A plate girder is a built up I-beam section, used to carry heavy loads which cannot be carried economically by rolled I-sections. It is made by riveting or welding the steel plates in I-beam shape. Components of a typical Plate girder and their functions are discussed in this article.
Components of Plate Girder
The components of typical plate girder are as follows :
The deep central vertical plate is called as a web in plate girder. It separates the two flange plates by a required distance. is responsible to resist shear developed in the plate girder.
Flanges or flange plates are horizontal elements of plate girder which are provided at the top and bottom and they are separated by the . The main purpose of flange plates is to resist the bending moment acting on the girder.
The top flange resists the bending moment by developing compression and the bottom flange resists the tensile force. They should be provided with a required width and thickness to offer good resistance against bending moment.
Stiffeners are classified into two types :
- Vertical Stiffeners
- Horizontal Stiffeners
Vertical stiffeners are provided at right angles to the flanges and they are also called as transverse stiffeners. These are again classified into two types namely end stiffeners and intermediate stiffeners based on their position in the plate girder.
End stiffeners are provided at both the ends of the girder. They receive the load from the beam and transfer it to the support. In plate girder, some part of the end portion of the web is subjected to compressive loads. Due to these loads, the web of the section may get crushed. Here, the end stiffeners play an important role by keeping the web safe from crushing. End stiffeners are also called as bearing stiffeners.
Intermediate stiffeners are required when there are concentrated loads acting on the plate girder. When the thickness of the web is very less (less than 1/85th of the depth of the web), then the web may buckle due to shear. In that scenario, intermediate stiffeners are provided in order to improve the buckling strength of the web.
Horizontal stiffeners are provided in parallel to the flange plates. They are also called as longitudinal stiffeners. These stiffeners will improve the buckling strength of the portion. Horizontal stiffeners are either continuous or discontinuous.
Continuous horizontal stiffeners connect all the traverse stiffeners and also take load coming from the flange and web portions. Discontinuous horizontal stiffeners are provided between the traverse stiffeners without touching them. They do not take any load coming from the flange or web portion, they just provide buckling resistance to the web.