**5. Conclusions**

The conclusion is that for accurate nonlinear seismic analysis we cannot use spectral methods but we have to use the methods of direct integration of the motion equation. We can use both methods (explicit and implicit) with a slight advantage of the explicit method with respect to time consumption. Another important conclusion is that the mathematical model of the concrete has a significant influence on the nonlinear transient response of structure (earthquake analysis) and reality is somewhere between analyzed elasto-plastic and elasto-damage behavior and thus we recommend using combination of plasticity and damage models simultaneously.

The analysis of different sources of damping showed that it is needed to use not only external damping but also (and mainly) internal damping using material inelasticity models (viscosity, plasticity/damage, friction) instead of simple Rayleigh damping which is insufficient for the huge nonlinear time-dependent response of structure on earthquake loading.
