Assessing the seismic vulnerability of masonry buildings - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 339

Table 13.2 Performance drift value for damage limit states

In-plane
experimental

Eurocode 8
Part 3

Out-of-plane
experimental

Eurocode 8
Part 3 Limit state

Damage
limitation (DL)

0.18-0.23 0.33

Signifi cant
damage (SD)

0.65-0.90 0.4-0.6 0.88 0.8-1.2 ( H 0 / D )*

Near collapse
(NC)

1.23-1.92 0.53-0.8 2.3 1.06-1.60 ( H 0 / D )

* According to EC8 defi ntion H 0 is the distance between the section where the
fl exural capacity is attained and the contrafl exure point and D is the in-plane
horizontal dimension of the wall (depth); so that their ratio represents the
slenderness of the wall.

diaphragm; however, the support conditions predefi ne the failure mode
with three horizontal cylindrical hinges (see also Griffi th et al. , 2004), and
were rather different from on site and laboratory observations collected by
D'Ayala et al. (2008). A testing scheme, corroborated by observation of
post-earthquake damage in existing masonry structures, has been devised
by Al Shawa et al. (2012); however, by predefi ning a state of damage and a
consequent separation between façade wall and transversal walls, the mech-
anism is also in this case predefi ned.
Ranges of existence for drift limit states can be computed for either in-
plane or out-of plane prevalent behaviour, using available experimental
datasets in the literature. These are summarised in Table 13.2 and compared
with the EC8 (CEN, 2005) values provided for URM for the damage limit
states of SD and NC. These values will be compared with the value of per-
formance drift obtained with the FaMIVE simulations for the damage
thresholds of structual damage and near collapse, respectively as defi ned in
Fig. 13.1 and above.

13.3.1 Derivation of capacity curves
The capacity curves are defi ned for each façade on the basis of the following
steps. The fi rst step is to calculate the lateral effective stiffness for each wall
and its tributary mass. The effective stiffness for a wall is calculated on the
basis of the type of mechanism attained, geometry of the wall (Fig. 13.3),
layout of opening, constraints to other walls and fl oors, and portion of other
walls involved in the mechanism:

Kk EI
H

EA
H

t eff t eff

= + k

[13.1]

eff 1 2

3

eff eff