Bond slip behaviour and *CONSTRAINED_BEAM_IN_SOLID

[Nava Farhadzadeh]

H James/Len

Just wondering in a two-storey frame model that is subjected to seismic motions in LS-DYNA, can we ignore steel-concrete bond-slip behaviour when we use the *CONSTRAINED_BEAM_IN_SOLID command?

This command assumes a perfect bond between steel bars and concrete, would you steel consider bond-slip behaviour?

Kind regards

[James M. Kennedy]

Dear Nava,

 

Please see *CONSTRAINED_BEAM_IN_SOLID entry which has bond-slip behaviour (axial

coupling force)

 

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

 

Examples are provided near the end of the data entry discussion.

 

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

 

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

 

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

Sincerely,

James M. Kennedy

KBS2 Inc.

September 7, 2021

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[Nava Farhadzadeh]

Hi James/Len

Following your guidance on my previous question on including bond-slip in * CONSTRAINED_BEAM_IN_SOLID formulation and the papers you forwarded to me, I'm facing some issues when I include bond-slip in my model. I have a two storey frame subject to seismic motions and I have defined the reinforcement bars using *SECTION_BEAM and *CONSTRAINED_BEAM_IN_SOLID. I have dynamic relaxation to apply gravity to my model before the actual earthquake starts. I have taken the following from a thesis and also CEB FIP code guidance:

*CONSTRAINED_BEAM_IN_SOLID
$   SLAVE    MASTER    SSTYP    MSTYP   empty(unused)empty (unused) NCOUP   CDIR
         8        17         1         1                                       1
$      START     END   ?(jay khalip-chera?)   axfor
         0         0          0       -10
---------------------------------------------------------------------------------------------

Then I have defined the user-defined function as follow:

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

*DEFINE_FUNCTION
 10
float force(float slip,float leng)
{
float force,pi,d,area,shear,pf,s1,s2,s3,tmax,tf;
pi = 3.1415926;
d = 0.014;
s1 = 0.6e-2;
tmax = 4472;
area = pi*d*leng;
if(slip < s1) {
shear = tmax*(slip/s1)**0.4;
} else{
shear = tmax;
}
force = shear*area;
return force;
}
$

(((((My units are in Kg, N,m and second and shear stress is N/m^2)))

I should mention that I have added the bond-slip to the longitudinal bars only which are anchored in the frame joints/connections. I am not sure if I should add bond-slip for the shear links as well?

The main problem is as the program starts to run and as it goes through the cycle of dynamic relaxation, it says elements fail (photo attached) and my model produces a lot of d3drlf files and it doesn't get to produce any d3plots. I am not sure what could be the reason as I have changed the shear stress (increased or decreased just to see the effect) also I have changed the "s" value to 1mm instead of 0.6mm (CEB FIP recommendations). I am wondering if you have some advice/experience on dealing with this problem? Also, do we include bond-slip for shear links as well?

Your help is very much appreciated.

Kind regards

Nava