## L

0 0.5 1 1.5 2 2.5 3 Figure 10. Collapse multipliers for EC8'03.

In terms of collapse multiplier a (Eqs. (11)^(12)), the condition (16) recommended in EC8'03 allows to obtain the curves plotted in the diagram h/b-a of Figure 10. Particularly in figure are reported: the curves (e) and (f) for the wall 2L; the curves (g) and (h) for the wall 3L; the curves (i) and (l) for the wall 4L. Each couple of curves is associated to the condition p2 = 0.75 or p2 = 1 that the EC6'03 considers in the definition of hef.

The limitations (17) and (18) of Italian code NTC'07 (seismic part) are plotted in the h/s-a diagrams of Figure 11 for wall 2L (curves (m) and (n)) and for wall 4L (curves (p) and (q)). The diagram shows that in high seismicity zones (curves (m) and (p)), the Italian code recommends a minimum value of collapse multiplier a higher than the case of low seis-micity (curves (n) and (q)). Moreover, the curves (p) and (q) associated to wall 4L show a constant trend in the range h/b = 0.5^1, i.e. in the most common range of aspect ratio h/b for the masonry walls. The presence of the horizontal plateau in the curves (p) and (q) depends on the fact that the Italian code uses the same expressions of the collapse mechanisms as the ones examined in ยง3.1 to define the reduction factor p.

In Figure 12 the comparison among the limitations of Rondelet, EC8'03 and NTC'07 (in seismic zones) on collapse multiplier a, is provided. In the cases of

Figure 12. Comparison among the limitations of Rondelet, EC8'03 and NTC'07 (in seismic zones) on collapse multiplier a.

Figure 12. Comparison among the limitations of Rondelet, EC8'03 and NTC'07 (in seismic zones) on collapse multiplier a.

walls 2L and 4L it is possible to note a certain coincidence among the plotted curves; particularly, it can be observed that the Rondelet's curve (d) is overlaid to the curve (q) (associated to NTC'07) and to the curve (g) of EC8'03 (wall 3L, p2 = 0.75) when h/b > 1 and h/b < 0.8, respectively.

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