mass eccentricity

[philiplukek]

hi i need to provide mass eccentricity in a symmetric bay frame. i have buit a symmetric bay frame with rigid diaphragm in each floor with the master node at the center. to provide the mass eccentricity, i plan to assign extra nodes at every floors with its position arbitrary and assign masses to these nodes so that the building is mass asymmetric only. but when i try to do that, i get the following error message

WARNING BandGenLinLapackSolver::solve() -LAPACK routine returned 4
WARNING NewtonRaphson::solveCurrentStep() -the LinearSysOfEqn failed in solve()
StaticAnalysis::analyze() - the Algorithm failed at iteration: 0 with domain at load factor 0.1
OpenSees > analyze failed, returned: -3 error flag

i guess the problem might be with my analysis options but cant figure it out. can someone please help me. these are my analysis options


set Tol 1.0e-8;
variable constraintsTypeGravity Plain;
if { [info exists RigidDiaphragm] == 1} {
if {$RigidDiaphragm=="ON"} {
variable constraintsTypeGravity Lagrange;
}; # if rigid diaphragm is on
}; # if rigid diaphragm exists

constraints $constraintsTypeGravity ;
numberer RCM;
system BandGeneral ;
test EnergyIncr $Tol 6 ;
algorithm Newton;
set NstepGravity 10;
set DGravity [expr 1./$NstepGravity];
integrator LoadControl $DGravity;
analysis Static;
analyze $NstepGravity;

[selimgunay]

To provide mass eccentricity, you need to remove the node at the middle of the rigid diaphragm and you need to make the node with eccentricity the master node and assign the floor mass to this node.

[philiplukek]

selimgunay wrote:
> To provide mass eccentricity, you need to remove the node at the middle of
> the rigid diaphragm and you need to make the node with eccentricity the
> master node and assign the floor mass to this node.

Thank You for the reply. i had already tried the same but the results were not satisfactory. What i need to observe is the rotation in plan for the building whenever there is mass eccentricity. But there seems to be no or absolutely negligible rotation for my model under time history loads.

[selimgunay]

Are you checking the gravity analysis results or the time history analysis results? please post your script.

[philiplukek]

selimgunay wrote:
> Are you checking the gravity analysis results or the time history analysis
> results? please post your script.

hii.. i am checking the results for time history analysis. and i rectified the above problem by using GJ instead of 10^10 while defining the tangent for torsion. i guess that is the appropriate formula to use. or am i wrong here ??

I have another doubt as well. can you please help me in clearing it

I am using the same coordinate system as that of the example(X towards right, Y upwards, Z coming out of the screen). In the example the transformation used is

geomTransf $ColTransfType $ColTransfId 0 0 1; #columns
geomTransf Linear $BeamXTransfId 0 0 1; #beams in X direction
geomTransf Linear $BeamZTransfId 1 0 0 ; #beams in Z direction

whereas in the manual ( http://opensees.berkeley.edu/OpenSees/m ... al/237.htm ) it is implied to use

geomTransf $ColTransfType $ColTransfId 0 0 -1; #columns
geomTransf Linear $BeamXTransfId 0 1 0; #beams in X direction
geomTransf Linear $BeamZTransfId 1 0 0 ; #beams in Z direction

Can u help me in understanding which case to use and how.

[selimgunay]

please read the below description for the local axes and let me know if you have questions

"he x-axis is a vector given by the two element nodes; The vector vecxz is a vector the user specifies that must not be parallel to the x-axis. The x-axis along with the vecxz Vector define the xz plane. The local y-axis is defined by taking the cross product of the x-axis vector and the vecxz vector (Vy = Vxz X Vx). The local z-axis is then found simply by taking the cross product of the y-axis and x-axis vectors (Vz = Vx X Vy). The section is attached to the element such that the y-z coordinate system used to specify the section corresponds to the y-z axes of the element."

http://opensees.berkeley.edu/wiki/index ... sformation