Analysis And Assessment Of A Seismically Isolated Bridge
Free (open access)
A. J. Kappos & E. Dimitrakopoulos
This paper focusses on the seismic response of a bridge currently being constructed, using the incremental launching method, as part of the Egnatia motorway in northern Greece. The bridge is seismically isolated via elastomeric and PTFE bearings, and has fluid dampers installed at its end abutments. The scope of the paper is firstly the seismic analysis (using methods adopted also in practical design), and secondly the assessment of the bridge’s earthquake performance (using advanced inelastic time-history analysis). Keywords: seismic isolation, bridges, damping, viscous dampers. 1 Introduction The structure, which is analysed herein (fig. 1), is curved in plan with a radius R=1175 m and the deck section is laterally inclined (in the transverse direction) by 4.5%. In elevation it has a slope of 4.9% while its piers are of unequal height that ranges from 12 to 28 m. The piers’ section is a rectangular hollow one, the same for all pies (3.0m ×5.8m). The deck is continuous, made of prestressed concrete and the total span reaches 482 m (36.7+9 ×45.5+35.5). The deck is a single-cell box girder (fig. 2) with 8 different sections along its length. All piers are connected to the deck via elastomeric or PTFE bearings, which are considered as low damping bearings. Two fluid dampers in each direction (longitudinal and transverse) are used at the end abutments, where the only joints of the bridge deck are located. The dampers have practically hysteretic behaviour, since they realize a velocity exponent a (F=C ⋅v a ) as low as 0.05. The maximum strength they provide is 750 kN and 450 kN per damper, in the longitudinal and transverse direction, respectively. The design of the actual bridge was carried out by the firm T. Tsiknias & Associates (Athens).
seismic isolation, bridges, damping, viscous dampers.