Source code for sympy.physics.continuum_mechanics.beam

"""
This module can be used to solve 2D beam bending problems with
singularity functions in mechanics.
"""

from __future__ import print_function, division

from sympy.core import S, Symbol, diff, symbols
from sympy.solvers import linsolve
from sympy.printing import sstr
from sympy.functions import SingularityFunction, Piecewise
from sympy.core import sympify
from sympy.integrals import integrate
from sympy.series import limit
from sympy.plotting import plot
from sympy.external import import_module
from sympy.utilities.decorator import doctest_depends_on


[docs]class Beam(object): """ A Beam is a structural element that is capable of withstanding load primarily by resisting against bending. Beams are characterized by their cross sectional profile(Second moment of area), their length and their material. .. note:: While solving a beam bending problem, a user should choose its own sign convention and should stick to it. The results will automatically follow the chosen sign convention. Examples ======== There is a beam of length 4 meters. A constant distributed load of 6 N/m is applied from half of the beam till the end. There are two simple supports below the beam, one at the starting point and another at the ending point of the beam. The deflection of the beam at the end is restricted. Using the sign convention of downwards forces being positive. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols, Piecewise >>> E, I = symbols('E, I') >>> R1, R2 = symbols('R1, R2') >>> b = Beam(4, E, I) >>> b.apply_load(R1, 0, -1) >>> b.apply_load(6, 2, 0) >>> b.apply_load(R2, 4, -1) >>> b.bc_deflection = [(0, 0), (4, 0)] >>> b.boundary_conditions {'deflection': [(0, 0), (4, 0)], 'slope': []} >>> b.load R1*SingularityFunction(x, 0, -1) + R2*SingularityFunction(x, 4, -1) + 6*SingularityFunction(x, 2, 0) >>> b.solve_for_reaction_loads(R1, R2) >>> b.load -3*SingularityFunction(x, 0, -1) + 6*SingularityFunction(x, 2, 0) - 9*SingularityFunction(x, 4, -1) >>> b.shear_force() -3*SingularityFunction(x, 0, 0) + 6*SingularityFunction(x, 2, 1) - 9*SingularityFunction(x, 4, 0) >>> b.bending_moment() -3*SingularityFunction(x, 0, 1) + 3*SingularityFunction(x, 2, 2) - 9*SingularityFunction(x, 4, 1) >>> b.slope() (-3*SingularityFunction(x, 0, 2)/2 + SingularityFunction(x, 2, 3) - 9*SingularityFunction(x, 4, 2)/2 + 7)/(E*I) >>> b.deflection() (7*x - SingularityFunction(x, 0, 3)/2 + SingularityFunction(x, 2, 4)/4 - 3*SingularityFunction(x, 4, 3)/2)/(E*I) >>> b.deflection().rewrite(Piecewise) (7*x - Piecewise((x**3, x > 0), (0, True))/2 - 3*Piecewise(((x - 4)**3, x - 4 > 0), (0, True))/2 + Piecewise(((x - 2)**4, x - 2 > 0), (0, True))/4)/(E*I) """ def __init__(self, length, elastic_modulus, second_moment, variable=Symbol('x'), base_char='C'): """Initializes the class. Parameters ========== length : Sympifyable A Symbol or value representing the Beam's length. elastic_modulus : Sympifyable A SymPy expression representing the Beam's Modulus of Elasticity. It is a measure of the stiffness of the Beam material. It can also be a continuous function of position along the beam. second_moment : Sympifyable A SymPy expression representing the Beam's Second moment of area. It is a geometrical property of an area which reflects how its points are distributed with respect to its neutral axis. It can also be a continuous function of position along the beam. variable : Symbol, optional A Symbol object that will be used as the variable along the beam while representing the load, shear, moment, slope and deflection curve. By default, it is set to ``Symbol('x')``. base_char : String, optional A String that will be used as base character to generate sequential symbols for integration constants in cases where boundary conditions are not sufficient to solve them. """ self.length = length self.elastic_modulus = elastic_modulus self.second_moment = second_moment self.variable = variable self._base_char = base_char self._boundary_conditions = {'deflection': [], 'slope': []} self._load = 0 self._applied_loads = [] self._reaction_loads = {} self._composite_type = None self._hinge_position = None def __str__(self): str_sol = 'Beam({}, {}, {})'.format(sstr(self._length), sstr(self._elastic_modulus), sstr(self._second_moment)) return str_sol @property def reaction_loads(self): """ Returns the reaction forces in a dictionary.""" return self._reaction_loads @property def length(self): """Length of the Beam.""" return self._length @length.setter def length(self, l): self._length = sympify(l) @property def variable(self): """ A symbol that can be used as a variable along the length of the beam while representing load distribution, shear force curve, bending moment, slope curve and the deflection curve. By default, it is set to ``Symbol('x')``, but this property is mutable. Examples ======== >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> E, I = symbols('E, I') >>> x, y, z = symbols('x, y, z') >>> b = Beam(4, E, I) >>> b.variable x >>> b.variable = y >>> b.variable y >>> b = Beam(4, E, I, z) >>> b.variable z """ return self._variable @variable.setter def variable(self, v): if isinstance(v, Symbol): self._variable = v else: raise TypeError("""The variable should be a Symbol object.""") @property def elastic_modulus(self): """Young's Modulus of the Beam. """ return self._elastic_modulus @elastic_modulus.setter def elastic_modulus(self, e): self._elastic_modulus = sympify(e) @property def second_moment(self): """Second moment of area of the Beam. """ return self._second_moment @second_moment.setter def second_moment(self, i): self._second_moment = sympify(i) @property def boundary_conditions(self): """ Returns a dictionary of boundary conditions applied on the beam. The dictionary has three kewwords namely moment, slope and deflection. The value of each keyword is a list of tuple, where each tuple contains loaction and value of a boundary condition in the format (location, value). Examples ======== There is a beam of length 4 meters. The bending moment at 0 should be 4 and at 4 it should be 0. The slope of the beam should be 1 at 0. The deflection should be 2 at 0. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> E, I = symbols('E, I') >>> b = Beam(4, E, I) >>> b.bc_deflection = [(0, 2)] >>> b.bc_slope = [(0, 1)] >>> b.boundary_conditions {'deflection': [(0, 2)], 'slope': [(0, 1)]} Here the deflection of the beam should be ``2`` at ``0``. Similarly, the slope of the beam should be ``1`` at ``0``. """ return self._boundary_conditions @property def bc_slope(self): return self._boundary_conditions['slope'] @bc_slope.setter def bc_slope(self, s_bcs): self._boundary_conditions['slope'] = s_bcs @property def bc_deflection(self): return self._boundary_conditions['deflection'] @bc_deflection.setter def bc_deflection(self, d_bcs): self._boundary_conditions['deflection'] = d_bcs
[docs] def join(self, beam, via="fixed"): """ This method joins two beams to make a new composite beam system. Passed Beam class instance is attached to the right end of calling object. This method can be used to form beams having Discontinuous values of Elastic modulus or Second moment. Parameters ========== beam : Beam class object The Beam object which would be connected to the right of calling object. via : String States the way two Beam object would get connected - For axially fixed Beams, via="fixed" - For Beams connected via hinge, via="hinge" Examples ======== There is a cantilever beam of length 4 meters. For first 2 meters its moment of inertia is `1.5*I` and `I` for the other end. A pointload of magnitude 4 N is applied from the top at its free end. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> E, I = symbols('E, I') >>> R1, R2 = symbols('R1, R2') >>> b1 = Beam(2, E, 1.5*I) >>> b2 = Beam(2, E, I) >>> b = b1.join(b2, "fixed") >>> b.apply_load(20, 4, -1) >>> b.apply_load(R1, 0, -1) >>> b.apply_load(R2, 0, -2) >>> b.bc_slope = [(0, 0)] >>> b.bc_deflection = [(0, 0)] >>> b.solve_for_reaction_loads(R1, R2) >>> b.load 80*SingularityFunction(x, 0, -2) - 20*SingularityFunction(x, 0, -1) + 20*SingularityFunction(x, 4, -1) >>> b.slope() (((80*SingularityFunction(x, 0, 1) - 10*SingularityFunction(x, 0, 2) + 10*SingularityFunction(x, 4, 2))/I - 120/I)/E + 80.0/(E*I))*SingularityFunction(x, 2, 0) + 0.666666666666667*(80*SingularityFunction(x, 0, 1) - 10*SingularityFunction(x, 0, 2) + 10*SingularityFunction(x, 4, 2))*SingularityFunction(x, 0, 0)/(E*I) - 0.666666666666667*(80*SingularityFunction(x, 0, 1) - 10*SingularityFunction(x, 0, 2) + 10*SingularityFunction(x, 4, 2))*SingularityFunction(x, 2, 0)/(E*I) """ x = self.variable E = self.elastic_modulus new_length = self.length + beam.length if self.second_moment != beam.second_moment: new_second_moment = Piecewise((self.second_moment, x<=self.length), (beam.second_moment, x<=new_length)) else: new_second_moment = self.second_moment if via == "fixed": new_beam = Beam(new_length, E, new_second_moment, x) new_beam._composite_type = "fixed" return new_beam if via == "hinge": new_beam = Beam(new_length, E, new_second_moment, x) new_beam._composite_type = "hinge" new_beam._hinge_position = self.length return new_beam
[docs] def apply_support(self, loc, type="fixed"): """ This method applies support to a particular beam object. Parameters ========== loc : Sympifyable Location of point at which support is applied. type : String Determines type of Beam support applied. To apply support structure with - zero degree of freedom, type = "fixed" - one degree of freedom, type = "pin" - two degrees of freedom, type = "roller" Examples ======== There is a beam of length 30 meters. A moment of magnitude 120 Nm is applied in the clockwise direction at the end of the beam. A pointload of magnitude 8 N is applied from the top of the beam at the starting point. There are two simple supports below the beam. One at the end and another one at a distance of 10 meters from the start. The deflection is restricted at both the supports. Using the sign convention of upward forces and clockwise moment being positive. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> E, I = symbols('E, I') >>> b = Beam(30, E, I) >>> b.apply_support(10, 'roller') >>> b.apply_support(30, 'roller') >>> b.apply_load(-8, 0, -1) >>> b.apply_load(120, 30, -2) >>> R_10, R_30 = symbols('R_10, R_30') >>> b.solve_for_reaction_loads(R_10, R_30) >>> b.load -8*SingularityFunction(x, 0, -1) + 6*SingularityFunction(x, 10, -1) + 120*SingularityFunction(x, 30, -2) + 2*SingularityFunction(x, 30, -1) >>> b.slope() (-4*SingularityFunction(x, 0, 2) + 3*SingularityFunction(x, 10, 2) + 120*SingularityFunction(x, 30, 1) + SingularityFunction(x, 30, 2) + 4000/3)/(E*I) """ if type == "pin" or type == "roller": reaction_load = Symbol('R_'+str(loc)) self.apply_load(reaction_load, loc, -1) self.bc_deflection.append((loc, 0)) else: reaction_load = Symbol('R_'+str(loc)) reaction_moment = Symbol('M_'+str(loc)) self.apply_load(reaction_load, loc, -1) self.apply_load(reaction_moment, loc, -2) self.bc_deflection = [(loc, 0)] self.bc_slope.append((loc, 0))
[docs] def apply_load(self, value, start, order, end=None): """ This method adds up the loads given to a particular beam object. Parameters ========== value : Sympifyable The magnitude of an applied load. start : Sympifyable The starting point of the applied load. For point moments and point forces this is the location of application. order : Integer The order of the applied load. - For moments, order= -2 - For point loads, order=-1 - For constant distributed load, order=0 - For ramp loads, order=1 - For parabolic ramp loads, order=2 - ... so on. end : Sympifyable, optional An optional argument that can be used if the load has an end point within the length of the beam. Examples ======== There is a beam of length 4 meters. A moment of magnitude 3 Nm is applied in the clockwise direction at the starting point of the beam. A pointload of magnitude 4 N is applied from the top of the beam at 2 meters from the starting point and a parabolic ramp load of magnitude 2 N/m is applied below the beam starting from 2 meters to 3 meters away from the starting point of the beam. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> E, I = symbols('E, I') >>> b = Beam(4, E, I) >>> b.apply_load(-3, 0, -2) >>> b.apply_load(4, 2, -1) >>> b.apply_load(-2, 2, 2, end = 3) >>> b.load -3*SingularityFunction(x, 0, -2) + 4*SingularityFunction(x, 2, -1) - 2*SingularityFunction(x, 2, 2) + 2*SingularityFunction(x, 3, 0) + 2*SingularityFunction(x, 3, 2) """ x = self.variable value = sympify(value) start = sympify(start) order = sympify(order) self._applied_loads.append((value, start, order, end)) self._load += value*SingularityFunction(x, start, order) if end: if order == 0: self._load -= value*SingularityFunction(x, end, order) elif order.is_positive: self._load -= value*SingularityFunction(x, end, order) + value*SingularityFunction(x, end, 0) else: raise ValueError("""Order of the load should be positive.""")
[docs] def remove_load(self, value, start, order, end=None): """ This method removes a particular load present on the beam object. Returns a ValueError if the load passed as an argument is not present on the beam. Parameters ========== value : Sympifyable The magnitude of an applied load. start : Sympifyable The starting point of the applied load. For point moments and point forces this is the location of application. order : Integer The order of the applied load. - For moments, order= -2 - For point loads, order=-1 - For constant distributed load, order=0 - For ramp loads, order=1 - For parabolic ramp loads, order=2 - ... so on. end : Sympifyable, optional An optional argument that can be used if the load has an end point within the length of the beam. Examples ======== There is a beam of length 4 meters. A moment of magnitude 3 Nm is applied in the clockwise direction at the starting point of the beam. A pointload of magnitude 4 N is applied from the top of the beam at 2 meters from the starting point and a parabolic ramp load of magnitude 2 N/m is applied below the beam starting from 2 meters to 3 meters away from the starting point of the beam. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> E, I = symbols('E, I') >>> b = Beam(4, E, I) >>> b.apply_load(-3, 0, -2) >>> b.apply_load(4, 2, -1) >>> b.apply_load(-2, 2, 2, end = 3) >>> b.load -3*SingularityFunction(x, 0, -2) + 4*SingularityFunction(x, 2, -1) - 2*SingularityFunction(x, 2, 2) + 2*SingularityFunction(x, 3, 0) + 2*SingularityFunction(x, 3, 2) >>> b.remove_load(-2, 2, 2, end = 3) >>> b.load -3*SingularityFunction(x, 0, -2) + 4*SingularityFunction(x, 2, -1) """ x = self.variable value = sympify(value) start = sympify(start) order = sympify(order) if (value, start, order, end) in self._applied_loads: self._load -= value*SingularityFunction(x, start, order) self._applied_loads.remove((value, start, order, end)) else: raise ValueError("""No such load distribution exists on the beam object.""") if end: if order == 0: self._load += value*SingularityFunction(x, end, order) elif order.is_positive: self._load += value*SingularityFunction(x, end, order) + value*SingularityFunction(x, end, 0) else: raise ValueError("""Order of the load should be positive.""")
@property def load(self): """ Returns a Singularity Function expression which represents the load distribution curve of the Beam object. Examples ======== There is a beam of length 4 meters. A moment of magnitude 3 Nm is applied in the clockwise direction at the starting point of the beam. A pointload of magnitude 4 N is applied from the top of the beam at 2 meters from the starting point and a parabolic ramp load of magnitude 2 N/m is applied below the beam starting from 3 meters away from the starting point of the beam. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> E, I = symbols('E, I') >>> b = Beam(4, E, I) >>> b.apply_load(-3, 0, -2) >>> b.apply_load(4, 2, -1) >>> b.apply_load(-2, 3, 2) >>> b.load -3*SingularityFunction(x, 0, -2) + 4*SingularityFunction(x, 2, -1) - 2*SingularityFunction(x, 3, 2) """ return self._load @property def applied_loads(self): """ Returns a list of all loads applied on the beam object. Each load in the list is a tuple of form (value, start, order, end). Examples ======== There is a beam of length 4 meters. A moment of magnitude 3 Nm is applied in the clockwise direction at the starting point of the beam. A pointload of magnitude 4 N is applied from the top of the beam at 2 meters from the starting point. Another pointload of magnitude 5 N is applied at same position. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> E, I = symbols('E, I') >>> b = Beam(4, E, I) >>> b.apply_load(-3, 0, -2) >>> b.apply_load(4, 2, -1) >>> b.apply_load(5, 2, -1) >>> b.load -3*SingularityFunction(x, 0, -2) + 9*SingularityFunction(x, 2, -1) >>> b.applied_loads [(-3, 0, -2, None), (4, 2, -1, None), (5, 2, -1, None)] """ return self._applied_loads def _solve_hinge_beams(self, *reactions): """Method to find integration constants and reactional variables in a composite beam connected via hinge. This method resolves the composite Beam into its sub-beams and then equations of shear force, bending moment, slope and deflection are evaluated for both of them separately. These equations are then solved for unknown reactions and integration constants using the boundary conditions applied on the Beam. Equal deflection of both sub-beams at the hinge joint gives us another equation to solve the system. Examples ======== A combined beam, with constant fkexural rigidity E*I, is formed by joining a Beam of length 2*l to the right of another Beam of length l. The whole beam is fixed at both of its both end. A point load of magnitude P is also applied from the top at a distance of 2*l from starting point. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> E, I = symbols('E, I') >>> l=symbols('l', positive=True) >>> b1=Beam(l ,E,I) >>> b2=Beam(2*l ,E,I) >>> b=b1.join(b2,"hinge") >>> M1, A1, M2, A2, P = symbols('M1 A1 M2 A2 P') >>> b.apply_load(A1,0,-1) >>> b.apply_load(M1,0,-2) >>> b.apply_load(P,2*l,-1) >>> b.apply_load(A2,3*l,-1) >>> b.apply_load(M2,3*l,-2) >>> b.bc_slope=[(0,0), (3*l, 0)] >>> b.bc_deflection=[(0,0), (3*l, 0)] >>> b.solve_for_reaction_loads(M1, A1, M2, A2) >>> b.reaction_loads {A1: -5*P/18, A2: -13*P/18, M1: 5*P*l/18, M2: -4*P*l/9} >>> b.slope() (5*P*l*SingularityFunction(x, 0, 1)/18 - 5*P*SingularityFunction(x, 0, 2)/36 + 5*P*SingularityFunction(x, l, 2)/36)*SingularityFunction(x, 0, 0)/(E*I) - (5*P*l*SingularityFunction(x, 0, 1)/18 - 5*P*SingularityFunction(x, 0, 2)/36 + 5*P*SingularityFunction(x, l, 2)/36)*SingularityFunction(x, l, 0)/(E*I) + (P*l**2/18 - 4*P*l*SingularityFunction(-l + x, 2*l, 1)/9 - 5*P*SingularityFunction(-l + x, 0, 2)/36 + P*SingularityFunction(-l + x, l, 2)/2 - 13*P*SingularityFunction(-l + x, 2*l, 2)/36)*SingularityFunction(x, l, 0)/(E*I) >>> b.deflection() (5*P*l*SingularityFunction(x, 0, 2)/36 - 5*P*SingularityFunction(x, 0, 3)/108 + 5*P*SingularityFunction(x, l, 3)/108)*SingularityFunction(x, 0, 0)/(E*I) - (5*P*l*SingularityFunction(x, 0, 2)/36 - 5*P*SingularityFunction(x, 0, 3)/108 + 5*P*SingularityFunction(x, l, 3)/108)*SingularityFunction(x, l, 0)/(E*I) + (5*P*l**3/54 + P*l**2*(-l + x)/18 - 2*P*l*SingularityFunction(-l + x, 2*l, 2)/9 - 5*P*SingularityFunction(-l + x, 0, 3)/108 + P*SingularityFunction(-l + x, l, 3)/6 - 13*P*SingularityFunction(-l + x, 2*l, 3)/108)*SingularityFunction(x, l, 0)/(E*I) """ x = self.variable l = self._hinge_position E = self._elastic_modulus I = self._second_moment if isinstance(I, Piecewise): I1 = I.args[0][0] I2 = I.args[1][0] else: I1 = I2 = I load_1 = 0 # Load equation on first segment of composite beam load_2 = 0 # Load equation on second segment of composite beam # Distributing load on both segments for load in self.applied_loads: if load[1] < l: load_1 += load[0]*SingularityFunction(x, load[1], load[2]) if load[2] == 0: load_1 -= load[0]*SingularityFunction(x, load[3], load[2]) elif load[2] > 0: load_1 -= load[0]*SingularityFunction(x, load[3], load[2]) + load[0]*SingularityFunction(x, load[3], 0) elif load[1] == l: load_1 += load[0]*SingularityFunction(x, load[1], load[2]) load_2 += load[0]*SingularityFunction(x, load[1] - l, load[2]) elif load[1] > l: load_2 += load[0]*SingularityFunction(x, load[1] - l, load[2]) if load[2] == 0: load_2 -= load[0]*SingularityFunction(x, load[3] - l, load[2]) elif load[2] > 0: load_2 -= load[0]*SingularityFunction(x, load[3] - l, load[2]) + load[0]*SingularityFunction(x, load[3] - l, 0) h = Symbol('h') # Force due to hinge load_1 += h*SingularityFunction(x, l, -1) load_2 -= h*SingularityFunction(x, 0, -1) eq = [] shear_1 = integrate(load_1, x) shear_curve_1 = limit(shear_1, x, l) eq.append(shear_curve_1) bending_1 = integrate(shear_1, x) moment_curve_1 = limit(bending_1, x, l) eq.append(moment_curve_1) shear_2 = integrate(load_2, x) shear_curve_2 = limit(shear_2, x, self.length - l) eq.append(shear_curve_2) bending_2 = integrate(shear_2, x) moment_curve_2 = limit(bending_2, x, self.length - l) eq.append(moment_curve_2) C1 = Symbol('C1') C2 = Symbol('C2') C3 = Symbol('C3') C4 = Symbol('C4') slope_1 = S(1)/(E*I1)*(integrate(bending_1, x) + C1) def_1 = S(1)/(E*I1)*(integrate((E*I)*slope_1, x) + C1*x + C2) slope_2 = S(1)/(E*I2)*(integrate(integrate(integrate(load_2, x), x), x) + C3) def_2 = S(1)/(E*I2)*(integrate((E*I)*slope_2, x) + C4) for position, value in self.bc_slope: if position<l: eq.append(slope_1.subs(x, position) - value) else: eq.append(slope_2.subs(x, position - l) - value) for position, value in self.bc_deflection: if position<l: eq.append(def_1.subs(x, position) - value) else: eq.append(def_2.subs(x, position - l) - value) eq.append(def_1.subs(x, l) - def_2.subs(x, 0)) # Deflection of both the segments at hinge would be equal constants = list(linsolve(eq, C1, C2, C3, C4, h, *reactions)) reaction_values = list(constants[0])[5:] self._reaction_loads = dict(zip(reactions, reaction_values)) self._load = self._load.subs(self._reaction_loads) # Substituting constants and reactional load and moments with their corresponding values slope_1 = slope_1.subs({C1: constants[0][0], h:constants[0][4]}).subs(self._reaction_loads) def_1 = def_1.subs({C1: constants[0][0], C2: constants[0][1], h:constants[0][4]}).subs(self._reaction_loads) slope_2 = slope_2.subs({x: x-l, C3: constants[0][2], h:constants[0][4]}).subs(self._reaction_loads) def_2 = def_2.subs({x: x-l,C3: constants[0][2], C4: constants[0][3], h:constants[0][4]}).subs(self._reaction_loads) self._hinge_beam_slope = slope_1*SingularityFunction(x, 0, 0) - slope_1*SingularityFunction(x, l, 0) + slope_2*SingularityFunction(x, l, 0) self._hinge_beam_deflection = def_1*SingularityFunction(x, 0, 0) - def_1*SingularityFunction(x, l, 0) + def_2*SingularityFunction(x, l, 0)
[docs] def solve_for_reaction_loads(self, *reactions): """ Solves for the reaction forces. Examples ======== There is a beam of length 30 meters. A moment of magnitude 120 Nm is applied in the clockwise direction at the end of the beam. A pointload of magnitude 8 N is applied from the top of the beam at the starting point. There are two simple supports below the beam. One at the end and another one at a distance of 10 meters from the start. The deflection is restricted at both the supports. Using the sign convention of upward forces and clockwise moment being positive. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols, linsolve, limit >>> E, I = symbols('E, I') >>> R1, R2 = symbols('R1, R2') >>> b = Beam(30, E, I) >>> b.apply_load(-8, 0, -1) >>> b.apply_load(R1, 10, -1) # Reaction force at x = 10 >>> b.apply_load(R2, 30, -1) # Reaction force at x = 30 >>> b.apply_load(120, 30, -2) >>> b.bc_deflection = [(10, 0), (30, 0)] >>> b.load R1*SingularityFunction(x, 10, -1) + R2*SingularityFunction(x, 30, -1) - 8*SingularityFunction(x, 0, -1) + 120*SingularityFunction(x, 30, -2) >>> b.solve_for_reaction_loads(R1, R2) >>> b.reaction_loads {R1: 6, R2: 2} >>> b.load -8*SingularityFunction(x, 0, -1) + 6*SingularityFunction(x, 10, -1) + 120*SingularityFunction(x, 30, -2) + 2*SingularityFunction(x, 30, -1) """ if self._composite_type == "hinge": return self._solve_hinge_beams(*reactions) x = self.variable l = self.length C3 = Symbol('C3') C4 = Symbol('C4') shear_curve = limit(self.shear_force(), x, l) moment_curve = limit(self.bending_moment(), x, l) slope_eqs = [] deflection_eqs = [] slope_curve = integrate(self.bending_moment(), x) + C3 for position, value in self._boundary_conditions['slope']: eqs = slope_curve.subs(x, position) - value slope_eqs.append(eqs) deflection_curve = integrate(slope_curve, x) + C4 for position, value in self._boundary_conditions['deflection']: eqs = deflection_curve.subs(x, position) - value deflection_eqs.append(eqs) solution = list((linsolve([shear_curve, moment_curve] + slope_eqs + deflection_eqs, (C3, C4) + reactions).args)[0]) solution = solution[2:] self._reaction_loads = dict(zip(reactions, solution)) self._load = self._load.subs(self._reaction_loads)
[docs] def shear_force(self): """ Returns a Singularity Function expression which represents the shear force curve of the Beam object. Examples ======== There is a beam of length 30 meters. A moment of magnitude 120 Nm is applied in the clockwise direction at the end of the beam. A pointload of magnitude 8 N is applied from the top of the beam at the starting point. There are two simple supports below the beam. One at the end and another one at a distance of 10 meters from the start. The deflection is restricted at both the supports. Using the sign convention of upward forces and clockwise moment being positive. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> E, I = symbols('E, I') >>> R1, R2 = symbols('R1, R2') >>> b = Beam(30, E, I) >>> b.apply_load(-8, 0, -1) >>> b.apply_load(R1, 10, -1) >>> b.apply_load(R2, 30, -1) >>> b.apply_load(120, 30, -2) >>> b.bc_deflection = [(10, 0), (30, 0)] >>> b.solve_for_reaction_loads(R1, R2) >>> b.shear_force() -8*SingularityFunction(x, 0, 0) + 6*SingularityFunction(x, 10, 0) + 120*SingularityFunction(x, 30, -1) + 2*SingularityFunction(x, 30, 0) """ x = self.variable return integrate(self.load, x)
[docs] def max_shear_force(self): """Returns maximum Shear force and its coordinate in the Beam object.""" from sympy import solve, Mul, Interval shear_curve = self.shear_force() x = self.variable terms = shear_curve.args singularity = [] # Points at which shear function changes for term in terms: if isinstance(term, Mul): term = term.args[-1] # SingularityFunction in the term singularity.append(term.args[1]) singularity.sort() singularity = list(set(singularity)) intervals = [] # List of Intervals with discrete value of shear force shear_values = [] # List of values of shear force in each interval for i, s in enumerate(singularity): if s == 0: continue try: shear_slope = Piecewise((float("nan"), x<=singularity[i-1]),(self._load.rewrite(Piecewise), x<s), (float("nan"), True)) points = solve(shear_slope, x) val = [] for point in points: val.append(shear_curve.subs(x, point)) points.extend([singularity[i-1], s]) val.extend([limit(shear_curve, x, singularity[i-1], '+'), limit(shear_curve, x, s, '-')]) val = list(map(abs, val)) max_shear = max(val) shear_values.append(max_shear) intervals.append(points[val.index(max_shear)]) # If shear force in a particular Interval has zero or constant # slope, then above block gives NotImplementedError as # solve can't represent Interval solutions. except NotImplementedError: initial_shear = limit(shear_curve, x, singularity[i-1], '+') final_shear = limit(shear_curve, x, s, '-') # If shear_curve has a constant slope(it is a line). if shear_curve.subs(x, (singularity[i-1] + s)/2) == (initial_shear + final_shear)/2 and initial_shear != final_shear: shear_values.extend([initial_shear, final_shear]) intervals.extend([singularity[i-1], s]) else: # shear_curve has same value in whole Interval shear_values.append(final_shear) intervals.append(Interval(singularity[i-1], s)) shear_values = list(map(abs, shear_values)) maximum_shear = max(shear_values) point = intervals[shear_values.index(maximum_shear)] return (point, maximum_shear)
[docs] def bending_moment(self): """ Returns a Singularity Function expression which represents the bending moment curve of the Beam object. Examples ======== There is a beam of length 30 meters. A moment of magnitude 120 Nm is applied in the clockwise direction at the end of the beam. A pointload of magnitude 8 N is applied from the top of the beam at the starting point. There are two simple supports below the beam. One at the end and another one at a distance of 10 meters from the start. The deflection is restricted at both the supports. Using the sign convention of upward forces and clockwise moment being positive. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> E, I = symbols('E, I') >>> R1, R2 = symbols('R1, R2') >>> b = Beam(30, E, I) >>> b.apply_load(-8, 0, -1) >>> b.apply_load(R1, 10, -1) >>> b.apply_load(R2, 30, -1) >>> b.apply_load(120, 30, -2) >>> b.bc_deflection = [(10, 0), (30, 0)] >>> b.solve_for_reaction_loads(R1, R2) >>> b.bending_moment() -8*SingularityFunction(x, 0, 1) + 6*SingularityFunction(x, 10, 1) + 120*SingularityFunction(x, 30, 0) + 2*SingularityFunction(x, 30, 1) """ x = self.variable return integrate(self.shear_force(), x)
[docs] def max_bmoment(self): """Returns maximum Shear force and its coordinate in the Beam object.""" from sympy import solve, Mul, Interval bending_curve = self.bending_moment() x = self.variable terms = bending_curve.args singularity = [] # Points at which bending moment changes for term in terms: if isinstance(term, Mul): term = term.args[-1] # SingularityFunction in the term singularity.append(term.args[1]) singularity.sort() singularity = list(set(singularity)) intervals = [] # List of Intervals with discrete value of bending moment moment_values = [] # List of values of bending moment in each interval for i, s in enumerate(singularity): if s == 0: continue try: moment_slope = Piecewise((float("nan"), x<=singularity[i-1]),(self.shear_force().rewrite(Piecewise), x<s), (float("nan"), True)) points = solve(moment_slope, x) val = [] for point in points: val.append(bending_curve.subs(x, point)) points.extend([singularity[i-1], s]) val.extend([limit(bending_curve, x, singularity[i-1], '+'), limit(bending_curve, x, s, '-')]) val = list(map(abs, val)) max_moment = max(val) moment_values.append(max_moment) intervals.append(points[val.index(max_moment)]) # If bending moment in a particular Interval has zero or constant # slope, then above block gives NotImplementedError as solve # can't represent Interval solutions. except NotImplementedError: initial_moment = limit(bending_curve, x, singularity[i-1], '+') final_moment = limit(bending_curve, x, s, '-') # If bending_curve has a constant slope(it is a line). if bending_curve.subs(x, (singularity[i-1] + s)/2) == (initial_moment + final_moment)/2 and initial_moment != final_moment: moment_values.extend([initial_moment, final_moment]) intervals.extend([singularity[i-1], s]) else: # bending_curve has same value in whole Interval moment_values.append(final_moment) intervals.append(Interval(singularity[i-1], s)) moment_values = list(map(abs, moment_values)) maximum_moment = max(moment_values) point = intervals[moment_values.index(maximum_moment)] return (point, maximum_moment)
[docs] def point_cflexure(self): """ Returns a Set of point(s) with zero bending moment and where bending moment curve of the beam object changes its sign from negative to positive or vice versa. Examples ======== There is is 10 meter long overhanging beam. There are two simple supports below the beam. One at the start and another one at a distance of 6 meters from the start. Point loads of magnitude 10KN and 20KN are applied at 2 meters and 4 meters from start respectively. A Uniformly distribute load of magnitude of magnitude 3KN/m is also applied on top starting from 6 meters away from starting point till end. Using the sign convention of upward forces and clockwise moment being positive. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> E, I = symbols('E, I') >>> b = Beam(10, E, I) >>> b.apply_load(-4, 0, -1) >>> b.apply_load(-46, 6, -1) >>> b.apply_load(10, 2, -1) >>> b.apply_load(20, 4, -1) >>> b.apply_load(3, 6, 0) >>> b.point_cflexure() [10/3] """ from sympy import solve, Piecewise # To restrict the range within length of the Beam moment_curve = Piecewise((float("nan"), self.variable<=0), (self.bending_moment(), self.variable<self.length), (float("nan"), True)) points = solve(moment_curve.rewrite(Piecewise), self.variable, domain=S.Reals) return points
[docs] def slope(self): """ Returns a Singularity Function expression which represents the slope the elastic curve of the Beam object. Examples ======== There is a beam of length 30 meters. A moment of magnitude 120 Nm is applied in the clockwise direction at the end of the beam. A pointload of magnitude 8 N is applied from the top of the beam at the starting point. There are two simple supports below the beam. One at the end and another one at a distance of 10 meters from the start. The deflection is restricted at both the supports. Using the sign convention of upward forces and clockwise moment being positive. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> E, I = symbols('E, I') >>> R1, R2 = symbols('R1, R2') >>> b = Beam(30, E, I) >>> b.apply_load(-8, 0, -1) >>> b.apply_load(R1, 10, -1) >>> b.apply_load(R2, 30, -1) >>> b.apply_load(120, 30, -2) >>> b.bc_deflection = [(10, 0), (30, 0)] >>> b.solve_for_reaction_loads(R1, R2) >>> b.slope() (-4*SingularityFunction(x, 0, 2) + 3*SingularityFunction(x, 10, 2) + 120*SingularityFunction(x, 30, 1) + SingularityFunction(x, 30, 2) + 4000/3)/(E*I) """ x = self.variable E = self.elastic_modulus I = self.second_moment if self._composite_type == "hinge": return self._hinge_beam_slope if not self._boundary_conditions['slope']: return diff(self.deflection(), x) if self._composite_type == "fixed": args = I.args slope = 0 conditions = [] prev_slope = 0 prev_end = 0 for i in range(len(args)): if i != 0: prev_end = args[i-1][1].args[1] slope_value = S(1)/E*integrate(self.bending_moment()/args[i][0], (x, prev_end, x)) if i != len(args) - 1: slope += (prev_slope + slope_value)*SingularityFunction(x, prev_end, 0) - \ (prev_slope + slope_value)*SingularityFunction(x, args[i][1].args[1], 0) else: slope += (prev_slope + slope_value)*SingularityFunction(x, prev_end, 0) prev_slope = slope_value.subs(x, args[i][1].args[1]) return slope C3 = Symbol('C3') slope_curve = integrate(S(1)/(E*I)*self.bending_moment(), x) + C3 bc_eqs = [] for position, value in self._boundary_conditions['slope']: eqs = slope_curve.subs(x, position) - value bc_eqs.append(eqs) constants = list(linsolve(bc_eqs, C3)) slope_curve = slope_curve.subs({C3: constants[0][0]}) return slope_curve
[docs] def deflection(self): """ Returns a Singularity Function expression which represents the elastic curve or deflection of the Beam object. Examples ======== There is a beam of length 30 meters. A moment of magnitude 120 Nm is applied in the clockwise direction at the end of the beam. A pointload of magnitude 8 N is applied from the top of the beam at the starting point. There are two simple supports below the beam. One at the end and another one at a distance of 10 meters from the start. The deflection is restricted at both the supports. Using the sign convention of upward forces and clockwise moment being positive. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> E, I = symbols('E, I') >>> R1, R2 = symbols('R1, R2') >>> b = Beam(30, E, I) >>> b.apply_load(-8, 0, -1) >>> b.apply_load(R1, 10, -1) >>> b.apply_load(R2, 30, -1) >>> b.apply_load(120, 30, -2) >>> b.bc_deflection = [(10, 0), (30, 0)] >>> b.solve_for_reaction_loads(R1, R2) >>> b.deflection() (4000*x/3 - 4*SingularityFunction(x, 0, 3)/3 + SingularityFunction(x, 10, 3) + 60*SingularityFunction(x, 30, 2) + SingularityFunction(x, 30, 3)/3 - 12000)/(E*I) """ x = self.variable E = self.elastic_modulus I = self.second_moment if self._composite_type == "hinge": return self._hinge_beam_deflection if not self._boundary_conditions['deflection'] and not self._boundary_conditions['slope']: if self._composite_type == "fixed": args = I.args conditions = [] prev_slope = 0 prev_def = 0 prev_end = 0 deflection = 0 for i in range(len(args)): if i != 0: prev_end = args[i-1][1].args[1] slope_value = S(1)/E*integrate(self.bending_moment()/args[i][0], (x, prev_end, x)) recent_segment_slope = prev_slope + slope_value deflection_value = integrate(recent_segment_slope, (x, prev_end, x)) if i != len(args) - 1: deflection += (prev_def + deflection_value)*SingularityFunction(x, prev_end, 0) \ - (prev_def + deflection_value)*SingularityFunction(x, args[i][1].args[1], 0) else: deflection += (prev_def + deflection_value)*SingularityFunction(x, prev_end, 0) prev_slope = slope_value.subs(x, args[i][1].args[1]) prev_def = deflection_value.subs(x, args[i][1].args[1]) return deflection base_char = self._base_char constants = symbols(base_char + '3:5') return S(1)/(E*I)*integrate(integrate(self.bending_moment(), x), x) + constants[0]*x + constants[1] elif not self._boundary_conditions['deflection']: base_char = self._base_char constant = symbols(base_char + '4') return integrate(self.slope(), x) + constant elif not self._boundary_conditions['slope'] and self._boundary_conditions['deflection']: if self._composite_type == "fixed": args = I.args conditions = [] prev_slope = 0 prev_def = 0 prev_end = 0 deflection = 0 for i in range(len(args)): if i != 0: prev_end = args[i-1][1].args[1] slope_value = S(1)/E*integrate(self.bending_moment()/args[i][0], (x, prev_end, x)) recent_segment_slope = prev_slope + slope_value deflection_value = integrate(recent_segment_slope, (x, prev_end, x)) if i != len(args) - 1: deflection += (prev_def + deflection_value)*SingularityFunction(x, prev_end, 0) \ - (prev_def + deflection_value)*SingularityFunction(x, args[i][1].args[1], 0) else: deflection += (prev_def + deflection_value)*SingularityFunction(x, prev_end, 0) prev_slope = slope_value.subs(x, args[i][1].args[1]) prev_def = deflection_value.subs(x, args[i][1].args[1]) return deflection base_char = self._base_char C3, C4 = symbols(base_char + '3:5') # Integration constants slope_curve = integrate(self.bending_moment(), x) + C3 deflection_curve = integrate(slope_curve, x) + C4 bc_eqs = [] for position, value in self._boundary_conditions['deflection']: eqs = deflection_curve.subs(x, position) - value bc_eqs.append(eqs) constants = list(linsolve(bc_eqs, (C3, C4))) deflection_curve = deflection_curve.subs({C3: constants[0][0], C4: constants[0][1]}) return S(1)/(E*I)*deflection_curve if self._composite_type == "fixed": args = I.args conditions = [] prev_slope = 0 prev_def = 0 prev_end = 0 deflection = 0 for i in range(len(args)): if i != 0: prev_end = args[i-1][1].args[1] slope_value = S(1)/E*integrate(self.bending_moment()/args[i][0], (x, prev_end, x)) recent_segment_slope = prev_slope + slope_value deflection_value = integrate(recent_segment_slope, (x, prev_end, x)) if i != len(args) - 1: deflection += (prev_def + deflection_value)*SingularityFunction(x, prev_end, 0) \ - (prev_def + deflection_value)*SingularityFunction(x, args[i][1].args[1], 0) else: deflection += (prev_def + deflection_value)*SingularityFunction(x, prev_end, 0) prev_slope = slope_value.subs(x, args[i][1].args[1]) prev_def = deflection_value.subs(x, args[i][1].args[1]) return deflection C4 = Symbol('C4') deflection_curve = integrate(self.slope(), x) + C4 bc_eqs = [] for position, value in self._boundary_conditions['deflection']: eqs = deflection_curve.subs(x, position) - value bc_eqs.append(eqs) constants = list(linsolve(bc_eqs, C4)) deflection_curve = deflection_curve.subs({C4: constants[0][0]}) return deflection_curve
[docs] def max_deflection(self): """ Returns point of max deflection and its coresponding deflection value in a Beam object. """ from sympy import solve, Piecewise # To restrict the range within length of the Beam slope_curve = Piecewise((float("nan"), self.variable<=0), (self.slope(), self.variable<self.length), (float("nan"), True)) points = solve(slope_curve.rewrite(Piecewise), self.variable, domain=S.Reals) deflection_curve = self.deflection() deflections = [deflection_curve.subs(self.variable, x) for x in points] deflections = list(map(abs, deflections)) if len(deflections) != 0: max_def = max(deflections) return (points[deflections.index(max_def)], max_def) else: return None
[docs] def plot_shear_force(self, subs=None): """ Returns a plot for Shear force present in the Beam object. Parameters ========== subs : dictionary Python dictionary containing Symbols as key and their corresponding values. Examples ======== There is a beam of length 8 meters. A constant distributed load of 10 KN/m is applied from half of the beam till the end. There are two simple supports below the beam, one at the starting point and another at the ending point of the beam. A pointload of magnitude 5 KN is also applied from top of the beam, at a distance of 4 meters from the starting point. Take E = 200 GPa and I = 400*(10**-6) meter**4. Using the sign convention of downwards forces being positive. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> R1, R2 = symbols('R1, R2') >>> b = Beam(8, 200*(10**9), 400*(10**-6)) >>> b.apply_load(5000, 2, -1) >>> b.apply_load(R1, 0, -1) >>> b.apply_load(R2, 8, -1) >>> b.apply_load(10000, 4, 0, end=8) >>> b.bc_deflection = [(0, 0), (8, 0)] >>> b.solve_for_reaction_loads(R1, R2) >>> b.plot_shear_force() Plot object containing: [0]: cartesian line: -13750*SingularityFunction(x, 0, 0) + 5000*SingularityFunction(x, 2, 0) + 10000*SingularityFunction(x, 4, 1) - 31250*SingularityFunction(x, 8, 0) - 10000*SingularityFunction(x, 8, 1) for x over (0.0, 8.0) """ shear_force = self.shear_force() if subs is None: subs = {} for sym in shear_force.atoms(Symbol): if sym == self.variable: continue if sym not in subs: raise ValueError('Value of %s was not passed.' %sym) if self.length in subs: length = subs[self.length] else: length = self.length return plot(shear_force.subs(subs), (self.variable, 0, length), title='Shear Force', xlabel='position', ylabel='Value', line_color='g')
[docs] def plot_bending_moment(self, subs=None): """ Returns a plot for Bending moment present in the Beam object. Parameters ========== subs : dictionary Python dictionary containing Symbols as key and their corresponding values. Examples ======== There is a beam of length 8 meters. A constant distributed load of 10 KN/m is applied from half of the beam till the end. There are two simple supports below the beam, one at the starting point and another at the ending point of the beam. A pointload of magnitude 5 KN is also applied from top of the beam, at a distance of 4 meters from the starting point. Take E = 200 GPa and I = 400*(10**-6) meter**4. Using the sign convention of downwards forces being positive. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> R1, R2 = symbols('R1, R2') >>> b = Beam(8, 200*(10**9), 400*(10**-6)) >>> b.apply_load(5000, 2, -1) >>> b.apply_load(R1, 0, -1) >>> b.apply_load(R2, 8, -1) >>> b.apply_load(10000, 4, 0, end=8) >>> b.bc_deflection = [(0, 0), (8, 0)] >>> b.solve_for_reaction_loads(R1, R2) >>> b.plot_bending_moment() Plot object containing: [0]: cartesian line: -13750*SingularityFunction(x, 0, 1) + 5000*SingularityFunction(x, 2, 1) + 5000*SingularityFunction(x, 4, 2) - 31250*SingularityFunction(x, 8, 1) - 5000*SingularityFunction(x, 8, 2) for x over (0.0, 8.0) """ bending_moment = self.bending_moment() if subs is None: subs = {} for sym in bending_moment.atoms(Symbol): if sym == self.variable: continue if sym not in subs: raise ValueError('Value of %s was not passed.' %sym) if self.length in subs: length = subs[self.length] else: length = self.length return plot(bending_moment.subs(subs), (self.variable, 0, length), title='Bending Moment', xlabel='position', ylabel='Value', line_color='b')
[docs] def plot_slope(self, subs=None): """ Returns a plot for slope of deflection curve of the Beam object. Parameters ========== subs : dictionary Python dictionary containing Symbols as key and their corresponding values. Examples ======== There is a beam of length 8 meters. A constant distributed load of 10 KN/m is applied from half of the beam till the end. There are two simple supports below the beam, one at the starting point and another at the ending point of the beam. A pointload of magnitude 5 KN is also applied from top of the beam, at a distance of 4 meters from the starting point. Take E = 200 GPa and I = 400*(10**-6) meter**4. Using the sign convention of downwards forces being positive. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> R1, R2 = symbols('R1, R2') >>> b = Beam(8, 200*(10**9), 400*(10**-6)) >>> b.apply_load(5000, 2, -1) >>> b.apply_load(R1, 0, -1) >>> b.apply_load(R2, 8, -1) >>> b.apply_load(10000, 4, 0, end=8) >>> b.bc_deflection = [(0, 0), (8, 0)] >>> b.solve_for_reaction_loads(R1, R2) >>> b.plot_slope() Plot object containing: [0]: cartesian line: -8.59375e-5*SingularityFunction(x, 0, 2) + 3.125e-5*SingularityFunction(x, 2, 2) + 2.08333333333333e-5*SingularityFunction(x, 4, 3) - 0.0001953125*SingularityFunction(x, 8, 2) - 2.08333333333333e-5*SingularityFunction(x, 8, 3) + 0.00138541666666667 for x over (0.0, 8.0) """ slope = self.slope() if subs is None: subs = {} for sym in slope.atoms(Symbol): if sym == self.variable: continue if sym not in subs: raise ValueError('Value of %s was not passed.' %sym) if self.length in subs: length = subs[self.length] else: length = self.length return plot(slope.subs(subs), (self.variable, 0, length), title='Slope', xlabel='position', ylabel='Value', line_color='m')
[docs] def plot_deflection(self, subs=None): """ Returns a plot for deflection curve of the Beam object. Parameters ========== subs : dictionary Python dictionary containing Symbols as key and their corresponding values. Examples ======== There is a beam of length 8 meters. A constant distributed load of 10 KN/m is applied from half of the beam till the end. There are two simple supports below the beam, one at the starting point and another at the ending point of the beam. A pointload of magnitude 5 KN is also applied from top of the beam, at a distance of 4 meters from the starting point. Take E = 200 GPa and I = 400*(10**-6) meter**4. Using the sign convention of downwards forces being positive. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> R1, R2 = symbols('R1, R2') >>> b = Beam(8, 200*(10**9), 400*(10**-6)) >>> b.apply_load(5000, 2, -1) >>> b.apply_load(R1, 0, -1) >>> b.apply_load(R2, 8, -1) >>> b.apply_load(10000, 4, 0, end=8) >>> b.bc_deflection = [(0, 0), (8, 0)] >>> b.solve_for_reaction_loads(R1, R2) >>> b.plot_deflection() Plot object containing: [0]: cartesian line: 0.00138541666666667*x - 2.86458333333333e-5*SingularityFunction(x, 0, 3) + 1.04166666666667e-5*SingularityFunction(x, 2, 3) + 5.20833333333333e-6*SingularityFunction(x, 4, 4) - 6.51041666666667e-5*SingularityFunction(x, 8, 3) - 5.20833333333333e-6*SingularityFunction(x, 8, 4) for x over (0.0, 8.0) """ deflection = self.deflection() if subs is None: subs = {} for sym in deflection.atoms(Symbol): if sym == self.variable: continue if sym not in subs: raise ValueError('Value of %s was not passed.' %sym) if self.length in subs: length = subs[self.length] else: length = self.length return plot(deflection.subs(subs), (self.variable, 0, length), title='Deflection', xlabel='position', ylabel='Value', line_color='r')
[docs] @doctest_depends_on(modules=('numpy', 'matplotlib',)) def plot_loading_results(self, subs=None): """ Returns Axes object containing subplots of Shear Force, Bending Moment, Slope and Deflection of the Beam object. Parameters ========== subs : dictionary Python dictionary containing Symbols as key and their corresponding values. .. note:: This method only works if numpy and matplotlib libraries are installed on the system. Examples ======== There is a beam of length 8 meters. A constant distributed load of 10 KN/m is applied from half of the beam till the end. There are two simple supports below the beam, one at the starting point and another at the ending point of the beam. A pointload of magnitude 5 KN is also applied from top of the beam, at a distance of 4 meters from the starting point. Take E = 200 GPa and I = 400*(10**-6) meter**4. Using the sign convention of downwards forces being positive. >>> from sympy.physics.continuum_mechanics.beam import Beam >>> from sympy import symbols >>> R1, R2 = symbols('R1, R2') >>> b = Beam(8, 200*(10**9), 400*(10**-6)) >>> b.apply_load(5000, 2, -1) >>> b.apply_load(R1, 0, -1) >>> b.apply_load(R2, 8, -1) >>> b.apply_load(10000, 4, 0, end=8) >>> b.bc_deflection = [(0, 0), (8, 0)] >>> b.solve_for_reaction_loads(R1, R2) >>> axes = b.plot_loading_results() """ from sympy import lambdify matplotlib = import_module('matplotlib', __import__kwargs={'fromlist':['pyplot']}) plt = matplotlib.pyplot numpy = import_module('numpy', __import__kwargs={'fromlist':['linspace']}) linspace = numpy.linspace length = self.length variable = self.variable if subs is None: subs = {} for sym in self.deflection().atoms(Symbol): if sym == self.variable: continue if sym not in subs: raise ValueError('Value of %s was not passed.' %sym) if self.length in subs: length = subs[self.length] else: length = self.length # As we are using matplotlib directly in this method, we need to change SymPy methods # to numpy functions. shear = lambdify(variable, self.shear_force().subs(subs).rewrite(Piecewise), 'numpy') moment = lambdify(variable, self.bending_moment().subs(subs).rewrite(Piecewise), 'numpy') slope = lambdify(variable, self.slope().subs(subs).rewrite(Piecewise), 'numpy') deflection = lambdify(variable, self.deflection().subs(subs).rewrite(Piecewise), 'numpy') points = linspace(0, float(length), num=5*length) # Creating a grid for subplots with 2 rows and 2 columns fig, axs = plt.subplots(4, 1) # axs is a 2D-numpy array containing axes axs[0].plot(points, shear(points)) axs[0].set_title("Shear Force") axs[1].plot(points, moment(points)) axs[1].set_title("Bending Moment") axs[2].plot(points, slope(points)) axs[2].set_title("Slope") axs[3].plot(points, deflection(points)) axs[3].set_title("Deflection") fig.tight_layout() # For better spacing between subplots return axs
[docs]class Beam3D(Beam): """ This class handles loads applied in any direction of a 3D space along with unequal values of Second moment along different axes. .. note:: While solving a beam bending problem, a user should choose its own sign convention and should stick to it. The results will automatically follow the chosen sign convention. This class assumes that any kind of distributed load/moment is applied through out the span of a beam. Examples ======== There is a beam of l meters long. A constant distributed load of magnitude q is applied along y-axis from start till the end of beam. A constant distributed moment of magnitude m is also applied along z-axis from start till the end of beam. Beam is fixed at both of its end. So, deflection of the beam at the both ends is restricted. >>> from sympy.physics.continuum_mechanics.beam import Beam3D >>> from sympy import symbols >>> l, E, G, I, A = symbols('l, E, G, I, A') >>> b = Beam3D(l, E, G, I, A) >>> q, m = symbols('q, m') >>> b.apply_load(q, 0, 0, dir="y") >>> b.apply_moment_load(m, 0, -1, dir="z") >>> b.shear_force() [0, -q*x, 0] >>> b.bending_moment() [0, 0, -m*x + q*x**2/2] >>> b.bc_slope = [(0, [0, 0, 0]), (l, [0, 0, 0])] >>> b.bc_deflection = [(0, [0, 0, 0]), (l, [0, 0, 0])] >>> b.solve_slope_deflection() >>> b.slope() [0, 0, l*x*(-l*q + 3*l*(A*G*l*(l*q - 2*m) + 12*E*I*q)/(2*(A*G*l**2 + 12*E*I)) + 3*m)/(6*E*I) + q*x**3/(6*E*I) + x**2*(-l*(A*G*l*(l*q - 2*m) + 12*E*I*q)/(2*(A*G*l**2 + 12*E*I)) - m)/(2*E*I)] >>> b.deflection() [0, -l**2*q*x**2/(12*E*I) + l**2*x**2*(A*G*l*(l*q - 2*m) + 12*E*I*q)/(8*E*I*(A*G*l**2 + 12*E*I)) + l*m*x**2/(4*E*I) - l*x**3*(A*G*l*(l*q - 2*m) + 12*E*I*q)/(12*E*I*(A*G*l**2 + 12*E*I)) - m*x**3/(6*E*I) + q*x**4/(24*E*I) + l*x*(A*G*l*(l*q - 2*m) + 12*E*I*q)/(2*A*G*(A*G*l**2 + 12*E*I)) - q*x**2/(2*A*G), 0] References ========== .. [1] http://homes.civil.aau.dk/jc/FemteSemester/Beams3D.pdf """ def __init__(self, length, elastic_modulus, shear_modulus , second_moment, area, variable=Symbol('x')): """Initializes the class. Parameters ========== length : Sympifyable A Symbol or value representing the Beam's length. elastic_modulus : Sympifyable A SymPy expression representing the Beam's Modulus of Elasticity. It is a measure of the stiffness of the Beam material. shear_modulus : Sympifyable A SymPy expression representing the Beam's Modulus of rigidity. It is a measure of rigidity of the Beam material. second_moment : Sympifyable or list A list of two elements having SymPy expression representing the Beam's Second moment of area. First value represent Second moment across y-axis and second across z-axis. Single SymPy expression can be passed if both values are same area : Sympifyable A SymPy expression representing the Beam's cross-sectional area in a plane prependicular to length of the Beam. variable : Symbol, optional A Symbol object that will be used as the variable along the beam while representing the load, shear, moment, slope and deflection curve. By default, it is set to ``Symbol('x')``. """ self.length = length self.elastic_modulus = elastic_modulus self.shear_modulus = shear_modulus self.second_moment = second_moment self.area = area self.variable = variable self._boundary_conditions = {'deflection': [], 'slope': []} self._load_vector = [0, 0, 0] self._moment_load_vector = [0, 0, 0] self._load_Singularity = [0, 0, 0] self._reaction_loads = {} self._slope = [0, 0, 0] self._deflection = [0, 0, 0] @property def shear_modulus(self): """Young's Modulus of the Beam. """ return self._shear_modulus @shear_modulus.setter def shear_modulus(self, e): self._shear_modulus = sympify(e) @property def second_moment(self): """Second moment of area of the Beam. """ return self._second_moment @second_moment.setter def second_moment(self, i): if isinstance(i, list): i = [sympify(x) for x in i] self._second_moment = i else: self._second_moment = sympify(i) @property def area(self): """Cross-sectional area of the Beam. """ return self._area @area.setter def area(self, a): self._area = sympify(a) @property def load_vector(self): """ Returns a three element list representing the load vector. """ return self._load_vector @property def moment_load_vector(self): """ Returns a three element list representing moment loads on Beam. """ return self._moment_load_vector @property def boundary_conditions(self): """ Returns a dictionary of boundary conditions applied on the beam. The dictionary has two keywords namely slope and deflection. The value of each keyword is a list of tuple, where each tuple contains loaction and value of a boundary condition in the format (location, value). Further each value is a list corresponding to slope or deflection(s) values along three axes at that location. Examples ======== There is a beam of length 4 meters. The slope at 0 should be 4 along the x-axis and 0 along others. At the other end of beam, deflection along all the three axes should be zero. >>> from sympy.physics.continuum_mechanics.beam import Beam3D >>> from sympy import symbols >>> l, E, G, I, A, x = symbols('l, E, G, I, A, x') >>> b = Beam3D(30, E, G, I, A, x) >>> b.bc_slope = [(0, (4, 0, 0))] >>> b.bc_deflection = [(4, [0, 0, 0])] >>> b.boundary_conditions {'deflection': [(4, [0, 0, 0])], 'slope': [(0, (4, 0, 0))]} Here the deflection of the beam should be ``0`` along all the three axes at ``4``. Similarly, the slope of the beam should be ``4`` along x-axis and ``0`` along y and z axis at ``0``. """ return self._boundary_conditions
[docs] def apply_load(self, value, start, order, dir="y"): """ This method adds up the force load to a particular beam object. Parameters ========== value : Sympifyable The magnitude of an applied load. dir : String Axis along which load is applied. order : Integer The order of the applied load. - For point loads, order=-1 - For constant distributed load, order=0 - For ramp loads, order=1 - For parabolic ramp loads, order=2 - ... so on. """ x = self.variable value = sympify(value) start = sympify(start) order = sympify(order) if dir == "x": if not order == -1: self._load_vector[0] += value self._load_Singularity[0] += value*SingularityFunction(x, start, order) elif dir == "y": if not order == -1: self._load_vector[1] += value self._load_Singularity[1] += value*SingularityFunction(x, start, order) else: if not order == -1: self._load_vector[2] += value self._load_Singularity[2] += value*SingularityFunction(x, start, order)
[docs] def apply_moment_load(self, value, start, order, dir="y"): """ This method adds up the moment loads to a particular beam object. Parameters ========== value : Sympifyable The magnitude of an applied moment. dir : String Axis along which moment is applied. order : Integer The order of the applied load. - For point moments, order=-2 - For constant distributed moment, order=-1 - For ramp moments, order=0 - For parabolic ramp moments, order=1 - ... so on. """ x = self.variable value = sympify(value) start = sympify(start) order = sympify(order) if dir == "x": if not order == -2: self._moment_load_vector[0] += value self._load_Singularity[0] += value*SingularityFunction(x, start, order) elif dir == "y": if not order == -2: self._moment_load_vector[1] += value self._load_Singularity[0] += value*SingularityFunction(x, start, order) else: if not order == -2: self._moment_load_vector[2] += value self._load_Singularity[0] += value*SingularityFunction(x, start, order)
def apply_support(self, loc, type="fixed"): if type == "pin" or type == "roller": reaction_load = Symbol('R_'+str(loc)) self._reaction_loads[reaction_load] = reaction_load self.bc_deflection.append((loc, [0, 0, 0])) else: reaction_load = Symbol('R_'+str(loc)) reaction_moment = Symbol('M_'+str(loc)) self._reaction_loads[reaction_load] = [reaction_load, reaction_moment] self.bc_deflection = [(loc, [0, 0, 0])] self.bc_slope.append((loc, [0, 0, 0]))
[docs] def solve_for_reaction_loads(self, *reaction): """ Solves for the reaction forces. Examples ======== There is a beam of length 30 meters. It it supported by rollers at of its end. A constant distributed load of magnitude 8 N is applied from start till its end along y-axis. Another linear load having slope equal to 9 is applied along z-axis. >>> from sympy.physics.continuum_mechanics.beam import Beam3D >>> from sympy import symbols >>> l, E, G, I, A, x = symbols('l, E, G, I, A, x') >>> b = Beam3D(30, E, G, I, A, x) >>> b.apply_load(8, start=0, order=0, dir="y") >>> b.apply_load(9*x, start=0, order=0, dir="z") >>> b.bc_deflection = [(0, [0, 0, 0]), (30, [0, 0, 0])] >>> R1, R2, R3, R4 = symbols('R1, R2, R3, R4') >>> b.apply_load(R1, start=0, order=-1, dir="y") >>> b.apply_load(R2, start=30, order=-1, dir="y") >>> b.apply_load(R3, start=0, order=-1, dir="z") >>> b.apply_load(R4, start=30, order=-1, dir="z") >>> b.solve_for_reaction_loads(R1, R2, R3, R4) >>> b.reaction_loads {R1: -120, R2: -120, R3: -1350, R4: -2700} """ x = self.variable l=self.length q = self._load_Singularity m = self._moment_load_vector shear_curves = [integrate(load, x) for load in q] moment_curves = [integrate(shear, x) for shear in shear_curves] for i in range(3): react = [r for r in reaction if (shear_curves[i].has(r) or moment_curves[i].has(r))] if len(react) == 0: continue shear_curve = limit(shear_curves[i], x, l) moment_curve = limit(moment_curves[i], x, l) sol = list((linsolve([shear_curve, moment_curve], react).args)[0]) sol_dict = dict(zip(react, sol)) reaction_loads = self._reaction_loads # Check if any of the evaluated rection exists in another direction # and if it exists then it should have same value. for key in sol_dict: if key in reaction_loads and sol_dict[key] != reaction_loads[key]: raise ValueError("Ambiguous solution for %s in different directions." % key) self._reaction_loads.update(sol_dict)
[docs] def shear_force(self): """ Returns a list of three expressions which represents the shear force curve of the Beam object along all three axes. """ x = self.variable q = self._load_vector m = self._moment_load_vector return [integrate(-q[0], x), integrate(-q[1], x), integrate(-q[2], x)]
[docs] def axial_force(self): """ Returns expression of Axial shear force present inside the Beam object. """ return self.shear_force()[0]
[docs] def bending_moment(self): """ Returns a list of three expressions which represents the bending moment curve of the Beam object along all three axes. """ x = self.variable q = self._load_vector m = self._moment_load_vector shear = self.shear_force() return [integrate(-m[0], x), integrate(-m[1] + shear[2], x), integrate(-m[2] - shear[1], x) ]
[docs] def torsional_moment(): """ Returns expression of Torsional moment present inside the Beam object. """ return self.bending_moment()[0]
def solve_slope_deflection(self): from sympy import dsolve, Function, Derivative, Eq x = self.variable l = self.length E = self.elastic_modulus G = self.shear_modulus I = self.second_moment if isinstance(I, list): I_y, I_z = I[0], I[1] else: I_y = I_z = I A = self.area load = self._load_vector moment = self._moment_load_vector defl = Function('defl') theta = Function('theta') # Finding deflection along x-axis(and corresponding slope value by differentiating it) # Equation used: Derivative(E*A*Derivative(def_x(x), x), x) + load_x = 0 eq = Derivative(E*A*Derivative(defl(x), x), x) + load[0] def_x = dsolve(Eq(eq, 0), defl(x)).args[1] # Solving constants originated from dsolve C1 = Symbol('C1') C2 = Symbol('C2') constants = list((linsolve([def_x.subs(x, 0), def_x.subs(x, l)], C1, C2).args)[0]) def_x = def_x.subs({C1:constants[0], C2:constants[1]}) slope_x = def_x.diff(x) self._deflection[0] = def_x self._slope[0] = slope_x # Finding deflection along y-axis and slope across z-axis. System of equation involved: # 1: Derivative(E*I_z*Derivative(theta_z(x), x), x) + G*A*(Derivative(defl_y(x), x) - theta_z(x)) + moment_z = 0 # 2: Derivative(G*A*(Derivative(defl_y(x), x) - theta_z(x)), x) + load_y = 0 C_i = Symbol('C_i') # Substitute value of `G*A*(Derivative(defl_y(x), x) - theta_z(x))` from (2) in (1) eq1 = Derivative(E*I_z*Derivative(theta(x), x), x) + (integrate(-load[1], x) + C_i) + moment[2] slope_z = dsolve(Eq(eq1, 0)).args[1] # Solve for constants originated from using dsolve on eq1 constants = list((linsolve([slope_z.subs(x, 0), slope_z.subs(x, l)], C1, C2).args)[0]) slope_z = slope_z.subs({C1:constants[0], C2:constants[1]}) # Put value of slope obtained back in (2) to solve for `C_i` and find deflection across y-axis eq2 = G*A*(Derivative(defl(x), x)) + load[1]*x - C_i - G*A*slope_z def_y = dsolve(Eq(eq2, 0), defl(x)).args[1] # Solve for constants originated from using dsolve on eq2 constants = list((linsolve([def_y.subs(x, 0), def_y.subs(x, l)], C1, C_i).args)[0]) self._deflection[1] = def_y.subs({C1:constants[0], C_i:constants[1]}) self._slope[2] = slope_z.subs(C_i, constants[1]) # Finding deflection along z-axis and slope across y-axis. System of equation involved: # 1: Derivative(E*I_y*Derivative(theta_y(x), x), x) - G*A*(Derivative(defl_z(x), x) + theta_y(x)) + moment_y = 0 # 2: Derivative(G*A*(Derivative(defl_z(x), x) + theta_y(x)), x) + load_z = 0 # Substitute value of `G*A*(Derivative(defl_y(x), x) + theta_z(x))` from (2) in (1) eq1 = Derivative(E*I_y*Derivative(theta(x), x), x) + (integrate(load[2], x) - C_i) + moment[1] slope_y = dsolve(Eq(eq1, 0)).args[1] # Solve for constants originated from using dsolve on eq1 constants = list((linsolve([slope_y.subs(x, 0), slope_y.subs(x, l)], C1, C2).args)[0]) slope_y = slope_y.subs({C1:constants[0], C2:constants[1]}) # Put value of slope obtained back in (2) to solve for `C_i` and find deflection across z-axis eq2 = G*A*(Derivative(defl(x), x)) + load[2]*x - C_i + G*A*slope_y def_z = dsolve(Eq(eq2,0)).args[1] # Solve for constants originated from using dsolve on eq2 constants = list((linsolve([def_z.subs(x, 0), def_z.subs(x, l)], C1, C_i).args)[0]) self._deflection[2] = def_z.subs({C1:constants[0], C_i:constants[1]}) self._slope[1] = slope_y.subs(C_i, constants[1])
[docs] def slope(self): """ Returns a three element list representing slope of deflection curve along all the three axes. """ return self._slope
[docs] def deflection(self): """ Returns a three element list representing deflection curve along all the three axes. """ return self._deflection