Issue 45

F. Brandão et alii, Frattura ed Integrità Strutturale, 45 (2018) 14-32; DOI: 10.3221/IGF-ESIS.45.02 26 A peak of tensile stress (Fig. 16) equal to 0.72 MPa at t=5.78 s was observed in correspondence of the connection be- tween the wall of the north lateral façade with the wall of the west main façade. The peak of tensile stress is due to the motion of the upper part of the wall of the west main façade out of the XZ plane. This value is higher than the assumed tensile strength, and it highlights a vulnerability of the pediment of the church (its overturning). Concerning the minimum principal stress, a peak of compression (Fig. 17) was also observed. In this case, this peak was evidenced at t=5.92 s and had a value of 0.71 MPa. A similar value was also found in the connection between the wall of the north lateral façade with the wall of the west main façade. This value is lower than the assumed compression strength (3.20 MPa), but is interesting since it confirms a vulnerability of the church: the overturning of the main façade during the Earthquake 1. Both the maximum principal stress peak (0.72 MPa at t=5.78 s) and the minimum principal stress peak (0.71 MPa at t = 5.92 s) were obtained after the peak ground acceleration of the Earthquake 1 accelerogram (the N00W component was 0.048 g at t=3.64 s, the N90W component was 0.019 g at t=4.45 s and the Vertical component was 0.018 g at t=4.31 s). Earthquake 2- El Centro The displacements obtained using the Earthquake 2 are shown in Fig. 18; the maximum displacements in the X direction, Figs. 18.(a) and 18.(b), are about 4.30 mm and are located at the top of the central region of the wall of the south lateral façade (and also in correspondence of the wall of the central arches that separates the two naves). The biggest displace- ment, however, occurs in the wall of the north lateral façade along the negative X direction and has a value of about 15. 90 mm. The displacements in the Y direction are shown in Fig. 18.(c) and 18.(d). It can be observed that the biggest value along the positive Y direction (the longitudinal one) is equal to 1.10 mm and is recorded on the wall of the north lateral façade and on the wall of the west main façade. The biggest displacement occurs in the negative Y direction, is located at the top of the lateral tower and corresponding to about 12.10 mm. In the region of the central arcs, displacements of ap- proximately 2.2 mm in negative Y direction are also evidenced. Figure 18 : Directional displacements after Earthquake 2: (a) and (b) direction X; (c) and (d) direction Y; (e) and (f) direction Z. Unit in mm. (a) (b) (c) (d) (e) (f)