def test_simply_supported_beam_unequal_non_symmetric_loads():
"""Simple beam: Two unequal concentrated loads non-symmetrically placed
load case 11
"""
P1 = -900
P2 = -1200
a = L / 4 # location of first load from right
b = L / 5 # location of second load from left
R1 = -(P1 * (L - a) + P2 * b) / L
R2 = -(P1 * a + P2 * (L - b)) / L
M1 = R1 * a
x = L / 2
Mx = R1 * x + P1 * (x - a)
M2 = R2 * b
p = [
PointLoad(magnitude=P1, location=a),
PointLoad(magnitude=P2, location=L - b)
]
r = [PinnedReaction(x) for x in [0, L]]
beam = Beam(length=L, loads=p, reactions=r, E=E, Ixx=Ixx)
beam.solve()
# verify reactions
for m, loc in zip((M1, Mx, M2), (a, L / 2, L - b)):
# assert approx(beam.reactions[0].value[0], rel=1e-4) == R1*1.25
validate(beam, loc=loc, R=[(R1, 0), (R2, 0)], M_loc=m, d_loc=None)
def test_deflection_for_fixed_cantilevered_beam_with_load_at_any_point():
P = -1000 # load in lbs down
a = 7 # position of load in inches
L = 25 # length of beam in inches
E = 29e6 # Young's modulus in psi
Ixx = 345 # area moment of inertia in in**4
b = L - a
# function to calculate deflection anywhere along the length of the beam
d1 = lambda x: P * b**2 / (6 * E * Ixx) * (3 * L - 3 * x - b) # x < a
d2 = lambda x: P * (L - x)**2 / (6 * E * Ixx) * (3 * b - L + x) # x > a
d3 = lambda x: P * b**3 / (3 * E * Ixx) # x == a
beam = Beam(L, [PointLoad(P, a)], [FixedReaction(L)], E, Ixx)
for x in [0, 7, 12.5, 25]:
# check the deflection of the beam at both end points, and the center
if x < a:
exact = d1(x)
elif x > a:
exact = d2(x)
else:
exact = d3(x)
assert pytest.approx(beam.deflection(x), rel=1e-12) == exact, \
f"Calculated deflection does not match expected deflection at {x}"
def test_simply_supported_beam_offset_load():
"""simple beam - concentrated load at arbitrary points
Load case 8
"""
locations = [2, 3, 5, 7, 8]
for location in locations:
# Exact setup
a = location
b = L - a
R1 = -P * b / L
R2 = -P * a / L
M_loc = -P * a * b / L # moment at load
d_loc = P * a**2 * b**2 / (3 * EI * L) # deflection at load
# numerical result
beam = Beam(
L,
loads=[PointLoad(P, location)],
reactions=[PinnedReaction(x) for x in [0, L]],
E=E,
Ixx=Ixx,
)
beam.solve()
# verify reactions
validate(beam,
loc=location,
R=[(R1, 0), (R2, 0)],
M_loc=M_loc,
d_loc=d_loc)
def test_stiffness_matrix_k():
beam = Beam(25, [PointLoad(-100, 25)], [FixedReaction(0)], 29e6, 345)
assert beam.K.shape == (4, 4), "stiffness matrix is not expected size"
# add another point load and verify the stiffness matrix changes size
# accordingly
beam.loads.append(PointLoad(-500, 12))
beam.remesh()
assert beam.K.shape == (6, 6), "stiffness matrix size did not update"
def test_plot_default_labels():
b = Beam(10, [PointLoad(10, 10)], [FixedReaction(0)])
fig, axes = b.plot()
x_labels = ("", "", "Beam position, x")
y_labels = ("shear", "moment", "deflection")
assert len(axes) == len(x_labels), "wrong number of sub-plots"
for ax, x_label, y_label in zip(axes, x_labels, y_labels):
assert ax.get_xlabel() == x_label
assert ax.get_ylabel() == y_label
def test_plot_custom_labels():
b = Beam(10, [PointLoad(10, 10)], [FixedReaction(0)])
diagrams = ("deflection", "deflection", "moment", "shear")
labels = ("def1", "def2", "M", "V")
fig, axes = b.plot(diagrams=diagrams, diagram_labels=labels)
assert len(axes) == len(diagrams), "wrong number of sub-plots"
x_labels = ["" for _ in range(len(diagrams) - 1)]
x_labels.append("Beam position, x")
for ax, x_label, y_label in zip(axes, x_labels, labels):
assert ax.get_xlabel() == x_label
assert ax.get_ylabel() == y_label
def test_solve_method():
beam = Beam(25, [PointLoad(-100, 25)], [FixedReaction(0)], 29e6, 345)
reaction = beam.reactions[0]
assert reaction.force is None, "Reaction force was not None before being solved"
assert reaction.moment is None, "Reaction moment was not None before being solved"
beam.solve()
reaction = beam.reactions[0]
assert reaction.force == 100, "Reaction force must be equal to and opposite load"
assert (
reaction.moment == 100 *
25), "Reaction moment must be equal to the load times the moment arm"
def test_apply_boundary_conditions():
beam = Beam(25,
[PointLoad(-100, 25), PointLoad(-100, 12)], [FixedReaction(0)],
29e6, 345)
k = beam.K
bcs = [(None, None), (0, 0)]
initial_shape = beam.K.shape
assert initial_shape == (
6, 6), "stiffness matrix does not match expected size"
ki = beam.apply_boundary_conditions(k, bcs)
final_shape = ki.shape
assert initial_shape == final_shape, ("stiffness matrix changed shape "
"when applying boundary conditions")
def test_shear():
beam = Beam(25, [PointLoad(-1000, 25)], [FixedReaction(0)])
for x in [0.5, 5, 13, 20, 24.5]:
assert pytest.approx(beam.shear(x), rel=1e-5) == 1000, \
f"shear does not equal load at location {x}"
# right now, the derivative function will try to calculate shear outside
# of the beam when calculating shear at or near endpoints. Verify that
# calculating shear at ends raises a ValueError. It should also raise a
# ValueError when the input is outside the beam
for x in [-5, 0, 25, 35]:
with pytest.raises(ValueError):
beam.shear(x)
def test_reaction_load_warnings():
reactions = [PinnedReaction(x) for x in [0, 120]]
loads = [PointLoad(magnitude=-120, location=50)]
#
with pytest.raises(TypeError):
# create a beam where the reactions are not a list
Beam(120, reactions=PinnedReaction(0), loads=loads)
with pytest.raises(TypeError):
# create a beam where the loads are not a list
Beam(120, reactions=reactions, loads=PointLoad(-10, 5))
with pytest.raises(ValueError):
# beam length must be positive
Beam(-10, reactions=reactions, loads=loads)
with pytest.raises(TypeError):
# beam length must be a number
Beam("length is not a number", reactions=reactions, loads=loads)
def test_simply_supported_beam_equal_symmetric_loads():
"""Simple beam: Two equal concentrated loads symmetrically placed
load case 9
"""
R = -P # both reactions are equal
a = L / 4
M_loc = -P * a # max moment (at center between loads)
d_loc = P * a / (24 * EI) * (3 * L**2 - 4 * a**2
) # max deflection (at center)
p = [PointLoad(magnitude=P, location=x) for x in [a, L - a]]
r = [PinnedReaction(x) for x in [0, L]]
beam = Beam(length=L, loads=p, reactions=r, E=E, Ixx=Ixx)
beam.solve()
# verify reactions
validate(beam, loc=L / 2, R=[(R, 0), (R, 0)], M_loc=M_loc, d_loc=d_loc)
def test_beam_params():
reactions = [PinnedReaction(x) for x in [1, 120]]
loads = [PointLoad(magnitude=-120, location=50)]
beam = Beam(length=120, loads=loads, reactions=reactions, E=29e6, Ixx=350)
# check parameters of the beam to ensure they match the input
assert beam.length == 120, "beam length does not match input"
assert beam.E == 29e6, "Young's modulus does not match input"
assert beam.Ixx == 350, "area moment of inertia does not match input"
# update parameters and verify update was successful
beam.length = 130
beam.E = 29.9e6
beam.Ixx = 345
assert beam.length == 130, "beam length does not match input"
assert beam.E == 29.9e6, "Young's modulus does not match input"
assert beam.Ixx == 345, "area moment of inertia does not match input"
def test_moment_for_fixed_cantilevered_beam_with_load_at_end():
P = -1000 # load in lbs down
L = 25 # length of beam in inches
E = 29e6 # Young's modulus in psi
Ixx = 345 # area moment of inertia in in**4
# function to calculate moment anywhere along the length of the beam
m = lambda x: P * x
beam = Beam(L, [PointLoad(P, 0)], [FixedReaction(L)], E, Ixx)
for x in [7, 12.5, 25]:
# check the deflection of the beam at both end points, and the center
assert pytest.approx(beam.moment(x), rel=0.01) == m(x), \
f"Calculated moment does not match expected moment at {x}"
with pytest.warns(UserWarning):
beam.moment(0)
def test_invalid_deflection_location():
beam = Beam(25, [PointLoad(-100, 25)], [FixedReaction(0)], 29e6, 345)
with pytest.raises(ValueError):
beam.deflection(-4) # a value less than 0
with pytest.raises(ValueError):
beam.deflection(beam.length + 5) # a value greater then the length
with pytest.raises(TypeError):
beam.deflection('a string (not a number)')
def test_node_deflections_at_free_end():
for load in [PointLoad(-100, 25), MomentLoad(-100, 25)]:
beam = Beam(25, [load], [FixedReaction(0)], 29e6, 345)
# check that the deflection at the free end is non-zero and negative
msgs = [
"displacement at free end is not negative",
"angular displacement at free end is not negative",
]
for i, msg in enumerate(msgs, 2):
assert beam.node_deflections[i][0] < 0, msg
def example_2():
"""
Cantilevered Beam with 3 Pinned Supports and End Loading
"""
print("=" * 79)
print("Example 2")
print("Show an example with 3 Pinned Supports and End Loading\n")
beam_len = 10
# Note that both the reaction and load are both lists. They must always be
# given to Beam as a list,
r = [PinnedReaction(0), PinnedReaction(2), PinnedReaction(6)] # define reactions
p = [PointLoad(magnitude=-2, location=beam_len)] # define loads
b = Beam(beam_len, loads=p, reactions=r, E=29e6, Ixx=125)
# an explicit solve is required to calculate the reaction values
b.solve()
print(b)
def test_node_deflections_at_fixed_end():
for load in [PointLoad(-100, 25), MomentLoad(-100, 25)]:
beam = Beam(25, [load], [FixedReaction(0)], 29e6, 345)
# check that the deflection at the fixed end is 0
msgs = [
"displacement at fixed end is non-zero",
"angular displacement at fixed end is non-zero",
]
for i, msg in enumerate(msgs):
assert beam.node_deflections[i][0] == 0, msg
def test_simply_supported_beam_center_load():
"""simple beam - concentrated load at center
Load case 7
"""
# Exact setup
R = -P / 2 # lbs, reactions
M_max = -P * L / 4 # psi, maximum moment
d_max = P * L**3 / (48 * EI) # max displacement
# Numerical setup
beam = Beam(
length=L,
loads=[PointLoad(magnitude=P, location=L / 2)],
reactions=[PinnedReaction(x) for x in [0, L]],
E=E,
Ixx=Ixx,
)
beam.solve()
validate(beam, loc=L / 2, R=[(R, 0), (R, 0)], M_loc=M_max, d_loc=d_max)
def test_invalid_load_placement():
reactions = [PinnedReaction(x) for x in [0, 50, 100]]
loads = [PointLoad(-100, x) for x in [0, 50, 100]]
# there should be a warning indicating that the load position was moved
# slightly so it does not line up with the reaction.
with pytest.warns(UserWarning):
beam = Beam(100, loads=loads, reactions=reactions)
for load, reaction in zip(beam.loads, beam.reactions):
assert load.location != reaction.location, \
'moved load is still the same as a reaction'
def example_1():
"""
Cantilevered Beam with Fixed Support and End Loading
"""
print("=" * 79)
print("Example 1")
print(
"Show an example with a cantilevered beam with a fixed support and "
"point load at the end\n"
)
beam_len = 10
# Note that both the reaction and load are both lists. They must always be
# given to Beam as a list,
r = [FixedReaction(0)] # define reactions as list
p = [PointLoad(magnitude=-2, location=beam_len)] # define loads as list
b = Beam(beam_len, loads=p, reactions=r, E=29e6, Ixx=125)
# an explicit solve is required to calculate the reaction values
b.solve()
print(b)
def test_cantilevered_beam_load_at_end():
"""fixed beam with concentrated load at free end
case 13
"""
R = -P
M_max = P * L # at fixed end
d_max = P * L**3 / (3 * EI) # at free end
beam = Beam(
length=L,
loads=[PointLoad(magnitude=P, location=0)],
reactions=[FixedReaction(L)],
E=E,
Ixx=Ixx,
)
beam.solve()
validate(beam, loc=0, R=[(R, M_max)], M_loc=0, d_loc=d_max)
assert pytest.approx(beam.moment(L), rel=TOL) == M_max
def test_simply_supported_beam_equal_non_symmetric_loads():
"""Simple beam: Two equal concentrated loads non-symmetrically placed
load case 10
"""
a = L / 4 # location of first load from right
b = L / 5 # location of second load from left
R1 = -P / L * (L - a + b)
R2 = -P / L * (L + a - b)
M1 = R1 * a # moment at first load
x = L / 2
Mx = R1 * x + P * (x - a) # moment at center
M2 = R2 * b # moment at second load
p = [PointLoad(magnitude=P, location=x) for x in [a, L - b]]
r = [PinnedReaction(x) for x in [0, L]]
beam = Beam(length=L, loads=p, reactions=r, E=E, Ixx=Ixx)
beam.solve()
# verify reactions
for m, loc in zip((M1, Mx, M2), (a, L / 2, L - b)):
validate(beam, loc=loc, R=[(R1, 0), (R2, 0)], M_loc=m, d_loc=None)
def test_shape_function():
reactions = [PinnedReaction(x) for x in [0, 50, 100]]
loads = [PointLoad(-100, x) for x in [0, 50, 100]]
beam = Beam(100, loads, reactions, 29e6, 345)
assert beam.shape(0).shape == (4, ), "unexpected shape of shape functions"
n1, n2, n3, n4 = beam.shape(0)
assert n1 == 1, "N1(x=0) != 1"
assert n3 == 0, "N3(x=0) != 0"
# verify changing the length will not change the end points
n1, n2, n3, n4 = beam.shape(0, L=15)
assert n1 == 1, "N1(x=0) != 1"
assert n3 == 0, "N3(x=0) != 0"
n1, n2, n3, n4 = beam.shape(100, L=100) # at x==L
assert n1 == 0, "N1(x=L) != 0"
assert n3 == 1, "N3(x=L) != 1"
def test_plot_one_diagram():
b = Beam(10, [PointLoad(10, 10)], [FixedReaction(0)])
fig, axes = b.plot(diagrams=("deflection", ))
assert len(axes) == 1, "expected length of axes was 1"
for ax, y_label in zip(axes, ("deflection", )):
assert ax.get_ylabel() == y_label
def beam_fixed(length):
yield Beam(length=length,
loads=[PointLoad(-100, length)],
reactions=[FixedReaction(0)])
def beam_simply_supported(length, reaction_simple, load_centered):
yield Beam(length=length, loads=load_centered, reactions=reaction_simple)
def test_plot_diagram_labels_without_diagrams():
with pytest.raises(ValueError):
b = Beam(10, [PointLoad(10, 10)], [FixedReaction(0)])
b.plot(diagram_labels=("V, lb", "M, in/lb", "delta, in"))
def test_invalid_reaction_errors():
# Check for an TypeError for a variety of invalid reactions
for invalid_reaction in ['a string', PointLoad(25, 15), [], 10]:
with pytest.raises(TypeError):
Beam(25, loads=[PointLoad(-100, 15)], reactions=[invalid_reaction])
def test_bending_stress_depreciation_warning():
with pytest.warns(DeprecationWarning):
b = Beam(10, [PointLoad(10, 10)], [FixedReaction(0)])
b.bending_stress(x=5, c=1)
def test_invalid_load_errors():
# Check for a TypeError for a variety of invalid loads
for invalid_load in ['a string', FixedReaction(0), [], 10]:
with pytest.raises(TypeError):
Beam(25, loads=[invalid_load], reactions=[FixedReaction(0)])
