Problem with Single-Point Constraint Load Pattern

[JiaweiChenKodomo]

Dear Dr. Zhu, I tried to apply a displacement pattern to one node using the single-point constraint sp(nodeTag, dof, dofValues) command. However, the output I got using the nodeDisp() and the eleForce() commands were all zeros. When I applied a load using the load(nodeTag, loadValues) command, I got what seemed to be a correct result. What is wrong with my use of the single-point constraint command? Thank you so much!

Here is the model:

import sys sys.path.append('E:/OpenseesFile/openseespy/win') from opensees import * import numpy as np import matplotlib.pyplot as plt

# ------------------------------ # Start of model generation # -----------------------------

# set modelbuilder wipe() model('basic', '-ndm', 2, '-ndf', 2)

# variables A = 1.0 Nsteps = 1000 Px = 400.0 Py = 0.0

#material fy=300.0 E0=200000.0 b=0.05 R0=10.0 cR1=0.925 cR2=0.15 params=[R0,cR1,cR2]

# create nodes node(1, 0.0, 1.0) node(2, 1.0, 0.0) node(3, 1.0, 1.0)

# set boundary condition fix(1, 1, 1) fix(2, 1, 1)

# define materials uniaxialMaterial("Steel02", 1, fy, E0, b, *params)

# define elements element("Truss",1,1,3,A,1) element("Truss",2,2,3,A,1)

# create TimeSeries timeSeries("Linear", 1)

# create a plain load pattern pattern("Plain", 1, 1)

# Create the nodal load #load(3, Px, Py) u_ref=1.0 sp(3, 1, u_ref)

# ------------------------------ # Start of analysis generation # ------------------------------

# create SOE system("ProfileSPD")

# create DOF number numberer("Plain")

# create constraint handler constraints("Plain")

# create integrator integrator("LoadControl", 1.0/Nsteps)

# create algorithm algorithm("Newton")

# create test test('NormUnbalance',1e-8, 10)

# create analysis object analysis("Static")

# ------------------------------ # Finally perform the analysis # ------------------------------

# perform the analysis data = np.zeros((Nsteps+1,2)) for j in range(Nsteps): analyze(1) data[j+1,0] = nodeDisp(3,1) data[j+1,1] =-eleForce(1,1)

plt.plot(data[:,0], data[:,1]) plt.xlabel('Horizontal Displacement') plt.ylabel('Horizontal Load') plt.show()

[zhuminjie]

I will take a look. Thank you!

[zhuminjie]

Please try a transformation constraint handler

constraints("Transformation")

the plain handler not work for non-homogeneous constraints

[JiaweiChenKodomo]

Thank you. That solves the problem.