Unit 3

Bridge Engineering桥梁工程

Leading in

Dialogue

Text

Exercises

Teaching Steps

Pictures to the Dialogue

Double Blind Arcade Viaduct Arch bridge

Beam bridge Cable-stayed bridge

Cantilever bridge Clapper bridge

Compression arch suspended-deck bridge

Wooden bridge

Dialogue

A. How many types of culverts have you learnt?

B. Four types. They are pipe culvert, box culvert, bridge culvert and arch culvert.

A. What is generally chosen for smaller openings?

B. Pipe in stock sizes is generally chosen.

A. Generally speaking, what are used for larger openings?

B. Single- or multiple-span box culverts are used.

A. When do bridge culverts replace box culverts?

B. When the foundation is nonnegotiable and a paved floor is unnecessary, bridge culverts replace box culverts.

A. Under normal circumstances, what are the selections of culverts and material based on?

B. Comparative costs.A. What are the most commonly used

materials for permanent bridges?B. Steel and Concrete.

Dialogue

A. What are the principle portions of a bridge?

B. Substructure and super-structure.A. What are the common elements of the

substructure?B. Abutments and piers.A. Where do piers and abutments often rest?B. They often rest on separately constructed

foundations or groups of bearing piles.

Dialogue

A. How many types of bridges can you list?B. Five. They are girder bridges, rigid frames, arch

bridges, cable-stayed bridges and suspension bridges.

A. Which type of bridge is most often used for spans in the range of 75 to 100ft. (22.9 m to 30.5 m)?

B. Rigid frame.A. Is it true that suspension bridges are used for

very long spans or for shorter spans where intermediate piers cannot be built?

B. Yes, it is.

Dialogue

Questions to the Dialogue

1. How many types of culverts have you learnt?

2. What are the most commonly used materials for permanent bridges?

3. What is generally chosen for smaller openings?

Lead-in Pictures

to the Text

Suspended Structure

Suspended Structure

Words and expressions1. combination 2. truss3. arch4. girder5. skeleton6. timber7. reinforced concrete8. timber structure9. wall bearing construction10. suspended structure

The first bridges were made by nature — as simple as a log fallen across a stream. The first bridges made by humans were probably spans of wooden logs or planks and eventually stones, using a simple support and crossbeam arrangement.

TextTextHistory History

History History TextText

The greatest bridge builders of antiquity were the ancient Romans.[8] The Romans built arch bridges and aqueducts that could stand in conditions that would damage or destroy earlier designs. Some stand today.[9] An example is the Alcántara Bridge, built over the river Tagus, in Spain. The Romans also used cement, which reduced the variation of strength found in natural stone.[10] One type of cement, called pozzolana, consisted of water, lime, sand, and volcanic rock. Brick and mortar bridges were built after the Roman era, as the technology for cement was lost then later rediscovered.

History History TextText

Although large Chinese bridges of wooden construction existed at the time of the Warring States, the oldest surviving stone bridge in China is the Zhaozhou Bridge, built from 595 to 605 AD during the Sui Dynasty. This bridge is also historically significant as it is the world's oldest open-spandrel stone segmental arch bridge. European segmental arch bridges date back to at least the Alconétar Bridge (approximately 2nd century AD), while the enormous Roman era Trajan's Bridge (105 AD) featured open-spandrel segmental arches in wooden construction.

Types of bridges Types of bridges TextText Beam bridges

Beam bridges are horizontal beams supported at each end by piers. The earliest beam bridges were simple logs that sat across streams and similar simple structures. In modern times, beam bridges are large box steel girder bridges. Weight on top of the beam pushes straight down on the piers at either end of the bridge.

Types of bridges Types of bridges TextText Cantilever bridges

Cantilever bridges are built using cantilevers — horizontal beams that are supported on only one end. Most cantilever bridges use two cantilever arms extending from opposite sides of the obstacle to be crossed, meeting at the center. The largest cantilever bridge is the 549 metres (1,800 ft) Quebec Bridge in Quebec, Canada.

Types of bridges Types of bridges TextText Arch bridges

Arch bridges are arch-shaped and have abutments at each end. The earliest known arch bridges were built by the Greeks and include the Arkadiko Bridge. The weight of the bridge is thrust into the abutments at either side. Dubai in the United Arab Emirates is currently building the Sheikh Rashid bin Saeed Crossing which is scheduled for completion in 2012. When completed, it will be the largest arch bridge in the world.

Types of bridges Types of bridges TextText Suspension bridges

Suspension bridges are suspended from cables. The earliest suspension bridges were made of ropes or vines covered with pieces of bamboo. In modern bridges, the cables hang from towers that are attached to caissons or cofferdams. The caissons or cofferdams are implanted deep into the floor of a lake or river. The longest suspension bridge in the world is the 12,826 feet (3,909 m) Akashi Kaikyo Bridge in Japan.[14] See simple suspension bridge, stressed ribbon bridge, underspanned suspension bridge, suspended-deck suspension bridge, and self-anchored suspension bridge.

Types of bridges Types of bridges TextText Cable-stayed bridges

Like suspension bridges, cable-stayed bridges are held up by cables. However, in a cable-stayed bridge, less cable is required and the towers holding the cables are proportionately shorter. [15] The first known cable-stayed bridge was designed in 1784 by C.T. Loescher.[16] The longest cable-stayed bridge is the Sutong Bridge over the Yangtze River in China.

TextTextBridge Structure

Questions

1. Does “wall bearing construction” mean that it only keeps out the weather? If not, what does it mean?

2. What does skeleton construction mean?

3. What kind of construction is used for a building of one hundred storeys high?

Translate the following words or phrases into English

　1 ． concrete box bridge2 ． continuous girder bridge3 ． cable-stayed bridge4 ． detour bridge5 ． arch bridge6 ． cable suspension bridge7 ． cantilever girder bridge8 ． chain suspension bridge9 ． pre-camber

Exercises

1. The hut _________mud, branches and leaves.

2 In hot dry countries houses are built __________ the heat.

3. The skyscraper is ____________ New York City.

4. Water ___________ hydrogen and oxygen. 5. ____________ the plan, a modern building will be

put up here next year. 6. ___________ bricks, people also used stones to build

houses. 7. I am a freshman of ___________Department in

SVTCC. 8. Now I can name many technical terms: beam,

column, truss, arch ____________.

Complete the sentences with the given words or expressions. Change the form where necessary.

is built of

to keep out

in the center of

consists of

According to

In addition to

Road and Bridge Engineering

and so on

Translation

Bridges generally are considered to be composed of three separate parts: substructure, superstructure, and deck. The substructure or foundation of a bridge consists of the piers and abutments which carry the superimposed load of the superstructure to the underlying soil or rock. The superstructure is that portion of a bridge or trestle lying above the piers and abutments. The deck or flooring is supported on the bridge superstructure; it carries and is in direct contact with the traffic for which passage is provided.