GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 2.2 469 For each log-wall the backbone parameters have been obtained by fitting the F - δ curves. The stiffness of the equivalent linear system is assessed based on the equivalence between the energy stored in non-linear shearwall and the linear substitute system. The procedure gives back the base shear force. Validation of the Modal-DBD analyses by Push-over analysis. To check the Modal- DDBD it is performed a Push-Over analysis in a 3D model using SAP2000 (CSI, 2019) The model (Fig. 2), fixed at the base, consists in horizontal EEEP springs located at the middle of the panel able to work only in the longitudinal direction (no stiffness it is considered out of plane since the EEEP curve englobe the effect of the orthogonal panels). Walls’springs are linked together by elastic frames with high stiffness. A rigid diaphragm is adopted for simplicity to represent the storey in which the storey mass is lumped. The modal load distribution is investigated in the primary directions (X and Y) comparing the base-shear and the top displacement (centre of mass of the roof). Conclusions. The CP level is widely verified (the stiffness of the actual lateral force resisting system, parallel to the east and west walls, is about 26~27% higher than the minimum required stiffness and the one parallel to south and north is 64% higher). As well as for the LS level (the stiffness of the actual lateral force resisting system, parallel to the east and west walls, is about 40% higher than the minimum required stiffness and the one parallel to south and north is 65% higher). Moreover, has been highlight that the fixed drift limit equal to 0.75% for IO is too conservative and is not verified (the stiffness of the actual lateral force resisting system, parallel to the east and west walls, is about 27% smaller than the minimum required stiffness and the one parallel to south and north is 18% smaller than the required). This issue is due the Blockhaus shearwall geometrical features (in particular the small mounting gaps in the corner joints). The model has been validated by performing a Push-over analysis. From the comparison is evident that the shear base reaction are well defined by Modal-DBD procedure and the top displacements are overestimated at last of 14%. Fig. 2 - Push-Over 3D model realized by SAP2000. Table 2 - Comparison between base shear forces and top displacements obtained by Modal-DBD procedure and Push over analysis in X-direction. X-direction       Modal DDBD      Push over       Var. [%] BaseShear DispTop BaseShear DispTop BaseShear DispTop [kN] [mm] [kN] [mm] CP 216 195.272 217.4 168.0 0.65 13.98 LS 184 127.072 184.5 118.5 0.24 6.77 IO 65 38.676 66.4 39.0 2.17 -0.84