WIT Press

Damping And Its Importance To Structure


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WIT Press


M. Rak, D. Mestrovic & A. Nizic


The bridge of Zeceva Draga is currently being built in Croatia. Its total length is 940.8 m. It is in a horizontal curve. Its spans are 2x40+16x50+1x40. The columns are very tall; the tallest of them is 53 m high. Because the columns are extremely high, and the structure itself has a longer period, the application of elastomeric bearings on the bridge is not significant. Therefore, the bridge was calculated with the action of hydraulic dampers at the ends of the span structure towards the abutments. Time history analysis was calculated for accelerograms of magnitudes 5.5, 6, 6.5 and 7 (Richter scale) with distances of 0 and 15 km from the epicentre, based on earthquakes occurring in Petrovac, in April 1979, with a magnitude of 6.8 and Ulcinj, in April 1979, with a magnitude of 5.3, in the region of the Adriatic coast. The damper was modelled using the Calvin’s model. Since it is not a classical damping, the damping of the structure was calculated separately, and then the influence of the damper was added. Damping of devices is modelled depending on velocity. The damping of devices itself significantly reduces the force. The rigidity of the damper is apparent and it was used to simulate the elastic behaviour of the device because of the hydraulic compressibility. In the laboratory of the Civil Engineering Faculty in Zagreb, the model with two spans was tested with and without dampers, in the longitudinal and transversal directions, and it was proved that dampers increase the damping of the system. The application of dampers is diverse, from silos, masts, towers, stands to bridges and factory chimneys. Keywords: damping, damper, earthquake, dynamic analysis, bridge. 1 Introduction The structures take on great quantity of energy generated by earthquakes. That energy can produce considerable deformations, even fracture of a structure. A structure must have capacity to dissipate that energy, either by permanent


damping, damper, earthquake, dynamic analysis, bridge.