Add docs, tests, get methods for yield moment

Author: robbievanleeuwen

docs/user_guide/results.rst

@@ -99,10 +99,12 @@ Geometric Analysis
     ~sectionproperties.analysis.section.Section.get_c
     ~sectionproperties.analysis.section.Section.get_eic
     ~sectionproperties.analysis.section.Section.get_ez
+    ~sectionproperties.analysis.section.Section.get_my
     ~sectionproperties.analysis.section.Section.get_rc
     ~sectionproperties.analysis.section.Section.get_eip
     ~sectionproperties.analysis.section.Section.get_phi
     ~sectionproperties.analysis.section.Section.get_ezp
+    ~sectionproperties.analysis.section.Section.get_my_p
     ~sectionproperties.analysis.section.Section.get_rp
     ~sectionproperties.analysis.section.Section.get_nu_eff
     ~sectionproperties.analysis.section.Section.get_e_eff

docs/user_guide/theory.rst

@@ -420,6 +420,11 @@ extreme (min. and max.) coordinates of the cross-section in the x and y-directio
   Z_{yy}^+ = \frac{I_{\overline{yy}}}{x_{max} - x_c} \\
   Z_{yy}^- = \frac{I_{\overline{yy}}}{x_c - x_{min}} \\
 
+Yield Moments
+~~~~~~~~~~~~~
+
+TODO
+
 .. _label-theory-plastic-section-moduli:
 
 Plastic Section Moduli

src/sectionproperties/analysis/section.py

@@ -202,6 +202,7 @@ def calculate_geometric_properties(self) -> None:
           - Centroidal section moduli
           - Radii of gyration
           - Principal axis properties
+          - Yield moments (composite only)
         """
 
         def calculate_geom(progress: Progress | None = None) -> None:
@@ -259,11 +260,21 @@ def calculate_geom(progress: Progress | None = None) -> None:
             )
             self.section_props.e_eff = self.section_props.ea / self.section_props.area
             self.section_props.g_eff = self.section_props.ga / self.section_props.area
+
+            # calculate derived properties
             self.section_props.calculate_elastic_centroid()
             self.section_props.calculate_centroidal_properties(
                 node_list=self.mesh["vertices"]
             )
 
+            # calculate yield moments
+            self.section_props.my_xx = 0.0
+            self.section_props.my_yy = 0.0
+            self.section_props.my_11 = 0.0
+            self.section_props.my_22 = 0.0
+
+            # TODO: calculate yield moments
+
             if progress and task is not None:
                 msg = "[bold green]:white_check_mark: Geometric analysis complete"
                 progress.update(task_id=task, description=msg)
@@ -1120,7 +1131,7 @@ def calculate_plastic_properties(
 
           - Plastic centroids (centroidal and principal axes)
           - Plastic section moduli (centroidal and principal axes)
-          - Shape factors, non-composite only (centroidal and principal axe)
+          - Shape factors, non-composite only (centroidal and principal axes)
         """
         # check that a geometric analysis has been performed
         if self.section_props.cx is None:
@@ -2240,6 +2251,32 @@ def get_ez(
             self.section_props.zyy_minus / e_ref,
         )
 
+    def get_my(self) -> tuple[float, float]:
+        """Returns the yield moment for bending about the centroidal axis.
+
+        This is a composite only property, as such this can only be returned if material
+        properties have been applied to the cross-section.
+
+        Returns:
+            Yield moment for bending about the centroidal ``x`` and ``y`` axes
+            (``my_xx``, ``my_yy``)
+
+        Raises:
+            RuntimeError: If material properties have *not* been applied
+            RuntimeError: If a geometric analysis has not been performed
+        """
+        if not self.is_composite():
+            msg = "Attempting to get a composite only property for a geometric analysis"
+            msg += " (material properties have not been applied). Consider using"
+            msg += " get_z()."
+            raise RuntimeError(msg)
+
+        if self.section_props.my_xx is None or self.section_props.my_yy is None:
+            msg = "Conduct a geometric analysis."
+            raise RuntimeError(msg)
+
+        return (self.section_props.my_xx, self.section_props.my_yy)
+
     def get_rc(self) -> tuple[float, float]:
         """Returns the cross-section centroidal radii of gyration.
 
@@ -2418,6 +2455,32 @@ def get_ezp(
             self.section_props.z22_minus / e_ref,
         )
 
+    def get_my_p(self) -> tuple[float, float]:
+        """Returns the yield moment for bending about the principal axis.
+
+        This is a composite only property, as such this can only be returned if material
+        properties have been applied to the cross-section.
+
+        Returns:
+            Yield moment for bending about the principal ``11`` and ``22`` axes
+            (``my_11``, ``my_22``)
+
+        Raises:
+            RuntimeError: If material properties have *not* been applied
+            RuntimeError: If a geometric analysis has not been performed
+        """
+        if not self.is_composite():
+            msg = "Attempting to get a composite only property for a geometric analysis"
+            msg += " (material properties have not been applied). Consider using"
+            msg += " get_zp()."
+            raise RuntimeError(msg)
+
+        if self.section_props.my_11 is None or self.section_props.my_22 is None:
+            msg = "Conduct a geometric analysis."
+            raise RuntimeError(msg)
+
+        return (self.section_props.my_11, self.section_props.my_22)
+
     def get_rp(self) -> tuple[float, float]:
         """Returns the cross-section principal radii of gyration.
 

src/sectionproperties/post/post.py

@@ -72,6 +72,10 @@ class SectionProperties:
             negative extreme value of the 11-axis
         r11_c: Radius of gyration about the principal 11-axis.
         r22_c: Radius of gyration about the principal 22-axis.
+        my_xx: Yield moment about the x-axis
+        my_yy: Yield moment about the y-axis
+        my_11: Yield moment about the 11-axis
+        my_22: Yield moment about the 22-axis
         j: Torsion constant
         omega: Warping function
         psi_shear: Psi shear function
@@ -165,6 +169,10 @@ class SectionProperties:
     r11_c: float | None = None
     r22_c: float | None = None
     j: float | None = None
+    my_xx: float | None = None
+    my_yy: float | None = None
+    my_11: float | None = None
+    my_22: float | None = None
     omega: npt.NDArray[np.float64] | None = None
     psi_shear: npt.NDArray[np.float64] | None = None
     phi_shear: npt.NDArray[np.float64] | None = None
@@ -278,7 +286,7 @@ def calculate_centroidal_properties(
             else:
                 self.phi = np.arctan2(self.ixx_c - self.i11_c, self.ixy_c) * 180 / np.pi
 
-            # initialise min, max variables TODO: check for `if xxx:` where xxx is float
+            # initialise min, max variables
             if self.phi is not None:
                 x1, y2 = fea.principal_coordinate(
                     phi=self.phi,

tests/analysis/test_yield_moment.py

@@ -0,0 +1,65 @@
+"""Tests for the yield moment calculation."""
+
+import pytest
+
+from sectionproperties.analysis import Section
+from sectionproperties.pre import Material
+from sectionproperties.pre.library import rectangular_section
+
+STEEL = Material(
+    name="Steel",
+    elastic_modulus=200e3,
+    poissons_ratio=0.3,
+    yield_strength=500,
+    density=7.85e-6,
+    color="grey",
+)
+
+
+def test_get_without_analysis():
+    """Test for raising an error if a geometric analysis has not been performed."""
+    geom = rectangular_section(d=50, b=50)
+    geom.create_mesh(mesh_sizes=0, coarse=True)
+    sec = Section(geometry=geom)
+
+    with pytest.raises(RuntimeError, match="Conduct a geometric analysis."):
+        sec.get_my()
+
+    with pytest.raises(RuntimeError, match="Conduct a geometric analysis."):
+        sec.get_my_p()
+
+
+def test_non_composite():
+    """Test for raising an error for non-composite analyses."""
+    geom = rectangular_section(d=50, b=50)
+    geom.create_mesh(mesh_sizes=0, coarse=True)
+    sec = Section(geometry=geom)
+    sec.calculate_geometric_properties()
+
+    with pytest.raises(RuntimeError, match="Attempting to get a composite only"):
+        sec.get_my()
+
+    with pytest.raises(RuntimeError, match="Attempting to get a composite only"):
+        sec.get_my_p()
+
+
+def test_rectangle():
+    """Test the yield moment of a simple rectangle."""
+    geom = rectangular_section(d=100, b=50, material=STEEL)
+    geom.create_mesh(mesh_sizes=0, coarse=True)
+    sec = Section(geometry=geom)
+    sec.calculate_geometric_properties()
+
+    my_xx, my_yy = sec.get_my()
+    my_11, my_22 = sec.get_my()
+
+    my_xx_calc = 50 * 100 * 100 / 4 * 500
+    my_yy_calc = 100 * 50 * 50 / 4 * 500
+
+    assert my_xx == pytest.approx(my_xx_calc)
+    assert my_yy == pytest.approx(my_yy_calc)
+    assert my_11 == pytest.approx(my_xx_calc)
+    assert my_22 == pytest.approx(my_yy_calc)
+
+
+# TODO: add more tests