Bridge Launching: Three Main Bridge Components
The process of bridge construction is a long and complex one. Since bridges are often built in crowded urban or topographically sensitive areas, construction companies follow a defined process for safety purposes.
As a concept bridge launching is about the designing and construction of different kinds of bridges using techniques like incremental bridge launching, heavy lifting, precast span-by-span technique and many more. Since bridges are considered to be vital infrastructure development, its construction process is dependent on a lot of factors. Factors like region, climate, accessibility, etc. Based on these factors, the construction technique is decided.
Many times incremental launch is the best-suited method since it requires a small geographic space. The reason is that the method is executed from one end of the bridge only. The principle of the incrementally launched bridge consists of building/placing the bridge superstructure behind the bridge abutment. The entire superstructure is then jacked forward by employing hydraulic jacks.
Even though different kinds of bridges demand different construction techniques, all bridge-building techniques primarily focus on the following three main areas of a bridge.
The foundation of any type of bridge is extremely crucial from all perspectives. It sets a base for the whole structure which further defines its formation. A foundation holds the shallow or deep base of the bridge. Depending on the depth, the foundation is divided into two, i.e, shallow foundation and deep foundation.
A shallow foundation is a type that spreads the structural load to soils that are nearer to the ground surface. They transfer loads to the ground through bearing pressure. The deep foundation on the other hand, as the name suggests goes deeper into the soil and spread structural load accordingly. While deep foundation transfer loads to the ground through bearding pressure along with transferring loads by friction with the soils along the length of the foundation.
The substructure is that area of the structure fabricated with the help of piers, abutments, caps, spandrels, bearings and other such components. This part of construction holds the upper construction in place and supports the superstructure by transferring the structural load to the foundations.
The design of each substructure differs as there are various factors involved like different soil conditions, site location as well as the weight of the structure which differs from project to project. The substructure of the bridge consists of the portion of the bridge that supports the entire structure on the given surrounding soil which gives the structure a more fixed shape to further lead to the fabrication of the superstructure.
The main and final area that bridge launching is based on is the superstructure. A superstructure is that part of the structure of the bridge which directly takes the load and transmits to the supports on either side. Building the superstructure firmly is highly crucial for supporting the bridge completely.
Superstructure covers all the element mounted on top of the supporting substructure system. These elements include slab, decking, girders along with everything every element placed above the main deck such as bridge girder, posts, cable-stayed system, steel truss system, cable-suspended systems etc
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