Its completion was a feat of engineering that was unmatched in its time: The idea of a bridge linking Manhattan to Brooklyn was first formalized in a petition to the state legislature in Feuerstein From the time Dutch settlers arrived in Brooklyn in , there had been a need to travel between Manhattan and Brooklyn Feuerstein There were many factors that made constructing a bridge there difficult, though.
The East River was a wide and busy waterway with large ships and was surrounded by a low-lying area. This required that the bridge have a high clearance to enable ships to enter, be longer than any bridge built before it and have a significant curve. For these reasons, the idea for the bridge was continuously put off in favor of ferry services.
The City of New York at the time consisted only of Manhattan, which had about double the population of Brooklyn. A bridge was seen as a way to relieve overcrowding in Manhattan, while at the same time aid in the expansion of Brooklyn. A man named John Roebling came up with the idea for the bridge in when he became frustrated while waiting for a ferry in Logson Roebling was born in in Germany where he trained to be an engineer.
He immigrated to the United States in and after a failed attempt at making a living as a farmer in Pennsylvania, he found work as a civil engineer Logson He originally worked on canals and in the process of designing them, he found that he needed better rope.
He came up with a new design and method of creating flexible wire ropes and received a patent for this in Logson He quickly found additional uses for the invention, one of which was bridges. After several more successful projects, Roebling began to lobby influential people in New York for a bridge he had designed to cross the East River. In , an act was passed to raise funding for the bridge and two years later, the design for the Brooklyn Bridge was approved.
His son, Washington, took over and ground was broken on the bridge on January 3, Logson The main design feature of the bridge were four fifteen-inch diameter steel cables that would support the enormous expanse of the bridge, which was to be over feet Switch In order to support those cables, the towers had to be enormous and they had to be sunk to the bedrock below the East River.
The method for digging the river bottom was to sink a wooden box using pressurized air and create an elevator so that workers could be lowered to the box which was called a caisson. In order to pressurize the air, other gases had to be used which were potentially toxic. At least two dozen people died during the construction, most of which occurred from this phenomena.
Workers were raised to the surface too quickly and experienced what were referred to as the bends. Granite finally reached 78 feet down on one side and 44 feet on the other and the towers were eventually finished in The construction of the roadway began in and finally finished in By , the longest suspension bridge in the world was finished after thirteen years of development and construction. For simple spans up to 25m and continuous spans up to 33m, rolled universal beams are economic and are available up to mm deep.
For longer span bridges, deeper girders are fabricated from plates. This gives scope to vary the web and flange sizes and the steel grades for an efficient design. Variable depth girders are often used to give greater economy, and also to enhance aesthetics. Such plate girders can be readily fabricated with curvature in plan and elevation.
Box girders are a particular form of plate girder, with two webs joined by common top and bottom flanges. Boxes may be used either singly or in multiples. They may be straight or curved in plan and be of constant or variable depth. Steel box girder bridges have great torsional rigidity, which makes them ideal for bridges that are highly curved in plan or where construction by launching is required.
In addition, they are widely used as the deck elements of cable-stayed and suspension bridges, where the torsional stiffness of a box is important for the dynamics of such long span bridges. A truss is a triangulated framework of elements that act primarily in tension and compression. It is a light-weight yet very stiff form of construction. Truss girders were common in early steel bridge construction as welding had yet to be developed pre s and rolled sections and plate sizes were of a limited range.
They are considered expensive to fabricate today, being labour intensive. Maintenance issues have to be carefully addressed for example, ease of access. However, they can still show advantages in particular applications such as footbridges and railway bridges. Typical spans in one form or other can range from 40m to m. Trusses may be used as girders below the deck level, or as through girders with the deck at the bottom chord level. Such through truss girders minimise the effective construction depth, and the length of approach embankments.
Hence, they are particularly suited to footbridges and railway bridges. Trusses can also be used as arch elements for example, the Sydney Harbour Bridge and as cantilever elements for example, Forth Rail Bridge in Scotland. They also have applications as stiffening girders on major suspension bridges. In the traditional form, a steel arch has a similar structural action to old masonry arch bridges.
The arch springs from the foundations and exerts horizontal thrusts on them. The arch elements act primarily in compression. The deck may either be supported on struts, resting on arch below, or it may be suspended on hangers from the arch above. The horizontal thrusts from the arching action are resisted by tension members between the arch springings. Effectively the deck acts as a tension tie, and is supported by hangers from the arch above. This form is suited to the soft soils of river banks, where the ground cannot withstand the large horizontal thrusts from arching action.
Steel arches in one form or another have been used for spans ranging from 30m to m. Cable-stayed bridges are a recent adaptation of the suspension bridge principle. The deck structure is supported by tension stays sloping from one or more towers. The towers act in compression and can have a variety of forms A-frame, H-frame or columns. The deck girders sustain compression forces as well as bending forces. The very large spans have only recently been feasible due to developments in dynamic analysis, and methods for damping oscillations.
In terms of aesthetics, the low profile decks, striking towers and raking cables are effective and dramatic. Such bridges are usually landmark structures. The deck of a suspension bridge is supported by vertical tension hangers, which are supported in turn by large tension cables extending over two towers from anchorage to anchorage.
The suspension concept dates back to antiquity, and it is because of their fundamental simplicity and economy of structural action that suspension bridges are used for the longest of modern bridge spans. A stiffening girder running the full length of each span is an essential part of a suspension bridge. It distributes the concentrated traffic loads and provides stiffness against bending, twisting and oscillation. For single decks, the trend is to use box girders to minimise weight and give maximum torsional stiffness.
However, where twin level decks are required for example, to carry road traffic and railway traffic then the general trend to use truss girders. Aesthetically, the graceful curve of the suspension bridge combined with the strong visual line of the deck give a pleasing effect.
The term is used to refer to a bridge-like structure which is movable. Typically, a drawbridge opens up to extend over the distance it is meant to span. A castlebridge, for example, opens like a door, serving as a doorway to the castle. It could be in the form of a plank that is pivoted to the center that rotates along a designated circumference. Sorry, but copying text is forbidden on this website. If you need this or any other sample, we can send it to you via email.
Types of Bridges Essay Sample There are 4 major types of bridges.
A bridge is a structure which provides passage over an obstacle without closing the way beneath.
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