INVESTIGATION ON DYNAMIC BEHAVIOR OF CABLE STAYED BRIDGES

Abstract

The concept of cable stayed bridges lies back in the seventeenth century. Due to their aesthetic appearance, efficient utilisation of material, and availability of new construction technologies these types of bridges have gained much popularity in last few decades. After successful construction of Stormsund Bridge, a lot of bridges of this type have been constructed and are under construction, which calls for extensive research work in this field. Literature review shows that rapid development taken place in this area in last forty years. Bridges of this type are entering a new era with main span lengths reaching 1000 m. Thus nowadays, very long span cable supported bridges are being built, and the ambition is to further increase the span length and use shallower and more slender girders for further bridges. To achieve this, accurate procedures need to be developed that can lead to a thorough understanding and a realistic prediction of the structural response. In present study, effort is made to characterise the seismic response of cable stayed bridges with one pylon and two equal side spans, with spans ranging from 120 in to 240 m. 3D models of cable stayed bridges in FEM software ANSYS 11(non commercial version) are first studied for their response under free vibration. Same models were analysed for their response to three load-time histories with different characteristics. Further models with curvature in deck varying from 10 deg. to 45 deg. are studied for free vibration response and forced vibration response. Study is then done for multidirectional forced vibration response of straight bridges. An attempt is made to understand and predict behaviour of cable stayed bridges under seismic loading so as to help the designers in understanding best suitable type of bridge under such loading.