Page 196 - Handbook of Materials Failure Analysis

192 CHAPTER 8 Seismic risk of RC water storage elevated tanks

This method is a simplified empirical method inspired by the CNR-GNDT
method. Its goal is to allow for the establishment of a seismic inventory of water stor-
age tanks on a large scale by the simple and rapid recording of structural parameters.
We have made some modifications to the methodology developed by Benedetti et al.
[5], where a resetting of the weighting coefficients is performed in order to better fit
to the geometric characteristics of elevated tanks. The main differences are the intro-
duction of three new parameters called clashing, seismic zone, and location of the
reservoir. Readers wishing for further details about this method can consult the ref-
erence by Hammoum et al. [10].
In Table 8.2 [11], for each parameter, we define three classes of vulnerability.
And for each class, will correspond an elementary score K i . Each parameter is
affected by a weighting factor W i . The elementary score K i of each parameter
can take three values (0, 5, or 15). The value of the weightings W i varies from
0.25 to 1.75. The value of 0.25 corresponds to a minimum penalty of the parameter
and 1.75 for a maximum penalty considering intermediate situations, as shown in
Table 8.2. The partial score of a parameter is obtained by the product K i W i Þ
ð
and the vulnerability index I V is expressed as the sum of the partial scores of different
parameters:
12
X
K i W i (8.1)
I V ¼
i¼1
Considering all the 12 analysis criteria, listed above, we propose the following
classification, divided into three levels of vulnerability (Table 8.3).

Table 8.2 Classification of Containers According to Their Vulnerability
Index I V5 [11]

Elementary Score K i
Weighting
No Parameters Class A Class B Class C Factor W i
1 Seismic behavior 0 5 15 1.75
2 The clashing 0 5 15 1.75
3 The bracing system 0 5 15 1.50
4 Regularity in plan 0 5 15 1.50
5 Regularity in elevation 0 5 15 1.50
6 Soil type 0 5 15 1.00
7 Site effect 0 5 15 1.00
8 Seismic zone 0 5 15 1.00
9 Quality of the nodes 0 5 15 0.75
10 Qualities of the bracing 0 5 15 0.75
system
11 Maintenance 0 5 15 0.50
12 Details 0 5 15 0.25