multiple support error non-homogenous constraint

[rwood]

I am running a 5-story modeling and interested in obtaining absolute displacement time histories. After changing my working script with the uniform excitation, the multiplesupport command keeps providing the following error.

"Warning PlainHandler::handler<> - non-homogenous constrain for node 1 homo assumed" and similarly, ""Warning PlainHandler::handler<> - non-homogenous constrain for node 2 homo assumed".

I have integrated my accel data and now input displacement to opensees and I did release the DOF at the fixed bases for the imposed motion histories...but still it will not run correctly.

Please help, see script excerpt below, thanks!

Ricky






# Single point constraints -- Boundary Conditions ---------------------------------------------
fix 1 0 1 1; # node DX DY RZ (node 1), release dir 1 for ms support command
fix 2 0 1 1; # fixing node 2 as well


# Define ELEMENTS --------------------------------------------------------------------------------
geomTransf Linear 1;

# define GRAVITY ---------------------------------------------------------------------------------------------------------
pattern Plain 1 Linear {
eleLoad -ele 11 12 13 14 15 -type -beamUniform -0.232
}
constraints Plain;
numberer Plain;
system BandGeneral;
test NormDispIncr 1.0e-8 6 ;
algorithm Newton;
integrator LoadControl 0.1;
analysis Static
analyze 10;
loadConst -time 0.0;

# DYNAMIC ground-motion analysis -------------------------------------------------------------------------------------------
set DispSeries "Series -dt 0.02 -filePath north_disp.txt -factor 1";
#displacement TH is in units of inches
set Npoints 2500;

pattern MultipleSupport 2 {
groundMotion 2 Plain -disp $DispSeries
groundMotion 3 Plain -disp $DispSeries
imposedMotion 1 1 2
imposedMotion 2 1 3
}


# create the analysis--------------------------------------------------------------------------------------------------------
constraints Plain;
numberer Plain;
system BandGeneral;
test NormDispIncr 1.0e-8 10;
algorithm Newton;
integrator Newmark 0.5 0.25 ;
analysis Transient;
analyze $Npoints 0.02;

[silvia]

you know, i typically keep the 1 there, try it, afterall, you are imposing a constraint.
how does your script compare with the example manual.

also, be careful when you integrate accelerations into displacements there is some shift you have to adjust for.

[rwood]

Thanks Silvia for your reply.

The additional shift in the displacement, as you pointed out, is is a result of the initial conditions.

When I place the "1" there in the fix command (fix 1 1 1 1), I get an additional error, but correct dynamic properties of my structure (fund periods). And I followed your example, Ex8.genericFrame3D.analyze.Dynamic.EQ.multipleSupport.tcl.

The prompt is: "Multiple single point constraints at DOF 0 for node 1 (and latter node 2)".

And I do not know how to correct for this, thanks for your help!

Ricky

[silvia]

please send me your files opensees-support at berkeley dot edu.
yes, you should check the dynamic properties using the fixed bc.
s-

[silvia]

When you are imposing non-homogeneous boundary conditions (homogeneous: u=0), such as multiple-support excitation, you cannot use the plain constraint handler. i recommend you use the transformation handler, it works for your files. -- see the manual for these details.