1. Engineering I Structural Engineering
Bridges

2. Engineering I Structural Engineering
Lesson Essential Question:
What must be considered when designing\building a bridge?

3. Bridge Types Composite Beam Arch Suspension Three Major Types
A simple type of bridge composed of horizontal beams supported by vertical posts.
Arch
A type of bridge in which its weight is carried outward along the curve to supports at each end.
Suspension
A bridge in which the roadway is hung from strong cables that pass over two towers.
Composite
Cable-stayed bridge

4. Forces Downward Forces Compression Forces Tension Forces
Gravity
Weight of bridge
Load (Dead/Live)
Can weather play a factor?
Compression Forces
A force that compacts a material inward, often condensing the material.
Tension Forces
A force that stretches a material apart, often making the material longer.

5. Forces Torsion Shear A twisting force applied to an object.
A force that pushes the parts of an object in opposite directions.

6. Truss Supports Truss Supports Shapes
A rigid frame composed of short, straight pieces joined to form a series of triangles or other stable shapes.
Shapes
Which are stronger?
Pratt Truss
James Warren Truss
K-Truss
William Howe Truss

7. Factors Influencing Design
Length of the bridge
Load it must carry
Strength of the riverbed earth
Effect of river current or ocean tide on the supports

8. Factors Influencing Design
Effect of wind, rain, temperature, and other weather conditions
Time required to building the bridge
Cost of building materials and labor

9. Models Scaled models are an important way for testing Testing shows:
Designed to hold 2-3 times more then expected load
Testing shows:
Sagging or buckling areas
Weak joint points
Areas to reduce material (save $)

10. Bridge Review How Bridges Work Worksheet howstuffworks.com #1-12
25pts.
Each student must submit his or her own worksheet