PSI - Issue 78

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

942

Fig. 5. Comparison among the base shear distributions

Table 1. Base shear ratios between the condition Mode 1 and SRSS Level  = 0,1  = 0,2

 = 0,3

 = 0,4

Top (9m)

0,93

0,95 0,99 0,95

0,97 0,98 0,93

0,95 0,92 0,98

Masonry-timber interface (6 m) 1,00

Base (0 m)

0,99

4. Concluding remarks The present paper reports some research results aimed at defining the seismic design rules for existing buildings with timber-based vertical additions. This represents a stimulating topic because timber vertical additions are gaining importance in urbanized contexts as a sustainable solution for resilient cities; nevertheless, no seismic design rules common shared among the researchers are available in the standards both at National and International level. In this perspective, it is intended as a contribution to the understanding and characterizing of the basic dynamic behavior of existing masonry buildings with CLT vertical extension, with a particular focus on the role of the mass ratio into defining the key design parameters affecting the evaluation of the seismic demand (i.e., vibration period and participating masses). To this purpose, with a reference to benchmark masonry structure having a single CLT vertical additions, analyzed by a finite element model, elastic modal analyses were conducted accounting for the effect of different mass ratios between the upper and lower structure on the global seismic response. The research outcomes pointed out the effect of the mass ratio on the dynamic parameters (periods and participating masses) of the structural system and the needs of adopting dynamic modal analysis as basic approach to analyze the seismic behavior of such a type of structures. Particular attention was paid to the evaluation of the seismic action profile along the building ’s height to be adopted in linear and nonlinear static analyses, as required by the standards. In this regard, it is shown that the shape of the seismic action profile strongly changes along the building’s height as a function of the mass ratio; moreover it has been proved that the effect of the different vibration modes can be not ever significant in the computation of the seismic actions, at list for the investigated cases which consider variable mass ratio and a constant stiffnesses. To better understand the role of the vertical additions on the seismic response, future studies will be necessary aimed at including the effect of the stiffness ratio on the global behavior.