Engineering is all about creation. Creating small things to big things, creating things for pleasure to creating things for comfort! Everything around us is a marvel created by engineers. And every small detail in every small to every big thing has a very big motivation behind it. For example, tip of screwdriver possess magnetic properties so that it becomes easy for you to collect nails and bolts. And, thickness of tall buildings gradually decreases and get curvy along with its height not just because it enhances its appearance, but also to create an airfoil to reduce the effect of wind and hence to stand intact even in intense hurricanes.
If we intend to understand all the reasons behind any engineered things especially about infrastructures, we will need hundreds of pages to get detailed information. Hence, in this article we will see the major issues involved while constructing bridges and brief explanation how engineers are taking care of those issues.
Types of Bridges
After reading the title “Type of bridges”, you must have thought that this paragraph is just about introduction to bridges. But choosing the right type of bridge is the first and the most difficult part of the problem statements. As there are different types of bridges like, Beam bridge, Truss bridge, Cantilever bridge, Arch bridge, Tied arch bridge, Suspension bridge, Cable-stayed bridge, etc. They all are different because of their structure, their way of fetching support, the material they use, the load they can carry and the maximum length they can cover. Because of all these types of bridges and their differences the engineers learn all the types in detail and they opt for the most preferable type of the bridge.
Availability of Material
Responsibility of an engineer is not to design the best possible structure, but to design the best possible structure within the budget. Also, the types that have been listed in above paragraph need different materials, hence engineers keep the record of the material available near the site, the manufacturers who will manufacture the parts and the transport medium which is the least expensive. Also, material should be rust free, or supplementary mixtures which eliminates rust and degradation of material is used.
Self-Weight and Support for Bridge
A bridge is used to carry a very large load, but the self-weight of bridge plays a significant role as the quantity of steel and/or concrete used to build the bridge is excessive. Hence, engineers try to minimize the weight of bridge as must as possible. Before even starting the design of bridge, the engineers choose a site which could provide enough support for bridge which carries thousands of tons on it. The properties of soil, type of rocks and the crust of earth is studied in detail before choosing the site.
Impact of Fire
Bridges are used to improve the transportation, hence, every type of vehicle hauls through it and traffic intensity also remains high. Because of this there always remain chances of accidents, and trucks carrying inflammable substance like gasoline extends the probability of blasts that advances fire. Also, the bridges which are used for trains can get fire due to sparks generated by friction between train wheels and track. Hence, the material like wood is not used for building bridges nowadays; also soft steel which has melting point is avoided. But also because hard steel has high density, it increases total self-weight of bridge, hence, engineers finds the most compatible solution.
Bridges near Water Bodies:
Most of the times, bridges are made over water bodies like lakes or rivers to create a quick alternative for transportation. For such bridges, water force is another parameter to consider. Also, extra efforts are needed to make the available land bear the load of bridges, by filling them with layers of rock or with the technique of riprap. At such places, effects of floods are also considered by the designers. In floods, water carries scrap, soil and tree parts with it, which gets accumulated at the beams of bridges and can destroy the bridge. Most of the time, bridges don’t get collapsed during the flood, but after months of flood, because flood damages the bridges. Because of this after floods, bridges are examined by the inspectors and necessary steps are taken.
Immunity from Earthquakes:
To build a bridge in an earthquake prone area involves a few more complications. Because of seismic effect not only the bridge itself but its foundation also gets sway, this may cause destruction of whole bridge. Bridges are built to withstand the maximum credible earthquake. Suitable place is discovered to build the supports, or by using tremor absorbing materials to the foundation. Material used for constructing bridges is comparably less hard than traditional bridges. Bearings, shock absorbers, shear links are additionally installed for further safety. Furthermore the lengths of bridges are reduced so that the complications get minimized.
Bridges are so massive that they represent the power and capability of that territory. Most of the bridges act as tourist attractions. Hence, even governments motivate engineers to make it symbolic.
To construct a successful bridge out of all these complications, many experts like Design Engineers, Archaeologists, Contractors, Skyway Engineers, Bridge Engineers, Superintendents, Safety Managers, Carpenters, Pile-drives, Crane-operators, Laborer, Iron Workers, comes together. When right type of people meet they take bridges to next level, and constructs Movable bridges, Double-decked bridges, viaducts, three way bridges, etc. Collapsing of bridges doesn’t only affects the self-esteem of all the engineers involved, but also affects lives of the people trapped in the accident. These things make a bridge a social, cultural and political heritage. Hence, just like other infrastructures, building great bridges are great achievement for all the people involved.