Construction Cost Estimating


Classification of Bridge Structures

Generally bridges are designed with various structural systems. Given below diverse categories of bridge structures :

1. Beam bridges
2. Box girder bridges
3. Arch bridges
4. Truss bridges
5. Cable suspension bridges
6. Cable-stayed bridges

Beam bridges: Beam bridges are considered as the easiest types of bridge structures. The bending moment and shear forces mainly function on these bridges. Beam bridges are perfect for short span bridges. These types of bridges are economical and can be built without any difficulty. The beam is formed with steel or concrete or wood.

Box girder bridges: Box girder bridge is identical to the beam bridge but the cross-section of box girder is designed like a box with hollow in middle. Besides, the size of box girder is generally bigger than the beam. The bridge contains good strength and it is applied to support an elongated bridge span.

In an Arch bridge, its main part that provides support to the bridge deck, is generally designed as a curve arch. The abutments are used to support the arch element at its ends. The purpose of developing this type of bridge is to remove or resist bending moment and shear forces, the primary load effects on beam and box girder bridges. By copying the shape of moment distribution all through the bridge, the primary force in arch-shaped element is compression force along the curve of the arch to the supports at each end. As all the loads of the bridge are transferred to abutments, durable abutments are required to avoid broadening of the bridge. The Proper design can make a bridge stronger.

Arch bridges: Truss bridges stand for the bridges supported with triangulated assemblies of slender members (generally build with steel). The members are attached with pin connection and thus the members act as two-force members. So, theoretically, there are compression or tension forces in members and there will be no bending moment and shear force.

Truss bridges: Generally this type of structure contains enough strength to weight performance as well as various repeated parts to minimize manufacturing cost and can be built in virtually any shapes.

Cable suspension bridges: Cable suspension bridges belong to bridges which are constructed by hanging the bridge deck from huge main cables, extending from one end of the bridge to the other end. The cables are generally supported with top of towers and anchorages are utilized to fasten each end. The tension forces act as primary forces on this type of bridge except the tower. Cable suspension bridge provides support to longer bridge span with regard to various other types of bridges. It is light and robust, but vulnerable to wind load if not carefully designed.

Cable-stayed bridges: Cable-stayed bridges belong to the bridges where the bridge deck is supported by cables which are directly fastened to towers (pylons). In cable-stayed bridges the pylons carry all the loads, so stronger pylons are needed. This type of bridge needs fewer cables with regard to suspension bridge. The bridge can be developed easily and quickly.

Types of Bridge Structures