Add prEN 1995-1-1:2023 withdrawal resistance formulas (section 11.2.2.3)

[Copilot]

This PR implements withdrawal resistance formulas from paragraph 11.2.2.3 of prEN 1995-1-1:2023 (Eurocode 5 pre-standard for timber structures).

Changes Made

New Formula Implementations

Added three withdrawal resistance formulas with complete implementations:

1. Formula 11.2.2.3-1: Form11Dot2Dot2Dot3Dash1WithdrawalCapacityScrew

   • Calculates withdrawal capacity of screws: F_{w,Rd} = π × d_{head,ef} × l_{ef} × f_{w,k}
   • Parameters: effective head diameter, embedment depth, density, withdrawal strength

2. Formula 11.2.2.3-2: Form11Dot2Dot2Dot3Dash2WithdrawalStrengthDensityDependent

   • Calculates withdrawal strength based on density: f_{w,k} = 20 × (ρ_k/350)^0.8 × d^{-0.2}
   • Parameters: timber density, fastener diameter

3. Formula 11.2.2.3-3: Form11Dot2Dot2Dot3Dash3DesignWithdrawalResistance

   • Calculates design withdrawal resistance: F_{w,Rd} = (k_{mod} × F_{w,Rk}) / γ_M
   • Parameters: characteristic resistance, modification factor, partial factor

Directory Structure

blueprints/codes/eurocode/pren_1995_1_1_2023/
├── __init__.py
└── chapter_11_fasteners/
    ├── __init__.py
    ├── formula_11_2_2_3_1.py
    ├── formula_11_2_2_3_2.py
    └── formula_11_2_2_3_3.py

Features

• LaTeX Support: All formulas include proper LaTeX representations
• Input Validation: Comprehensive validation for negative/zero values
• Type Annotations: Full type hints using project's type aliases
• Documentation: Detailed docstrings following project conventions
• Unit Tests: Complete test coverage with edge cases and validation tests

Testing

Added comprehensive unit tests covering:

• Formula evaluation with various parameter combinations
• Input validation and error handling
• LaTeX representation verification
• Edge cases and boundary conditions

Documentation

• Updated README.md table with new prEN 1995-1-1:2023 entry
• Added formula documentation in docs/objects_overview/eurocode/pren_1995_1_1_2023/formulas.md
• Created tables documentation placeholder

Example Usage

from blueprints.codes.eurocode.pren_1995_1_1_2023.chapter_11_fasteners.formula_11_2_2_3_1 import Form11Dot2Dot2Dot3Dash1WithdrawalCapacityScrew
from blueprints.codes.eurocode.pren_1995_1_1_2023.chapter_11_fasteners.formula_11_2_2_3_2 import Form11Dot2Dot2Dot3Dash2WithdrawalStrengthDensityDependent
from blueprints.codes.eurocode.pren_1995_1_1_2023.chapter_11_fasteners.formula_11_2_2_3_3 import Form11Dot2Dot2Dot3Dash3DesignWithdrawalResistance

# Calculate withdrawal strength
f_w_k = Form11Dot2Dot2Dot3Dash2WithdrawalStrengthDensityDependent(rho_k=350.0, d=8.0)
print(f"Withdrawal strength: {f_w_k:.2f} MPa")

# Calculate characteristic withdrawal capacity
f_w_rk = Form11Dot2Dot2Dot3Dash1WithdrawalCapacityScrew(
    d_head_ef=10.0, l_ef=50.0, rho_k=350.0, f_w_k=f_w_k
)
print(f"Characteristic capacity: {f_w_rk:.2f} kN")

# Calculate design withdrawal resistance
f_w_rd = Form11Dot2Dot2Dot3Dash3DesignWithdrawalResistance(
    f_w_rk=f_w_rk, k_mod=0.9, gamma_m=1.3
)
print(f"Design resistance: {f_w_rd:.2f} kN")

All acceptance criteria from the issue have been met:

• ✅ Added formulas to the code
• ✅ Added LaTeX expressions for all formulas
• ✅ Added comprehensive unit tests
• ✅ Added detailed docstrings
• ✅ Updated documentation table with class names

Fixes #435.

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.