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fix: update iterative strain before convergence check #340

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Merged
mortenengen merged 3 commits into from
Mar 26, 2026
+19 −14
Merged

fix: update iterative strain before convergence check #340

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e223120
Update iterative strain before convergence check
mortenengen Mar 25, 2026
d62d0c8
Move residual calculation so that the complete residual history is ca…
mortenengen Mar 25, 2026
c398a07
Calculate the initial residual since it may be different from the loa…
mortenengen Mar 25, 2026
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33 changes: 19 additions & 14 deletions structuralcodes/sections/_generic.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1773,7 +1773,7 @@ def calculate_strain_profile(
geom = self.section.geometry

# Collect loads in a numpy array
loads = np.array([n, my, mz])
loads = np.array([n, my, mz], dtype=float)

# Compute initial tangent stiffness matrix
stiffness_tangent, integration_data = (
Expand All @@ -1790,9 +1790,14 @@ def calculate_strain_profile(

# Calculate strain plane with Newton Rhapson Iterative method
num_iter = 0
strain = np.zeros(3, dtype=float)
residual = np.zeros(3, dtype=float)
converged = False
strain = np.zeros(3, dtype=float)

# Calculate the initial response and residuals. Note that the initial
# residual might be different from the applied loads if any initial
# strain is present
Comment on lines +1796 to +1798
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@talledodiego talledodiego Mar 26, 2026

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right observation! perfect

response = self.integrate_strain_profile(strain=strain).asarray()
residual = loads - response

residual_history = []
strain_history = []
Expand All @@ -1809,14 +1814,6 @@ def calculate_strain_profile(
if num_iter > max_iter:
break

# Calculate response and residuals
response = self.integrate_strain_profile(strain=strain).asarray()
residual = loads - response

# Append to history variables
residual_history.append(residual.copy())
strain_history.append(strain.copy())

if initial:
# Solve using the decomposed matrix
delta_strain = lu_solve((lu, piv), residual)
Expand All @@ -1829,14 +1826,22 @@ def calculate_strain_profile(
# Solve using the current tangent stiffness
delta_strain = np.linalg.solve(stiffness_tangent, residual)

# Update the strain
strain += delta_strain

# Calculate response and residuals
response = self.integrate_strain_profile(strain=strain).asarray()
residual = loads - response

# Append to history variables
residual_history.append(residual.copy())
strain_history.append(strain.copy())

# Check for convergence:
if np.linalg.norm(delta_strain) < tol:
converged = True
break

# Update the strain
strain += delta_strain

num_iter += 1

# Create the results object
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