the connection of two continuous elements

[borjiajia]

There are two continuous reinforced concrete elements,each length is L . Is the longitudinal bar in the section two disconnected bars length of L. or a integral bar length of 2L ?
In other words, is the bar disconnected in two different elements ?

If it is not a integral bar ,how to connect them like a bar?
################################################


Maybe you think my question is weird. Here is the reason:
I modeled a simply supported beam with two elements and three nodes. I need to apply a concentrated force on the mid node.
But after I applying the gravity, I found the deformation was so big. What's more, it didn't move at all when it was applied the concentrated force.
Therefore, I guess the steel bar is not a integral 2L bar.

Or does it mean my model is wrong? The bar would not be broken by a node?

[vesna]

How did you define the steel bars?

[borjiajia]

vesna wrote:
> How did you define the steel bars?
========================================================================

I define the steel bar as fiber.I wonder if the node 3 break the steel bar into two bars.
the element and section codes are follows:

#----------------------------------
element nonlinearBeamColumn 11 1 3 5 17 $IDBeamTransf;
element nonlinearBeamColumn 12 3 5 5 17 $IDBeamTransf;

section fiberSec 17 {
# Define the core patch
patch quadr $IDconcCoreC70 10 1 -0.208 0.058 -0.208 -0.058 0.208 -0.058 0.208 0.058;
patch quadr $IDconcCoverC70 1 10 -0.25 0.10 -0.208 0.058 0.208 0.058 0.25 0.10;#左侧那块
patch quadr $IDconcCoverC70 1 10 -0.208 -0.058 -0.25 -0.10 0.25 -0.10 0.208 -0.058;#右侧那块
patch quadr $IDconcCoverC70 1 2 -0.25 0.10 -0.25 -0.10 -0.208 -0.058 -0.208 0.058;#下侧那块
patch quadr $IDconcCoverC70 1 2 0.208 0.058 0.208 -0.058 0.25 -0.10 0.25 0.10;#上侧那块
layer straight $IDSteelHRB400 2 $barArea25 0.208 0.058 0.208 -0.058;
layer straight $IDSteelHRB400 2 $barArea25 -0.208 0.058 -0.208 -0.058;
};

#---------------------------------

[borjiajia]

And no offense, I especially want to know when you are on this forum to answer the questions every day generally.
I eagerly expect to communicate with you as you are online. Because I have a time lag of 16 hours with you. Every time it takes me a whole day to solve a question. And it is far from enough to my progress.
I want to fix my model as soon as possible.

If it is convenient, could you please tell me when you are here in your time zone? Thank you.

[vesna]

That should be fine then. The node does not break the bar. It is continuous, no matter how many nodes you have in between.

I check the message board sporadically during the day. First time I check it in the morning (my time) between 8 and 12.

[borjiajia]

==========================================================================================

OK, if the bar is not broken by node, what other may the reason be for the large deformation ?
I do think the result makes no sense. the gravity I applied is distributed along the whole beam element, but the deformation after it is shape of "V". And what's more then, the deformation remain precisely same when applying the concentrated force.

Maybe the process of applying loads have problem? I will be waiting on line at 11 (your time) .
Here is the codes of applying loads:

#--------------------------gravity load-------------------
set P1 -300e3;
set p1 -2.6e3;

pattern Plain 101 Linear {
eleLoad -ele 11 12 -type -beamUniform $p1;
}
set Tol 1.0e-8;
variable constraintsTypeGravity Plain;
if { [info exists RigidDiaphragm] == 1} {
if {$RigidDiaphragm=="ON"} {
variable constraintsTypeGravity Lagrange;
}; };
constraints $constraintsTypeGravity ;
numberer RCM;
system BandGeneral ;
test NormDispIncr $Tol 6 ;
algorithm Newton;
set NstepGravity 10;
set DGravity [expr 1./$NstepGravity];
integrator LoadControl $DGravity;

analysis Static;
analyze $NstepGravity;

#------------------------the concentrated force--------------

set Dmax [expr 0.3*$m ];
set Dincr [expr 0.001*$m ];
set IDctrlNode 3;
set IDctrlDOF 1;

pattern Plain 102 Linear {
load 3 0.0 $P1 0.0;

}

constraints Plain;
numberer RCM;
system BandGeneral;
test NormUnbalance 1.0e-6 400;
algorithm Newton;
integrator DisplacementControl $IDctrlNode $IDctrlDOF $Dincr;
analysis Static;
set Nsteps [expr int($Dmax/$Dincr)];
set ok [analyze $Nsteps];
puts "Pushover complete";
#---------------------------------------------------------------------------

[vesna]

Both load definitions look fine to me.

Are you using display command to see the deformation of your element?

What do you mean by this: "the deformation remain precisely same when applying the concentrated force"?

[borjiajia]

Yes ,It has display command and by which ,I know it is V shape after applied gravity. _________________ It means the element does not move at all !

[borjiajia]

You must go to lunch...ok, I will go back to my sleep ...

[vesna]

The display command is not very precise in displaying a deformed shape. Having a displacements at two nodes it connects it with a linear line. That is why you see it as a "V" (assuming that your beam has tree nodes).

Do you have this line in your code between the two gravity and pushover analysis:

loadConst -time 0.0.

If you did not have it add it and see if it is going to help.

[borjiajia]

===================
Thank you very much for coming back...
In my opinion, Since the middle node did not break the bar into two parts, Since the gravity I applied is distributed, then the deformation should be a curve not a "V", isn't it?

I have had the line you referred...It didnot help.

There are still two problems:
one is the shape after gravity is "V",
one is the result after the concentrated force is as follows, which means analyze failed.

#------------------------------------------------------------------------------------------------
WARNING - ForceBeamColumn2d::update - failed to get compatible element forces &
deformations for element: 11(dW: << 27.5952)
WARNING - ForceBeamColumn2d::update - failed to get compatible element forces &
deformations for element: 12(dW: << 0.000499223)
Domain::update - domain failed in update
DisplacementControl::update - model failed to update for new dU
WARNING NewtonRaphson::solveCurrentStep() -the Integrator failed in update()
StaticAnalysis::analyze() - the Algorithm failed at iteration: 0 with domain at
load factor 5.91644e+014
OpenSees > analyze failed, returned: -3 error flag
Pushover complete
#--------------------------------------------------------------------------------------------------

[borjiajia]

I am very confused with my code. I have examined my model like node, section, element, load, all those seem ok, What could the reason be?
I have read the code in the example.chm about the canti2d column. I thought since it is suiItable for canti column,in theory, it must be ok with simply supported beam. However, my model didn't work out properly.
I have seen a few example about the cantilever beam and simply supported beam in your website, unfornately which are not suitable for reinforced concrete material.
I really don't know how to solve this...Please help me!
Waiting online about 11 o'clock...

[vesna]

In my earlier message I explained a reason for a "V" shape of your deformed shape. It is not about your model it is about the display command (read my earlier message again).

The warning message indicates the problem with your model. If you want you can post your model and I'll take a look.

[borjiajia]

ok, I have sent my codes as a email to you. Thank you for checking up for me.

[vesna]

your section is defined in a clockwise direction while it has to be defined in the counter clockwise direction (http://opensees.berkeley.edu/wiki/index ... ch_Command). try changing it and see if it is going to help.