diff --git a/structuralcodes/codes/ec2_2023/__init__.py b/structuralcodes/codes/ec2_2023/__init__.py
index c8662148..4cff7a80 100644
--- a/structuralcodes/codes/ec2_2023/__init__.py
+++ b/structuralcodes/codes/ec2_2023/__init__.py
@@ -50,8 +50,10 @@
     wk_cal,
     wk_cal2,
 )
+from ._section_8_6_partially_loaded_areas import sigma_Rd_u
 
 __all__ = [
+    'sigma_Rd_u',
     'A_phi_correction_exp',
     'alpha_c_th',
     'alpha_s_th',
diff --git a/structuralcodes/codes/ec2_2023/_section_8_6_partially_loaded_areas.py b/structuralcodes/codes/ec2_2023/_section_8_6_partially_loaded_areas.py
new file mode 100644
index 00000000..fb7b826e
--- /dev/null
+++ b/structuralcodes/codes/ec2_2023/_section_8_6_partially_loaded_areas.py
@@ -0,0 +1,65 @@
+"""Functions from Section 8.6 of EN 1992-1-1:2023."""
+
+import math
+
+
+def sigma_Rd_u(
+    fcd: float,
+    a0: float,
+    b0: float,
+    a1: float,
+    b: float,
+    ea: float = 0,
+    eb: float = 0,
+    nu_part: float = 3.0,
+) -> float:
+    """Calculate the design resistance for partially loaded areas without
+    horizontal force components.
+
+    EN1992-1-1:2023 Eq. (8.126).
+
+    Args:
+        fcd (float): Design value of concrete compressive strength in MPa.
+        a0 (float): Length of the loaded area in the direction perpendicular to
+            the closest edge in mm.
+        b0 (float): Width of the loaded area in mm.
+        a1 (float): Length of the load introduction block parallel to a0 in mm.
+        b (float): Total width of the supporting area in mm.
+        ea (float): Eccentricity of the applied load parallel to a0 in mm.
+            Default is 0.
+        eb (float): Eccentricity of the applied load parallel to b0 (mm).
+            Default is 0.
+        nu_part (float): Confinement factor. Default is 3.0.
+
+    Returns:
+        float: Design resistance in MPa.
+
+    Raises:
+        ValueError: If any of the input dimensions or resistances are negative.
+    """
+    if fcd < 0:
+        raise ValueError(f'fcd must not be negative. Got {fcd}')
+    if a0 < 0:
+        raise ValueError(f'a0 must not be negative. Got {a0}')
+    if b0 < 0:
+        raise ValueError(f'b0 must not be negative. Got {b0}')
+    if a1 < 0:
+        raise ValueError(f'a1 must not be negative. Got {a1}')
+    if b < 0:
+        raise ValueError(f'b must not be negative. Got {b}')
+    if ea < 0:
+        raise ValueError(f'ea must not be negative. Got {ea}')
+    if eb < 0:
+        raise ValueError(f'eb must not be negative. Got {eb}')
+
+    # Eccentrically reduced loaded area
+    a0_red = a0 - 2 * ea
+    b0_red = b0 - 2 * eb
+    Ac0_red = a0_red * b0_red  # in mm²
+
+    # Contributing concrete area
+    Ac1 = a1 * min(b0 + (a1 - a0), b)  # in mm²
+
+    # Design resistance
+    sigma_Rdu = fcd * math.sqrt(Ac1 / Ac0_red)
+    return min(sigma_Rdu, nu_part * fcd)
diff --git a/tests/test_ec2_2023/test_ec2_2023_section_8_6_partially_loading_areas.py b/tests/test_ec2_2023/test_ec2_2023_section_8_6_partially_loading_areas.py
new file mode 100644
index 00000000..8761bea5
--- /dev/null
+++ b/tests/test_ec2_2023/test_ec2_2023_section_8_6_partially_loading_areas.py
@@ -0,0 +1,30 @@
+"""Test for Functions from Section 8.6 of EN 1992-1-1:2023."""
+
+import pytest
+
+from structuralcodes.codes.ec2_2023 import _section_8_6_partially_loaded_areas
+
+
+@pytest.mark.parametrize(
+    'f_cd, a0, b0, a1, b, ea, eb, nu_part, expected',
+    [
+        (25, 300, 200, 350, 500, 0, 0, 3.0, 30.19),
+        (30, 400, 300, 450, 600, 20, 10, 3.0, 37.5),
+        (40, 500, 400, 550, 700, 30, 20, 3.0, 50.0),
+    ],
+)
+def test_calculate_design_resistance(
+    f_cd, a0, b0, a1, b, ea, eb, nu_part, expected
+):
+    """Test calculate_design_resistance with various
+    inputs to verify correctness.
+    """
+    assert (
+        pytest.approx(
+            _section_8_6_partially_loaded_areas.sigma_Rd_u(
+                f_cd, a0, b0, a1, b, ea, eb, nu_part
+            ),
+            rel=1e-2,
+        )
+        == expected
+    )