Public Infrastructure Bridges
What bridges do How do you design a bridge? Types of bridges
What Bridges Do Cross over a natural obstacle River/creek Canyon/valley Cross over a man-made facility Road Railroad Canal
How Do You Design Bridges? For most of history: Trial & error Beginning in 1800’s: Structural engineering Today: Use computers to model bridges & performance Bridge engineers need to understand physics, materials, construction methods, math
How Do You Design a Bridge? Safety Carry intended loads Economy Construction cost Maintenance cost Esthetics How it looks How it fits in to surrounding neighborhood
Bridge Forces How are forces resisted? Transfer Dissipation Tension Compression
3 Basic Types of Bridges Beam bridge Up to 200 feet Arch bridge Up to 800 feet Suspension bridge Up to 7,000 feet
Beam Bridges The first bridges Logs across a stream Simple Cheap Need strong materials
Beam Bridge
Transfer of Force
Arch Bridges Ancient design Can last a long time Expensive & hard to build
Arch Bridge
Dissipate Force
Suspension Bridges Can bridge long distances Wide, high, clearances
Suspension Bridge
Transfer of Force
Cable-Stayed Bridges
Truss Bridges Use wood or steel to make triangles Early railroad bridges
Cantilever Bridges
Box Girder Bridges
Box Girder Sections Concrete Steel composite with concrete Polymer composites
Culverts Smallest Usually carry water under roads
Movable Bridges
Covered Bridges
Date of Construction of US Bridges
Chicago Skyway Opened miles Current $250 million renovation
Chicago Movable Bridges Types Vertical lift Swing Bascule Different types Many designs developed in Chicago 52 movable bridges in Chicago today Some immobilized