VSH Turòa nad Bodvou - Nemetschek Scia

The presented project is about the realisation of special small vessels
for very dangerous nuclear waste treatment. This project includes
more than twenty different apparatus which were produced by
the Slovak company TECHNOS Ltd. The main task for our firm was
to perform the structural calculation of the vessel shells, nozzles
and anchoring of the vessels. The input for the calculations was
taken from data sheets and from the shop drawings of the vessels.
All designed tanks were also checked for seismic resistance. The
main aim of the calculations was to calculate the internal force
stresses: in test condition, in normal operation and extraordinary
operation, including also seismic effects.
Structural calculation
The design of the vessel is always connected with the use of
relevant codes like ASME, AD-Merkblat and Eurocodes. Relevant
codes usually calculate the mechanical resistance of the parts of
the vessel with some influence of the connected parts. The advantage
of such an approach is a relatively simply calculation based on
formulas. The accuracy of such an approach depends on the shape
and on the character of the loads.
For the calculation of the vessels with different shapes and different
loads as mentioned in the code, we can use a similar vessel. For
the calculation of such “uncommon “ vessels we can use the finite
elements method.
Computational model
Vessel shells are modelled by shell elements and legs and other
supporting parts are modelled by beam elements. The modelling
of the main parts is clear. An important task is how to model the
connection of the parts as reinforcing plates, rings and collars by
welds. The reinforcing part is connected with the shell, which is
reinforced only in the part of the welds.
The connection of the parts could be modelled as part of the shell,
which is perpendicular to main shape. In this case we can use intersections
of the shells very effectively. Intersection of the shells in
the ESA-Prima Win and SCIA•ESA PT is a very effective tool for the
modelling of the vessel. Without these tools it is unimaginable to
create a computational model of the vessel where nozzles connections
supports reinforcing parts.
Vessel for dangerous liquid waste treatment calculation
Method of calculation
Calculations of the seismic response of the vessel with liquid
inside can be performed by two approaches, firstly a time history
response on the accelerogram. The liquid in this case is modelled
by fluids elements. Secondly we can use the linear response
spectra method for the calculation of the forces in the supporting
parts and quasi-static method for calculation vessel shells. Important
for this approach is to use appropriate modelling of the liquid.
Part of the liquid inside of the vessel has to move unisons with the
vessel (impulsive mass) and a smaller part of the mass moves independently
on the vessel (convective mass). The first portion of the
liquid mass can be modelled as a mass connected with the shell.
The second part can be modelled as elastically connected with
the shell by the springs. The system of the springs has to have the
same frequency as calculated by the code. From the analysis of the
system by linear response spectra we received internal forces and
stresses in the shell. It is important where the anchoring points of
the vessel are located. Modal shapes and own frequency of vibration
are important for the bending mode approximation. On the
basis of the frequency of the bending mode of vibration, we are
able to approximate seismic acceleration.
Method of checking
Stresses in the shell are compared with stresses allowed by codes.
As is known in the location of singularities the stresses are very high.
For singularity problems solution we used formulas mentioned
in codes and check the stresses accordance with the codes. Very
important is origin of the stresses. Different values are allowed for
stresses from bending moments a different from membrane forces.
Software use
Calculation was performed by ESA-Prima Win. MathCad 2001
Professional was used to perform additional calculation.
Obtained result & conclusions
Internal forces stress deformation and also modal parameters of the
vessel were obtained from calculation. Without usage of the complex
model of the vessel the results would not be so precise. Based on this
calculation, the vessel was checked according to the code.
Vessel for dangerous liquid waste treatment calculation
The presented project regards the design of special small vessels for very dangerous nuclear
waste treatment. It includes more than twenty different apparatus which were produced by
the Slovak company TECHNOS Ltd
The structural analysis of the vessels is performed by a combination of the FEM method and
the analytical method. For the shell, the modelling intersection modulus of
ESA-Prima Win is used. The seismic response is solved by the linear response spectra. Stresses
in the shells are checked according to the codes.
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