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Steel Bridges Types and Benefits

Steel Bridges Types and Benefits

Steel Bridges Types and Benefits have been adopted in the past for major bridges on highways and more commonly on the railways, The Howrah bridge in Kolkata is an excellent illustration of steel building. Because of the shortage of steel, not many steel bridges have been built in India in recent years. General concepts about steel bridges are discussed.

Compared to concrete construction, steel superstructure will be of lighter weight, and will facilitate faster construction. Furthermore, by prefabricating some of the components at a nearby plant, the steel superstructure construction activities at the bridge site can be reduced. Within the span of 120 to 140 meters,for which prestressed concrete cantilever bridges are being adopted, steel construction can lend to time savings, as in the rail-cum-road bridges across the Brahmaputra river at Jogigoppa in Assam.Concrete bridges don’t require as much maintenance as steel ones do. For instance, constant painting is required on the Forth Railway Bridge. One coat requires three years to complete, then the procedure is repeated.

Steel bridges could be a preferred option in Build Operate Transfer (BOT) projects where speed in construction is crucial. For urban flyover elevated road projects, steel structures may also be advantageous because of their quicker construction times and potential for prefabrication, which reduce traffic disruption.

The following categories of steel bridges:

  1. Beam bridges
  2. Plate girder bridges
  3. Box girder bridges
  4. Truss bridges
  5. Arch bridges
  6. Cantilever bridges
  7. Cable-stayed bridges
  8. Suspension bridges

Beam bridges

Beam bridges are used for culverts, using rolled steel joists as the main supporting members.

In order to provide a path over the barrier, a bridge may be erected to conceal a road, valley, water body, or other natural barriers. Depending on the soil conditions where the bridge is to be built, a variety of bridge types are used. The earliest and most basic type of bridge among them are beam bridges, which are made up of horizontal beams and vertical piers and resemble simple planks or blocks of stone. They are made up of horizontal beams and vertical piers.

The strength of a beam bridge is multiplied by the route’s strength and increases with the number of piers added. Beam bridges often have a narrow span, or the space between neighboring piers, despite their length.

Girder bridges are adopted for simply supported spans less than 50 m and for continuous spans up to 260 m. Truss bridges can span between 40 and 375 meters. Arch bridges are competitive for the 200 to 500 m medium span range. Main spans of 320 to 549 meters have been successfully built on cantilever bridges. Cable-stayed bridges are economical when the span is about 200 to 800 m. Suspension bridges offer the most cost-effective option for spans longer than 800 meters.

Plate girder bridges with an example

Since the days of early steel bridge construction, there has been a marked preference for the plate girder bridge system, in view of the elegant aesthetics obtainable with this type and also the conference in e. Deterrence.

Plate girder bridges can be of two types:

  1. Deck type
  2. Dhalf-through type.

Deck type is normally preferred.

When constructing an extra embankment to increase the train level would be expensive, the half-through form would be used. The components of a plate girder highway bridge are the deck slab, which is often made of reinforced concrete, and longitudinal stringers that rest on transverse floor beams, which are supported by the plate girdere.

In the case of a railway bridge, the plate girders carry the wooden sleepers over which the steel raile are fastened. The girder bridges will be braced laterally at the level of the top lange and the bottom flange, besides cross bracings to resist the lateral load due to wind. The cross bracings consist of angles and are provided at the ends and at intervals of about 4 to 5 m.

Steel Bridges Types and Benefits

There is usually a choice available between

  • With the deck supported by the cross-girder system and two longitudinal girders considerably spaced apart,
  • Providing multiple longitudinal girders with small spacing.

In the first scenario, a system of cross-girders may be made up of cross-girders alone that are closely spaced or cross-girders that support a system of longitudinal stringers. The two-girder system necessitates deeper girders and may lead to the economy in certain circumstances. For the deck type, the distance between the two girders is kept slightly larger than the gauge of the track to reduce the severity of the impact loads on those girders. The lower flange of a half-through bridge is where the railway load is supported.

Steel Bridges Types and Benefits

Also Read:- Suspension bridges

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