Bridge Construction Methods and the Principle Factors
Bridges are a typical feature of the built environment and one of the vital components of civil engineering and structural designing. The fundamental standards of bridge design are reliant upon the load-bearing structure; regardless of whether level, convex or concave. The height, ground conditions, and the clear span required will control the decision of bridge design. Construction of the foundations is the initial step toward building a bridge. This process includes definite geotechnical examinations of the bridge site. Most of the bridge construction company have to follow the different Bridge Construction Methods according to their capacity.
Building a bridge is a perplexing endeavor requiring information and expertise. A few factors, including designing limitations, costs, and natural effects, become possibly the most important factor when choosing which construction strategy to use and bridge type to build.
The type of bridge foundation must be chosen, like the good foundation, pile foundation, and the opened foundation and in this case, the bridge Construction Company in Bangladesh will help you. Every foundation is appropriate for explicit soil layers, and the ideal bridge qualities. The soil characteristics will decide the load-bearing capacity and other significant parameters. Dependent on the area and bridge type, you need to adopt various strategies for bridge construction. There are different methods of bridge construction, each of them is explained below.
Different Bridge Construction Methods
1. Precast bridge construction methods
The precast bridge construction method has been parted into three sections specifically I beams and super Tee, Segmental and full span. Precast construction implies that bridge members or fragments are pre-assembled at an area unique in relation to the site, moved to the site, and introduced there. Construction with precast sections enjoys a few benefits in examination with cast-in-place segmental bridges. The casting of the fragments can be performed under controlled, plant-like conditions at the pre-casting yard.
This industrialized cycle permits simple quality control of sections before position in the superstructure and sets aside cash through the reuse of the pre-casting formwork. Surface completing works, for example, finishing, sandblasting, painting, and covering can be performed on the ground level without platform when the fragments are as yet open from all sides before establishment in the superstructure.
2. Cast in-situ bridge construction method
In this method strength concrete just as high strength materials like wires, bars, and steel strands ought to be used. After concrete hardening, the strands which have been gone through the concrete, have been pulled by an exceptional jack and in the wake of getting pre-decided force, the strands would be locked. This strategy enjoys a few benefits in particular diminishing direct expense, decreasing the necessary material, work cost, rebar, and transportation costs, and speeding up formwork.
3. Balanced cantilever bridge construction method
Balanced cantilever construction signifies building a bridge construction from both sides of the pier table in a scales-like fashion. This erection method is also known under the name free cantilever construction. It is one of the most popular bridge construction methods used by the engineers. When two contrasting free cantilever structures are attached as a single structure and erected in the same step, it is known as ‘balanced cantilever’. The cost-effective range of span lengths for cast-in-situ cantilever construction begins at roughly 70m and extends to beyond 250m.
Substantial savings can be achieved by using this method rather than conformist bridge construction. The benefit of using this method exclusively in urban areas refers to its characteristic that it does not need any temporary shoring and it can interrupt traffic over water channels and in deep gorges which is very dangerous for construction workers. Balanced cantilevering can be carried out with cast-in-place or precast segments. For cast-in place balanced cantilevering a set of two form travelers is required, one for each arm of the cantilever. For multi-span bridges the form travelers can be dismantled after finishing cantilevering from one pier and can be set up for new use on the next cantilever.
4. Span by Span casting bridge construction method
Span-by-span erection is the most widely recognized, least difficult, and frequently most effective construction method for precast segmental bridge. It is normally addressed to long bridges with an incredible number of 25-45m spans with an enormous arrangement radius, and it is viable with basically upheld and continuous spans. The maximum gradient of the bridge oversees the plan of the erection hardware; however a 4-5% gradient is rarely a major problem. Although external post-tensioning works with segment production and upgrades strand insurance in the non-inconsistent instance of releasing joints, many range by-length spans have been post-tensioned with inner ligaments. With this type of construction, there is a breaking point on the range length because of the capacity of the gantry to range between the backings and furthermore to take the extra weight of the deck with controlled diversion. Notwithstanding, spans in the scope of 35 to 55 m are common of this construction method.
5. Incremental Launching bridge construction method
The Incremental launch is a method in civil engineering of building a total bridge deck from one projection of the bridge only, fabricating the superstructure of the bridge by segments to the opposite side. In current applications, the method is profoundly mechanized and uses pre-focused on concrete. Incremental launching construction of 50-60m spans with half-length portions is commonly founded on week after week section cycles and by-weekly span cycles with one shift each day.
The bridges are generally of the container brace plan and work with straight or steady Arch shapes, with a consistent sweep. 15-to-30-meter (49 to 98 ft.) box brace segments of the bridge deck are fabricated toward one side of the bridge in factory conditions. Each segment is fabricated in around a multi-week. The primary segment of the dispatch, the starting nose, isn’t made of cement, however is a solidified steel plate brace and is around 60% of the length of a scaffold range, and diminishes the cantilever second. The areas of the bridge deck slide over sliding direction, which are substantial squares covered with hardened steel and built up elastomeric cushions.
6. Cable-stayed bridge construction method
The Cable-stayed bridge method uses a structure where the heaviness of the deck is supported by various almost straight inclining cables in strain running straightforwardly to at least one vertical tower. The towers move the cable forces to the foundations through vertical pressure. The elastic forces in the cable also put the deck into horizontal compression.
Construction of cable-stayed bridges frequently follows the cantilever method, so their construction starts with the sinking of caissons and the erection of towers and moorings. After the tower is constructed, one cable and a segment of the deck are built toward every path. Each segment of the deck is pre-focused prior to proceeding. The process is rehashed until the deck segments compromise, where they are associated. The ends are attached at the abutments.
7. Arch bridge construction method
Arch bridge construction method uses abutments at each end molded as a bended arch. Arch bridges work by moving the heaviness of the bridges and its loads mostly into a flat pushed controlled by the projections at one or the other side. A viaduct (a long bridge) might be produced using a progression of arches, although other more affordable constructions are regularly used today. The presentation of these new materials permits arch bridges to be longer with lower ranges. Rather than pushing straight down, the load of an arch bridge is conveyed outward along the bend of the arch to the backings at each end. The weight is moved to the backings at one or the flip side.
8. Advanced shoring bridge construction method
Advanced shoring system is a strategy that was as of recently used as a high level construction method in bridge construction. This method requires a high starting expense due to the hefty gear and number of teams that are used. It has been created for multi-range spans over troublesome territory or water where platform would be costly or basically not possible. A starting support pushes ahead on the bridge wharfs, length by-range to permit the putting of the cast-in-situ concrete. The technique – both under-threw and overhead – is exceptionally versatile for a wide range of span.
The Principle Factors for the Selection Method of Bridge Construction
- Regularity of the span lengths
- Horizontal and vertical profiles of the bridge decks
- Soil strata
- Site accessibility
- The time allowed for construction
Depending on the project requirement you have to adopt the method that suits your requirements. There are different types of methods and each comes with specific advantages. Choose the contractor that has experience and follow the best Bridge Construction Methods.