any eigenvalue

extraction. To force the implicit solver to auto-adjust the timestep such that the

abscissa time point in NEIGV is met, it is recommended that the parameter DTMAX

in *CONTROL_IMPLICIT_AUTO is used. However, in versions 971R3 and higher,

the points specified in NEIGV will be treated as key points and the solver will auto-

adjust the timestep to solve at the points and extract the eigenvalues. A sample curve

for intermittent eigenvalue extraction using NEIGV is shown in the following figure:

 

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As I understand it, there is no special theory for intermittent eigenvalue analysis.

It is basically using the theory of general eigenvalue analysis. Perhaps the following

report might offer some help:

 

Chowdhury, M.R., and Tabiei, A., "Development of an Air Gun Simulation Model

Using LS-DYNA", Report ARL-TR-3016, U.S. Army Research Laboratory,

Aberdeen Proving Grounds, Maryland, July, 2003.

 

http://www.arl.army.mil/arlreports/2003/ARL-TR-3016.pdf

 

2.2.6 Intermittent Eigenvalues Analysis

 

To understand the frequency content in this simulation, an intermittent eigenvalue

analysis is conducted. The LS-DYNA code allows for the extraction of frequency

contents during an impact simulation. This is performed to relate the frequency

content to the event and deformation mode in the OBR. The FFT of the unfiltered

acceleration of the OBR is depicted in figure 36. One can see several important

peaks in the data. The largest peak corresponds to the first fundamental mode. The

next peak is at about 7400 Hz. The next ones are at about 8000, 14600, 21000, 23800,

27700, and 29500 Hz. The intermittent eigenvalue analysis revealed the sources of

these frequencies. One hundred modes were extracted from the analysis.

 

-------------------------------------------------

 

Sincerely,

James M. Kennedy

KBS2 Inc.

April 15, 2021

Sincerely,

James M. Kennedy

KBS2 Inc.

April 15, 2021

James M. Kennedy

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Apr 15, 2021, 3:00:15 PM4/15/21
to Somayeh Mollaei, LS-DYNA2

Dear Somayeh,

 

Several presentations perhaps of interest:

 

Li, L., and Grimes, R., "Introduction of Rotor Dynamics Using Implicit Method

in LS-DYNA", 13th International LS-DYNA Users Conference, Dearborn, Michigan,

June, 2014.

 

http://www.dynalook.com/13th-international-ls-dyna-conference/aerospace/introduction-of-rotor-dynamics-using-implicit-method-in-ls-dyna-r

 

Li, L., Grimes, R., and Borrvall, T. "Introduction of Rotor Dynamics Using Implicit

Method in LS-DYNA", 14th International LS-DYNA Users Conference, Dearborn, Michigan,

June, 2016.

 

https://www.dynalook.com/conferences/14th-international-ls-dyna-conference/simulation/introduction-of-rotor-dynamics-using-implicit-method-in-ls-dyna-r

 

Sincerely,

James M. Kennedy

KBS2 Inc.

April 15, 2021

 

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