Assessment of Existing Structures and Repairs - Offshore Structures: Design, Construction and Maintenance - page 514

4. Determine the probability of failure using the equation P f = Φ ( −β ), (2.3-2),

where Φ is the CDF of a standard normal variable.

7.9.6 Software Requirement
The fundamental requirement for the software is that it should adequately represent
the relevant failure modes for the basic components in framed offshore structures:

Members ●

Joints

●

Foundation

●

Loading.

●

Thesoftwareshouldhavecleardocumentation of which facilities are
available and how they should be applied. The software should include spe-
cification of any limits of validity for special features (e.g., D/t limits for a
particular local buckling formulation, β -range for a joint capacity formula-

tion, etc.).
From the quality assurance point of view, it is essential that the software can
document compliance with theoretical solutions and test results for single com-
ponents, substructures and structural systems.
If there is any doubt about the formulation, a simple model should be sub-
jected to a well-defined load and deformation path. This will allow the results to
be judged and calibrated against engineering practice.
Simple program input reduces the possibilities for modeling errors and
errors in result interpretation. The input should be given in familiar engineering
terms. Unfamiliar or specialized input parameters increase the possibilities for
input errors.
The software should include pre-processing tools and default parameters to
reduce the need for detailed information from the user. This is especially rele-
vant for specialized information outside the main engineering focus, such as
parameters concerning numerical integration, mathematical stability or detail
parameters for special program features.
Program default parameters should be listed with a description of what they
imply and what any variation may represent.
The primary and essential validation of nonlinear analysis results comes
from understanding the development of the global collapse mechanism.
The software should present the analysis results efficiently, so that the struc-
tural behavior is easily understood by the engineer and is readily conveyed to
others. Extensive use of computer graphic capabilities is recommended.
Critical members should be identified, along with documentation of their
strength and buckling load.
The software should contain a self-checking mechanism so that clear indi-
cations are given if, at any stage in the analysis, the results violate basic
assumptions of the theory.