Civil Engineering Reference
In-Depth Information
TABLE 8.39
Acceptable Minimum Reserve Strength Ratios
Reserve Strength Ratio (RSR)
API RP2A 19
th
Edition and Earlier
API RP2A 20
th
Edition and Later
Assessment
Category
Offshore Location
Gulf of Mexico
A-1
1.2
*
1.6 (draft)
A-2
0.8
1.2 (draft)
A-3
0.6
**
1.0 (draft)
Other U.S. offshore
areas
A-1
1.6
2.0
*
This RSR is applicable only for continued use of the platform for its present purpose. Not applicable
for change-of-use conditions.
**
Not to be used for water depth greater than 400 ft.
Mitigation includes such measures as demanding, either during a forecast
event or completely, a hydrocarbon inventory reduction that reduces the sever-
ity and consequence of platform failure. Mitigations like repairs should be
designed to meet the requirements of this section, so that they do not reduce
the overall strength of the platform.
Owners or operators who wish to continue to operate structures that have
been assessed in accordance with API RP2A Section 6 and do not meet the fit-
ness-for-purpose acceptance criteria appropriate for their consequence of failure
category are required to reduce the risk of operating the platform. Either or both
of the following can reduce the operating risk:
Mitigate the consequences of structural failure.
●
Reduce the probability of structural failure.
●
Competent assessment engineering should determine the need for, and
appropriate selection of, risk-reduction options.
8.7.1 Consequence Mitigation
If mitigation is an action taken to reduce the consequences of failure of the plat-
form, and if the consequence of failure is related to life safety, then mitigation
measures have to reduce the risk to life safety sufficiently to lower the conse-
quence category. For example, implementing operational procedures to evacuate
a manned platform, such as in the Gulf of Mexico during an extreme event,
reduces the consequence of failure during that event from high to medium. If
the consequence of failure is related to environmental impact or some other
consequence consideration, then other mitigation measures will be required
and may include one or more of the following.
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