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steel_column.py
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steel_column.py
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# -*- coding: utf-8 -*-
"""
Created on Mon Jul 01 12:49:18 2019
@author: D. Loukrezis
Steel column cost-reliability function, retrieved from
https://www.sfu.ca/~ssurjano/steelcol.html
"""
import numpy as np
def steel_column(x):
"""Steel column reliability-cost function"""
Fs = x[0] # yield stress (MPa)
Pd = x[1] # dead weight load (N)
P1 = x[2] # variable load 1 (N)
P2 = x[3] # variable load 2 (N)
B = x[4] # flange breadth (mm)
D = x[5] # flange thickness (mm)
H = x[6] # profile height (mm)
F0 = x[7] # initial deflection (mm)
E = x[8] # Young's modulus (MPa)
L = x[9] # column length
#
P = Pd + P1 + P2 # total load
Eb = (np.pi*np.pi)*E*B*D*H*H/(2*L*L) # Euler buckling load
#
frac1 = 1./(2*B*D)
frac2 = (F0*Eb)/(B*D*H*(Eb-P))
#
response = Fs - P*(frac1 + frac2)
return response