It is shown that in many cases while calculating bridge spans it is necessary to take into account the soil-structure interaction. If the pier is higher than 5 m, energy dissipation for the main oscillation mode is determined substantially by energy losses, caused by wave propagation in the soil base, thereby the dynamic ratio drops significantly. Furthermore, if a bridge span is shorter than 55 m and the base modulus of deformation Eo < 30 MPa, the force in the piers can be determined by the second mode, for which the superstructure and piers oscillate in antiphase. For bridges with spans over 80 m long at Eo > 30 MPa, seismic forces for spans and piers are determined by the first oscillation mode. 

The comments consider the possibility of using the response-spectra method (RSM) taking damping into account in seismic calculations. The results of the paper under consideration are fair if the influence of damping on the shape modes has not been taken into consideration. At present there exists a variant of RSM, which takes into account the damping influence on shape modes. This variant of RSM has been described in the comments. In this case complex eigenvalues and eigenvectors of the damped system are calculated. The imaginary part of the eigenvalues determines the modal frequency, and the real part of the eigenvalues determines the modal damping. Seismic forces are calculated taking into account the amendments caused by modal damping.