Ciljano ubrzanje u višemodalnoj metodi naguravanja u potresnoj analizi A/B konstrukcija

This thesis presents a new nonlinear static multimodal pushover analysis with the inclusion of a large amount of equivalent viscous damping. The term of target acceleration and the formulation of the procedure for determining the target acceleration are presented. The targeted acceleration is defined as the minimum acceleration of the base that leads to the ultimate limit state of structure, which represents the lowest seismic resistance. The targeted acceleration is achieved with iterative multimodal pushover method according to the envelope principle. Two combinations of modes are analysed, linear (L) and square root of sum of square combination (SRSS). Examples of presented R/C frames and mixed frame and wall system show that the L combination is more unfavourable than the SRSS combination of modes because of the lower level of the target acceleration. Interference of modes on linear and non-linear level also shows that the linear (L) combination is more frequently unfavourable than the root (SRSS) combination of modes. As a part of this thesis a new formulation for determining the equivalent viscous damping of construction is developed. A validation of the targeted acceleration method in multimodal pushover procedure with dynamic response of the R/C frames is conducted. Real earthquake accelerograms are used for seismic excitation. Taking into account the calculated equivalent viscous damping and usability of capacity curve up to 3/3 of maximum displacement, by comparing the targeted acceleration of multimodal pushover method and failure peak ground acceleration obtained by dynamic response of construction proves to be an excellent agreement between the target acceleration and the failure peak ground acceleration. This proves that the equivalent viscous damping calculated according to the new formulation exposed in this thesis is real and that it is significantly higher than what is suggested in the literature. A practical procedure for determining the targeted acceleration in multimodal pushover method was shown, which can also become a simple tool for practical nonlinear static analysis of R/C structures exposed to earthquake action.