PSI - Issue 78

Franco Braga et al. / Procedia Structural Integrity 78 (2026) 285–292

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the stress state on the floor slab is contained and significantly lower than the rupture value f ctd . If we extend the evaluation of R to a wider set of cases, varying the PGA, the number of floors and, for Fig.6 , the plan dimensions of the building, we obtain the results of Fig.5 and Fig.6 which show the value of R recorded on the first deck (in blue) and in the critical conditions (maximum value for the entire building, in yellow). The diagram of Fig.5 a, which refers to a frame with a structural mesh of 4 x 8 columns (plan dimensions 16.5 m x 38.5 m) and without a stiffening core, shows R-values far from the tensile failure limit of the concrete slab; in all cases investigated, the maximum stresses on the slab are localised on the upper floors. This trend is also confirmed with a stiffening core ( Fig.5 b), but showing a greater difference between R at the first deck, which never exceeds 60%, and maximum R, which has a value between 100% and 300%.

Fig.5 . R for buildings without a stiffening core (a) and with a stiffening core (b) when varying the number of storeys and PGA.

Even varying the plan dimensions of the building and considering, as shown in Fig.6 , instead of the 4 x 8 mesh, the 4 x 3, 8 x 4, 10 x 5, 20 x 5 meshes, and referring to 4 storeys ( Fig.6 a, b) or 6 storeys ( Fig.6 c, d), the maximum R is located in the storeys above the first one; in correspondence of the first deck the value of R is in all cases less than 75%. However, even when referring to different meshes, the situation without ( Fig.6 a and c) and with stiffening core ( Fig.6 b and d) is always considered.