ENG-1010 Lecture 16 Bridge Design

Table of contents What is a bridge.? Different types of bridges. Descriptions. History Working. Culverts Type of culverts Depiction References.

Bridge Bridge is a structure built to span a valley, road, river, body of water, or any other physical obstacle. Designs of bridges will vary depending on the function of the bridge and the nature of the area where the bridge is to be constructed.

Great Stone Bridge in China History of Bridge Development 100 B.C. Romans 2,104 years ago 700 A.D. Asia 1,304 years ago Clapper Bridge Roman Arch Bridge Tree trunk Stone Arch design evenly distributes stresses Natural concrete made from mud and straw Great Stone Bridge in China Low bridge Shallow arch Allows boats and water to pass through

History of Bridge Development 1900 1920 Truss Bridges Mechanics of Design Wood 2000 Suspension Bridges Use of steel in suspending cables Prestressed Concrete Steel

Basic Concepts Span - the distance between two bridge supports, whether they are columns, towers or the wall of a canyon. Force - Compression Tension Compression – Tension - Concrete has good compressive strength, but extremely weak tensile strength. What about steel cables?

Basic Concepts Beam - a rigid, usually horizontal, structural element Pier Pier - a vertical supporting structure, such as a pillar Cantilever - a projecting structure supported only at one end, like a shelf bracket or a diving board Load - weight on a structure

Types of Bridges There are six main types of bridges: beam bridges cantilever bridges arch bridges suspension bridges cable-stayed bridges and truss bridges

Bridge Design Engineering Considerations Ground conditions Availability of materials Aesthetic properties

Beam Bridges Consists of a horizontal beam supported at each end by piers. The weight of the beam pushes straight down on the piers. The farther apart its piers, the weaker the beam becomes. This is why beam bridges rarely span more than 75m.

Box Girder Bridge Box shaped cross section Good in torsion More expensive to maintain Commonly precast

Segmented Bridge

Beam bridge Forces When something pushes down on the beam, the beam bends. Its top edge is pushed together, and its bottom edge is pulled apart.

cantilever bridges A cantilever bridge is a bridge built using cantilevers: structures that project horizontally into space, supported on only one end.

Cantilever Bridge

Arch bridges The arch has great natural strength. Thousands of years ago, Romans built arches out of stone. Today, most arch bridges are made of steel or concrete, and they can span up to 800 feet.

Arch Bridges Forces The arch is squeezed together, and this squeezing force is carried outward along the curve to the supports at each end. The supports, called abutments, push back on the arch and prevent the ends of the arch from spreading apart.

Suspension Bridges This kind of bridges can span 800m to 2500m -- way farther than any other type of bridge! Most suspension bridges have a truss system beneath the roadway to resist bending and twisting.

Forces In all suspension bridges, the roadway hangs from massive steel cables, which are draped over two towers and secured into solid concrete blocks, called anchorages, on both ends of the bridge. The cars push down on the roadway, but because the roadway is suspended, the cables transfer the load into compression in the two towers. The two towers support most of the bridge's weight.

Cable-stayed Bridges The cable stayed bridge is newer than the other types of bridge. Large upright steel supports are used to transmit the load into the ground.

Cable Stayed Bridge

Truss Bridge Typical Span Lengths 40m - 500m World's Longest Pont de Quebec Total Length 863m Center Span 549m A Matsuo Example 2nd Mameyaki Bridge All beams in a truss bridge are straight. Trusses are comprised of many small beams that together can support a large amount of weight and span great distances

Floating Bridge Pontoon bridges are supported by floating pontoons with sufficient buoyancy to support the bridge and dynamic loads. While pontoon bridges are usually temporary structures, some are used for long periods of time. Permanent floating bridges are useful for traversing features lacking strong bedrock for traditional piers. Such bridges can require a section that is elevated, or can be raised or removed, to allow ships to pass.

Culvert Basics Must be large enough for volume of water….

Culvert Hydraulically short conduit which conveys stream flow through a roadway embankment or past some other type of flow obstruction

Hybrid Bridges

Clyde Arc, Scotland

Think about Forces – Braking on High Speed Trains at 300km/h.

Bridge Construction

Onsite Construction Cast onsite and jack Use formwork

Precast Construction Jacking sections Precast deck panels

Building a Suspension Bridge

Building a Suspension Bridge

Use Temporary Works

Construction Process Foundations(and Caissons) Towers Decks Finishing

Make sure the calculations are correct!

Bridge Failure

Bridge in USA

Tacoma Narrows (USA)

Tacoma Narrows (USA)

Another failure in USA..