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Dear fmk,
is it possible to get modal mass participation ratios after an eigen analysis?

Thank you so much for your kind response

Thankyou for your kind response, i actually start to get positive values on the 3rd time step and i think that's elastic too because cracking doesn't start that early stage....so the possibility seems to be the gravity analysis as you have pointed out.... but why would there be negative shear due to gravity analysis?

one more question please, if i apply monotonically increasing lateral loads on my infilled frame and at every time step extract the result for shear in cols, what i am getting is a slight negative values on the first time step ( which is the elastic shears) and later as the load increase they become positive and start to increase until the infill breaks....why is there a negative shear profile initially?

no it is not.....

thanks for your response, but this explanation is acceptable for bottom story as also verified by my calculations where the total force at col base plus the horizontal component of the axial force in strut adds up to total base shear... but again what about the upper stories where the forces from strut are eventually transferred to the columns, shouldn't the sum of column shears there be equivalent to the applied nodal force.. if yes it isnt coming out to be this way... and that is what make me perplexed....

Define cross-section for nonlinear beam
# ------------------------------------------

# set some paramaters
set BeamWidth 150
set BeamDepth 600

set cover 40

set As 113.1; # area of 12mm bars

# some variables derived from the parameters
set y2 [expr $BeamDepth/2.0]
set z2 [expr $BeamWidth/2.0]

section Fiber 2 {

# Create the concrete core fibers
patch rect 4 10 1 [expr $cover-$y1] [expr $cover-$z1] [expr $y1-$cover] [expr $z1-$cover]

# Create the concrete cover fibers (top, bottom, left, right)
patch rect 2 10 1 [expr -$y2] [expr $z2-$cover] $y2 $z2
patch rect 2 10 1 [expr -$y2] [expr -$z2] $y2 [expr $cover-$z2]
patch rect 2 2 1 [expr -$y2] [expr $cover-$z2] [expr $cover-$y2] [expr $z2-$cover]
patch rect 2 2 1 [expr $y2-$cover] [expr $cover-$z2] $y2 [expr $z2-$cover]

# Create the reinforcing fibers (left, middle, right)
layer straight 3 3 $As [expr $y2-$cover] [expr $z2-$cover] [expr $y2-$cover] [expr $cover-$z2]
layer straight 3 3 $As [expr $cover-$y2] [expr $z2-$cover] [expr $cover-$y2] [expr $cover-$z2]

}

# Define ELEMENTS -------------------------------------------------------------
# define geometric transformation: performs a linear geometric transformation of beam stiffness and resisting force from the basic system to the global-coordinate system
geomTransf PDelta 1; # associate a tag to transformation

# Create the coulumns using Beam-column elements
# connectivity:
element nonlinearBeamColumn 101 11 12 5 $ColSecTag 1
element nonlinearBeamColumn 201 21 22 5 $ColSecTag 1
# Geometry of beam elements
# tag
geomTransf PDelta 2

# Create the beam element
element nonlinearBeamColumn 1001 12 22 5 $BeamSecTag 2

# Define infill element.

# tag ndI ndJ A mattag
element truss 10 21 12 73620.9 5
element truss 11 11 22 73620.9 5

set LCol $height
set LBeam $width

recorder Node -file Storey1(infill-PUSHOVER)/FrameDFree(RC).out -time -node 12 22 -dof 1 2 3 disp; # displacements of free nodes
recorder Node -file Storey1(infill-PUSHOVER)/FrameRnodes(RC).out -time -node 11 21 12 22 -dof 1 reaction; # displacements of support nodes
recorder Node -file Storey1(infill-PUSHOVER)/FrameRBase(RC).out -time -node 11 21 -dof 1 2 3 reaction; # support reaction
recorder Drift -file Storey1(infill-PUSHOVER)/FrameDrift(RC).out -time -iNode 21 -jNode 22 -dof 1 -perpDirn 2 ; # lateral drift
recorder Element -xml Storey1(infill-PUSHOVER)/eleGlobal.out -time -ele 10 12 localForce
recorder Element -xml Storey1(infill-PUSHOVER)/colstress5.out -time -ele 101 201 section 5 fiber -185 0 stressStrain
recorder Element -xml Storey1(infill-PUSHOVER)/colstress1(-185,0).out -time -ele 101 201 section 1 fiber -185 0 stressStrain
recorder Element -xml Storey1(infill-PUSHOVER)/colstress(225,0).out -time -ele 101 201 section 1 fiber 225 0 stressStrain
recorder Element -xml Storey1(infill-PUSHOVER)/trusses.out -time -ele 10 basicDeformation
recorder Element -xml Storey1(infill-PUSHOVER)/beamstress1.out -time -ele 1001 section 1 fiber -260 0 stressStrain
recorder Element -xml Storey1(infill-PUSHOVER)/colbeamforces.out -time -ele 101 201 1001 localForce

Dear all i am modelling an infilled rc frame using a truss for infill... im doing pushover analysis....when i compare my local forces for columns the sum of total shear force in the column base does not come equal to total base shear.......but if sum shear forces at the base of columns for bare frame at a given timestep they come exactly equal to the total reactions at the support....can somebody explain me why is that so and how do i get story shears for my frames?

I am getting it from the element

hello everybody,
I am a little perplexed with the results of my pushover..if at a same time step i check my shear forces at the base of col for a single story one bay rc infilled frame... they come out to be colv1=31.16kn and colv2=45.48kn whereas if i extract results at the nodes for base shear it gives me r1x=-31.89 and r2x= -203.669kn ......y is this happening?

DEAR ALL,
As i do pushover analysis of a single story one bay RC frame, if for the lateral load i apply a force of 10N the pushover for the frame is different as compared to a 1 mm reference displacement applied at the same node using sp command...also both the analysis are displacement controlled to a max of 500mm displacement value.....Please help me understand the difference
the result is attached below;
https://drive.google.com/open?id=0BxvVI ... 2pWMktLeEk

Dear all,
i am trying to do pushover analysis for a seven story rc frame using truss element as an infill.....but the results im getting doesnt show that the infills break...although for lower story frames the infills break and then the frame act as a bare frame....even if i compare my results with other software the pushover shows a decending branch after infill breaks and acts as a bare frame.....please can anybody tell me why is this happening?

Dear fmk,
i want to run dynamic analysis on a structure such that scaling factor changes automatically and analysis runs again and again until all ground motions are done and their outputs saved in respective files....is that possible? how ? can someone share with me any related script...

Thankyou....

here's a pic to explain the problem better....
https://drive.google.com/open?id=0BxvVI ... Wd3UDJ5M00

Dear all,
i am trying to do pushover analysis in opensees of a one bay one storey RC frame... i have done a similar analysis using seismostruct.....the pushover that i get has a stiffer pre-cracking branch n then a slightly lower stiffness branch which is prudent....similarly when i am doing pushover in OpenSees, i cannot find the initial stiffer branch no matter how small displacement increment i input......both the softwares give me identical pushovers otherwise...even initial time periods are the same implying that initial stiffness calculated by both the softwares shall match.....please guide me how shall i perform pushover in OpenSees that i do not miss the initial stiffer branch of pushover curve......

Thanx....