Issue 51

G. Ramaglia et alii, Frattura ed Integrità Strutturale, 51 (2020) 288-312; DOI: 10.3221/IGF-ESIS.51.23 300 confining stress values. Therefore, on the entire experimental sample the model provides a weak estimation of the axial capacity of masonry columns wrapped with composites. Furthermore, it results strongly influenced by the tensile strength of masonry providing confinement curves strongly different while changing the tensile strength of masonry. Fig. 7 a) shows the comparison between the Hencky-Von Mises model and the experimental results; while Fig. 7 b) shows the comparison between the theoretical confinement curves and the experimental points. (a) (b) Figure 7 : Comparison between experimental results and Hencky-Von Mises models: a) experimental and theoretical results comparison, b) confinement curve comparison independent on α . This model does not depend on the normalized tensile strength of confined material, α. The theoretical and experimental comparison shows a clear underestimation of the experimental values. This effect is clear for the entire confining stress field. The Fig. 8 a) shows the comparison between the Mohr-Coulomb model with the experimental results; while Fig. 8 b) shows the comparison between the theoretical confinement curves with the experimental points. This theoretical model is strongly influenced by the normalized tensile strength of masonry, α. Furthermore, an overestimation of the experimental results is clear for the entire experimental example sample. Also for low values of the effective confining stresses the experimental results are not so well fitted by the theoretical results (Fig. 8 a). In order to confirm previous qualitative dissertation, the statistical parameters: MAPE, MSE and R 2 have been calculated for the mechanical models. They are shown in Tabs. 2 and 3 for the comparison between the experimental and theoretical results. The effective confining stress, , l eff f has been calculated according to the previous Eqns. (13) and (18). The statistical parameters calculated according to Eqns. (13) and (18) are shown in Tab. 26 and 27 respectively.