PSI - Issue 64

Alba Hyseni et al. / Procedia Structural Integrity 64 (2024) 246–253 Alba Hyseni / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 5. o utcome of the predicted masonry creep’s law.

4. Seismic analysis Based on the knowledge acquired in the state-of-play phase, the first seismic analysis was performed by FEM reproducing the entire structure as illustrated in Fig. 6a using Midas FEA (2013) software. All the different structural elements were meshed, including arches, vault, curved staircases, steel reinforcements (Fig. 6b), and the beforementioned RC-framed roof. The base of the columns was assumed ideally fixed. The chiasm of beams (see Fig. 2) was modelled with a group of beam-elements (i.e. mono-dimensional). The Thorenfeldt (1987) and Cornelissen et al. (1986) models were adopted for the constitutive law in compression and tension, respectively. The dead load was applied on all the nodes proportionally to the mass density, while the lateral pushing load (earthquake simulating) was assumed in a linear distribution with null value at the ground level. The capacity of the structures was higher than the demand for the considered seismic-prone zone. Thus, the structure was considered not seismic vulnerable at the 0 age. a b

Fig. 6. FEM model. (a) mesh; (b) rigid links to simulate steel ties.

According to Fig. 1, the CASA-method can be now adopted based on the creep’s law found in the previous section. Accordingly, the material mechanical parameters were reduced to simulate the ages of the tank-tower in the B, C, and D critical points within the creep curve (see again Fig. 5 and Table 2). In fact, these data-inputs (elastic modulus and stiffness) were progressively reduced in the further three simulations. Multiple pushover analysis was run. A graphical representation having spectral acceleration S e (T) as ordinate and spectral displacement as abscissa was performed in Fig. 7 referring to the Acceleration Displacement Response Spectrum (ADRS) for demand (imposing 5% damping and q=2.5 for structural behaviour factor) based on the EC8 method. The main findings were summarized in four capacity bilinearized curves also described in Table 2.