A bridge’s structure is basically divided into two major parts: superstructure which is the upper portion of the bridge above the beams where vehicles move and pedestrians walk, this includes beams, bearings, deck, sidewalks etc., and substructure that is below the superstructure and actually caries the entire weight of the bridge, this includes bridge’s foundation, piles, beam seats etc.
Bridges are complex structures and must be carefully engineered using only strong, long-lasting materials that are light-weight as well to support the entire structure with minimum strain. Some of the typical materials used in bridge construction are steel, concrete, stone, aluminium, asphalt and iron etc.
Stone is one of the oldest bridge construction materials, is heavy and involves high installation costs. It is used to build piers and footers which allow the upper portions of the bridge to be built with lighter materials. Stone is naturally strong and resists erosion by wind and water to a great extent rendering it an ideal bridge construction material.
Another very commonly employed material in bridge construction is concrete which, although is strong and affordable, is considered unattractive because of its dull finish. Concrete can be easily shaped into whatever form the constructor desires but does not hold up well against erosion and is often used coupled with steel.
10 to 100 times stronger than concrete and light-weight as well, steel alone has probably revolutionised the entire construction industry like no other material ever did. It is mostly employed in bridges’ superstructure in the form of expansion joints, beams, bearings, floor beams, girders, reinforcing bars in concrete, traffic barriers and trusses. It is not corrosion-resistant and many steel bridges are painted to resist rust and corrosion and improve appearance.
Steel is commonly used in the bridge superstructure for armoring expansion joints, beams, bearings, floor beams, girders, reinforcing bars in concrete, traffic barriers and trusses. It is used in the substructure for the reinforcing bars in concrete, armoring for expansion joints, anchor bolts, etc. It is also used for piles to support the abutments and piers.
A recent replacement for steel in bridge construction that is not only light-weight but resists corrosion caused by wind and water, aluminium has been making its way into the construction industry for quite some time now. It is often used in place of steel where high corrosion rate of steel is expected and is used to make bridge railings.
Not as reliable as steel, concrete and aluminium, wood is often used to construct smaller bridges where very less traffic and people are supposed to use it at one time. It is one of the most affordable bridge materials, easy to use and work with using only the basic building tools, equipment and machinery. Wooden bridges are usually found in Northern regions and look beautiful against the serene backdrop. They are made to last longer through a chemical treatment because moisture can cause the wood to swell and rot.
Other bridge building materials used along with these basic ones are composites, asphalt, iron and rubber.