10. COMPUTATIONAL ENGINEERING FOR STRUCTURE ANALYSIS

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					__________________________________________COMPUTATIONAL ENGINEERING FOR STRUCTURE ANALYSIS



       10. COMPUTATIONAL ENGINEERING FOR
                STRUCTURE ANALYSIS
10.1 Introduction
In the year 2001 the activities regarded both analyses and studies, directed in particular
towards a thermodynamic solar project using the general purpose system CASTEM 2000 and the
calculation code HITECOSP, and a strong action of definition and specification of project
proposals to be funded by EC. In such activity the negotiation phase with EU was completed for
the funding of the UPTUN project, where ENEA has, with TNO in Delft, the role of co-
coordination of 39 partners including the main organisms, institutions, research centres,
industries involved in the problem of tunnel safety under fire risk.




10.2 Castem 2000 Project
ENEA has had a collaboration agreement for more than 15 years with CEA in Saclay for the
development, qualification, validation and promotion of the finite element general purpose
Castem2000.
According to its strong effort ENEA was identified by the DMT CEA as exclusive licenser of
the system in Italy and has therefore the task to diffuse the use and to take care of the
promotion among Italian potential users.
At present through ENEA action, there are in Italy about 15 different Castem2000 users and a
total number of about 20 system installations.
Among the main users we can mention Roma University “La Sapienza", Pisa University, Milano
Polytechnic, Torino Polytechnic, and Padova University.
In May 2001 the new version of Castem2000 system was taken from CEA and implemented on
different computer types and operative systems (PC Windows e Linux, IBM Risc6000 AIX, HP
Unix, etc.). Some versions were implemented and checked on the ENEA computer system located
in Casaccia Research Centre (IBM, HP, PC), so as to be used in the various computer simulations
planned in the different ENEA projects.
Due to the large number of studies and of the few available human resources, it was not really
possible to make any action either of promotion of the system or of distribution of the new
available version to the various users during the year 2001.




10.3 Solar Thermal Energy Production Project
At the beginning of the year ENEA started a R&D project called “Solar Thermal Energy
Production” directed to the study, the design and the construction of a solar power plant of
parabolic linear collectors for electric energy production. The principal innovative
characteristics of this plant are the high temperatures of the cooling fluid (about 550 °C), the
ability to produce power even when the solar flux is absent (presence of the storage system) and
the possibility, later on, to drastically reduce the KWh cost compared to the existing plants.
SIEC Division was involved in this project to analyse the mechanical and thermal mechanical


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behaviour of some fundamental components of the plant. In particular attention was drawn
towards two typical components of the solar plant: the concentrator and the receiver [10.3-1],
[10.3-2].



10.3.1     Thermal Mechanical Analysis of a Linear Receiver
To perform the thermal mechanical analysis of the linear receiver, the work was divided in two
steps. At first a thermal analysis of the linear receiver was performed so as to obtain the
temperature distributions on various sections
of the absorbing tube [Figure 10.3-1]. Then
thermal mechanical analyses were performed
on the tube in order to evaluate the stress
state arising from the thermal and the
mechanical loads. The numerical simulations,
made with the use of the finite elements code
Castem2000, were performed in the elastic
field and took into account both steady-state
and transient working conditions. After the
simulations, verifications of durability both
for creep and creep-fatigue were performed,
using the ASME Code Case N47. The results
obtained showed the various phenomena
generating stress states and the capability of    Figure 10.3-1 Temperature Distribution on
the component to resist if applied both           the terminal section of the linear receiver.
instantly and in time.


10.3.2 Mechanical Analysis of a Linear Parabolic Collector
Mechanical analyses of various types of parabolic linear collectors were performed to evaluate
                                             the stress state and the deformation level. The
                                             latter is strictly connected to the system optical
                                             performance and must therefore be subjected
                                             to strong limits. Both classical (beam framed
                                             structures which sustain thick plain mirrors) and
                                             innovative solutions (composite sandwich panels
                                             on which a thin mirror is attached, sustained by
                                             beams connected to the main tube) were
                                             analysed [Figure 10.3-2]. The main load which
                                             acts on the collectors is due to the action of the
                                             wind. The calculation performed allowed a first
                                             dimensioning of the components of the collector.
                                             The innovative solution analysed was submitted
 Figure 10.3-2 Displacement distribution     to obtain an ENEA patent (RM2001A000350,
  for a innovative solution of a sandwich.   Modulo di Concentratore Solare Parabolico, 18
                                             June 2001).




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10.4      Mechanical Analysis of Reinforced Panels for Naval and
          Railway Applications
In the framework of a collaboration with the ENEA NUMA Division, the following work was
performed concerning the mechanical verification of :
• Aluminium panels to be used in the cardek of fast ships;
• Stainless steel panels to be used as vertical sidings in railway applications.
All the various panel types are built up through laser welding. The structural verification of the
panels was performed through a series of numerical simulations by linear finite element analysis
using the general purpose Castem2000. Analyses of the stress strain field were also carried out,
compared and verified with standard limits, on the various elements (panels, weldings,
strengthening supports).


10.4.1 Naval Applications
In case of naval applications, three types of panels, with beams having different longitudinal and
transverse profile, were mechanically verified. These were subjected to the mechanical load due
to the weight of the vehicles parked there, comprising the dynamic effects imposed on the ship.
The panels were reinforced accordingly with: a) a longitudinal C beam and a transverse double T
one, b) a longitudinal Ω reinforcement, c) a longitudinal TC beam. The panels dimensions are
4910 x 4500 x 150 mm. The material used for the panels and the underlying beams is an
aluminium alloy (5083/H321). The load acting on the panels consists of the footprint of the 8
tyres of 2 vehicles parked there and is equivalent to a pressure of about 0.2 Mpa, comprising the
dynamic effects [10.4-1].
Table 10.4-1 shows the maximum stress values found on the panels, on the reinforcements and
on the weldment lines.

                                                                  Maximum
                   Type          Element verified                 stress
                                                                  MPa
                                 Loaded sheet (4.0 mm)            152
                   Panel 1       Reinforcing beams                72
                                 Weldment lines                   50
                                 Loaded sheet (3.5 mm)            172
                   Panel 2       Reinforcing beams                60
                                 Weldment lines                   60
                                 Loaded sheet (4.0 mm)            156
                   Panel 3       Reinforcing beams                82
                                 Weldment lines                   42

                    Table 10.4-1 Maximum stress values on the naval panels.

The results obtained show stress values on the panel well below the yield limits of the material
(203 MPa). The maximum stress state was for case n. 2, but it should be said that this is due to
the fact that in this case the panel thickness is 3.5 mm, while for the other cases is 4.0 mm.
Regarding the weldment lines it can be seen that the ratio between the yield stress and the
maximum calculated stress is grater than 3. This value is a good safety factor for the weldment



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resistance. From the analyses performed it is possible to see that in all 3 configurations the
stress level is well below the material yield limit and therefore the panels under load continue to
work in the elastic field. In conclusion it is possible to say that it is panel 1 which generally has a
more limited stress state (lower displacements compared with the other solutions). In
alternative also solution 2 and 3 can be used without particular problems.


10.4.2      Railway Applications
In case of panels for railway applications, three types of panels were mechanically verified: two
relative to the vertical sidings of passengers trucks and one relative to the vertical sidings of
goods trucks. The material used for the panels and the reinforcing beams is S275J0 UNI EN
10025 steel. The load acting on the panels is not known at first, but can be obtained from the
examination of the design loads on the whole truck. These loads are those required by the
European codes for the testing of the railway trucks and realistically reproduce the ones in real
life. Therefore it was necessary to perform a first analysis on a simplified model of the whole
truck to obtain a displacement field to apply to the detailed model of the panel examined. It
consists of the footprint of the 8 tyres of 2 vehicles there parked and is equivalent of a
pressure of about 0.2 Mpa, including the dynamic effects. Table 10.4-2 shows the maximum
stress values found on the panels, on the reinforcements and on the weldment lines [10.4-2].

                                                                     Maximum
                    Type           Element verified                  stress
                                                                     Mpa
                                   Sheet                             90
                    Panel 1        Reinforcing beams                 80
                                   Weldment lines                    70
                                   Sheet                             80
                    Panel 2        Reinforcing beams                 79
                                   Weldment lines                    79
                                   Sheet                             120
                    Panel 3        Reinforcing beams                 86
                                   Weldment lines                    75

                    Table 10.4-2 Maximum stress values on the railway panels.

The results obtained show stress values on the panel and on the reinforcements well below the
yield limits of the material (250 MPa). Regarding the weldment lines it can be seen that the ratio
between the yield stress and the maximum calculated stress is grater than 3. This value is a
good safety factor for the weldment resistance. From the analyses performed it is possible to
see that in all 3 configurations the stress level is well below the material yield limit and
therefore the panels under load continue to work in the elastic field. Of the 3 solutions that
with the highest stress state is the 3rd, the one relative to the goods truck. This is justified by
the fact that the panel considered is near an entrance to the goods truck. This causes lesser
rigidity induced by the remaining part of the structure and so greater deformations. These are
localised on the part of the panel nearer to the entrance.




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10.5 Tunnel Safety and Fire
During the year 2001 various actions concerning the abovesaid subject were conducted.


10.5.1 FIT ENEA Project
The definition of the subproject VESTRU (VErifiche STRUtturali) was completed. Ad hoc
meetings with Autostrade SpA and ENEA Faenza allowed defining and organizing the various
objectives and deliverables as well as detailing and optimizing the contribution of the different
partners expecting the funding requested from the competent national organisms.


10.5.2 UE FIT Network
The kick-off meeting has just been held in Malmoe and the ENEA participation in workpackage
n.3 “Compilation of guidelines for fire safe design” was defined and approved.


10.5.3 R&D UPTUN Project
In the year 2001 the final version of the technical project content was completed, detailing the
various aims and the different contributions in the partnership.
With the detailing of the various administrative formats discussed and approved by the UE
officer the negotiation phase of the UPTUN project was closed (Cost-effective, Sustainable and
Innovative Upgrading Methods for Fire Safety in Existing Tunnels).
The project aims to define procedures and to produce measures able to limit the probability and
to reduce the effects and the disastrous consequences in the existing tunnels in case of fire
accidents.
The main project objective is to develop, validate and promote innovative, durable, sustainable,
low cost (detecting, monitoring and mitigating) measures to allow owners, stakeholders,
designers and emergency teams to upgrade the safety level of existing tunnels.
The workplan is divided in 7 technical workpackages. The first four are to increase insight and
develop new mitigating measures. The fifth and sixth are mainly to develop the innovative
integral upgrading approach. The last work-package is to promote and disseminate the results.
Furthermore, since not all problems can be foreseen now, nor can be solved within UPTUN,
strong links will be established with existing relevant research projects on national and
international level.
A specific workpackage is also foreseen for the management and co-ordination as the project is
a very complex one that asks for activity and R&D action of a very large partnership (this
includes 39 partners among the main organisms, institutions, industries working to solve the
safety problem of fire risk in existing tunnels). In detail the partnership include: 19 among
industries and consulting engineering companies; 11 research centres; 4 among tunnels owners
and governmental organisms responsible of tunnel safety and standards and 5 Universities.




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10.6 HITECOSP Calculation Code
The actions aimed at optimizing of the present HITECOSP version and in particular the
necessity of a software able to solve the problems and obtain the objectives planned both in the
UPTUN project and in the EUREKA NEWCON project, at present in the definition phase,
produced the editing of a document “specifiche di sviluppo” for the model development, analyses,
numerical simulations and studies foreseen as ENEA task.
In the meantime a service contract was signed with INSA University in Lyon, whose aim is the
construction of the informatic structure able to include the different calculation potentialities
asked by ENEA.
A critical revision of the modelling and a series of checking and qualification analyses allowed
within a fruitful action with Cachan University, the detailed definition of the efforts,
procedures and models necessary to have a simulation software tool able to predict the possible
spalling phenomena for the various HPCs (high performance concretes).
Among the actions aimed at optimizing HITECOSP we can mention the implementation of a
parallel calculation system by the use of a cluster of Personal Computers with LINUX operative
system. As communicator, which controls the data exchange between the various processes, MPI
was used (the free distribution MPICH). This allowed the use a multifrontal solutor, specific for
parallel systems [10.6-1].




10.7 References
[10.3-1] A. Miliozzi, G. M. Giannuzzi, C. Caroli, "Comportamento termomeccanico del segmento
         collettore di un impianto solare. Analisi di sensibilità", ENEA SIEC CT-SBE-00036
         14/6/2001.

[10.3-2] A. Antonaia, M. Avitabile, G. Calchetti, T. Crescenzi, G. Cara, G. M. Giannuzzi, A. Maccari,
         A. Miliozzi, M. Rufoloni, D. Prischich, M. Vignolini, C. Rubbia, "Progetto di massima del
         collettore parabolico lineare per impianto solare", ENEA TM/PRES/2001/09/2001.

[10.3-3] A. Miliozzi, G. M. Giannuzzi, P. Tarquini, A. La Barbera, "Fluido termovettore: dati di
         base della miscela di nitrati di sodio e potassio", ENEA/SOL/RD/2001/07/ 2001.

[10.3-4] A. Miliozzi, G. M. Giannuzzi, L. Sipione, "Proprietà termo-meccaniche dell’acciaio 316L in
         funzione della temperatura", ENEA/SOL/RD/2001/09/2001.

[10.3-5] A. Miliozzi, "Ottimizzazione delle dimensioni del pannello riflettente sandwich e degli
         appoggi di un concentratore", ENEA/SOL/RD/2001/10/ 2001.

[10.3-6] A. Miliozzi, G. M. Giannuzzi, L. Sipione, "Comportamento termomeccanico del tubo
         assorbitore di un impianto solare. Analisi termica semplificata e termomeccanica",
         ENEA/SOL/RD/2001/08/ 2001.




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[10.4-1] A. Miliozzi, I. Chiricozzi, L. Sipione, "Verifica meccanica di pannelli in alluminio per i
         cardeck delle imbarcazioni veloci da realizzare mediante saldature laser", ENEA SIEC
         CT-SBE-00038 27/8/2001.

[10.4-2] A. Miliozzi, I. Chiricozzi, L. Sipione, "Verifica meccanica di moduli di parete per
         applicazioni ferroviarie", ENEA SIEC CT-SBE-00039 27/8/2001.

[10.6-1] L. Sipione, I. Chiricozzi, "Implementazione di un sistema di calcolo parallelo costituito da
         Personal Computer Pentium, sistema operativo Linux e comunicatore MPI, per
         l'esecuzione del codice agli elementi finiti HITECOSP con solutore parallelo", ENEA
         SIEC CT-SBE-00040 14/12/2001.




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