Important feature of calculating bridges under seismic action

¹ JSC Research Center of Construction, 2-nd Institutskaya st., 6, Moscow, 109428, Russia
² Emperor Alexander I St. Petersburg State Transport University, Moskovsky pr., 9, Saint Petersburg, 190031, Russia
³ Transmost JSC, Podyezdnoy per., 1, Saint-Petersburg, 190013, Russia

^* Corresponding author: lyubovsmirnova80@gmail.com

Abstract

The purpose of the research is to show the main features of calculating bridge taking into account the inhomogeneous acceleration field along the structure length. The bridge is considered to be a linear structure with point bearings on the soil base. For long bridges it is typical, that their bearings are located in different seismogeological conditions. This result in inhomogeneity of the acceleration field under the piers and non-synchronous pier excitations. The motion equations of the system under consideration are constructed and their decomposition into vibration modes is performed without the account of external and internal damping in the system and with the account of it. Based on the proposed decomposition, formulas for determining seismic loads taking into account various seismicity under piers are obtained. The result obtained show that the peculiarities considered can be easily taken into account in existing software packages. As an example, the authors analyzed the results of calculating a four-span beam railway bridge. In calculating it was taken into account that the first and second piers are located on sandstone, and the rest of them are on water-saturated loose sand. The analysis showed that the account of the non-synchronous support point excitation of the extended system reduces inertial seismic loads on its elements significantly.