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Influence line rotation

Influence line rotation#

Click –> Live Code on the top right corner of this screen to investigate some influence lines!

figuur 1

import micropip
await micropip.install("ipympl")

import numpy as np
import sympy as sym
import matplotlib.pylab as plt
from ipywidgets import widgets, interact
from matplotlib.patches import Arc,StepPatch

%matplotlib widget

EI, x = sym.symbols('EI, x',real=True)

Av, Am = sym.symbols('Av, Bv',real=True)
a, L= sym.symbols('a, L ',positive=True,real=True)
C1, C2, C3, C4 = sym.symbols('C1, C2, C3, C4')

Find rotation line \(\phi\)#

q = -Am * sym.SingularityFunction(x,0,-2) - Av * sym.SingularityFunction(x,0,-1) + 1*sym.SingularityFunction(x,a,-1)
V = -sym.integrate(q,x)+C1
M = sym.integrate(V,x)+C2
kappa = M / EI
phi = sym.integrate(kappa,x)+C3 
w = - sym.integrate(phi,x)+C4 
eq1 = sym.Eq(w.subs(x,0),0)
eq2 = sym.Eq(phi.subs(x,0),0)
eq3 = sym.Eq(M.subs(x,-1),0)
eq4 = sym.Eq(M.subs(x,L+1),0)
eq5 = sym.Eq(V.subs(x,-1),0)
eq6 = sym.Eq(V.subs(x,L+1),0)
sol = sym.solve([eq1,eq2,eq3,eq4,eq5,eq6],[C1,C2,C3,C4,Av,Am])
w_sol = w.subs(sol)
w_subs = w_sol.subs([(L,6),(a,2),(EI,1500)])
w_numpy = sym.lambdify([L,a,EI,x],w_sol.rewrite(sym.Piecewise))
phi_sol = phi.subs(sol)
phi_subs = phi_sol.subs([(L,6),(a,2),(EI,1500)])
phi_numpy = sym.lambdify([L,a,EI,x],phi_sol.rewrite(sym.Piecewise))

display(sym.simplify(phi_subs.rewrite(sym.Piecewise)))
plt.figure()
x_plot = np.linspace(0,6,100)
plt.plot([0,6],[0,0],color='black',linewidth=2)
plt.plot(x_plot,phi_numpy(L=6,a=6,EI=1500,x=x_plot),color="blue")
plt.xlabel('$x$')
plt.ylabel('rotation')
axs = plt.gca()
axs.grid()
axs.invert_yaxis()
title0 = 'rotation for force at $x_F =  6 $'
axs.set_title(title0);
plt.show()
\[\begin{split}\displaystyle \begin{cases} - \frac{1}{750} & \text{for}\: x > 2 \\\frac{x \left(x - 4\right)}{3000} & \text{for}\: x > 0 \\0 & \text{otherwise} \end{cases}\end{split}\]

Find influence line \(\phi\)#

q = -Am * sym.SingularityFunction(x,0,-2) - Av * sym.SingularityFunction(x,0,-1) + 1*sym.SingularityFunction(x,a,-2)
V = -sym.integrate(q,x)+C1
M = sym.integrate(V,x)+C2
kappa = M / EI
phi = sym.integrate(kappa,x)+C3 
w = - sym.integrate(phi,x)+C4 
eq1 = sym.Eq(w.subs(x,0),0)
eq2 = sym.Eq(phi.subs(x,0),0)
eq3 = sym.Eq(M.subs(x,-1),0)
eq4 = sym.Eq(M.subs(x,L+1),0)
eq5 = sym.Eq(V.subs(x,-1),0)
eq6 = sym.Eq(V.subs(x,L+1),0)
sol = sym.solve([eq1,eq2,eq3,eq4,eq5,eq6],[C1,C2,C3,C4,Av,Am])
w_sol = w.subs(sol)
w_subs = w_sol.subs([(L,6),(a,6),(EI,1500)])
w_inf_numpy = sym.lambdify([L,a,EI,x],w_sol.rewrite(sym.Piecewise))

display(sym.simplify(w_subs.rewrite(sym.Piecewise)))
plt.figure()
x_plot = np.linspace(0,6,100)
plt.plot([0,6],[0,0],color='black',linewidth=2)
plt.plot(x_plot,w_inf_numpy(L=6,a=6,EI=1500,x=x_plot),color="blue")
plt.xlabel('$x_F$')
plt.ylabel('Influence factor rotation')
axs = plt.gca()
axs.grid()
axs.invert_yaxis()
title0 = 'Influence line for rotation at $x_w =  6 $'
axs.set_title(title0);
plt.show()
\[\begin{split}\displaystyle \begin{cases} \frac{3 - x}{250} & \text{for}\: x > 6 \\- \frac{x^{2}}{3000} & \text{for}\: x > 0 \\0 & \text{otherwise} \end{cases}\end{split}\]

Comparison displacement with \(\phi\) and influence line for \(\phi\) at \(x = ...\)#

x = np.linspace(0,6,100)
fig, axs = plt.subplots(2, 1, figsize=(7, 6))
def func(a,b):
    axs[0].clear()  # Clear the existing plot
    axs[1].clear()
    axs[0].plot([0,6],[0,0],color='black',linewidth=2)
    axs[0].grid()
    axs[0].plot(x,w_numpy(6,b,1500,x),color='blue')
    axs[0].plot([a-0.4,a,a+0.4],[w_numpy(6,b,1500,a)+phi_numpy(6,b,1500,a)*0.4,w_numpy(6,b,1500,a),w_numpy(6,b,1500,a)-phi_numpy(6,b,1500,a)*0.4],linewidth=3)
    axs[0].plot([a-0.4,a,a+0.4],[w_numpy(6,b,1500,a),w_numpy(6,b,1500,a),w_numpy(6,b,1500,a)],color='black')
    if phi_numpy(6,b,1500,a) > 0:
        axs[0].annotate(text='', xytext=(a+0.5,w_numpy(6,b,1500,a)), xy=(a+0.5,w_numpy(6,b,1500,a)-phi_numpy(6,b,1500,a)*0.5), arrowprops=dict(arrowstyle='simple',connectionstyle="arc3,rad=.5"))
    else:
        axs[0].annotate(text='', xytext=(a+0.5,w_numpy(6,b,1500,a)), xy=(a+0.5,w_numpy(6,b,1500,a)-phi_numpy(6,b,1500,a)*0.5), arrowprops=dict(arrowstyle='simple',connectionstyle="arc3,rad=-.5"))
    axs[0].annotate('%.5f rad' % phi_numpy(6,b,1500,a),xy = [a+0.6,(w_numpy(6,b,1500,a)+w_numpy(6,b,1600,a)-phi_numpy(6,b,1500,a)*0.3)/2])
    axs[0].annotate(text='', xy=(b,0), xytext=(b,-0.01), arrowprops=dict(arrowstyle='simple'))
    axs[0].set_ylim([-0.009,0.05])
    axs[0].invert_yaxis()
    title0 = 'Rotation for force at at $x_F = '+str(b)+'$, showing rotation at $x_w = '+str(a)+'$'
    axs[0].set_title(title0)
    axs[1].plot([0,6],[0,0],color='black',linewidth=2)
    axs[1].grid()
    axs[1].plot(x,w_inf_numpy(6,a,1500,x),color='blue')
    axs[1].plot(b,w_inf_numpy(6,a,1500,b),marker='o')
    axs[1].annotate('%.5f rad' % np.round(w_inf_numpy(6,a,1500,b),5),xy = [b,w_inf_numpy(6,a,1500,b)-0.00005])
    axs[1].set_ylim([-0.013,0.001])
    axs[1].invert_yaxis()
    title1 = 'Influence line for displacement at $x_w = '+str(a)+'$'
    axs[1].set_title(title1)
    axs[0].spines['right'].set_color('none')
    axs[0].spines['top'].set_color('none')
    axs[0].spines['bottom'].set_position('zero')
    axs[0].spines['left'].set_position('zero')
    axs[1].spines['right'].set_color('none')
    axs[1].spines['top'].set_color('none')
    axs[1].spines['bottom'].set_position('zero')
    axs[1].spines['left'].set_position('zero')
    plt.draw() 
    
interact(func, a = widgets.FloatSlider(min=0, max=6, value=2, step=0.1, description="Location rotation x_phi = ... (m)",readout_format='.1f',style= {'description_width': '250px'},layout = {'width': '500px'}),
         b = widgets.FloatSlider(min=0, max=6, value=2, step=0.1, description="Location force x_F = ... (m)",readout_format='.1f',style= {'description_width': '250px'},layout = {'width': '500px'}) );
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