Fundamentals for the Up-and-Coming Bridge Engineer
Outline
Beam Strength and Deflection
Moment of Inertia
Types of Forces Applied
Young’s Modulus (stress and strain)
Optimization
Beam Deflection
Every object acts as a spring – it will deflect when a force is applied
Extent of deflection depends on force applied, material properties and object shape
Moments of Inertia
A measure of resistance to deflection
A larger moment of inertia means that the beam will be more resistant to deflection
To Increase the Moment of Inertia
Increase the size:
But as you increase the size, you increase the weight and cost

Change the cross-sectional shape:
A hollow cross-section is stronger for the amount of material used
Differences in Deflection
Types of Forces on a Bending Beam
Compression, Tension, and Torsion
Stress and Strain of Different Materials
Design Optimization
Engineering is not about building the strongest possible bridge
Engineering is about building a bridge that is strong enough and balances cost, strength, time required to build, etc
Engineering is about trade-offs and meeting design specifications

Design Optimization
Engineering is not about building the strongest possible bridge
Engineering is about building a bridge that is strong enough and balances cost, strength, time required to build, etc
Engineering is about trade-offs and meeting design specifications
Summary
Beam strength depends on force applied, material properties and object shape
Important material properties include moment of inertia and Young’s Modulus (stress and strain)
Three types of forces are compression, tension, and torsion
These concepts will be helpful in the West Point Bridge Designer