## DYNA6.1 FAQs - PAGE 2

** Question:** Can the foundation/pile
stiffness values calculated by the software by used by popular
structural engineering software such as SAP.

** Answer:** Definitely yes.

** Question:** The vertical and
horizontal stiffness are not identical, but if I just divide the group
stiffness values by 12 then clearly the values for each individual pile
will be the same as each other regardless of the shape of the pile
group or their position within the group. It that correct?

** Answer:** The individual pile stiffness will
differ depending on its position within the group. However, the group
stiffness already accounts for the interaction between the piles, which
depends on the configuration of the pile group. When we divide the
group stiffness by the number of piles, we get the average stiffness
per pile. This is sufficiently accurate for the purpose of getting the
dynamic response of the machine-foundation system (global behaviour).

** Question:** Currently we model our turbine and
generator foundations using finite element models (concrete plate
elements) where the soil is represented as simple springs and the
harmonic forces are placed on concentrated masses at the rotor support
points. What I would like to be able to do is to compare the output
from DYNA6.1 to our finite element output for the same problem.

** Answer:** The main advantage of DYNA6.1 is its ability to
calculate the frequency dependant stiffness and damping constants of
both shallow (footing) and deep (pile) foundations. These stiffness and
damping constants can then be used to represent the foundation
flexibility in your finite element modeling to obtain the response. For
the case where the foundation can be considered to behave as a rigid
body, the program can also calculate the dynamic response to different
types of dynamic loads (harmonic, transient, impact or random).

The program DYNA6.1 complements the FE design tool you have. As a matter
of fact, it offers an essential component of the design. As you
probably know, the stiffness and damping constant of a foundation
system subjected to dynamic loading (which is the case for foundations
supporting turbines and generators) are a function of the frequency of
the loading, which is in turn a function of the operating speed of the
equipment. This is particularly crucial for deep foundations, and for
shallow foundations resting on layered soil or homogeneous soil with
Poisson’s ratio approaching 0.5. In any of these cases, successful
design requires the evaluation of the stiffness and damping constants
representing the soil (what you describe as simple springs) must be
calculated with due consideration of the loading frequency. Only
DYNA6.1,
not the FE model, can calculate these stiffness and damping constants.

To summarize, The program DYNA6.1 can be used to calculate stiffness and
damping constants, as well as the response of all types of foundations
(assuming rigid body models) to different types of dynamic loads. It
can also calculate stiffness and damping constants that can be later in
an FE model to represent the soil (soil or pile springs).

** Question:** We have a power plant project
and are now designing a foundation for the gas turbine and generators.
I would like to know could DYNA6.1 generate more than one natural
frequency of the system (consists of machines + foundation + soil). And
how to do that.

* Answer:* DYNA6.1 will show at least 6 modes (i.e. 6 natural
frequencies) associated with the rigid body movements. This means you
will have a natural frequency along the vertical and 2 horizontal
directions as well as torsional and 2 rocking directions. After you run
DYNA6.1, you can plot the responses vs. frequency at the C.G. of the
machine-foundation system. These responses will display peaks. The
location of the peak identifies the natural frequency.

** Question:** Our company has pump
foundation design which need be dynamic analysis.

* Answer:* DYNA6.1 can solve the problem
you cited. It is very widely used in the industry for similar
projects.

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