Bridge is a structure which covers a gap. A bridge that span physical obstacles such as river ,valley or road is structure built. The first bridges consisted of fallen logs over rivers. Designs of bridges vary depending on the function of the bridge
Arch bridges are one of the oldest types of bridges and have been around for thousands of years. Arch bridges have great natural strength. They were originally built of stone or brick but these days are built of reinforced concrete or steel.
Arch bridges are always under compression. The tension in an arch isn’t considered important. Consequently, materials have that use at arch bridges, weak tension. Instead of pushing straight down, the load of an arch bridge is carried outward along the curve of the arch to the supports at each end. The weight is transferred to the supports at either end. These supports, called abutments, carry the load and keep the ends of the bridge from spreading out.
The load at the top of the key stone makes each stone on the arch of the bridge press on the one next to it.
This happens until the push is applied to the end supports or abutments, which are embedded in the ground.
The design of the arch, the semicircle, naturally diverts the weight from the bridge deck to the abutments.
When the load is divided between a series of smaller arches.The thrust at the internal supports balance each other and thrust is reduced .
A beam or "girder" bridge is the simplest kind of bridge and two parallel beams supported by piers of bridge. Span can be supported by trestle. Pratt warren The beam weight pushes straight down on the piers. They have bigger internal forces compared to arch bridges because of trying to bend. You can use wooden, reinforced concrete, prestressed-concrete or steel as materials. Large span structures have poor aesthetic appearance of the truss bridge but for moderate spans its best to provide at simple and regular structures.
When loads are applied to a truss at the joints, forces are transmitted only in the direction of each of its member. Other bridge types have high fabrication cost compared to truss bridges. Trusses have a high strength to weight ratio and consequently are used in many structures.
Cantilever bridge that built using cantilever is a bridge . A cantilever bridge is made from beams supported on one side only. The bridge formed with two design trusses that join in the center by a connecting member as pin-connected .
The diagram shows a cantilever bridge supporting a load . Wooden cantilever bridges were popular in Asia. The steel cantilever truss bridge was huge breakthrough. The most famous example of cantilever bridge is the Forth Railway Bridge in Scotland which was the longest span in the world until 1919 . After The Quebec Bridge was built in Canada.
History of Suspension Bridges
The first use of suspension bridge extends to prehistoric times.
Ancient people used some plants as like vine and bamboo for create suspension bridge. Native Suspension Bridge One of the First Discovered in Asia The first suspension bridge was built by Chinese people with chains and ropes.
The First modern steel cable was created by Albert Rop in 1834.
Undoubtedly ,. Steel cable are the most important factor in the development of the suspension bridge.
Bosphorus Bridge Today, suspension bridge cables are made of thousands of individual steel wires bound tightly together.
Steel is strong under tension, and an ideal material for cables.
A single steel wire, only 0.1 inch thick, can support load over half a ton without breaking. The suspension bridge is most preferred bridge to overcome the long spans.
Suspension bridge can provide to overcome the long spans, but there are serious drawbacks They are very flexible ,and traffic load can lead to a large collapse.
Thus, a support beam or a box beam is added to Golden Gate Bridge help the cable. Mostly everyone chooses suspension bridge in long span because Cable wires are cheaper and more durable than steel beams.
The Akashi Kaikyo Suspension Bridge is the longest suspension bridge in the world The suspension bridge's carrier system consists of the following elements:
1. Deck
2. Suspension cables
3. Main cables
4. Towers
5. The anchor blocks • Tower carries the main cables.
• Anchors provides remain to tense of main cable.
• Suspension cables transfer load of deck to main cable .
• Towers can be made from steel or reinforced concrete.
• Usually , deck made from shaped steel cage sytems. How Suspension Bridges Work
The main cables are tense with vertical cables that attach to the deck.
These cables support the deck of the bridge, transferring the weight to the towers at the end.
The main cables continue past the tower, and they are anchored past the far ends of the bridge.
They are carefully balanced so that the force pulling inward on the towers is equal to the force pulling outward. . As a result, the weight pulls directly down into the base of the tower. Cable-stayed bridges are a type of suspension bridge. Cable-stayed bridges have tall towers like suspension bridges, but in a cable- stayed bridge, the roadway is attached directly to the towers by a series of diagonal cables. A cable-stayed bridge is constructed in much the same way as a suspension bridge is, but without the main cables.
Advantages a cable-stayed bridge has over a standard suspension bridge include speed of construction and lower cost, since anchorages are not necessary. The cable-stayed bridge is optimal for spans longer than cantilever bridges and, shorter then suspension bridges.
Cable-stayed designs are used for intermediate- length spans. T here are no main cables, as with suspension bridges, making cable repair or replacement simpler. Harp Design Fan Design
• There are two major classes of cable- stayed bridges: harp and fan. Harp Design Cable-Stayed Bridges
In the harp or parallel design, the cables are nearly parallel. Fan Design Cable-Stayed Bridges
In the fan design, the cables all connect to or pass over the top of the towers.