SEISMIC PERFORMANCE OF A FIBER-REINFORCED PLASTIC CABLE-STAYED BRIDGE

This paper presents an investigation into the seismic response charact eristics of a proposed ligh-weight pedestrian cable-stayed bridge made entirely from Glass Fiber Reinforced Plastics(GFRP). The study employ s three dimensional finite element models to study and compare the dyn amic characteristics and the seismic response of the GFRP bridge to a conventional Steel-Concrete (SC) cable-stayed bridge alternative. The two bridges were subjected to three synthetic earthquakes that differ in the frequency content characteristics. The performance of the GFRP bridge was compared to that of the SC bridge by normalizing the live l oad and the seismic internal forces with respect to the dead load inte rnal forces. The normalized seismically induced internal forces were c ompared to the normalized live load internal forces for each design al ternative. The study shows that the design alternatives have different dynamic characteristics. The light GFRP alternative has more flexible deck motion in the lateral direction than the heavier SC alternative. While the SC alternative has more vertical deck modes than the GFRP a lternative, it has less lateral deck modes than the GFRP alternative i n the studied frequency range. The GFRP towers are more flexible in th e lateral direction than the SC towers. The GFRP bridge tower attracte d less normalized base shear force than the SC bridge towers. However, earthquakes, with peak acceleration of only 0.1 g, and with a variety of frequency content could induce high enough seismic internal forces at the tower bases of the GFRP cable-stayed bridge to govern the stru ctural design of such bridge. Careful seismic analysis, design, and de tailing of the tower connections are required to achieve satisfactory seismic performance of GFRP long span bridges.