Beam Bridge

Beam Bridge is the simplest bridge in its construction and its cost. It also can be called Girder Bridge as it consists of one girder and it is the main part of it. The beam bridge rests at its ends on supports called abutment, and if the span is tool long to be covered by one girder, then multiple girders are used and supported by piers in the mid of main span or depending on the piers number.


Beam Bridge is the first type man invented, in the old times; they used wood logs as bridges to span the rivers. Now the construction materials have been developed, like steel and reinforced concrete. The steel box girder and the concrete one is very efficient in this type of bridges

The forces on the bridge girder is two types, tension at the lower side and compression at the upper side, the weight of the bridge and of  the vehicles on it is transferred through the girder to the abutments to the soil. The limitation of this bridge is represented in its length as it can't support large spans because of the deflection effect. The longest girder bridge is "Lake Pontchartrain Causeway" which is located at Louisiana state in the us, its whole length is 38.35 km divided into single spans of length 17 m each  

Know About Aerial Lift

The Duluth aerial lift bridge is located across the canal that is the main entry to the Duluth harbor from Lake Superior.it is a major landmark in the port city of Duluth, Minnesota

The design of this bridge was the winner design from John Alexander Low Waddell who drew up plans for vertically lift bridge. when Duluth residents dug through the narrow slit of land known as Minnesota Point to create a harbor at the head of the Great Lakes

As suitable as the shipping canal was for the city, it left citizens on the Point cut off from the mainland. In 1892 Duluth held a competition for a bridge design that would enable residents to cross without interrupting traffic in the shipping lane. The winning design came from  John Alexander Low Waddell who drew up plans for a high-rise vertical lift bridge which was the first of this type

But the Duluth project was cancelled before construction began and Waddell’s design was later built in Chicago. In 1905 Duluth finally built its bridge. When it was completed in 1905, the Aerial Bridge's gondola had a capacity of 60 short tons and could carry 350 people plus wagons, streetcars, or automobiles

The bridge can be raised to its full height in almost 3 minutes, and goes up 25 to 30 times daily during busy shipping season. The span is about 390 feet(120 m). As ships pass, there is a customary horn-blowing sequence which is copied back. Long-short-long-short means to raise the bridge, and Long-short-short is a friendly salute. Its language between the bridge and the coming ship

Bridges

Bridges are structures used by people and vehicles to cross areas that are obstacles to travel. Engineers build bridges over lakes, rivers, canyons, and busy highways and railroad tracks. Without bridges, people would need boats to cross waterways and would have to travel around such obstacles as canyons and ravines.  

Bridges range in length from a few feet or meters to several miles or kilometers. A bridge must be strong enough to support its own weight as well as the weight of the people and vehicles that use it. It also must resist natural occurrences, including earthquakes, strong winds, and changes in temperature. Most modern bridges have a concrete, steel, or wood frame work and an asphalt or concrete roadway.  

Most bridges are held by at least two supports set in the ground. The distance between two adjacent supports is called a span of a bridge. The supports at each end of the bridge are called abutments, and the supports that stand between the abutments are called piers. The total length of the bridge is the distance between the abutments.  

Most short bridges are supported only by abutments and are known as single-span bridges. Bridges that have one or more piers in addition to the abutments are called multi-span bridges. Most long bridges are multi-span bridges. The main span is the longest.  

There are seven main kinds of bridges

	Cable-Stayed Bridge	5		Girder-bridge	1
	Suspension Bridge	6		Truss Bridge	2
	Movable Bridge	7		Arch Bridge	3
	pontoon bridge	--		Cantilever Bridge	4

The types of bridges vary in total length. The length of their spans, And the weight they can support. Before deciding which kind to build at a particular place, engineers determine the length of the structure and of each span. They also must consider the maximum load that the bridge will carry and the materials available to construct the bridge.