Figure 3. Comparison among the limitations of EC6 '03 and NTC'07 on h/s ratio.
where: hef is the effective height of the wall; sef is the effective thickness of the wall, that is usually taken equal to the actual thickness s (for cavity walls the EC6'03 suggests the following formula: sef = (tj +1|) 1/3 where ti and t2 are the actual thickness of the leaves; the Italian code NTC'07, instead, in every case assumes sef = s)1; p is a reduction factor depending on the edge restraint or stiffening of the wall.
In the examined codes (EC6'03 and NTC'07) the suggested values of the coefficient of restraint p are related to the aspect ratio h/b and to the degree of the edge restraints. Particularly, with reference to the walls of Figure 2, the EC6'03 makes the difference among the following three cases:
- wall 2L (Fig. 2b): the value of p (appointed as p2) is depending on the degree of restraint (p2 = 0.75 in presence of r. c. floors at the top and bottom of the wall; p2 = 1.0 for walls restrained at the top and bottom by timber floors);
1 In the following part of this paper, we will assume sef = s.
Figure 2. Edge restraints of the wall: (a) wall restrained at the bottom (wall 1L); (b) wall restrained at the top and bottom (wall 2L); (c) wall restrained at the top, at the bottom and on one vertical edge, with the other vertical edge free (wall 3L); (d) wall with 4 edges restrained (wall 4L).
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