def sum_forces_moments_elements(model: BDF, p0: int, loadcase_id: int,
eids: List[int], nids: List[int],
cid: int=0,
include_grav: bool=False,
xyz_cid0: Optional[Dict[int, NDArray3float]]=None,
) -> Tuple[NDArray3float, NDArray3float]:
"""
Sum the forces/moments based on a list of nodes and elements.
Parameters
----------
model : BDF()
a BDF object
eids : List[int]
the list of elements to include (e.g. the loads due to a PLOAD4)
nids : List[int]
the list of nodes to include (e.g. the loads due to a FORCE card)
p0 : int; (3,) ndarray
the point to sum moments about
type = int
sum moments about the specified grid point
type = (3, ) ndarray/list (e.g. [10., 20., 30]):
the x, y, z location in the global frame
loadcase_id : int
the LOAD=ID to analyze
include_grav : bool; default=False
includes gravity in the summation (not supported)
xyz_cid0 : None / Dict[int] = (3, ) ndarray
the nodes in the global coordinate system
Returns
-------
forces : NUMPY.NDARRAY shape=(3,)
the forces
moments : NUMPY.NDARRAY shape=(3,)
the moments
Nodal Types : FORCE, FORCE1, FORCE2,
MOMENT, MOMENT1, MOMENT2,
PLOAD
Element Types: PLOAD1, PLOAD2, PLOAD4, GRAV
If you have a CQUAD4 (eid=3) with a PLOAD4 (sid=3) and a FORCE
card (nid=5) acting on it, you can incldue the PLOAD4, but
not the FORCE card by using:
For just pressure:
.. code-block:: python
eids = [3]
nids = []
For just force:
.. code-block:: python
eids = []
nids = [5]
or both:
.. code-block:: python
eids = [3]
nids = [5]
.. note:: If you split the model into sections and sum the loads
on each section, you may not get the same result as
if you summed the loads on the total model. This is
due to the fact that nodal loads on the boundary are
double/triple/etc. counted depending on how many breaks
you have.
.. todo:: not done...
"""
if not isinstance(loadcase_id, integer_types):
raise RuntimeError('loadcase_id must be an integer; loadcase_id=%r' % loadcase_id)
p = _get_load_summation_point(model, p0, cid=0)
if eids is None:
eids = list(model.element_ids)
if nids is None:
nids = list(model.node_ids)
#for (key, load_case) in model.loads.items():
#if key != loadcase_id:
#continue
loads, scale_factors, unused_is_grav = model.get_reduced_loads(
loadcase_id, skip_scale_factor0=True)
F = array([0., 0., 0.])
M = array([0., 0., 0.])
xyz = get_xyz_cid0_dict(model, xyz_cid0)
unsupported_types = set()
shell_elements = {
'CTRIA3', 'CQUAD4', 'CTRIAR', 'CQUADR',
'CTRIA6', 'CQUAD8', 'CQUAD', 'CSHEAR'}
skip_loads = {'QVOL'}
for load, scale in zip(loads, scale_factors):
#if load.type not in ['FORCE1']:
#continue
#print(load.type)
loadtype = load.type
if loadtype == 'FORCE':
if load.node_id not in nids:
continue
if load.Cid() != 0:
cp_ref = load.cid_ref
#from pyNastran.bdf.bdf import CORD2R
#cp = CORD2R()
f = load.mag * cp_ref.transform_vector_to_global(load.xyz) * scale
else:
f = load.mag * load.xyz * scale
node = model.Node(load.node_id)
r = xyz[node.nid] - p
m = cross(r, f)
F += f
M += m
elif load.type == 'FORCE1':
not_found_nid = False
for nid in load.node_ids:
if nid not in nids:
not_found_nid = True
break
if not_found_nid:
continue
f = load.mag * load.xyz * scale
node = model.Node(load.node_id)
r = xyz[node.nid] - p
m = cross(r, f)
F += f
M += m
elif load.type == 'FORCE2':
not_found_nid = False
for nid in load.node_ids:
if nid not in nids:
not_found_nid = True
break
if not_found_nid:
continue
f = load.mag * load.xyz * scale
node = model.Node(load.node_id)
r = xyz[node.nid] - p
m = cross(r, f)
F += f
M += m
elif load.type == 'MOMENT':
not_found_nid = False
for nid in load.node_ids:
if nid not in nids:
not_found_nid = True
break
if not_found_nid:
continue
if load.Cid() != 0:
cp_ref = load.cid_ref
m = cp_ref.transform_vector_to_global(load.xyz)
else:
m = load.xyz
M += load.mag * m * scale
elif load.type == 'MOMENT1':
not_found_nid = False
for nid in load.node_ids:
if nid not in nids:
not_found_nid = True
break
if not_found_nid:
continue
m = load.mag * load.xyz * scale
M += m
elif loadtype == 'MOMENT2':
not_found_nid = False
for nid in load.node_ids:
if nid not in nids:
not_found_nid = True
break
if not_found_nid:
continue
m = load.mag * load.xyz * scale
M += m
elif loadtype == 'PLOAD':
nodes = load.node_ids
nnodes = len(nodes)
nodesi = 0
if nnodes == 3:
n1, n2, n3 = xyz[nodes[0]], xyz[nodes[1]], xyz[nodes[2]]
axb = cross(n1 - n2, n1 - n3)
centroid = (n1 + n2 + n3) / 3.
elif nnodes == 4:
n1, n2, n3, n4 = xyz[nodes[0]], xyz[nodes[1]], xyz[nodes[2]], xyz[nodes[3]]
axb = cross(n1 - n3, n2 - n4)
centroid = (n1 + n2 + n3 + n4) / 4.
if nodes[3] in nids:
nodesi += 1
else:
raise RuntimeError('invalid number of nodes on PLOAD card; '
'nodes=%s' % str(nodes))
if nodes[0] in nids:
nodesi += 1
if nodes[1] in nids:
nodesi += 1
if nodes[2] in nids:
nodesi += 1
area, normal = _get_area_normal(axb, nodes, xyz)
r = centroid - p
f = load.pressure * area * normal * scale
m = cross(r, f)
node_scale = nodesi / float(nnodes)
F += f * node_scale
M += m * node_scale
elif loadtype == 'PLOAD1':
_pload1_elements(model, loadcase_id, load, scale, eids, xyz, F, M, p)
elif loadtype == 'PLOAD2':
pressure = load.pressure * scale
for eid in load.element_ids:
if eid not in eids:
continue
elem = model.elements[eid]
if elem.type in shell_elements:
normal = elem.Normal()
area = elem.Area()
f = pressure * normal * area
r = elem.Centroid() - p
m = cross(r, f)
F += f
M += m
else:
#model.log.warning('case=%s etype=%r loadtype=%r not supported' % (
#loadcase_id, elem.type, loadtype))
raise NotImplementedError('case=%s etype=%r loadtype=%r not supported' % (
loadcase_id, elem.type, loadtype))
elif loadtype == 'PLOAD4':
_pload4_elements(loadcase_id, load, scale, eids, xyz, F, M, p)
elif loadtype == 'GRAV':
if include_grav: # this will be super slow
g = load.GravityVector() * scale
for eid, elem in model.elements.items():
if eid not in eids:
continue
centroid = elem.Centroid()
mass = elem.Mass()
r = centroid - p
f = mass * g
m = cross(r, f)
F += f
M += m
elif loadtype in skip_loads:
continue
else:
# we collect them so we only get one print
unsupported_types.add(loadtype)
for loadtype in unsupported_types:
model.log.warning('case=%s loadtype=%r not supported' % (loadcase_id, loadtype))
#model.log.info("case=%s F=%s M=%s\n" % (loadcase_id, F, M))
if cid == 0:
return F, M
cid0 = 0
F2, M2 = transform_load(F, M, cid0, cid, model)
return F2, M2
def sum_forces_moments(model: BDF, p0: np.ndarray, loadcase_id: int,
cid: int=0,
include_grav: bool=False,
xyz_cid0: Optional[Dict[int, NDArray3float]]=None,
) -> Tuple[NDArray3float, NDArray3float]:
"""
Sums applied forces & moments about a reference point p0 for all
load cases.
Considers:
- FORCE, FORCE1, FORCE2
- MOMENT, MOMENT1, MOMENT2
- PLOAD, PLOAD2, PLOAD4
- LOAD
Parameters
----------
model : BDF()
a BDF object
p0 : NUMPY.NDARRAY shape=(3,) or integer (node ID)
the reference point
loadcase_id : int
the LOAD=ID to analyze
cid : int; default=0
the coordinate system for the summation
include_grav : bool; default=False
includes gravity in the summation (not supported)
xyz_cid0 : None / Dict[int] = (3, ) ndarray
the nodes in the global coordinate system
Returns
-------
forces : NUMPY.NDARRAY shape=(3,)
the forces
moments : NUMPY.NDARRAY shape=(3,)
the moments
.. warning:: not full validated
.. todo:: It's super slow for cid != 0. We can speed this up a lot
if we calculate the normal, area, centroid based on
precomputed node locations.
Pressure acts in the normal direction per model/real/loads.bdf and loads.f06
"""
if not isinstance(loadcase_id, integer_types):
raise RuntimeError('loadcase_id must be an integer; loadcase_id=%r' % loadcase_id)
p = _get_load_summation_point(model, p0, cid=0)
loads, scale_factors, unused_is_grav = model.get_reduced_loads(
loadcase_id, skip_scale_factor0=True)
F = array([0., 0., 0.])
M = array([0., 0., 0.])
xyz = get_xyz_cid0_dict(model, xyz_cid0=xyz_cid0)
unsupported_types = set()
for load, scale in zip(loads, scale_factors):
#if load.type not in ['FORCE1']:
#continue
if load.type == 'FORCE':
if load.Cid() != 0:
cp_ref = load.cid_ref
#from pyNastran.bdf.bdf import CORD2R
#cp_ref = CORD2R()
f = load.mag * cp_ref.transform_vector_to_global(load.xyz) * scale
else:
f = load.mag * load.xyz * scale
node = model.Node(load.node_id)
r = xyz[node.nid] - p
m = cross(r, f)
F += f
M += m
elif load.type == 'FORCE1':
f = load.mag * load.xyz * scale
node = model.Node(load.node_id)
r = xyz[node.nid] - p
m = cross(r, f)
F += f
M += m
elif load.type == 'FORCE2':
f = load.mag * load.xyz * scale
node = model.Node(load.node_id)
r = xyz[node.nid] - p
m = cross(r, f)
F += f
M += m
elif load.type == 'MOMENT':
if load.Cid() != 0:
cp = load.cid_ref
#from pyNastran.bdf.bdf import CORD2R
#cp = CORD2R()
m = load.mag * cp.transform_vector_to_global(load.xyz) * scale
else:
m = load.mag * load.xyz * scale
M += m
elif load.type == 'MOMENT1':
m = load.mag * load.xyz * scale
M += m
elif load.type == 'MOMENT2':
m = load.mag * load.xyz * scale
M += m
elif load.type == 'PLOAD':
nodes = load.node_ids
nnodes = len(nodes)
if nnodes == 3:
n1, n2, n3 = xyz[nodes[0]], xyz[nodes[1]], xyz[nodes[2]]
axb = cross(n1 - n2, n1 - n3)
centroid = (n1 + n2 + n3) / 3.
elif nnodes == 4:
n1, n2, n3, n4 = xyz[nodes[0]], xyz[nodes[1]], xyz[nodes[2]], xyz[nodes[3]]
axb = cross(n1 - n3, n2 - n4)
centroid = (n1 + n2 + n3 + n4) / 4.
else:
msg = 'invalid number of nodes on PLOAD card; nodes=%s' % str(nodes)
raise RuntimeError(msg)
area, normal = _get_area_normal(axb, nodes, xyz)
r = centroid - p
f = load.pressure * area * normal * scale
m = cross(r, f)
F += f
M += m
elif load.type == 'PLOAD1':
_pload1_total(model, loadcase_id, load, scale, xyz, F, M, p)
elif load.type == 'PLOAD2':
pressure = load.pressure * scale
for eid in load.element_ids:
elem = model.elements[eid]
if elem.type in ['CTRIA3', 'CQUAD4', 'CSHEAR', 'CQUADR', 'CTRIAR']:
n = elem.Normal()
area = elem.Area()
f = pressure * n * area
r = elem.Centroid() - p
m = cross(r, f)
F += f
M += m
else:
model.log.warning('case=%s etype=%r loadtype=%r not supported' % (
loadcase_id, elem.type, load.type))
elif load.type == 'PLOAD4':
_pload4_total(loadcase_id, load, scale, xyz, F, M, p)
elif load.type == 'GRAV':
if include_grav: # this will be super slow
gravity = load.GravityVector() * scale
for eid, elem in model.elements.items():
centroid = elem.Centroid()
mass = elem.Mass()
r = centroid - p
f = mass * gravity
m = cross(r, f)
F += f
M += m
else:
# we collect them so we only get one print
unsupported_types.add(load.type)
for load_type in unsupported_types:
model.log.warning('case=%s loadtype=%r not supported' % (loadcase_id, load_type))
#forces, moments = sum_forces_moments(self, p0, loadcase_id,
#include_grav=include_grav, xyz_cid0=xyz_cid0)
if cid == 0:
return F, M
cid0 = 0
F2, M2 = transform_load(F, M, cid0, cid, model)
return F2, M2
