Bridge Project 2025

Structural analysis tool for validating a matboard bridge design under train loading conditions. Calculates factors of safety across tension, compression, shear, and glue-line shear failure modes using the PyCBA continuous beam analysis library.

Overview

The project models a 1200 mm span bridge and analyzes its response to a multi-vehicle train configuration (locomotive + light freight car + heavy freight car). It computes critical moments and shear forces, then checks them against material strengths to determine factors of safety and maximum allowable loads.

Project Structure

File	Description
beam_functions.py	Core BeamModel class wrapping PyCBA for beam modeling, support definition, train creation, and analysis
bridge.py	Main analysis script defining beam geometry, material properties, and running FOS / failure load calculations
test of beam_functions.py	Example script demonstrating basic BeamModel usage with multiple supports and point loads

Requirements

• Python 3
• PyCBA
• NumPy
• Matplotlib

Install dependencies:

pip install pycba numpy matplotlib

Usage

Run the main analysis:

python bridge.py

This will:

1. Create a beam model with a 1200 mm span and roller support
2. Run a train analysis with a 100 N baseline car load
3. Print factors of safety for tension, compression, shear, and glue shear
4. Display beam diagrams and train interaction plots

To find the maximum load before failure, uncomment the analyze_max_P() call in bridge.py. This iteratively increases the car load from 135 N to 1000 N and reports which failure mode is reached first.

Beam Properties

Property	Value
Span length	1200 mm
Elastic modulus (E)	4000 N/mm²
Moment of inertia (I)	629,372 mm⁴
Centroidal axis (from bottom)	81.5 mm
Total height	103.81 mm

Material Strengths

Mode	Strength
Tension	30 MPa
Compression	6 MPa
Shear	4 MPa
Glue shear	2 MPa

License

MIT