# 14.8.1. Simple cantilever for load-controlled sensitivity analysisÂ¶

1. The source code is developed by Marin GrubiÅ¡iÄ‡ at University of Osijek, Croatia.

2. The numerical model with the associated analysis was described in detail by Prof. Michael Scott within OpenSees Days 2011.

3. The source code is shown below, which can be downloaded here.

4. Run the source code in your favorite Python program and should see following plot.

  1"""
2- The source code is developed by Marin GrubiÅ¡iÄ‡ https://github.com/mgrubisic
3  at University of Osijek, Croatia.
4- The numerical model with the associated analysis was described in detail by
5  Prof. Michael Scott within OpenSees Days 2011
6  https://opensees.berkeley.edu/OpenSees/workshops/OpenSeesDays2011/B5_MHS.pdf
7- Run the source code in your favorite Python program and should see following plot.
8"""
9
10import time
11import sys
12import numpy as np
13import matplotlib.pyplot as plt
14import openseespy.opensees as ops
15
16# +===============================================================================+
18# +===============================================================================+
19nSpaces = 90
22                  "header_02": "OpenSees -- Open System For Earthquake Engineering Simulation",
23                  "header_03": "Pacific Earthquake Engineering Research Center (PEER)",
24                  "header_04": "OpenSees " + ops.version() + " 64-Bit",
25                  "header_05": "Python " + sys.version,
27                  "header_07": "(c) Copyright 1999-2021 The Regents of the University of California",
32                  }
35
36
37def title(title="Title Example", nSpaces=nSpaces):
38    header = (nSpaces-2) * "-"
39    print("+" + header.center((nSpaces-2), " ") + "+")
40    print("|" + title.center((nSpaces-2), " ") + "|")
41    print("+" + header.center((nSpaces-2), " ") + "+")
42
43
44# +===============================================================================+
45# |                                   Units                                       |
46# +===============================================================================+
47m, kN, sec = 1.0, 1.0, 1.0  # meter for length, kilonewton for force, second for time
48
49# Angle
52
53# Length, Area, Volume, Second moment of area
54m2, m3, m4 = m**2, m**3, m**4
55cm, cm2, cm3, cm4 = m*1E-2, m*1E-4, m*1E-6, m*1E-8
56mm, mm2, mm3, mm4 = m*1E-3, m*1E-6, m*1E-9, m*1E-12
57inch = 0.0254*m
58ft = 0.3048*m
59
60# Force
61N = kN*1E-3
62g = 9.80665*m/(sec**2)
63
64# Mass
65kg = N*sec**2/m
66ton = kg*1E3
67lbs = 0.45359237*kg
68kip = 453.59237*kg
69
70# Pressure
71Pa, kPa, MPa, GPa = N/m**2, 1E3*N/m**2, 1E6*N/m**2, 1E9*N/m**2
72pcf = lbs/(ft**3)
73ksi = kip/(inch**2)
74psi = ksi/1E3
75
76Inf = 1.0E12  # a really large number
77Null = 1/Inf  # a really small number
78
79LunitTXT = "m"  # (Length) define basic-unit text for output
80FunitTXT = "kN"  # (Force) define basic-unit text for output
81TunitTXT = "seconds"  # (Time) define basic-unit text for output
82
83# +===============================================================================+
84# |                            Define some functions                              |
85# +===============================================================================+
86
87
88def run_sensitivity_analysis(ctrlNode, dof, baseNode, SensParam, steps=500, IOflag=False):
89    """
91    """
92    ops.wipeAnalysis()
93    start_time = time.time()
94
95    title("Running Load-Control Sensitivity Analysis ...")
96
97    ops.system("BandGeneral")
98    ops.numberer("RCM")
99    ops.constraints("Transformation")
100    ops.test("NormDispIncr", 1.0E-12, 10, 3)
101    ops.algorithm("Newton")  # KrylovNewton
103    ops.analysis("Static")
104    ops.sensitivityAlgorithm("-computeAtEachStep")  # automatically compute sensitivity at the end of each step
105
106    outputs = {"time": np.array([]),
107               "disp": np.array([]),
108               "force": np.array([]),
109               }
110
111    for sens in SensParam:
112        outputs[f"sensDisp_{sens}"] = np.array([]),
113
114    for i in range(steps):
115        ops.reactions()
116        if IOflag:
117            print(
118                f"Single Cycle Response: Step #{i}, Node #{ctrlNode}: {ops.nodeDisp(ctrlNode, dof):.3f} {LunitTXT} / {-ops.nodeReaction(baseNode, dof):.2f} {FunitTXT}.")
119        ops.analyze(1)
120        tCurrent = ops.getTime()
121
122        outputs["time"] = np.append(outputs["time"], tCurrent)
123        outputs["disp"] = np.append(outputs["disp"], ops.nodeDisp(ctrlNode, dof))
124        outputs["force"] = np.append(outputs["force"], -ops.nodeReaction(baseNode, dof))
125
126        for sens in SensParam:
127            # sensDisp(patternTag, paramTag)
128            outputs[f"sensDisp_{sens}"] = np.append(outputs[f"sensDisp_{sens}"], ops.sensNodeDisp(ctrlNode, dof, sens))
129
130    title("Sensitvity Analysis Completed!")
131    print(f"Analysis elapsed time is {(time.time() - start_time):.3f} seconds.\n")
132
133    return outputs
134
135
136# +===============================================================================+
137# |                                Define model                                   |
138# +===============================================================================+
139# Create ModelBuilder
140# -------------------
141ops.wipe()
142ops.model("basic", "-ndm", 2, "-ndf", 3)
143
144# Create nodes
145# ------------
146L = 5*m
147ops.node(1, 0.0, 0.0)  # Fixed end
148ops.node(2, L, 0.0)  # Free end
149
150# Fixed support
151# -------------
152ops.fix(1, 1, 1, 1)
153
154# Define material
155# ---------------
156matTag = 1
157Fy = 410*MPa  # Yield stress
158Es = 200*GPa  # Modulus of Elasticity of Steel
159b = 2/100     # 2% Strain hardening ratio
160Hkin = b/(1-b)*Es
161
162# Sensitivity-ready steel materials: Hardening, Steel01, SteelMP, BoucWen, SteelBRB, StainlessECThermal, SteelECThermal, ...
163# Hardening Sensitivity Params: sigmaY/fy/Fy, E, H_kin/Hkin, H_iso/Hiso
164ops.uniaxialMaterial("Hardening", matTag, Es, Fy, 0, Hkin)
165
166# ops.uniaxialMaterial("Steel01", matTag, Fy, Es, b) # Sensitivity Params: sigmaY/fy/Fy, E, b, a1, a2, a3, a4
167# ops.uniaxialMaterial("SteelMP", matTag, Fy, Es, b) # Sensitivity Params: sigmaY/fy, E, b
168
169# Define sections
170# ---------------
171# Sections defined with "canned" section ("WFSection2d"), otherwise use a FiberSection object (ops.section("Fiber",...))
172beamSecTag = 1
173beamWidth, beamDepth = 10*cm, 50*cm
174#                          secTag,     matTag, d,         tw,        bf,       tf, Nfw, Nff
175ops.section("WFSection2d", beamSecTag, matTag, beamDepth, beamWidth, beamWidth, 0, 20, 0)  # Beam section
176
177# Define elements
178# ---------------
179beamTransTag, beamIntTag = 1, 1
180# Linear, PDelta, Corotational
181ops.geomTransf("Corotational", beamTransTag)
182
183nip = 5
184# Lobatto, Legendre, NewtonCotes, Radau, Trapezoidal, CompositeSimpson
185ops.beamIntegration("Legendre", beamIntTag, beamSecTag, nip)
186
187# Beam elements
188numEle = 5
189meshSize = L/numEle  # mesh size
190
191eleType = "dispBeamColumn"  # forceBeamColumn, "dispBeamColumn"
192#           tag, Npts, nodes, type, dofs, size, eleType, transfTag,    beamIntTag
193ops.mesh("line", 1, 2, *[1, 2], 0, 3, meshSize, eleType, beamTransTag, beamIntTag)
194
195# Create a Plain load pattern with a Sine/Trig TimeSeries
196# -------------------------------------------------------
197#                 tag, tStart, tEnd, period, factor
198ops.timeSeries("Trig", 1, 0.0, 1.0, 1.0, "-factor", 1.0)  # "Sine", "Trig" or "Triangle"
199ops.pattern("Plain", 1, 1)
200
201P = 1710*kN
202# Create nodal loads at node 2
203#       nd  FX   FY  MZ
205
206# +===============================================================================+
207# |                       Define Sensitivity Parameters                           |
208# +===============================================================================+
209# /// Each parameter must be unique in the FE domain, and all parameter tags MUST be numbered sequentially starting from 1! ///
210ops.parameter(1)  # Blank parameters
211ops.parameter(2)
212ops.parameter(3)
213ops.parameter(4)
214for ele in range(1, numEle+1):  # Only column elements
215    ops.addToParameter(1, "element", ele, "E")  # E
216    # Check the sensitivity parameter names in *.cpp files ("sigmaY" or "fy" or "Fy")
217    # https://github.com/OpenSees/OpenSees/blob/master/SRC/material/uniaxial/HardeningMaterial.cpp
218    ops.addToParameter(2, "element", ele, "Fy")  # "sigmaY" or "fy" or "Fy"
219    ops.addToParameter(3, "element", ele, "Hkin")  # "H_kin" or "Hkin" or "b"
220    ops.addToParameter(4, "element", ele, "d")  # "d"
221
222ops.parameter(5, "node", 2, "coord", 1)  # parameter for coordinate of node 2 in DOF "1" (PX=1, PY=2, MZ=3)
223# Map parameter 6 to vertical load at node 2 contained in load pattern 1 (last argument is global DOF, e.g., in 2D PX=1, PY=2, MZ=3)
225
226ParamSym = ["E", "F_y", "H_{kin}", "d", "L", "P"]
227ParamVars = [Es, Fy, Hkin, beamDepth, L, P]
228
229title("Model Built")
230
231# +===============================================================================+
232# |                              Run the analysis                                 |
233# +===============================================================================+
234# Run analysis with 500 steps
235# -------------------------
236outputs = run_sensitivity_analysis(
237    ctrlNode=2, dof=2, baseNode=1, SensParam=ops.getParamTags(), steps=500, IOflag=False)
238
239# +===============================================================================+
240# |                               Plot results                                    |
241# +===============================================================================+
242rows, columns = 7, 2
243grid = plt.GridSpec(rows, columns, wspace=0.25, hspace=0.25)
244plt.figure(figsize=(10, 15))
245
246
247def plot_params():
248    plt.rc("axes", axisbelow=True)
249    plt.tick_params(direction="in", length=5, colors="k", width=0.75)
250    plt.grid(True, color="silver", linestyle="solid",
251             linewidth=0.75, alpha=0.75)
252
253
254# Subplot #1
255# ----------
256plt.subplot(grid[0]), plot_params()
257plt.plot(outputs["time"],
258         outputs["force"], "-k", linewidth=1.5)
259plt.ylabel(r"Load, $P$ [kN]")
260
261# Subplot #2
262# ----------
263plt.subplot(grid[1]), plot_params()
264plt.plot(outputs["disp"],
265         outputs["force"], "-k", linewidth=2.0, label="$U$")
266plt.ylabel(r"Load, $P$ [kN]"), plt.legend(fontsize=9)
267
268i, j = 2, 0
269for p in ParamVars:
270    # Subplot #i
271    # ----------
272    plt.subplot(grid[i]), plot_params()
273    plt.plot(outputs["time"], outputs[f"sensDisp_{j+1}"]*p, "-.k", linewidth=1.5, label="DDM")
274    plt.fill_between(outputs["time"], outputs[f"sensDisp_{j+1}"]*p, color='grey', alpha=0.15)
275    plt.ylabel(f"$(\partial U/\partial {ParamSym[j]}){ParamSym[j]}$ [m]")
276    plt.legend(fontsize=9)
277    if j == 5:
278        plt.xlabel(r"Time, $t$")
279
280    # Subplot #ii
281    # -----------
282    plt.subplot(grid[i+1]), plot_params()
283    plt.plot(outputs["disp"], outputs["force"], "-k", linewidth=2.0, label="$U$")
284    plt.plot(outputs["disp"] + outputs[f"sensDisp_{j+1}"] * 0.1*p,
285             outputs["force"], "--k", linewidth=1.5, label=f"$U + (\partial U/\partial {ParamSym[j]})0.1{ParamSym[j]}$")
286    plt.plot(outputs["disp"] - outputs[f"sensDisp_{j+1}"] * 0.1*p,
287             outputs["force"], "-.k", linewidth=1.5, label=f"$U - (\partial U/\partial {ParamSym[j]})0.1{ParamSym[j]}$")
288
289    plt.fill_betweenx(outputs["force"], outputs["disp"] +
290                      outputs[f"sensDisp_{j+1}"] * 0.1*p, outputs["disp"] - outputs[f"sensDisp_{j+1}"] * 0.1*p, color='grey', alpha=0.15)
291
292    plt.ylabel(r"Load, $P$ [kN]")
293    plt.legend(fontsize=9)
294    if j == 5:
295        plt.xlabel(r"Displacement, $U$ [m]")
296    i += 2
297    j += 1
298
299
300# Save figure
301# -----------