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DNV-OS-C502 Offshore Concrete Structures
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App.C
A 100 Linear elastic static analysis
App.C A
101 It is generally acceptable for the behaviour of a structure or
component to be based on linear elastic static analysis unless there
is a likelihood of significant dynamic or non-linear response to
a given type of loading. In such cases, dynamic or non-linear analysis
approaches shall be required, as defined in A200 - A400.
App.C A
102 Static analysis is always permissible where all actions on
the component being considered are substantially invariant with
time. Where actions are periodic or impulsive in nature, the magnitude
of dynamic response shall be evaluated in accordance A200 and static
analysis shall only be permitted when dynamic effects are small.
App.C A
103 Reinforced concrete is typically non-linear in its behaviour,
but it is generally acceptable to determine global load paths and
sectional forces for ultimate, serviceability and fatigue limit
states based on an appropriate linear elastic analysis, subject
to the restrictions presented below. Non-linear analysis is normally
required for accidental limit states, ductility level earthquakes
and local analysis.
App.C A
104 Linear stiffness is acceptable provided that the magnitudes
of all actions on the structure are not sufficient to cause significant
redistribution of stresses due to localised yielding or cracking.
Response to deformational loads, in particular, is very susceptible
to the level of non-linearity in the structure and shall be carefully
assessed for applicability once the level of cracking in the structure
is determined.
App.C A
105 Reduction of the stiffness of components should be considered
if it can be shown that, due to excessive cracking, for example,
more accurate load paths might be determined by such modelling.
Such reduced stiffness shall be supported by appropriate calculations
or by non-linear analysis.
App.C A
106 A linear analysis preserves equilibrium between external applied
loads and internal reaction forces. Linear solutions are thus always
equilibrium states. The equations of a linear system need to be
solved only once and the solution results may be scaled to any load
level. A solution is hence always obtained, irrespective of the
load levels. Linear analysis can be carried out for many independent
load cases at the time. The independent load cases may be superimposed
into combined cases without new solution of the equation system.NOTE: Practise has shown that the use of a system representing
all actions as unit loadcases that afterwards can be scaled in magnitude
and added to represent complete load combinations i.e. loading scenarios
is very effective.
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