Assessment of Existing Structures and Repairs - Offshore Structures: Design, Construction and Maintenance - page 505

Frame
geometric

Software
validation

Component
behavior

FE Modeling

Analysis

System's
failure mode

Verification

Finish

FIGURE 7.21 Nonlinear ultimate strength analysis.

Certain techniques have been developed specifically for ultimate strength
analysis of frame structures. The elements have been derived to model beam
column behavior, and each column member is usually represented by one
single element member in the model that takes the buckling effect into
consideration.
Plasticity may be presented by modeling the propagation of yield through
the section and along the element sections.
Depending on the structure element, hinges will form at the ends or in the
midpoint of the member, based on the whole structure system.
Elastic plastic behavior analysis or gradual strain hardening can be
expressed as the energy dissipated in the element. Specification can be adjusted
to account for imperfection, rather than mean component strength provided by
the material test data.

Phenomenological Models
In phenomenological models, component responses are prescribed with force
and deformation relationships, which can be empirically related to element