from gekko import GEKKO

m = GEKKO()

#%% Constants
pi = m.Const(3.14159,'pi')
P = 2300        # compressive load (kg_f)
o_y = 450       # yield stress (kg_f/cm^2)
E = 0.65e6      # elasticity (kg_f/cm^2)
p = 0.0020      # weight density (kg_f/cm^3)
l = 300         # length of the column (cm)

#%% Variables
d = m.Var(value=8.0,lb=2.0,ub=14.0) # mean diameter (cm)
t = m.Var(value=0.3,lb=0.2,ub=0.8)  # thickness (cm)
cost = m.Var()