engleski

The variation of internal forces of the bridge superstructure under influence of the vertical component of the seismic action

In the paper authors investigated the variation of the magnitude of internal forces of the prestressed box-girder bridge superstructure under influence of the vertical component of the seismic action. That influence is particularly important for the structures located near earthquake epicenter, where they have to sustain high vertical seismic loads due to intensive vertical vibrations. The calculation is based on the Eurocode standard, according to the clause that the effects of the vertical seismic component acting in the upward direction on prestressed concrete decks should be always taken into account. Static and dynamic analysis are performed using a computer software package Robot Millennium on spatial model of box-girder bridge with three spans (41+55+41m). Each of the three bridge spans consists of eight beam elements, while the columns are formed with two beam elements. Bridge superstructure is based on the abutments and columns over bearings, two on each support. According to standard HRN ENV 1998-2, response spectrum analysis is conducted. Elastic ground spectrum has been designed according to the above regulations and for the parameters of soil categories B and design ground acceleration of 0, 2g. Extreme values of the forces are determined by the square root of the sum of the squares rule. Dynamic analysis is conducted for the 10 shapes. The impact of seismic activity on the bridge is analysed by the method of Complete Quadratic Combination. Beside the seismic load, a traffic load is also applied to the model of the bridge described as Load Model 1, according to European standards. The result of the research are diagrams showing the relationships between the internal forces magnitude with and without the influence of the vertical component of the seismic action.

Bridge superstructure; internal forces; vertical seismic action

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