Models for Simulating the Seismic Response of Concrete Structures - Dynamic Behavior of Concrete and Seismic Engineering - page 239

Multi-fiber or multi-layer models have several advantages in comparison to
global models. First, the parameters of the model are the characteristics of the
material and the section geometry instead of the curvature-moment or displacement-
stress global curve. Thus, a section analysis with a fiber model allows us to identify
the first-load curve of a curvature-moment global model. Figure 7.4 shows the
results of the section analysis of a column and a beam.
Figure 7.5. Influence of the axial stress on the resistance and ductility of a column
Secondly, modeling takes into account the effect of the normal stress on both the
bending moment and the ductility of the section. The curvature-moment
relationships in Figure 7.5 derive from the analysis of a column section submitted to
different axial stresses, and clearly show not only the section modulus increase, but
also the decrease of ductility caused by the normal stress rise.
7.2.3. 2D and 3D fine models
The subject here involves the most exhaustive finite element description
possible. Among others, mass elements will be used in 3D, as well as shell elements,
interface or joint elements or even plane or asymmetric elements for associated 2D
problems (see Figures 7.19 and 7.30). For further details, refer to the wide literature
on the subject.
At this level of modeling, each material - masonry, concrete, reinforcement,
mortar joints or dry joints - can be represented. Associating these laws can then
allow us to predict the global behavior of a structure as well as its local response, but
heavy calculation often restricts their use to the analysis of a structure element,
geometrically simple specific structures or structures with simplified loading (static