PSI - Issue 78

Allegretti M. et al. / Procedia Structural Integrity 78 (2026) 852–858

856

Table 2. Modal parameters of the models.

Model

Parameters Dir. X Parameters Dir. Y T [ sec ] / M p [%] T [ sec ] / M p [%]

Model LV0 1.030 / 73.23 Model LV1 0.856 / 72.61 Model LV2 0.645 / 77.84

0.847 / 40.85 0.720 / 42.40 0.673 / 53.00

Fig. 3. Principal mode shapes of the models (a) LV1 X-direction (b) LV1 Y-direction (c) LV2 X-direction (d) LV2 Y-direction

The mode shapes are identical for the LV0 and LV1 models with the first mode occurring in the longitudinal direction, although with lower periods for the LV1 model which is sti ff er. Of particular interest, however, is the behavior of the LV2 model, for which the first mode is transverse to the structure rather than longitudinal. From the observation of the deformed shapes in Fig. 3, it can be seen that, in the longitudinal direction, in the first two models the deformation also involves the arches, which exhibit their own deformation; conversely, in the LV2 model, the deformed shape of the structure appears more similar to that of a rigid body, leaving the shape of the arches unaltered. Subsequently, a pushover analysis was performed, considering load profiles proportional to the previously identi fied vibration modes, in order to determine the characteristic capacity curves (base shear vs. displacement of a control node). The actual multi-degree-of-freedom (MDOF) system was then converted into an equivalent single-degree-of freedom (SDOF) bilinearized system, following the N2 procedure FAJFAR and GASˇPERSˇICˇ (1996), taking as the control point the one associated with the maximum displacement in the modal analyses.

Fig. 4. Capacity curves equivalent SDoF systems (a) X-direction (b) Y-direction