Add a point load¶

Apply a concentrated force and/or moment at every node of a named target (a physical group or label). Reach for this when the load lives on a node set — a column top, an anchor point, a loaded pin.

Recipe¶

Declare the load on the session with g.loads.point.force(...), scoped inside a named case. Loads are opt-in (ADR 0051): the session declaration resolves onto fem.nodes.loads and persists to model.h5, but it reaches the runnable deck only when a bridge pattern imports the case with p.from_model("Lateral"). (Alternatively, skip g.loads entirely and author the force directly on a bridge pattern with p.load(...) — see the bridge section below.)

from apeGmsh import apeGmsh
from apeGmsh.opensees import apeSees

with apeGmsh(model_name="cantilever") as g:
    box = g.model.geometry.add_box(0, 0, 0, 10, 1, 1, label="body")

    eps = 1e-6
    base = g.model.queries.entities_in_bounding_box(
        -eps, -eps, -eps, eps, 1 + eps, 1 + eps, dim=2)
    tip = g.model.queries.entities_in_bounding_box(
        10 - eps, -eps, -eps, 10 + eps, 1 + eps, 1 + eps, dim=2)

    g.physical.add(3, ["body"], name="Body")
    g.physical.add_surface([t for _, t in base], name="Base")
    g.physical.add_surface([t for _, t in tip], name="Tip")

    # Concentrated force on the tip node set — grouped under case "Lateral".
    with g.loads.case("Lateral"):
        g.loads.point.force("Tip", (0.0, 0.0, -5e4))

    g.mesh.sizing.set_global_size(1.0)
    g.mesh.generation.generate(dim=3)
    fem = g.mesh.queries.get_fem_data(dim=3)   # <- loads resolve here

# Bridge: import the "Lateral" case into a pattern so it reaches the deck.
ops = apeSees(fem)
ops.model(ndm=3, ndf=3)
conc = ops.nDMaterial.ElasticIsotropic(E=30e9, nu=0.2, rho=2400)
ops.element.FourNodeTetrahedron(pg="Body", material=conc)
ops.fix(pg="Base", dofs=(1, 1, 1))
with ops.pattern.Plain(series=ops.timeSeries.Linear()) as p:
    p.from_model("Lateral")
ops.py("out/cantilever.py")

g.loads.point.force("Tip", ...) resolves to one nodal load per node of the Tip target. Every targeted node receives the same force — so for a single concentrated force apply it to a single-node target (e.g. a point label or point.force_closest), not a multi-node face. Use g.loads.point.moment("Tip", (Mx, My, Mz)) for rotational DOFs.

Notes / gotchas¶

Import the case, or it won't apply. A g.loads.point.force is not auto-emitted — without p.from_model("Lateral") (or an ad-hoc p.load) the force never reaches the deck. The deck is authoritative: the bridge applies exactly the cases you import and doesn't audit the geometry's case-list, so a case you don't import is simply not applied. Because nothing auto-emits, there is no 2× double-count trap.
One force per node, not per target. point.force gives every node of the target the full vector. To split a single force across a face, use g.loads.surface.force_resultant_center_mass(...); to hit one node, target a single-node entity.
No raw tags. Target by PG name or label ("Tip"), never by entity tag.
2-D moment: pass a length-1 tuple g.loads.point.moment("Tip", (Mz,)).
Coordinate-driven variant: when the point isn't on a named entity, use g.loads.point.force_closest(xyz, ...) to snap to the nearest mesh node.

Bridge alternative (`p.load`)¶

If you'd rather drive the force entirely from the bridge — e.g. you have no session-side g.loads declaration to import — author it directly on a pattern:

ts = ops.timeSeries.Linear()
with ops.pattern.Plain(series=ts) as p:
    p.load(pg="Tip", forces=(0.0, 0.0, -5e4))

p.load fans pg= across the group's nodes at build time. p.from_model(case) and p.load(...) mix freely in the same pattern — import the session cases you want and add ad-hoc bridge loads alongside.

Add a point load¶

Recipe¶

Notes / gotchas¶

Bridge alternative (p.load)¶

See also¶

Bridge alternative (`p.load`)¶