From 7cbf202c5c43931486639b77eeebb97bc4af9a05 Mon Sep 17 00:00:00 2001
From: Diego Talledo <38036285+talledodiego@users.noreply.github.com>
Date: Tue, 17 Mar 2026 08:16:20 +0100
Subject: [PATCH 01/12] minor fix to next previous and set step for
 MomentCurvatureResults

---
 structuralcodes/core/_section_results.py | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/structuralcodes/core/_section_results.py b/structuralcodes/core/_section_results.py
index 3dbde253..b40d0fd5 100644
--- a/structuralcodes/core/_section_results.py
+++ b/structuralcodes/core/_section_results.py
@@ -318,17 +318,13 @@ def create_detailed_result(self, num_points=1000):
 
     def next_step(self):
         """Advance to the next step in the detailed result."""
-        if self.detailed_result is None:
-            return
-        if self.current_step < len(self.m_y) - 1:
+        if self.detailed_result and self.current_step < len(self.m_y) - 1:
             self.current_step += 1
             self._create_detailed_result()
 
     def previous_step(self):
         """Go back to the previous step in the detailed result."""
-        if self.detailed_result is None:
-            return
-        if self.current_step > 0:
+        if self.detailed_result and self.current_step > 0:
             self.current_step -= 1
             self._create_detailed_result()
 
@@ -338,9 +334,7 @@ def set_step(self, step: int):
         Arguments:
             step (int): the step to set for the datailed_result object.
         """
-        if self.detailed_result is None:
-            return
-        if 0 <= step < len(self.m_y):
+        if self.detailed_result and 0 <= step < len(self.m_y):
             self.current_step = step
             self._create_detailed_result()
 

From 8724c33fa80defb44dad8d5b793b743610c58a19 Mon Sep 17 00:00:00 2001
From: Diego Talledo <38036285+talledodiego@users.noreply.github.com>
Date: Tue, 17 Mar 2026 10:16:48 +0100
Subject: [PATCH 02/12] refactor: rename eps_axial to eps_a for consistency in
 MomentCurvatureResults

---
 structuralcodes/core/_section_results.py                | 8 ++++----
 structuralcodes/sections/_generic.py                    | 2 +-
 tests/test_sections/test_rc_sections/test_rc_results.py | 4 ++--
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/structuralcodes/core/_section_results.py b/structuralcodes/core/_section_results.py
index b40d0fd5..4eef75a0 100644
--- a/structuralcodes/core/_section_results.py
+++ b/structuralcodes/core/_section_results.py
@@ -278,7 +278,7 @@ class MomentCurvatureResults:
     n: float = 0  # axial load - mantained constant during analysis
     chi_y: ArrayLike = None  # the curvatures
     chi_z: ArrayLike = None  # the curvatures
-    eps_axial: ArrayLike = 0  # the axial strain (at section 0,0)
+    eps_a: ArrayLike = None  # the axial strain (at section 0,0)
     m_y: ArrayLike = None  # the moment
     m_z: ArrayLike = None  # the moment
 
@@ -292,7 +292,7 @@ class MomentCurvatureResults:
     def _create_detailed_result(self):
         self.detailed_result = SectionDetailedResultState(
             section=self.section,
-            eps_a=self.eps_axial[self.current_step],
+            eps_a=self.eps_a[self.current_step],
             chi_y=self.chi_y[self.current_step],
             chi_z=self.chi_z[self.current_step],
             n=self.n,
@@ -368,7 +368,7 @@ def get_point_strain(
         """
         return _get_point_response(
             section=self.section,
-            eps_a=np.asarray(self.eps_axial),
+            eps_a=np.asarray(self.eps_a),
             chi_y=np.asarray(self.chi_y),
             chi_z=np.asarray(self.chi_z),
             y=y,
@@ -411,7 +411,7 @@ def get_point_stress(
         """
         return _get_point_response(
             section=self.section,
-            eps_a=np.asarray(self.eps_axial),
+            eps_a=np.asarray(self.eps_a),
             chi_y=np.asarray(self.chi_y),
             chi_z=np.asarray(self.chi_z),
             y=y,
diff --git a/structuralcodes/sections/_generic.py b/structuralcodes/sections/_generic.py
index ccfe7ff9..7b840a10 100644
--- a/structuralcodes/sections/_generic.py
+++ b/structuralcodes/sections/_generic.py
@@ -1204,7 +1204,7 @@ def calculate_moment_curvature(
             self._rotate_integration_data(theta)
         res.chi_y = chi_y
         res.chi_z = chi_z
-        res.eps_axial = eps_a
+        res.eps_a = eps_a
         res.m_y = my
         res.m_z = mz
 
diff --git a/tests/test_sections/test_rc_sections/test_rc_results.py b/tests/test_sections/test_rc_sections/test_rc_results.py
index 1d1fb8e9..6cf25fab 100644
--- a/tests/test_sections/test_rc_sections/test_rc_results.py
+++ b/tests/test_sections/test_rc_sections/test_rc_results.py
@@ -266,7 +266,7 @@ def test_moment_curvature_result_point(simple_rc_section):
     stress = res.get_point_stress(y=y1, z=z1, group_label='bottom')
     assert isinstance(stress, np.ndarray)
 
-    assert len(stress) == len(res.eps_axial)
+    assert len(stress) == len(res.eps_a)
 
     # Check that at the end the stress on the bar is the yield strength of
     # reinforcement.
@@ -283,7 +283,7 @@ def test_moment_curvature_result_point(simple_rc_section):
     stress = res.get_point_stress(y=y2, z=z2, group_label='top')
     assert isinstance(stress, np.ndarray)
 
-    assert len(stress) == len(res.eps_axial)
+    assert len(stress) == len(res.eps_a)
 
 
 def test_moment_curvature_result(simple_rc_section):

From a9f666fbed04af9e4ed4dd720934a840358042f7 Mon Sep 17 00:00:00 2001
From: Diego Talledo <38036285+talledodiego@users.noreply.github.com>
Date: Tue, 17 Mar 2026 10:19:18 +0100
Subject: [PATCH 03/12] refactor: encapsulate detailed_result with property in
 Results classes. Auto-construct the object when first accessed.

---
 structuralcodes/core/_section_results.py      | 50 +++++++++++++++----
 .../test_rc_sections/test_rc_results.py       |  7 ---
 2 files changed, 39 insertions(+), 18 deletions(-)

diff --git a/structuralcodes/core/_section_results.py b/structuralcodes/core/_section_results.py
index 4eef75a0..8080c6bb 100644
--- a/structuralcodes/core/_section_results.py
+++ b/structuralcodes/core/_section_results.py
@@ -284,13 +284,13 @@ class MomentCurvatureResults:
 
     section = None
 
-    detailed_result: SectionDetailedResultState = None
+    _detailed_result: SectionDetailedResultState = None
     seed: int = None
     current_step: int = None
     num_points: int = None
 
     def _create_detailed_result(self):
-        self.detailed_result = SectionDetailedResultState(
+        self._detailed_result = SectionDetailedResultState(
             section=self.section,
             eps_a=self.eps_a[self.current_step],
             chi_y=self.chi_y[self.current_step],
@@ -302,6 +302,13 @@ def _create_detailed_result(self):
             seed=self.seed,
         )
 
+    @property
+    def detailed_result(self) -> SectionDetailedResultState:
+        """Returns the detailed result."""
+        if self._detailed_result is None:
+            self.create_detailed_result()
+        return self._detailed_result
+
     def create_detailed_result(self, num_points=1000):
         """Create the detailed result object.
 
@@ -318,13 +325,13 @@ def create_detailed_result(self, num_points=1000):
 
     def next_step(self):
         """Advance to the next step in the detailed result."""
-        if self.detailed_result and self.current_step < len(self.m_y) - 1:
+        if self._detailed_result and self.current_step < len(self.m_y) - 1:
             self.current_step += 1
             self._create_detailed_result()
 
     def previous_step(self):
         """Go back to the previous step in the detailed result."""
-        if self.detailed_result and self.current_step > 0:
+        if self._detailed_result and self.current_step > 0:
             self.current_step -= 1
             self._create_detailed_result()
 
@@ -334,7 +341,7 @@ def set_step(self, step: int):
         Arguments:
             step (int): the step to set for the datailed_result object.
         """
-        if self.detailed_result and 0 <= step < len(self.m_y):
+        if self._detailed_result and 0 <= step < len(self.m_y):
             self.current_step = step
             self._create_detailed_result()
 
@@ -690,7 +697,7 @@ class UltimateBendingMomentResults:
 
     section = None
 
-    detailed_result: SectionDetailedResultState = None
+    _detailed_result: SectionDetailedResultState = None
 
     def create_detailed_result(self, num_points=1000):
         """Create the detailed result object.
@@ -699,7 +706,7 @@ def create_detailed_result(self, num_points=1000):
             num_points (int): Number of random points to sample for each
                 surface geometry (default = 1000).
         """
-        self.detailed_result = SectionDetailedResultState(
+        self._detailed_result = SectionDetailedResultState(
             section=self.section,
             eps_a=self.eps_a,
             chi_y=self.chi_y,
@@ -710,6 +717,13 @@ def create_detailed_result(self, num_points=1000):
             num_points=num_points,
         )
 
+    @property
+    def detailed_result(self) -> SectionDetailedResultState:
+        """Returns the detailed result."""
+        if self._detailed_result is None:
+            self.create_detailed_result()
+        return self._detailed_result
+
     def get_point_strain(
         self,
         y: float,
@@ -830,7 +844,7 @@ class StrainProfileResult:
     # For context store the section
     section: t.Any = None  # Note for future: if I want to type this I also have problem of circular import? #noqa E501
     # The detailed result data structure
-    detailed_result: SectionDetailedResultState = None
+    _detailed_result: SectionDetailedResultState = None
 
     @property
     def residual_norm_history(self) -> t.List:
@@ -866,6 +880,13 @@ def residual_norm(self) -> float:
         """Returns the norm of the residual at last iteration."""
         return float(np.linalg.norm(self.residual))
 
+    @property
+    def detailed_result(self) -> SectionDetailedResultState:
+        """Returns the detailed result."""
+        if self._detailed_result is None:
+            self.create_detailed_result()
+        return self._detailed_result
+
     def to_list(self) -> t.List:
         """Returns the strain profile coefficients in a list."""
         return [self.eps_a, self.chi_y, self.chi_z]
@@ -877,7 +898,7 @@ def create_detailed_result(self, num_points=1000):
             num_points (int): Number of random points to sample for each
                 surface geometry (default = 1000).
         """
-        self.detailed_result = SectionDetailedResultState(
+        self._detailed_result = SectionDetailedResultState(
             section=self.section,
             eps_a=self.eps_a,
             chi_y=self.chi_y,
@@ -1008,7 +1029,7 @@ class IntegrateStrainForceResult:
     # For context store the section
     section: t.Any = None  # Note for future: if I want to type this I also have problem of circular import? #noqa E501
     # The detailed result data structure
-    detailed_result: SectionDetailedResultState = None
+    _detailed_result: SectionDetailedResultState = None
 
     def asarray(self, dtype=np.float64) -> NDArray:
         """Return an array representation of the forces."""
@@ -1018,6 +1039,13 @@ def astuple(self) -> tuple[float, float, float]:
         """Return a tuple representation of the forces."""
         return (self.n, self.m_y, self.m_z)
 
+    @property
+    def detailed_result(self) -> SectionDetailedResultState:
+        """Returns the detailed result."""
+        if self._detailed_result is None:
+            self.create_detailed_result()
+        return self._detailed_result
+
     def create_detailed_result(self, num_points=1000):
         """Create the detailed result object.
 
@@ -1025,7 +1053,7 @@ def create_detailed_result(self, num_points=1000):
             num_points (int): Number of random points to sample for each
                 surface geometry (default = 1000).
         """
-        self.detailed_result = SectionDetailedResultState(
+        self._detailed_result = SectionDetailedResultState(
             section=self.section,
             eps_a=self.eps_a,
             chi_y=self.chi_y,
diff --git a/tests/test_sections/test_rc_sections/test_rc_results.py b/tests/test_sections/test_rc_sections/test_rc_results.py
index 6cf25fab..2c94c2dd 100644
--- a/tests/test_sections/test_rc_sections/test_rc_results.py
+++ b/tests/test_sections/test_rc_sections/test_rc_results.py
@@ -292,8 +292,6 @@ def test_moment_curvature_result(simple_rc_section):
 
     res = section.section_calculator.calculate_moment_curvature()
 
-    res.create_detailed_result()
-
     stresses_bottom = res.get_point_stress(
         y=-160.0, z=-160.0, group_label='bottom'
     )
@@ -326,8 +324,6 @@ def test_bending_strength_result(simple_rc_section):
 
     res = section.section_calculator.calculate_bending_strength()
 
-    res.create_detailed_result()
-
     stress_bottom = res.get_point_stress(
         y=-160.0, z=-160.0, group_label='bottom'
     )
@@ -403,9 +399,6 @@ def test_calc_strain_profile_results(
         y=-160.0, z=-160.0, group_label='bottom'
     )
 
-    # Get detailed result
-    strain_res.create_detailed_result()
-
     assert np.isclose(
         stress_bottom, strain_res.detailed_result.point_data['stress'][0]
     )

From 74838cbb2d9a7df29a4035d111d542d29acb71c0 Mon Sep 17 00:00:00 2001
From: Diego Talledo <38036285+talledodiego@users.noreply.github.com>
Date: Tue, 17 Mar 2026 10:41:10 +0100
Subject: [PATCH 04/12] bugfix: pass section to IntegrateStrainStiffnessResult

---
 structuralcodes/sections/_generic.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/structuralcodes/sections/_generic.py b/structuralcodes/sections/_generic.py
index 7b840a10..4650e693 100644
--- a/structuralcodes/sections/_generic.py
+++ b/structuralcodes/sections/_generic.py
@@ -912,6 +912,7 @@ def integrate_strain_profile(
                 n=result[0],
                 m_y=result[1],
                 m_z=result[2],
+                section=self.section,
             )
         if integrate == 'modulus':
             return s_res.IntegrateStrainStiffnessResult(tangent=result[0])

From 9f3dba4f74c62b815dccf7755aa8299a750deb75 Mon Sep 17 00:00:00 2001
From: Diego Talledo <38036285+talledodiego@users.noreply.github.com>
Date: Tue, 17 Mar 2026 15:17:32 +0100
Subject: [PATCH 05/12] refactor: rename interaction domain classes and update
 type hints for clarity

---
 structuralcodes/core/_section_results.py | 80 ++++++++++++++++--------
 structuralcodes/sections/_generic.py     | 29 ++++++---
 2 files changed, 73 insertions(+), 36 deletions(-)

diff --git a/structuralcodes/core/_section_results.py b/structuralcodes/core/_section_results.py
index 8080c6bb..3458fd21 100644
--- a/structuralcodes/core/_section_results.py
+++ b/structuralcodes/core/_section_results.py
@@ -1149,7 +1149,7 @@ def get_point_stress(
 
 
 @dataclass
-class InteractionDomain:
+class InteractionDomainResult:
     """Class for storing common data on all interaction domain results.
 
     Attributes:
@@ -1157,16 +1157,12 @@ class InteractionDomain:
             ky and kz.
         forces (numpy.Array): A numpy array with shape (n, 3) containing n, my
             and mz.
-        field_num (numpy.Array): a numpy array with shape (n,) containing a
-            number between 1 and 6 indicating the failure field.
     """
 
     # array with shape (n,3) containing ea, ky, kz:
-    strains: ArrayLike = None
+    strains: NDArray[np.float64] = None
     # array with shape(n,3) containing N, My, Mz
-    forces: ArrayLike = None
-    # array with shape(n,) containing the field number from 1 to 6
-    field_num: ArrayLike = None
+    forces: NDArray[np.float64] = None
 
     @property
     def n(self):
@@ -1190,46 +1186,78 @@ def m_z(self):
         return self.forces[:, 2]
 
     @property
-    def e_a(self):
-        """Return ea."""
+    def eps_a(self):
+        """Return eps_a (axial strain at 0, 0)."""
         if self.strains is None:
             return None
         return self.strains[:, 0]
 
     @property
-    def k_y(self):
-        """Return ky."""
+    def chi_y(self):
+        """Return chi_y (curvature about y-axis."""
         if self.strains is None:
             return None
         return self.strains[:, 1]
 
     @property
-    def k_z(self):
-        """Return kz."""
+    def chi_z(self):
+        """Return chi_z (curvature about z-axis)."""
         if self.strains is None:
             return None
         return self.strains[:, 2]
 
 
-@dataclass
-class NMMInteractionDomain(InteractionDomain):
-    """Class for storing the NMM interaction domain results."""
+class NMMInteractionDomainResult(InteractionDomainResult):
+    """Class for storing the NMM interaction domain results.
 
-    num_theta: int = 0  # number of discretizations along the angle
-    num_axial: int = 0  # number of discretizations along axial load axis
+    Attributes:
+        num_theta (int): the number of discretizations from 0 to 2pi.
+        field_num (numpy.Array): a numpy array with shape (n,) containing a
+            number between 1 and 6 indicating the failure field.
+    """
+
+    # number of discretizations along the angle
+    num_theta: int = 0
+
+    # number of points from discretization of ultimate strain profiles
+    num_points: int = 0
+
+    # array with shape(n,) containing the field number from 1 to 6
+    field_num: NDArray[np.float64] = None
 
 
 @dataclass
-class NMInteractionDomain(InteractionDomain):
-    """Class for storing the NM interaction domain results."""
+class NMInteractionDomainResult(InteractionDomainResult):
+    """Class for storing the NM interaction domain results.
 
-    theta: float = 0  # the inclination of n.a.
-    num_axial: float = 0  # number of discretizations along axial load axis
+    Attributes:
+        theta (float): the inclination of n.a.
+        field_num (numpy.Array): a numpy array with shape (n,) containing a
+            number between 1 and 6 indicating the failure field.
+    """
+
+    # the inclination of n.a.
+    theta: float = 0
+
+    # number of points from discretization of ultimate strain profiles
+    num_points: int = 0
+
+    # array with shape(n,) containing the field number from 1 to 6
+    field_num: NDArray[np.float64] = None
 
 
 @dataclass
-class MMInteractionDomain(InteractionDomain):
-    """Class for storing the MM interaction domain results."""
+class MMInteractionDomainResult(InteractionDomainResult):
+    """Class for storing the MM interaction domain results.
+
+
+    Attributes:
+        num_theta (int): the number of discretizations from 0 to 2pi.
+        theta (numpy.Array): a numpy array with shape (n,) the angle theta
+    """
+
+    # number of discretizations along the angle
+    num_theta: float = 0
 
-    num_theta: float = 0  # number of discretizations along the angle
-    theta: ArrayLike = None  # Array with shape (n,) containing the angle of NA
+    # Array with shape (n,) containing the angle of NA
+    theta: NDArray[np.float64] = None
diff --git a/structuralcodes/sections/_generic.py b/structuralcodes/sections/_generic.py
index 4650e693..65bb7a33 100644
--- a/structuralcodes/sections/_generic.py
+++ b/structuralcodes/sections/_generic.py
@@ -1284,7 +1284,7 @@ def calculate_nm_interaction_domain(
         type_5: t.Literal['linear', 'geometric', 'quadratic'] = 'linear',
         type_6: t.Literal['linear', 'geometric', 'quadratic'] = 'linear',
         complete_domain: bool = False,
-    ) -> s_res.NMInteractionDomain:
+    ) -> s_res.NMInteractionDomainResult:
         """Calculate the NM interaction domain.
 
         Arguments:
@@ -1326,7 +1326,7 @@ def calculate_nm_interaction_domain(
             NMInteractionDomain: The calculation results.
         """
         # Prepare the results
-        res = s_res.NMInteractionDomain()
+        res = s_res.NMInteractionDomainResult()
         res.theta = theta
 
         # Process num if given.
@@ -1396,6 +1396,7 @@ def calculate_nm_interaction_domain(
             forces[i, 2] = Mz
 
         # Save to results
+        res.num_points = len(strains)
         res.strains = strains
         res.forces = forces
         res.field_num = field_num
@@ -1563,7 +1564,7 @@ def _np_space(a, b, n, type, endpoint):
 
     def calculate_nmm_interaction_domain(
         self,
-        num_theta: int = 32,
+        num_theta: int = 33,
         num_1: int = 1,
         num_2: int = 2,
         num_3: int = 15,
@@ -1577,12 +1578,12 @@ def calculate_nmm_interaction_domain(
         type_4: t.Literal['linear', 'geometric', 'quadratic'] = 'linear',
         type_5: t.Literal['linear', 'geometric', 'quadratic'] = 'linear',
         type_6: t.Literal['linear', 'geometric', 'quadratic'] = 'linear',
-    ) -> s_res.NMMInteractionDomain:
+    ) -> s_res.NMMInteractionDomainResult:
         """Calculates the NMM interaction domain.
 
         Arguments:
             num_theta (int): Number of discretization of angle of neutral axis
-                (Optional, Default = 32).
+                (Optional, Default = 33).
             num_1 (int): Number of strain profiles in field 1
                 (Optional, default = 1).
             num_2 (int): Number of strain profiles in field 2
@@ -1615,7 +1616,7 @@ def calculate_nmm_interaction_domain(
         Returns:
             NMInteractionDomain: The calculation results.
         """
-        res = s_res.NMMInteractionDomain()
+        res = s_res.NMMInteractionDomainResult()
         res.num_theta = num_theta
 
         # Process num if given.
@@ -1630,6 +1631,7 @@ def calculate_nmm_interaction_domain(
         thetas = np.linspace(0, np.pi * 2, num_theta)
         # Initialize an empty array with the correct shape
         strains = np.empty((0, 3))
+        num_points = 0
         for theta in thetas:
             # Get ultimate strain profiles for theta angle
             strain, field_num = self._compute_ultimate_strain_profiles(
@@ -1647,6 +1649,12 @@ def calculate_nmm_interaction_domain(
                 type_5=type_5,
                 type_6=type_6,
             )
+            if num_points == 0:
+                num_points = len(strain)
+            if num_points != len(strain):
+                raise AssertionError(
+                    'All strain arrays should have the same number of points!'
+                )
             strains = np.vstack((strains, strain))
 
         # integrate all strain profiles
@@ -1666,6 +1674,7 @@ def calculate_nmm_interaction_domain(
             forces[i, 2] = Mz
 
         # Save to results
+        res.num_points = num_points
         res.strains = strains
         res.forces = forces
         res.field_num = field_num
@@ -1675,15 +1684,15 @@ def calculate_nmm_interaction_domain(
     def calculate_mm_interaction_domain(
         self,
         n: float = 0,
-        num_theta: int = 32,
+        num_theta: int = 33,
         max_iter: int = 100,
         tol: float = 1e-2,
-    ) -> s_res.MMInteractionDomain:
+    ) -> s_res.MMInteractionDomainResult:
         r"""Calculate the My-Mz interaction domain.
 
         Arguments:
             n (float): Axial force, default = 0.
-            n_theta (int): Number of discretization for theta, default = 32.
+            n_theta (int): Number of discretization for theta, default = 33.
             max_iter (int): the maximum number of iterations in the iterative
                 process (default = 10).
             tol (float): the tolerance for convergence test in terms of
@@ -1693,7 +1702,7 @@ def calculate_mm_interaction_domain(
             MMInteractionDomain: The calculation results.
         """
         # Prepare the results
-        res = s_res.MMInteractionDomain()
+        res = s_res.MMInteractionDomainResult()
         res.num_theta = num_theta
         # Create array of thetas
         res.theta = np.linspace(0, np.pi * 2, num_theta)

From b412bade5a740f76d85aaed7f3c6bc8e84b55a29 Mon Sep 17 00:00:00 2001
From: Diego Talledo <38036285+talledodiego@users.noreply.github.com>
Date: Tue, 17 Mar 2026 15:19:04 +0100
Subject: [PATCH 06/12] refactor: add slots=True to result dataclasses

---
 structuralcodes/core/_section_results.py | 27 +++++++++++++++---------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/structuralcodes/core/_section_results.py b/structuralcodes/core/_section_results.py
index 3458fd21..1c8461e4 100644
--- a/structuralcodes/core/_section_results.py
+++ b/structuralcodes/core/_section_results.py
@@ -11,7 +11,7 @@
 from shapely import Point
 
 
-@dataclass
+@dataclass(slots=True)
 class SectionProperties:
     """Simple dataclass for storing section properties."""
 
@@ -143,8 +143,10 @@ def isclose(self, other, rtol=1e-5, atol=1e-8):
         if not isinstance(other, self.__class__):
             return NotImplemented
 
-        a = np.array(list(vars(self).values()))
-        b = np.array(list(vars(other).values()))
+        field_names = [f.name for f in fields(self)]
+        a = np.array([getattr(self, name) for name in field_names])
+        b = np.array([getattr(other, name) for name in field_names])
+
         return np.allclose(a, b, rtol=rtol, atol=atol)
 
 
@@ -267,7 +269,9 @@ def _get_point_response(
     return None
 
 
-@dataclass
+# TODO: to be able using slots = True we mush type annotate section, but this
+# would trigger a circular import @mortenengen
+@dataclass(slots=True)
 class MomentCurvatureResults:
     """Class for storing moment curvature results.
 
@@ -282,7 +286,7 @@ class MomentCurvatureResults:
     m_y: ArrayLike = None  # the moment
     m_z: ArrayLike = None  # the moment
 
-    section = None
+    section: t.Any = None
 
     _detailed_result: SectionDetailedResultState = None
     seed: int = None
@@ -681,7 +685,9 @@ def point_data(self):
         return self._point_data
 
 
-@dataclass
+# TODO: to be able using slots = True we mush type annotate section, but this
+# would trigger a circular import @mortenengen
+@dataclass(slots=True)
 class UltimateBendingMomentResults:
     """Class for storing the ultimate bending moment computation for a given
     inclination of n.a. and axial load.
@@ -695,7 +701,7 @@ class UltimateBendingMomentResults:
     chi_z: float = 0  # the curvature corresponding to the ultimate moment
     eps_a: float = 0  # the axial strain at 0,0 corresponding to Mult
 
-    section = None
+    section: t.Any = None
 
     _detailed_result: SectionDetailedResultState = None
 
@@ -1148,7 +1154,7 @@ def get_point_stress(
         )
 
 
-@dataclass
+@dataclass(slots=True)
 class InteractionDomainResult:
     """Class for storing common data on all interaction domain results.
 
@@ -1207,6 +1213,7 @@ def chi_z(self):
         return self.strains[:, 2]
 
 
+@dataclass(slots=True)
 class NMMInteractionDomainResult(InteractionDomainResult):
     """Class for storing the NMM interaction domain results.
 
@@ -1226,7 +1233,7 @@ class NMMInteractionDomainResult(InteractionDomainResult):
     field_num: NDArray[np.float64] = None
 
 
-@dataclass
+@dataclass(slots=True)
 class NMInteractionDomainResult(InteractionDomainResult):
     """Class for storing the NM interaction domain results.
 
@@ -1246,7 +1253,7 @@ class NMInteractionDomainResult(InteractionDomainResult):
     field_num: NDArray[np.float64] = None
 
 
-@dataclass
+@dataclass(slots=True)
 class MMInteractionDomainResult(InteractionDomainResult):
     """Class for storing the MM interaction domain results.
 

From b1eb25e3d13ace076ca6b1e7de21bf43e5f71054 Mon Sep 17 00:00:00 2001
From: Diego Talledo <38036285+talledodiego@users.noreply.github.com>
Date: Tue, 17 Mar 2026 15:28:22 +0100
Subject: [PATCH 07/12] refactor: improve error handling for forces and strains
 in InteractionDomainResult properties

---
 structuralcodes/core/_section_results.py | 44 ++++++++++++++----------
 1 file changed, 26 insertions(+), 18 deletions(-)

diff --git a/structuralcodes/core/_section_results.py b/structuralcodes/core/_section_results.py
index 1c8461e4..3badb404 100644
--- a/structuralcodes/core/_section_results.py
+++ b/structuralcodes/core/_section_results.py
@@ -1173,44 +1173,44 @@ class InteractionDomainResult:
     @property
     def n(self):
         """Return axial force."""
-        if self.forces is None:
-            return None
-        return self.forces[:, 0]
+        if self.forces is not None:
+            return self.forces[:, 0]
+        raise ValueError('Forces are not available in this result object.')
 
     @property
     def m_y(self):
         """Return my."""
-        if self.forces is None:
-            return None
-        return self.forces[:, 1]
+        if self.forces is not None:
+            return self.forces[:, 1]
+        raise ValueError('Forces are not available in this result object.')
 
     @property
     def m_z(self):
         """Return mz."""
-        if self.forces is None:
-            return None
-        return self.forces[:, 2]
+        if self.forces is not None:
+            return self.forces[:, 2]
+        raise ValueError('Forces are not available in this result object.')
 
     @property
     def eps_a(self):
         """Return eps_a (axial strain at 0, 0)."""
-        if self.strains is None:
-            return None
-        return self.strains[:, 0]
+        if self.strains is not None:
+            return self.strains[:, 0]
+        raise ValueError('Strains are not available in this result object.')
 
     @property
     def chi_y(self):
         """Return chi_y (curvature about y-axis."""
-        if self.strains is None:
-            return None
-        return self.strains[:, 1]
+        if self.strains is not None:
+            self.strains[:, 1]
+        raise ValueError('Strains are not available in this result object.')
 
     @property
     def chi_z(self):
         """Return chi_z (curvature about z-axis)."""
-        if self.strains is None:
-            return None
-        return self.strains[:, 2]
+        if self.strains is not None:
+            return self.strains[:, 2]
+        raise ValueError('Strains are not available in this result object.')
 
 
 @dataclass(slots=True)
@@ -1232,6 +1232,14 @@ class NMMInteractionDomainResult(InteractionDomainResult):
     # array with shape(n,) containing the field number from 1 to 6
     field_num: NDArray[np.float64] = None
 
+    # TODO: in the future we could also add methods for returning the results
+    # as a structured mesh for easy plotting. Maybe for increasing values of
+    # N and for increasing values of theta (from 0 to 2pi), so having a nicely
+    # structured grid of points, and maybe also adding the possibility to
+    # the results as a dataframe, with columns for N, theta, field_num, etc.
+    # This would make it easier to analyze the results and to create custom
+    # plots.
+
 
 @dataclass(slots=True)
 class NMInteractionDomainResult(InteractionDomainResult):

From cc0d67c48c9c96bf0519e64efd25d0ff14359a8a Mon Sep 17 00:00:00 2001
From: Diego Talledo <38036285+talledodiego@users.noreply.github.com>
Date: Tue, 17 Mar 2026 15:42:57 +0100
Subject: [PATCH 08/12] test: add more tests for results

---
 .../test_rc_sections/test_rc_results.py       |   3 +
 tests/test_sections/test_results.py           | 235 ++++++++++++++++++
 2 files changed, 238 insertions(+)
 create mode 100644 tests/test_sections/test_results.py

diff --git a/tests/test_sections/test_rc_sections/test_rc_results.py b/tests/test_sections/test_rc_sections/test_rc_results.py
index 2c94c2dd..ea27924e 100644
--- a/tests/test_sections/test_rc_sections/test_rc_results.py
+++ b/tests/test_sections/test_rc_sections/test_rc_results.py
@@ -372,6 +372,9 @@ def test_calc_strain_profile_results(
     assert np.allclose(
         strain_res.residual, f_ext - f_int, rtol=1e-7, atol=1e-7
     )
+    assert math.isclose(
+        strain_res.residual_norm, np.linalg.norm(f_ext - f_int), abs_tol=1e-7
+    )
 
     # Check the the correct data are stored from convergence
     assert math.isclose(strain_res.tolerance, tol)
diff --git a/tests/test_sections/test_results.py b/tests/test_sections/test_results.py
new file mode 100644
index 00000000..d99df92d
--- /dev/null
+++ b/tests/test_sections/test_results.py
@@ -0,0 +1,235 @@
+"""Test for results objects."""
+
+import math
+
+import numpy as np
+import pytest
+
+from structuralcodes.geometry import RectangularGeometry
+from structuralcodes.materials.basic import ElasticMaterial
+from structuralcodes.sections import GenericSection
+
+width = 200
+height = 400
+E = 10000
+eps_u = 0.01
+
+
+@pytest.fixture
+def elastic_rec_section() -> GenericSection:
+    """Create a simple rectangular section with known properties."""
+    # Square section centered at (0, 0)
+    mat = ElasticMaterial(E=E, density=700, ultimate_strain=eps_u)
+
+    geo = RectangularGeometry(width, height, mat)
+
+    # It should not be concrete
+    assert not geo.concrete
+
+    return GenericSection(geo, integrator='marin')
+
+
+# Test the string representation of gross properties
+def test_gross_properties_text(elastic_rec_section):
+    """A test for gross properties result string representation."""
+    sec = elastic_rec_section
+
+    str_res = sec.gross_properties.__str__()
+
+    # Check the string starts with the expected title
+    assert str_res.startswith('Section Properties:')
+
+    # Check that there are 30+1 rows of properties
+    assert len(str_res.split('\n')) == 31
+
+    # Check that last item is principal axis angle
+    last_entry = str_res.split('\n')[-2]
+    assert last_entry.startswith('Principal axis angle (theta):')
+
+    str_fmt = sec.gross_properties.__format__('.2f')
+    # Check the string starts with the expected title
+    assert str_fmt.startswith('Section Properties:')
+
+    # Check that there are 30+1 rows of properties
+    assert len(str_fmt.split('\n')) == 31
+
+    # Check that last item is principal axis angle
+    last_entry = str_fmt.split('\n')[-2]
+    assert last_entry.startswith('Principal axis angle (theta):')
+
+    last_val = last_entry.split(':')[-1].strip()
+    assert last_val == '0.00'
+
+    # Check the value of Iyy as an example meeting the format required
+    Iyy = sec.gross_properties.iyy
+    Iyy_str = format(Iyy, '.2f')
+    for entry in str_fmt.split('\n'):
+        if entry.startswith('Second moment (Iyy):'):
+            val = entry.split(':')[-1].strip()
+            assert val == Iyy_str
+            break
+
+
+def test_detailed_result_none_point(elastic_rec_section):
+    """Test that point data in detailed result is empty."""
+    sec = elastic_rec_section
+
+    mult = sec.section_calculator.calculate_bending_strength()
+
+    mult.create_detailed_result()
+
+    # Now detailed result should not be None anymore
+    assert mult.detailed_result
+
+    # But point data should be None
+    assert not mult.detailed_result.point_data
+
+
+def test_detailed_result_bending_strength(elastic_rec_section):
+    """Test detailed result for beinding strength."""
+    sec = elastic_rec_section
+
+    Iyy = sec.gross_properties.iyy
+
+    mult = sec.section_calculator.calculate_bending_strength()
+
+    # Check detailed_result data correspond with results
+    assert mult.n == mult.detailed_result.n
+    assert mult.m_y == mult.detailed_result.m_y
+    assert mult.m_z == mult.detailed_result.m_z
+    assert np.allclose(
+        np.array([mult.eps_a, mult.chi_y, mult.chi_z]),
+        mult.detailed_result.strain,
+    )
+
+    # Check the ultimate moment result
+    fy = eps_u * E
+    # - due to sign convention
+    m_y_expected = -width * height**2 / 6 * fy
+
+    assert math.isclose(m_y_expected, mult.m_y)
+
+    # Check stress and strain in top and bottom fiber
+    stress_top_expected = m_y_expected / Iyy * height / 2
+    strain_top_expected = stress_top_expected / E
+
+    stress_bottom_expected = m_y_expected / Iyy * (-height / 2)
+    strain_bottom_expected = stress_bottom_expected / E
+
+    stress_top = mult.get_point_stress(0, height / 2)
+    stress_bottom = mult.get_point_stress(0, -height / 2)
+
+    strain_top = mult.get_point_strain(0, height / 2)
+    strain_bottom = mult.get_point_strain(0, -height / 2)
+
+    assert math.isclose(stress_top_expected, stress_top)
+    assert math.isclose(stress_bottom_expected, stress_bottom)
+    assert math.isclose(strain_top_expected, strain_top)
+    assert math.isclose(strain_bottom_expected, strain_bottom)
+
+
+def test_detailed_result_moment_curvature(elastic_rec_section):
+    """Test detailed result for moment curvature."""
+    sec = elastic_rec_section
+
+    mcurv = sec.section_calculator.calculate_moment_curvature()
+
+    # Check detailed_result data correspond with results
+    assert mcurv.n == mcurv.detailed_result.n
+
+    for i in range(len(mcurv.chi_y)):
+        mcurv.set_step(i)
+        assert mcurv.chi_y[i] == mcurv.detailed_result.chi_y
+        assert mcurv.chi_z[i] == mcurv.detailed_result.chi_z
+
+        assert np.allclose(
+            np.array([mcurv.eps_a[i], mcurv.chi_y[i], mcurv.chi_z[i]]),
+            mcurv.detailed_result.strain,
+        )
+
+
+@pytest.mark.parametrize(
+    'n, my',
+    [
+        (0, -30e6),  # pure bending
+        (-10e3, -30e6),  # bending with compression
+        (10e3, -30e6),  # bending with tension
+    ],
+)
+def test_detailed_result_plane_strain(elastic_rec_section, n, my):
+    """Test detailed result for plane strain calculation."""
+    sec = elastic_rec_section
+
+    Iyy = sec.gross_properties.iyy
+    A = sec.gross_properties.area
+
+    strain_res = sec.section_calculator.calculate_strain_profile(
+        n=n, my=my, mz=0
+    )
+
+    assert math.isclose(strain_res.n_ext, n)
+    assert math.isclose(strain_res.m_y_ext, my)
+    assert math.isclose(strain_res.m_z_ext, 0)
+
+    # Check detailed_result data correspond with results
+    assert strain_res.n == strain_res.detailed_result.n
+    assert strain_res.m_y == strain_res.detailed_result.m_y
+    assert strain_res.m_z == strain_res.detailed_result.m_z
+
+    stress_top_expected = n / A + my / Iyy * height / 2
+    strain_top_expected = stress_top_expected / E
+
+    stress_bottom_expected = n / A - my / Iyy * height / 2
+    strain_bottom_expected = stress_bottom_expected / E
+
+    stress_top = strain_res.get_point_stress(0, height / 2)
+    stress_bottom = strain_res.get_point_stress(0, -height / 2)
+
+    strain_top = strain_res.get_point_strain(0, height / 2)
+    strain_bottom = strain_res.get_point_strain(0, -height / 2)
+
+    assert math.isclose(stress_top_expected, stress_top)
+    assert math.isclose(stress_bottom_expected, stress_bottom)
+    assert math.isclose(strain_top_expected, strain_top)
+    assert math.isclose(strain_bottom_expected, strain_bottom)
+
+
+@pytest.mark.parametrize(
+    'eps_a, chi_y',
+    [
+        (0, -1e-7),  # pure bending
+        (-1e-4, -1e-7),  # bending with compression
+        (1e-4, -2e-7),  # bending with tension
+    ],
+)
+def test_detailed_result_integrate_plane_strain(
+    elastic_rec_section, eps_a, chi_y
+):
+    """Test detailed result for integration of stresses."""
+    sec = elastic_rec_section
+
+    int_res = sec.section_calculator.integrate_strain_profile(
+        strain=np.array([eps_a, chi_y, 0])
+    )
+
+    # Check detailed_result data correspond with results
+    assert int_res.n == int_res.detailed_result.n
+    assert int_res.m_y == int_res.detailed_result.m_y
+    assert int_res.m_z == int_res.detailed_result.m_z
+
+    strain_top_expected = eps_a + height / 2 * chi_y
+    stress_top_expected = strain_top_expected * E
+
+    strain_bottom_expected = eps_a - height / 2 * chi_y
+    stress_bottom_expected = strain_bottom_expected * E
+
+    stress_top = int_res.get_point_stress(0, height / 2)
+    stress_bottom = int_res.get_point_stress(0, -height / 2)
+
+    strain_top = int_res.get_point_strain(0, height / 2)
+    strain_bottom = int_res.get_point_strain(0, -height / 2)
+
+    assert math.isclose(stress_top_expected, stress_top)
+    assert math.isclose(stress_bottom_expected, stress_bottom)
+    assert math.isclose(strain_top_expected, strain_top)
+    assert math.isclose(strain_bottom_expected, strain_bottom)

From 238370621e451c53f287d74df9bbc68f0795a2e8 Mon Sep 17 00:00:00 2001
From: Diego Talledo <38036285+talledodiego@users.noreply.github.com>
Date: Tue, 17 Mar 2026 15:43:19 +0100
Subject: [PATCH 09/12] docs: update section results documentation

---
 docs/api/sections/section_calculator.md  | 57 +++++++++++++++++++-----
 structuralcodes/core/_section_results.py | 16 +++++++
 2 files changed, 62 insertions(+), 11 deletions(-)

diff --git a/docs/api/sections/section_calculator.md b/docs/api/sections/section_calculator.md
index 8df78ece..5f46bef6 100644
--- a/docs/api/sections/section_calculator.md
+++ b/docs/api/sections/section_calculator.md
@@ -51,6 +51,7 @@
 ```{eval-rst}
 .. autoclass:: structuralcodes.core._section_results.MomentCurvatureResults
 
+    .. autoproperty:: detailed_result
     .. automethod:: create_detailed_result
     .. automethod:: next_step
     .. automethod:: previous_step
@@ -62,38 +63,72 @@
 ```{eval-rst}
 .. autoclass:: structuralcodes.core._section_results.UltimateBendingMomentResults
 
+    .. autoproperty:: detailed_result
     .. automethod:: create_detailed_result
     .. automethod:: get_point_strain
     .. automethod:: get_point_stress
 ```
 
 ```{eval-rst}
-.. autoclass:: structuralcodes.core._section_results.NMInteractionDomain
+.. autoclass:: structuralcodes.core._section_results.StrainProfileResult
+
+    .. autoproperty:: strain_plane
+    .. autoproperty:: residual_norm
+    .. autoproperty:: residual_norm_history
+    .. autoproperty:: delta_strain_history
+    .. autoproperty:: delta_strain_norm_history
+    .. autoproperty:: response_history
+    .. autoproperty:: detailed_result
+    .. automethod:: to_list
+    .. automethod:: create_detailed_result
+    .. automethod:: get_point_strain
+    .. automethod:: get_point_stress
+```
+
+```{eval-rst}
+.. autoclass:: structuralcodes.core._section_results.IntegrateStrainStiffnessResult
+
+    .. automethod:: asarray
+```
+
+```{eval-rst}
+.. autoclass:: structuralcodes.core._section_results.IntegrateStrainForceResult
+
+    .. autoproperty:: detailed_result
+    .. automethod:: asarray
+    .. automethod:: astuple
+    .. automethod:: create_detailed_result
+    .. automethod:: get_point_strain
+    .. automethod:: get_point_stress
+```
+
+```{eval-rst}
+.. autoclass:: structuralcodes.core._section_results.NMInteractionDomainResult
 
     .. autoproperty:: n
     .. autoproperty:: m_y
-    .. autoproperty:: e_a
-    .. autoproperty:: k_y
+    .. autoproperty:: eps_a
+    .. autoproperty:: chi_y
 ```
 
 ```{eval-rst}
-.. autoclass:: structuralcodes.core._section_results.NMMInteractionDomain
+.. autoclass:: structuralcodes.core._section_results.NMMInteractionDomainResult
 
     .. autoproperty:: n
     .. autoproperty:: m_y
     .. autoproperty:: m_z
-    .. autoproperty:: e_a
-    .. autoproperty:: k_y
-    .. autoproperty:: k_z
+    .. autoproperty:: eps_a
+    .. autoproperty:: chi_y
+    .. autoproperty:: chi_z
 ```
 
 ```{eval-rst}
-.. autoclass:: structuralcodes.core._section_results.MMInteractionDomain
+.. autoclass:: structuralcodes.core._section_results.MMInteractionDomainResult
 
     .. autoproperty:: n
     .. autoproperty:: m_y
     .. autoproperty:: m_z
-    .. autoproperty:: e_a
-    .. autoproperty:: k_y
-    .. autoproperty:: k_z
+    .. autoproperty:: eps_a
+    .. autoproperty:: chi_y
+    .. autoproperty:: chi_z
 ```
diff --git a/structuralcodes/core/_section_results.py b/structuralcodes/core/_section_results.py
index 3badb404..a5028bd3 100644
--- a/structuralcodes/core/_section_results.py
+++ b/structuralcodes/core/_section_results.py
@@ -319,6 +319,10 @@ def create_detailed_result(self, num_points=1000):
         Arguments:
             num_points (int): Number of random points to sample for each
                 surface geometry (default = 1000).
+
+        Notes:
+            It is called with default values when first accessing the property
+                `detailed_result`.
         """
         if self.seed is None:
             self.seed = np.random.randint(1, 100, 1)[0].item()
@@ -711,6 +715,10 @@ def create_detailed_result(self, num_points=1000):
         Arguments:
             num_points (int): Number of random points to sample for each
                 surface geometry (default = 1000).
+
+        Notes:
+            It is called with default values when first accessing the property
+                `detailed_result`.
         """
         self._detailed_result = SectionDetailedResultState(
             section=self.section,
@@ -903,6 +911,10 @@ def create_detailed_result(self, num_points=1000):
         Arguments:
             num_points (int): Number of random points to sample for each
                 surface geometry (default = 1000).
+
+        Notes:
+            It is called with default values when first accessing the property
+                `detailed_result`.
         """
         self._detailed_result = SectionDetailedResultState(
             section=self.section,
@@ -1058,6 +1070,10 @@ def create_detailed_result(self, num_points=1000):
         Arguments:
             num_points (int): Number of random points to sample for each
                 surface geometry (default = 1000).
+
+        Notes:
+            It is called with default values when first accessing the property
+                `detailed_result`.
         """
         self._detailed_result = SectionDetailedResultState(
             section=self.section,

From b9cd3307f0b5bf16f9990819cee123628fd2bfc6 Mon Sep 17 00:00:00 2001
From: Diego Talledo <38036285+talledodiego@users.noreply.github.com>
Date: Wed, 18 Mar 2026 14:35:07 +0100
Subject: [PATCH 10/12] refactor: update section type annotations

---
 structuralcodes/core/_section_results.py | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/structuralcodes/core/_section_results.py b/structuralcodes/core/_section_results.py
index a1e89690..00654bb0 100644
--- a/structuralcodes/core/_section_results.py
+++ b/structuralcodes/core/_section_results.py
@@ -10,6 +10,7 @@
 from numpy.typing import ArrayLike, NDArray
 from shapely import Point
 
+from ..geometry import CompoundGeometry
 from .base import Geometry, Section
 
 
@@ -158,16 +159,16 @@ def isclose(self, other, rtol=1e-5, atol=1e-8):
 
 
 def _matching_geometries(
-    section: Section,
+    geometry: CompoundGeometry,
     name: t.Optional[str] = None,
     group_label: t.Optional[str] = None,
     case_sensitive: bool = True,
 ):
     """Return (surfaces, points) that match name/group filters."""
-    geometries_name = section.geometry.name_filter(
+    geometries_name = geometry.name_filter(
         name, return_mode='split', case_sensitive=case_sensitive
     )
-    geometries_group = section.geometry.group_filter(
+    geometries_group = geometry.group_filter(
         group_label, return_mode='split', case_sensitive=case_sensitive
     )
 
@@ -707,7 +708,7 @@ class UltimateBendingMomentResults:
     chi_z: float = 0  # the curvature corresponding to the ultimate moment
     eps_a: float = 0  # the axial strain at 0,0 corresponding to Mult
 
-    section: t.Any = None
+    section: Section = None
 
     _detailed_result: SectionDetailedResultState = None
 
@@ -858,7 +859,7 @@ class StrainProfileResult:
     strain_history: list[NDArray[np.float64]] = field(default_factory=list)
 
     # For context store the section
-    section: t.Any = None  # Note for future: if I want to type this I also have problem of circular import? #noqa E501
+    section: Section = None
     # The detailed result data structure
     _detailed_result: SectionDetailedResultState = None
 
@@ -1047,7 +1048,7 @@ class IntegrateStrainForceResult:
     m_z: float = 0.0  # Bending moment Mz
 
     # For context store the section
-    section: t.Any = None  # Note for future: if I want to type this I also have problem of circular import? #noqa E501
+    section: Section = None
     # The detailed result data structure
     _detailed_result: SectionDetailedResultState = None
 

From 1eb6fdaa2caaffe246810b07fe2b1972f1be873d Mon Sep 17 00:00:00 2001
From: Diego Talledo <38036285+talledodiego@users.noreply.github.com>
Date: Wed, 18 Mar 2026 14:47:30 +0100
Subject: [PATCH 11/12] fix tests

---
 structuralcodes/core/_section_results.py                | 2 +-
 tests/test_sections/test_rc_sections/test_rc_results.py | 8 +++++---
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/structuralcodes/core/_section_results.py b/structuralcodes/core/_section_results.py
index 00654bb0..fd58853b 100644
--- a/structuralcodes/core/_section_results.py
+++ b/structuralcodes/core/_section_results.py
@@ -230,7 +230,7 @@ def _get_point_response(
         return None
 
     surfaces, points = _matching_geometries(
-        section, name, group_label, case_sensitive
+        section.geometry, name, group_label, case_sensitive
     )
 
     if all_results:
diff --git a/tests/test_sections/test_rc_sections/test_rc_results.py b/tests/test_sections/test_rc_sections/test_rc_results.py
index ea27924e..ec695e05 100644
--- a/tests/test_sections/test_rc_sections/test_rc_results.py
+++ b/tests/test_sections/test_rc_sections/test_rc_results.py
@@ -62,17 +62,19 @@ def test_matching_geometries_intersection_case_sensitive(simple_rc_section):
     section = simple_rc_section
 
     # Case sensitive: "con*" matches "concrete" but "CON*" does not
-    surfaces, points = s_res._matching_geometries(section, name='con*')
+    surfaces, points = s_res._matching_geometries(
+        section.geometry, name='con*'
+    )
     assert len(surfaces) == 1
     assert surfaces[0].name == 'concrete'
     assert len(points) == 0
 
-    surfaces, _ = s_res._matching_geometries(section, name='CON*')
+    surfaces, _ = s_res._matching_geometries(section.geometry, name='CON*')
     assert len(surfaces) == 0
 
     # Case insensitive: "CON*" matches "concrete"
     surfaces, _ = s_res._matching_geometries(
-        section, name='CON*', case_sensitive=False
+        section.geometry, name='CON*', case_sensitive=False
     )
     assert len(surfaces) == 1
     assert surfaces[0].name == 'concrete'

From 710df345d140f46d2c4d8c52e357c53863172d19 Mon Sep 17 00:00:00 2001
From: Morten Engen <morten.engen@multiconsult.no>
Date: Wed, 18 Mar 2026 20:10:28 +0100
Subject: [PATCH 12/12] Remove todos and add optional annotations

---
 structuralcodes/core/_section_results.py | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/structuralcodes/core/_section_results.py b/structuralcodes/core/_section_results.py
index fd58853b..c5c111ea 100644
--- a/structuralcodes/core/_section_results.py
+++ b/structuralcodes/core/_section_results.py
@@ -272,8 +272,6 @@ def _get_point_response(
     return None
 
 
-# TODO: to be able using slots = True we mush type annotate section, but this
-# would trigger a circular import @mortenengen
 @dataclass(slots=True)
 class MomentCurvatureResults:
     """Class for storing moment curvature results.
@@ -692,8 +690,6 @@ def point_data(self):
         return self._point_data
 
 
-# TODO: to be able using slots = True we mush type annotate section, but this
-# would trigger a circular import @mortenengen
 @dataclass(slots=True)
 class UltimateBendingMomentResults:
     """Class for storing the ultimate bending moment computation for a given
@@ -708,7 +704,7 @@ class UltimateBendingMomentResults:
     chi_z: float = 0  # the curvature corresponding to the ultimate moment
     eps_a: float = 0  # the axial strain at 0,0 corresponding to Mult
 
-    section: Section = None
+    section: t.Optional[Section] = None
 
     _detailed_result: SectionDetailedResultState = None
 
@@ -859,7 +855,7 @@ class StrainProfileResult:
     strain_history: list[NDArray[np.float64]] = field(default_factory=list)
 
     # For context store the section
-    section: Section = None
+    section: t.Optional[Section] = None
     # The detailed result data structure
     _detailed_result: SectionDetailedResultState = None
 
@@ -1048,7 +1044,7 @@ class IntegrateStrainForceResult:
     m_z: float = 0.0  # Bending moment Mz
 
     # For context store the section
-    section: Section = None
+    section: t.Optional[Section] = None
     # The detailed result data structure
     _detailed_result: SectionDetailedResultState = None