Managing risk and achieving reliable geotechnical designs using Eurocode 7 - Risk and Reliability in Geotechnical Engineering - page 421

Table 10.11 Consequences Classes, associated Reliability Classes, and β values from EN 1990
Consequences
Class

CC1 CC2 CC3

Description Low consequence for loss

of human life, or small or
negligible economic,
social or environmental
consequences

Medium consequence for
loss of human life, or
considerable economic,
social or environmental
consequences

High consequence for loss
of human life and very
great economic, social, or
environmental
consequences

Examples of
buildings or civil
engineering
works

Agricultural buildings
where people do not
normally enter (e.g.,
storage buildings,
greenhouses)

Residential and office
buildings, public buildings
where consequences of
failure are medium (e.g.,
office buildings)

Grandstands, public
buildings where
consequences of failure
are high (e.g., concert
halls)

Reliability Class RC1 RC2 RC3

3.3 3.8 4.3

β

1990 as sets of physical conditions representing the real conditions occurring during a
certain time interval for which the design will demonstrate that relevant limit states are not
exceeded. The following four Design Situations are distinguished in EN 1990:

• Transient Design Situations
• Persistent Design Situations
• Accidental Design Situations
• Seismic Design Situations

As noted above, the recommended ULS partial factor values given in Eurocode 7 are for
transient and persistent Design Situations. Referring to the partial factor values, Eurocode 7
states in §2.4.7.1(4) and (5) that More severe values than those recommended … should be
used in cases of abnormal risk or unusual or exceptionally difficult ground or loading condi-
tions , and that less severe value than those recommended … may be used for temporary
structures or transient design situations where the likely consequences justify it, that is, the
values of the partial factors in Eurocode 7 should be increased or decreased, and hence the
level of reliability increased or decreased, to take account of Design Situations where the
level of risk may be more severe or less severe.
Examples of CEN member states that have introduced reliability differentiation involving
Consequences Classes and Design Situations to introduce more severe or less severe partial
factor values are Austria and Germany. Different sets of partial material factor values are
given in the Austrian NA for the three Consequences Classes for the design of slopes and
anchorages. These are related to the particular Design Situation (BS) as shown in Table
10.12 . The highest partial factor values are for persistent Design Situations (BS 1), interme-
diate values are for transient Design Situations (BS 2), and lowest values are for accidental
Design Situations (BS 3). In the German NA, the values of the partial action factors to
be used with Eurocode 7 are related to the Design Situation for persistent, transient, and
accidental Design Situations, labeled as BS-P, BS-T, and BS-A, for all types of geotechnical
designs, as shown in Table 10.13 . As in the case of the Austrian partial material factors, the
highest partial action factors are for persistent situations, BS-P.
In France, a form of reliability differentiation has been introduced that corresponds to
the second method for managing risk and differentiating reliability in geotechnical design
described at the start of this section. This method does not involve changes to the partial fac-
tor values but links the Consequences Classes to the Geotechnical Categories and hence, to