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Is it possible to consider the
staged construction ?
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Why the analysis stops with error
after initial stage ?
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How do I start the numerical
analysis for the first time ?
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When is K0-value
used ?
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When does the analysis converge for
elastic-plastic model ?
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What is the main difference between
the geotechnical modeling and the structural one ?
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How does the current version read
the previous versions of input data ?
Yes, PENTAGON-2D and PENTAGON-3D have the
feature of considering the staged construction in any form and in
any sequence. You can arrange your ideas in modeling. For
example, the excavation processes for the temporairy earth
retaining structure can be easily modeled with the initial stage
followed by the construction stages and the load stages. The
successive stages include the step-by-step excavations and the
step-by-step support addition processes.
In most cases, the initial stage requires the
perfect elastic stress state because the plastic region means the
undesirable failure before the man-made construction. This
situation happens when you underestimate the shear strength or
there are some mistakes in the boundary conditions. If there is
any structure of different stiffness in the ground, you should
not model the structure in the initial stage but in the
construction stage though the structure already exists before
your construction. In the old versions of PENTAGON, if there
existed any yield zone, the program stoped to restrict the bad
results.
However, the recent version after 13 August
1998 will continue the elasto-plastic analysis if the elastic
stress violate the yield condition. In some cases, user want to
make the plastic state in the initial stage due to complicated
geological conditions. This means that the program modifies the
stress condition to fit the yield condition. Normally, it is
strongly recommended for you to run the model elastically first,
and then, to establish new model not to violate the yield
condition.
To learn a program is always difficult to
everyone. You can learn the program via the ScreenCam files in
the CD-ROM first. The files shows how to make the input data
including FE mesh generation, the attributes of the mesh and the
whole construction situations. The files also shows the execution
methods including error correction procedures as well as the
post-processing. You can also refer to the example manual and the
basics chapter of users manual alternatively.
The K0 is used only at the initial
stage. The initial stage is the stage for the calculation of
insitu stress that is the starting point of stress and potential
load due to excavation. To model the elastic-plastic behavior,
the initial stage is necessary. To model the influence of
artificial load elastically, the initial stage is not needed.
The program checks whether three criteria
converge after every iteration, i.e., the displacement, the
residual force, and the internal energy. We input the convergence
tolerance of incremental internal energy; then, the other
tolerance is internally determined.
Most of all, The primary difference between two
models may be the existence of initial stresses. Of course, there
are initial stresses in the structural material, but for the
geotechnical problems, the initital stress has the importance of
contribution to the material properties. For the frictional
material like sand, the frictional shear strength is estimated
from the confinig stresses multiplied by the coefficient of
friction. As a viewpoint of loading condition, the load for the
geotechnical problem is simple relative to the structural
problem. In the structural problem, most efforts are assigned to
the estimation of load itself. On the other hand, most efforts
are given to the estimation of material properties of ground.
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All the versions of input data can be read by
the current version of the main processor. All the versions of
mesh data can be read by the AUTOMESH and PENTMESH. But, the
stage files cannot be read by AUTOMESH and PENTMESH sometimes.
The previous output files cannot be often read by the current
post-processors. In this case, please calculate the same data
again to get new version of output.
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