Importance of steel in bridge construction
Amongst bridge materials steel is considered as the most recognized elements in bridge construction as it contains greater strength qualities. It is frequently utilized in most leading bridges with lengthiest extents. Normal building steel contains compressive and tensile strengths of 370 N/mm2, about ten times the compressive strength of a medium concrete and a hundred times its tensile strength.
An exclusive feature of steel is that it deforms well prior to split due to it’s strong ductility as well as it starts to yield over a specific stress level. This yield strength is considered as the first term in standard quality terms.
In bridges, high strength steel is mostly preferred. If the strength is increased, proportional variation among the yield strength and the tensile strength is reduced. It signifies that high strength steels are not as ductile as those having normal strength. Besides, fatigue strength is not increased in proportion to the tensile strength.
So, it is essential to have clear idea on the behavior of these special steels prior to utilize them. In building, steel is fabricated in the shape of plates (6 to 80mm thick) using rolling when red hot. Cast steel is preferred for bearings and some other items.
Special steels prepared in various ways are utilized for members under tension only, similar to ropes or cables. These are useful to develop bold suspension or cable-stayed bridges.
The high strengths of steel are ideal for small cross-sections of beams or girders and consequently a low dead load of the structure. So, it is necessary to construct the light-weight "orthotropic plate" steel decks for roadways, which are now mostly recognized with an asphalt wearing course, 60 to 80 mm thick..
The pioneers of this orthotropic plate construction are known as "stiffened steel slabs". Plain steel plate, reinforced by cells or rlbs, develops the chord of both the transverse cross girders and the longitudinal main-girders.
At the same time it functions as a wind girder. This bridge deck is successfully used in mechanized welding and thus significantly impacts the design of steel bridges.
Therefore, plate girder construction now exists, in which large thin steel plates should be reinforced against buckling.
Earlier, vertical stiffeners were arranged mainly on the exterior faces; longitudinal stiffeners were then set up on the inside.
For more information, go through the following article aboutcivil.org