Cable Stayed Bridges
CHAPTER 1 INTRODUCTION
1.1 Introduction A bridge consists of super structure of steel or reinforced concrete member that is supported on one or more points by cables extending from one or more tower is known as cable stayed bridge. The cable-stayed bridge is one of the most modern bridges. It consists of a continuous strong beam (girder) with one or more pillars or towers (pylons) in the middle Cables stretch diagonally between these pylons and the beam, these cables forms intermediate supports for deck and the cables are anchored in the tower rather than at the end. Most of the cable stayed bridges have been build across the navigable rivers where dimensions of bridge are decided by the navigation requirements. The cable stayed bridge is ideal for spanning the natural barriers of wide rivers, deep valley and for the vehicular and pedestrian bridge crossing the wide highways because there are no pier that will form obstructions. 1.2 Basic concept The basic concept of cable stayed bridges is to provide intermediate support using inclined cables. The pre-tension force in cable is design such that the bending moment or deflection at that point is as per design requirements. Closely spaced stay cables reduces the required depth and bending stiffness of girder. This leads to simple cross section and superior dynamic behavior. The multi-cable-stayed system allows main span up to about 200m for concrete and up to 1000m for steel with considerable saving on steel over suspension bridges (Berg, 2003).
01
Figure 1.1: Force in cable and pylon. Courtesy: www.intel.com/.../bridge/cablestayed The tower is responsible for absorbing and dealing with compression forces Tension occurs along the cable lines, this works because a moving load is not applied evenly across the bridge, and as it moves one set or the other of the diagonals will find itself in tension (Figure 1.1). This system is advantageous because it uses single support, A Well-balanced Cables can be fabricated
1.1 Introduction A bridge consists of super structure of steel or reinforced concrete member that is supported on one or more points by cables extending from one or more tower is known as cable stayed bridge. The cable-stayed bridge is one of the most modern bridges. It consists of a continuous strong beam (girder) with one or more pillars or towers (pylons) in the middle Cables stretch diagonally between these pylons and the beam, these cables forms intermediate supports for deck and the cables are anchored in the tower rather than at the end. Most of the cable stayed bridges have been build across the navigable rivers where dimensions of bridge are decided by the navigation requirements. The cable stayed bridge is ideal for spanning the natural barriers of wide rivers, deep valley and for the vehicular and pedestrian bridge crossing the wide highways because there are no pier that will form obstructions. 1.2 Basic concept The basic concept of cable stayed bridges is to provide intermediate support using inclined cables. The pre-tension force in cable is design such that the bending moment or deflection at that point is as per design requirements. Closely spaced stay cables reduces the required depth and bending stiffness of girder. This leads to simple cross section and superior dynamic behavior. The multi-cable-stayed system allows main span up to about 200m for concrete and up to 1000m for steel with considerable saving on steel over suspension bridges (Berg, 2003).
01
Figure 1.1: Force in cable and pylon. Courtesy: www.intel.com/.../bridge/cablestayed The tower is responsible for absorbing and dealing with compression forces Tension occurs along the cable lines, this works because a moving load is not applied evenly across the bridge, and as it moves one set or the other of the diagonals will find itself in tension (Figure 1.1). This system is advantageous because it uses single support, A Well-balanced Cables can be fabricated