Gordana Hrelja

Cable Vibrations at Dubrovnik Bridge

The only cable-stayed bridge in Croatia, the Dubrovnik bridge, was opened for traffic in 2002. The main cable-stayed bridge with composite superstructure is jointed in span to the prestressed concrete approach bridge by a hinge-type connection. The bridge has experienced vibrations of cable stays under certain wind conditions, as with many other cable-stayed bridges around the world. After a short review of results of wind tunnel tests and various numerical analyses, field observations of cable-stay vibrations are highlighted. Only after extremely violent movements of cable stays and the superstructure under a heavy, damp snowstorm occurred, resulting in substantial damage, was it decided to apply vibration mitigation measures. Adjustable cable dampers, based on the latest MagnetoRheological (MR) technology, were installed on the bridge to raise low structural damping of the most affected cable stays.

Analysis and Design of Peljesac Bridge in Croatia

The construction of a new 2.4km long bridge, crossing the sea strait between the Croatian Mainland and the Peljeaac Peninsula to provide the fixed road link between the whole of Croatia, has just begun. The bridge location is in a highly seismic zone with the design ground acceleration of 0.41g and on extremely bad soil. Extensive off-shore site investigations were carried out, including continuous shear wave survey and geotechnical explorations from a specially equipped drill ship, to obtain soil parameters for the design of bridge foundations. A site-specific seismic study was undertaken based on the seismic source zone characterization and attenuation relationships for the south of Croatia. The four lane road bridge consists of two approach bridges and the main cable stayed bridge with continuous steel trapezoidal box superstructure.