PSI - Issue 78

Gennaro Vesce et al. / Procedia Structural Integrity 78 (2026) 936–943

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that of understanding the basic dynamic behavior of masonry buildings with vertical CLT extensions, focusing the attention on the role of the dynamic parameters influencing the calculation of seismic forces profile along the building ’s height. The latter are of paramount importance in engineering practice to perform linear and nonlinear static analysis. With reference to a selected masonry building, whose geometrical characteristics and material properties are showed in Fig. 1, linear dynamic modal analyses were conducted by considering as a variable: a ) the number of CLT vertical additions varying from one to three, and b ) the presence and absence of the mechanical connections placed at connecting level between upper and lower structure (and between two consecutive CLT vertical additions). Note that w/o connections means that the continuity between the lower and upper structure in the numerical model is ensured as a continuous. Upper and lower structure are connected at the interface by means of hold-downs and angle brackets typically adopted in platform CLT construction technology (Izzi et al. 2018). Here, it has been assumed the presence of a reinforced concrete curb having the main function of regularizing the surface where to locate the vertical CLT panels. The building was assumed to have in-plane rigid floors and characterized by three aligned equal walls, so that the single masonry wall represented in Fig. 1, associated to a seismic mass equal to one third of the entire floor mass is assumed to be representative of the whole building behavior in the selected direction. The structural system was modelled through two-dimensional finite element model (2D shell) provided with both flexural and shear stiffness, while the masses were concentrated at floor level. The masonry material was modelled as isotropic, while the CLT as an equivalent orthotropic material having normal and shear elastic moduli having values reduced as a function of the effective number of layers in vertical and horizontal direction (Sandoli et al. 2016). Hold downs, angle brackets and timber-to-concrete contact were schematized through linear elastic links available in the SAP 2000 software library, enabling to define zero length elements. They are characterized by linear-elastic behavior whose constitutive force-displacement behavior was calibrated from the experimental results collected in Gravric et al. 2011. Analyses results coming from the conducted research highlighted that both mechanical connections and the number of vertical extensions affect the dynamic behavior of masonry building with CLT vertical extensions. The local deformability of the mechanical connections, combined with the presence of the additional masses, produce an elongation of the vibration periods and a reduction of the participating masses (M * ) associated with the first vibration mode if compared with the structure without vertical extensions. It emerged that the participating masses relative to the first vibration mode reduces significantly as the number of vertical additions increases and that they also influence the seismic action profile; this remarks the role of both mass and stiffness ratios between upper and lower structure becoming key seismic design parameters.

Fig. 1. Characteristics of the selected building and response spectrum