Vol.2, No 8, 1998 pp. 811 - 816
UDC: 531:518.12
ADVANCES IN COMPUTATIONAL STRUCTURAL MECHANICS
Dubravka Mijuca
Faculty of Mathematics, University of Belgrade
Abstract. In this report some new advances in computational structural
mechanics presented at the Fourth International Conference on Computational
Structures Technology (here CST'98) August 18 to 20 1998 - Edinburgh, Scotland,
are described. The conference was organized by Civil-Comp Press from Edinburgh.
It convened about 150 selected scientist, researchers and professionals
from computational mechanics, computer science and related areas to advance
the state of the art in the developing of reliable and efficient computational
structures technology procedures.
1. THE SCOPE OF THE CONFERENCE
This was a fourth time that the researches from all side of the world congregated
to share ideas and solutions applicable to almost any kind of design. The
conference was held in the wonderful surroundings of the Scotland's capital
city of Edinburgh during the worldwide famous festivals times in August.
The aim of the conference was to bring together researches in computational
mechanics and software developers in the field of solid mechanics. The
main goal of the conference was to present new advances in the reliable
numerical simulation of real mechanical systems, with special emphasis
on implementation and application. Further, attention was paid to fostering
a common understanding of the nowadays needs and demands posed in front
of the computational mechanics procedures, techniques and actions. The
Conference proceedings are printed in a form of four books with a catalogue
records available from the British Library.
About 150 speakers and attendees provided a brief overview of recent
advances in various topics. These are related to finite element procedures
and techniques, civil and structural engineering computing for practice,
engineering computational technology and computational structural mechanics.
Attendees came (in alphabetical order) from Australia, Austria, Bangladesh,
Brazil, Canada, Chech Republic, China, Croatia, Egypt, France, Greece,
Germany, India, Israel, Italy, Iran, Ireland, Japan, Korea, Macedonia,
New Zealand, Spain, State of Bahrain, Palestine, Poland, Portugal, Sweden,
Switzerland, Taiwan, Turkey, United Kingdom, United States of America and
Yugoslavia.
The conference program contained the following topics: Structural dynamics,
multy-body systems, parallel and distributed computations, finite volume
calculations, boundary elements methods, mixed finite element approaches,
numerical and solution procedures, element technology, analysis of plates,
contact and impact problems, bio-mechanics problems, fluid-structures interactions
problems, design and analysis of steel structures, design and analysis
of connections, neural computing for engineering computations, mesh generations,
error estimations, adaptivity, crack modeling with adaption, composites,
fracture mechanics, object oriented technology, knowledge-based systems,
soil-structures interactions problems, genetic and simulated annealing
algorithms for engineering computations, design loading, modeling of reinforced
concrete, plastic and elasto-plastic modeling, design and analysis of geotechnical
structures, computational software developments.
Looking back at the conference, most of the lectures were concerned
with implementing the known and new computational procedures in solving
the real mechanical problems. Solutions of some of these problems are supported
by miscellaneous Projects currently running in European Union Community.
The hosts of this conference was Heriot-Watt University, one of the
three universities in Edinburgh. It was founded in 1821 as a School of
Arts and Mechanical Institute. It became in 1854 the Watt Institution and
School of Arts, and from 1885 was the Heriot-Watt College until its elevation
to university status in 1966. Its Science Park has a close working relationship
with commerce. Many of the Heriot-watt students come from abroad and there
is a close connection with a Norway for example [1]. All lectures were
held at the Mechanical and Chemical Engineering department. The chairman
of organizing committee was professor Barry H.V. Topping, from the same
department. Among his many successful activities he is an editor in chief
of the international journal "Computers and structures".
From our country there was a only one paper "On the efficiency of the
primal-mixed finite element scheme" [5] by the present author and professor
Mladen Berkovic also from Faculty of Mathematics, Belgrade. The paper is
included in the book "Advances in computational structural mechanics" edited
by B.H.V Topping and published by Civil-Comp Press UK.
2. THE OVERVIEW OF THE CONFERENCE
Overview of the Conference will be done trough a brief review of lectures
presented at the conference CST'98, with special emphasis on opening plenary
lectures were given by several respected scientists.
The first one was given by Professor A.K. Noor, from the Centre for
Advanced Computational Technology, NASA Langley Research Centre, Hampton
and University of Virginia, USA. The title of his lecture was "ISE-Intelligent
Synthesis Environment for Future Aerospace Systems and its Impact on Engineering
Research and education." The ISE environment is developed by NASA, the
University of Virginia and the Jet Propulsion Laboratory. Its main purpose
is enhancing the fast design and missions procedures that are optimal in
the ratio of the cost-efficiency. "...ISE uses a synergistic combination
of leading edge technologies, including high performance computing, high
capacity communications and networking, human centered computing, knowledge-based
engineering, computational intelligence, virtual product development and
product information management...". Under the high performance computing,
an adaptive or configurable computing systems are explained. Such a kind
of computing systems have information processing elements that can change
and adapt their hardware circuits based on the type of the problem that
have to be solved. Further, quantum computing is based on quantum parallelism
logic that allows exponentially many computations to take place simultaneously.
Next, chemical and biochemical computers were explained, where molecules
are used as the active components in a computer circuit.
For example DNA computers, albeit much more slower than conventional
electronic computer, are well suited for combinatoric problems. Finally,
optical and optoelectronic computers in the future will take a part as
an interconnections network at the hart of electronic computers. Also,
special attention is drawn to the powerful microprocessors and visual computers,
with motion-video instructions from which is expected to significantly
enhance the capability of desktop multimedia PC, for example for visual
communications. It is expected that for the September 1999 Intel and Alpha
processors with MVI instruction facilities will reach 600 and 1200 MHz,
respectively. The next component of the ISE is rapid synthesis and simulation
tools. Many of the ISE tools are provided by commercial modeling and simulation
system and CAD/CAM/CAE suites.
Further distinguish characteristics include seamless interfaces from
CAE systems to the virtual environment and associated soft computing tools
to solve complex design problems with system uncertainties together with
the real time generation of a model. The ISE component that covers life-cycle
integration and validation has four subelements: engineering process assessment,
integration methods, large scale research and development applications
and large scale projects and demonstrations.
Interesting is that large scope numerical simulation involving diverse
geographically dispersed teams will be perform in testbeds. As a concluding
remark professor Noor has said that universities can work with industry,
government labs and professional societies in developing effective instructional
and training facilities for the new research and synthesis approach [2].
The second plenary lecture named "Advances in analysis of structures
and fluid-structures interactions" was given by professor Klaus J. Bathe
from Massachusetts Institute of Technology and who is a general director
of Adina R&D Inc USA also. The lecture started with the observation
that has been amply recognized that many problems in solid and fluid mechanics
cannot be solved efficiently using finite element discretisation with only
one unknown variable. The solution is the finite element formulation based
on the mixed principle. In the mixed formulations several fields of interests
are simultaneously approximated. For example in the solid mechanics displacement
and stress, or displacement, deformation and stress and in the fluid mechanics
displacement and pressure. However, the key to whether a mixed formulation
is actually valuable lies in the convergence properties of the formulations.
Unfortunately, on the first glance, convergence criteria are not obvious
as it is in the primal formulations. In his paper a rather simple convergence
criteria in the form of a numerical test is given. This test actually represent
the known inf-sup test related to the saddle point problems [3].
The third plenary lecture was in the section of the Forming problems,
under the name "New trends in the finite element modeling of metal forming
process" by professor J.L. Chenot, School of Mines Paris, France."...The
main constitutive equations describing the mechanical behavior of metal
are recalled with usual friction laws modeling contact at the tool part
interface and the thermal coupling for hot forming. Automatic remeshing
is compulsory to model a large strain which are usually produced by forming
process. Adaptive refinement must also be considered if one wishes to control
the accuracy during the whole deformation....Inverse method are also investigated
in the field of the metal forming and their application to computer aided
rheology....".
Professor Earnest Hinton from Department of Civil Engineering, University
if Wales Swansea, United Kingdom gave us a lecture named "On the reliability
of optimized shells". "Shells are analyzed using shape and size optimization
and numerical approximation is based on linear elastic small displacement
Reissner-Mindlin shell models. Once the optimal shape and thickness distributions
have been determined, the nonlinear buckling loads of the initial and optimized
shells are investigated using a geometrically nonlinear analysis tool capable
of dealing with complex load-displacement paths including snap-trough and
snap back..." [4].
Professor H.S. Turkman from Istanbul Technical University held a lecture
"Structural response of isotropic plates subject to blast loading". Paper
is also concerned with the presenting correlation between the theoretical
analysis and the experimental results of the strain time histories. The
plate is clamped at its all edges. The equation of motion are derived by
the use of the virtual work principle within the framework of the Love's
theory of thin elastic shells. A finite element analyses is presented and
the effects of material properties are examined on the dynamic behavior.
Professor G. Thierauf from University of Essen, Germany, presented
a lecture "Optimum design of reinforced concrete structures". The natural
draught cool tower is analyzed. A parallelization concept, applied on the
eight processors, is presented in the stage of gradient calculation. Examples
are included to illustrate the practical use and the time efficiency of
the parallelization in the area of engineering design.
Professors R. Push from Geodevelopment Ideon Research centre applied
Sweden and R.A. Addey from UK presented a lecture "Accurate computation
of stress and strain of rock with discontinuities". Repository concept
for the deep disposal of radioactive waste demand a deposition tunnels
and holes at the several hundred metros depth. A numerical study of the
resulting stress state at the intersections of the tunnels is presented
and the impact of discrete weakness predicted.
Professors E. Deletombe and B. Malhebre from ONERA Lille France presented
a lecture "Fluid Structure Simulation of Hydraulic Ram Pressure in Fuel
Tanks". An original method has been developed to study the fluid/structure
interaction problem of hydraulic ram pressure generated by bullets penetrating
fuel tanks. The basic idea consists in modeling the bullet by an equivalent
conic projectile, the radius of which (not the tumbling angle) varies accordingly
to a reference drag coefficient evolution.
The present author held a lecture with the name "On the efficiency
of the primal-mixed finite element scheme". In the paper a coordinate independent
finite element primal–mixed approach based on the stationary Reissner's
principle, having both the displacement and stress boundary conditions
exactly satisfied and solvable by direct Gaussian elimination procedure,
is presented. The main goal of this paper is to show that the proposed
procedure is easy for implementation, robust and more efficient, in the
sense of the execution time needed for the prescribed accuracy, than classical
displacement finite element procedure. Furthermore it has been shown, that
the present approach is stable near singularities, at variance with some
other closely related procedures. In order to illustrate the efficiency
of the present primal–mixed finite element method two–dimensional plane
stress linear isotropic elastic model problems were examined. It can be
concluded that mixed elements with complete continuity can be practically
realized, in addition simple and clear measures for the enhancement of
the stability of a solution of the resulting equations are available, and
finally the present mixed procedure is about two orders of magnitude more
efficient than the classical finite element analysis. As it can be seen,
the subject of the paper satisfy main demands posed in plenary lectures.
It is a special encouragement for the future research especially in the
three-dimensional mechanical problem situation, where for example, excellent
prediction of shell (observed as a full solid body) behavior is expected.
Some of the members of the conference editorial board were professors
H. Adeli USA, K. J. Bathe USA, T. Belytschko USA, D.E. Beskos Greece, C.
S. Desai USA, P. Hajela USA, E. Hinton USA, M. Kleiber Poland, E. Onate
Spain, M. N. Pavlović UK, B.A. Szabo USA.
Among the number of researches participated this conference I want
to mention professor Sankaran Mahdevan from Vanderbilt University, Nashville
USA & NASA, Professor Georg Thierauf from University of Essen Germany,
Dr John P. Wolf from Swiss Federal Inst. Of Technology, Lausanne, Switzerland,
professor. Demetres Briassoulis from Agricalture University of Athens and
professor A.Kaveh I.U.S.T. Teheran, Iran, as well as Rosemary Brodie from
Civil-Comp Edinburgh UK.
3.CONCLUSIONS
Attendance at "The Fourth International Conference on Computational Structures
Technology" even more strengthened my impression that computational mechanics
is considered as a field of a top priority and of vital importance for
the economy and security of many countries. Further, the relevant position
of the current state of the computational mechanics in our country, viewing
from the available manpower and technical recourses is satisfactory, but
not yet widely recognized as an irreplaceable cheap and fast analysis and
design tool. From that point of view, attendance at this conference has
been inspirative and important for a future research.
REFERENCES
1. www.efr.hw.ac.uk/EDC/guide/univer.html
2. A.K. Noor ISE-Intelligent Symthesis Environment for Future
Aerospace Systems and its Impact on Engineering Research
and education., Advances in Engineering Computational
Technology, Civil-Comp Press, pp 1-11,1998.
3. D. Chapelle and K.J. Bathe The inf-sup test Computers&Structures,
Vol 47, No 4/5, pp537-545, 1993.
4. S.J. Lee and E. Hinton On the reliability of optimized shells,
Advances in Computational Structural Mechanics,
Civil-Comp Press, pp 371-383, 1998.
5. D. Mijuca and M. Berković On the eficiency of the primal-mixed
finite element scheme, Advances in Computational
Structural Mechanics, Civil-Comp Press, pp
61-71, 1998.
DOSTIGNUĆA U RAČUNSKOJ MEHANICI
STRUKTURE
Nova dostignuća u računskoj mehanici strukture prikazana na Četvrtoj internacionalnoj
konferenciji računske tehnologije struktura (ovde CTS'98) avgusta 18 do
20, 1998 u Edinburgu su ovde opisana. Konferenciju je organizovala Civil-Comp.
Press iz Edinburga. Oko 15 izabranih naučnika, istraživača i stručnjaka
iz računske mehanike, kompjuterske nauke i srodnih oblasti prikazalo je
svoja naučna dostignuća koja predstavljaju "poslednju reč" nauke u ovim
oblastima.
