Page 215 - Handbook of Materials Failure Analysis

5 Case Study 211

tank is isolated. So, there is no risk of clashing. This parameter is classified as
class A.

5.10 SITE EFFECT
Tanks may be threatened by some effects of the implantation site (as liquefaction of
sands, landslides, presence of surface faults, and rockfalls) that can significantly
amplify the oscillations of the soil and cause the loss of all structure even para-
seismic. Structures located there can sometimes undergo seismic loads up to five
times higher than similar structures located in a less dangerous zone [4]. It is there-
fore imperative to take into account the site effect in a vulnerability study and the
resort to a geotechnical engineer or geologist is desirable. Our tank is located
in site that presents no risk. So, this parameter is classified as class A.

5.11 DETAILS
We often hear about the detail parameter as the state and quality of nonstructural
elements that can influence the tank behavior during an earthquake and the status
of various networks related to the functionality of the tank. The elements to consider
for this parameter are the state of hydraulic equipment (various distribution pipe-
lines, etc.), the cover roofing, the cornice, and the stairs. All nonstructural elements
are in bad condition. This parameter is classified as class C.

5.12 MAINTENANCE
Cracks on resistant components of the tank shall result in the loss of stability and loss
of the sealing function. Quantifying the cracking state is made according to the LPC
method [18] which is a quick and easy way to characterize in conventional manner of
the state of reinforced concrete wall damage at a given time. This method concerns
all existing cracks in a given area. The method consists of taking in an exhaustive
manner all cracks intercepting four axes drawn in an area of one square meter on
the part of the facing to study. A landmark consisting of four axes graduated from
0.1 to 0.1 m (a vertical axis of 1 m length, a horizontal axis of 1 m length, and
two axes arranged at 45° relative to the horizontal axis with 1.4 m length) is drawn
on the facing using the jig (Figure 8.10). The tracing is performed carefully to avoid
altering the lips of the cracks.
Cracking zone is shown on the cylindrical wall, where seepage is observed, on
which we have drawn the landmark with four axes (see Figure 8.11).
All the cracks with openings greater than 0.05 mm, intersecting with the axis of
the landmark are identified and measured up to 2 mm opening. For each of the four
axes, we calculate the total accumulated of the opening, the average opening per
crack, and the average opening per meter length axis. The cracking index is calcu-
lated by taking the average of the four openings per meter obtained on each axis. The
detail of this calculation is given in Table 8.21.