PSI - Issue 62

Stefano Stacul et al. / Procedia Structural Integrity 62 (2024) 617–624 Stefano Stacul and Nunziante Squeglia / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 4. Kinematic response factor I u – fixed-head single pile

The solution in Equation 4 (fixed-head single pile) is particularly useful as it corresponds to the case of a rigid cap connecting a large number of piles (i.e. the rotational component of the foundation motion is close to zero). In the case of free-head single pile some solutions are available for the assessment of I u and I θ (see as an example: Nikolaou et al., 2001; Anoyatis et al., 2013; Stacul and Squeglia, 2023) in homogenous, inhomogeneous, and two-layered soil conditions. The available solutions for these two extreme cases (fixed- and free-head conditions) can be easily combined to derive the kinematic factors I u and I θ of a generic group of piles connected by a rigid cap (see as an example the indications provided in Di Laora et al., 2017). Once I u and I θ are obtained the FIM can be easily assessed. 3. Pile-supported structure The relevance of FIM on the seismic response of pile-supported bridge piers is now investigated considering the simple case of a typical viaduct (Figure 5) with spans of approximately 20 m, pier height ( h s ) of 8 m, pier diameter ( d pier ) of 1.5 m and characterized by a fundamental period of 0.6 s (under fixed base hypothesis). The bridge pier is supported by a 2x2 pile group, and three soil profiles have been considered. Soil profiles properties, pile diameters and lengths are those used in the previous section (see Table 1).

Fig. 5. Pile-supported bridge pier in three different soil profiles (Table 1)