PSI - Issue 44

Francesco Morelli et al. / Procedia Structural Integrity 44 (2023) 574–581 Francesco Morelli, Agnese Natali, Gabriele Poggi / Structural Integrity Procedia 00 (2022) 000–000

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maximum base shear do not occur simultaneously, as better shown in Fig. 9. It shows also that the maximum base shear is nor reached when the deformed shape is characterized by the in-phase movement of all the masses, but when there is an out-of-phase movement.

Fig. 9. Deformed shape associated to the instant of maximum base shear and maximum top displacement.

4. Simplified multimodal pushover analysis The analysis of the dynamic behavior of the HCWS system studied highlighted that it is not possible to neglect the dynamic properties of the system and it is impossible to describe its behavior using only the first mode of vibration. To better understand the difference between the static pushover and the different IDA curves, a first comparison was carried out adopting the same FE model but using “classical” pushover analyses: • Uniform pattern: based on lateral forces that are proportional to mass regardless of elevation (uniform response acceleration). • Modal Pattern: based on lateral forces proportional to first mode shape, evaluated considering a linear elastic behavior (for the wall it was considered cracked stiffness). T b e 1. Modal properties of the ase study. Mode T [s] Participant Mass [%] Sum M% 1 1.03 0.69 0.69 2 0.21 0.19 0.88 3 0.08 0.06 0.94 4 0.04 0.03 0.98 Fig. 10 shows that the two “classical” pushover curves are not able to represent the behavior of the structural system evidenced by the IDA analyses mainly because the latter is also influenced by the higher vibration modes.