Types+of+Bridges

= ~*~ Types of Bridges ~*~  = = Beam bridges: = A beam bridge is also referred to as a "girder" bridge and is the simplest type of bridge. In earlier times, the beam bridge could be constructed using simple environmental materials, such as logs and vines. Today, they are built using materials such as iron or steel. The main characteristic a beam bridge must maintain is being sturdy so it can support the **load.** A load is what the bridge supports so it can pass. In order for the bridge to support the load, it has tension forces which work upwards on the load as the load (compression force) itself works downwards. The load travels over the deck of the bridge. The deck and the other constructional features of the beam bridge are supported by abutments **.** An abutment is a structure built to support the lateral pressure that is placed on a bridge at a certain time. One of the most famous examples of a beam bridge is the Confederation Bridge in Canada. It is the longest bridge in the world that spans over ice-covered water. The Confederation Bridge is only one type of the many beam bridges. There are three main types of beam bridges: the box section, the I section, and the L section. These bridges get their categorical names from the distinct construction form of their abutments. The box shape beam bridge is unique in the fact that its abutments are hallow and the steel is shaped into the form of a box. It's because of this single characteristic that most professionals say that the box shaped beam bridge is the sturdiest form of the beam bridge. An I section beam bridge gets its name from the cross section of the bridge which is shaped like a capitol I. The middle support of the cross section is called a web and the two side supports are known as flanges. There isn't much known about the specific construction features of an L section beam bridge but what is known is that the L section characteristic is utilized when special requirements need to be meant for certain terrains, climates, etc.

The Confederation Bridge in Canada (as pictured below):



= Arch bridges: = An arch bridge is where the **load** is held up by the **abutments** to keep the ends of the bridge from spreading out. Most bridges are hinge-less, two hinged, three hinged, or tied. The weight is around the curve.

 Instead of pushing straight down on the load, the bridge is carried outward along the curve at the end of the arch on each end.

 So then the ground around the abutments are squeezed and pushed back onto the abutments.

 For every action there is an equal and opposite reaction. The ground pushes back on the abutments which creates resistance eventually pushing on the stone supporting the load.

Arch bridges are one of the oldest types of bridges which also has natural great strength. They were first originally built out of stone and brick. Today they are made out of concrete or steal.

An arch bridge now a days: Zhaozhou Bridge in Hebei province, China

A Roman arch bridge:  These bridges were used and built by the ancient Romans before a new form of arch bridges were built. These were the first long lasting bridges that were made from stone and concrete. = Suspension bridges: = A suspension bridge is a type of bridge in which the deck (load-bearing portion) is hung below suspension cables on vertical suspenders. Suspension bridges are ideal to cover busy waterways because they can cover up to 2,000 to 7,000 feet far longer than most other types of bridges. Main supporting parts of a suspenson bridge are cables, towers, and anchors. When building a suspension bridge, traffic flow is considered to determine the width. Trusses in a suspension bridge serve the purpose to distribute concentrated loads (such as snow, concrete, etc.) and to secure aerodynamic stability. Different types of suspension bridges are: - Simple suspension bridges: A simple suspension bridge has a flexible deck that lies on the main cables. - Self-anchored suspension bridge: A self-anchored suspension bridge has many main cables anchored at both ends of the deck. - Underspanned suspension bridge: The deck is raised on posts above the main cables. The earliest suspension bridge had cables anchored at both ends of the bridge in the ground, some of our more modern bridges anchor the cables to the end of the bridge itself.

The Golden Gate Bridge in San Francisco, California is known to be one of the most beautiful bridges. The bridge is 1.7 miles long and can be traveled by car, foot, or bicycle. There are parking and viewing area at both ends of the bridge. The Golden Gate Bridge took 4 years to build and $35 million. President Frankilin D. Roosevelt opened the bridge to traffic on May 28, 1937. The bridge's two towers rise 746 feet making them 191 feet taller than the Washington Monument.