Bridge Engineering (9-1) Suspension Bridges I. *Components: Anchorage (blocks or tunnel type),...

Bridge Engineering (9-1) Suspension Bridges

I. *Components: Anchorage (blocks or tunnel type), towers, main cabl

es, hangers, stiffened (box) girder and deck, substructure and foundation

II. Form: an arch upside down or the shape of a catenary

1 Wednesday, April 19, 2023

Bridge Engineering (9-1) Suspension Bridges *III. Anchorage 3.1 The anchorage, constru

cted as a concrete block or by tunneling the ground, forms a giant weight to anchor the bridge and transmit the tension generated through the cables firmly to ground.

3.2 The anchorage type is determined by the terrain where the anchorage points are constructed.


Bridge Engineering (9-1) Suspension Bridges III. Anchorage

3.3 A general type anchorage that supports unidirectional forces transmitting through cables. (One block for one bridge).


Bridge Engineering (9-1) Suspension Bridges III. Anchorage 3.4 An anchorage of a type

that supports bi-directional forces transmitting through cables. (One block for two bridges)

__located between two bridges and serving as two anchorage points.

__cable strands crossing each other in the air before entering the anchorage.



3.4 Bi-directional forces transmitting type __The Kurushima Kaikyo Bridge use four anchorages for which three types of forms are employed.



3.5 .1 A tunnel type anchorage which allows minimum alterations to be made to the existing landform.



3.5.2 Cable anchor frames securing the cables to the tunnels.


Bridge Engineering (9-1) Suspension Bridges IV. Tower

4.1 The main tower functions to transmit forces through the cables and into the main tower foundation.


Bridge Engineering (9-1) Suspension Bridges IV. Tower 4.1 The towers can be pr

efabricated in the plants or cast in situ.The blocks for the main tower were fabricated at the shop in blocks 6 m in length. The blocks are erected in the field using a climbing type of tower crane in building-block fashion to form the main tower. 9 Wednesday, April 19, 2023

Bridge Engineering (9-1) Suspension Bridges IV. Tower 4.1 Towers of Kurushima K

aikyo Bridge: The blocks for the main tower were fabricated at the shop in blocks 6 m in length. The blocks are erected in the field using a climbing type of tower crane in building-block fashion to form the main tower.


Bridge Engineering (9-1) Suspension Bridges V. Cables

5.1 Cables usu. of high tensile steel wires support bridge girders and other loads, including vehicle loads, and transmit these dead and live loads into the anchorage points.

5.2 Wires, strands, and ropes


Bridge Engineering (9-1) Suspension Bridges V. Cables5.2 Wires, strands, and ropes5.2.1Galvanized bridge wire fo

r parallel wire bridge cables. Recommended diameter .196 inch.

5.2.2 Galvanized bridge strand--consists of several bridge wires, of various diameterstwisted together.

5.2.3Galvanized bridge rope--consists of six strands twisted around a strand core.


Bridge Engineering (9-1) Suspension Bridges 5.3 Types of Cables 5.3.1 Parallel wire cables: This t

ype of cable is made up of a large number of individual wires parallel to one another. Neither the cables nor the wires are twisted in any manner. The wire is shipped to the site of the bridge on reels and the individual wires are installed or' "spun" on the bridge and later compacted together to form a round cross section. Cables of this type are used on monumental structures, such as the Golden Gate Bridge and the George Washington Bridge.


Bridge Engineering (9-1) Suspension Bridges 5.3.2 Parallel Strand Cables, Closed Construction--These consist of

several prefabricated Galvanized Bridge Strands, all laid parallel and in contact with one another. Wood or aluminum fillers are used to bring the cable to a circular cross-section, after which the whole cable is wrapped with wire for protection. The cable may contain 7, 19 37, 61, 91 or 127 strands.


Bridge Engineering (9-1) Suspension Bridges 5.3.3 Parallel Strand Cables, Open Constructio

n--This type of cable consists of several prefabricated galvanized bridge Strands which are all laid parallel to one another and not in contact. The strands are usually arranged in the form of a rectangle and the cable may contain 2, 4, 6, 9, 12, 16, 20, 24 or 30 strands.


Bridge Engineering (9-1) Suspension Bridges 5.3.4 Parallel Rope Cables,

Open Construction--These are the same as Parallel Strand Cables except that Galvanized Bridge Rope is used in place of Bridge Strand.



5.3.5 Single Rope or Single Strand Cables--These are used for small structures.


Bridge Engineering (9-1) Suspension Bridges 5.4 A single-stranded

cable with a hexagonal in cross section is formed by tying together 127 high-tension galvanized steel wires each about 5 mm in diameter. (as used for Kurushima Kaikyo Bridge)


Bridge Engineering (9-1) Suspension Bridges V. Cables

5.5 Erecting cables


Bridge Engineering (9-1) Suspension Bridges 5.6 Squeezing the cables

__After all the strands are laid, they are squeezed to form one single cable with a circular cross section.

__The strands are first tapped manually using a wooden maul to form a cable roughly circular and then squeezed using a hydraulic squeezing machine to form a circular cross section.


Bridge Engineering (9-1) Suspension Bridges 5.7 Cable strength 5.7.1 Strength of cables

One single steel wire (about 5 mm in diameter) is strong enough to hoist three passenger cars (1.2 tons each), and one stranded cable (consisting of 127 steel strands) is strong enough to hoist six space shuttles (74 tons each). 5.7.2 Length of cables The main cables for the Kurushima Kaikyo Bridges weigh 16,000 tons, and the strands are long enough to run round the earth two and one half times.


Bridge Engineering (9-1) Suspension Bridges VI. Stiffening Girder6.1 The stiffening girder functions as a driveway for veh

icles. The girder was designed with a cross section in the shape of a slim box to reduce vibrations in strong winds to a minimum. 23 Wednesday, April 19, 2023

Bridge Engineering (9-1) Suspension Bridges VI. Stiffening Girder6.2 Erecting box girder with b

arge Stiffening girder sections, e

ach 36m in length, are prefabricated in the plant and loaded on a self-propelled barge for transport to a site directly below each erection points. There they are lifted into position by a lifting beam and secured to hanger ropes.


Bridge Engineering (9-1) Suspension Bridges VII. Features of suspension

bridges

7.1. Aesthetic, light, and strong

7.2 Span range: 2,000 to 7,000 feet -- far longer than any other kind of bridge

7.3 Most expensive to build

7.4 Complicated in force bearing and distribution


Bridge Engineering (9-1) Suspension Bridges I. *Components: Anchorage (blocks or tunnel type),...

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