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Analysis of space trusses by difference equations
The middle of 20th Century was the beginning of wide
applications of prefabricated, metal elements in
structural design. Large span roofs, composed of thousands of
elements, radio and television masts andtelescope supporting
systems are examples showing this tendency. With a limited, those
times,computational possibilities, I undertook the research aimed
on analytical solutions of mentionedstructures by means of
difference equations. Results, in this field, were summarized in
1973, in series oflectures, given by leading scientists in the
field, in International Center for Mechanical Sciences ( CISM)in
Udine , in 1973.
Representative publications:
The stability of lattice struts in ZAMM, vol.43, pp 284-286,
1963A generalized micro approach to two-dimensional latticed
structures ( co-author C. Ugarte) inproceedings of EMD Special
Conference, Raleigh, USA, 1967On the Analysis of Polar Lattice
Plates ( co-author J. Bauer) in Int. J. Mech. Sci., vol. 12, pp
949-958,1970.Discrete Field Analysis of Structural Systems
(co-authors I.D. Achenbach, D.L. Dean) and in CISMCourse, Springer
Verlag,1976.Mechanical problems of elastic lattice structures, in
Progress in Aerospace Science, vol.15, pp 230-263D. Kuchemann (ed.)
1974, Oxford: Pergamon Press.
Discrete structural optimization
The engineering design of structures and machines consists often
in finding the best solution among afinite number of feasible
decisions. The design consists of looking for appropriate set of
elements, fromcommercially available prefabricated parts, which is
giving an optimum solution. However, with verylarge numbers of
possible combination, ranging ten to the power ten, search for
optimum solution,applying simple enumeration, is impossible. I
undertook, with my co-workers, a series of works to thiscomplex and
important, from the practical point of view, problem. Three
different approaches arediscussed. The first one is based on
controlled enumeration method. In the second approach,
geneticalgorithm with controlled, by stresses, mutation is
proposed. The third one, and the simplest one, isbased on removing
redundant material, in succeeding iterations .
Representative publications:
A discrete method for lattice structures optimization (
co-authors; J. Bauer and Z. Iwanow ) inEngineering Optimization
Vol. 5, pp. 121-128, 1981.Controlled enumeration with constraints
variations in structural optimization in ZAMM, Vo. 72,
T447-452,1992.Support number and allocation for optimum structures
(co-authors J. Bauer, Z. Iwanow) in DiscreteStructural Optimization
. Proc. Symp. IUTAM W. Gutkowski, J. Bauer eds. pp.168-177.
Springer, 1993.Structural Optimization with Discrete Design
Variables, in Euro. J. Mech., A/Solids, vol.16, 1997, specialissue,
107-126An effective method for discrete structural optimization (
co-authors J.Bauer, J. Zawidzka) inEngineering Computations, 17, 4,
2000, 417-426Controlled mutation in evolutionary structural
optimization (co-authors Z. Iwanow, J.Bauer) in Structuraland
Multidisciplinary Optimization 21, 5 , 2001, 355 360Discrete
minimum weight design of steel structures using EC3 code
(co-authors G.Guerlement, R.
Targowski, J.Zawidzka, J. Zawidzki) in Structural and
Multidisciplinary Optimization, 22, 2001, 322 327
Continuous structural optimization
In the last three decades, a lot of attention has been paid to
structural optimization. Due to thecomplexity of the problems, most
research has been performed under an assumption of one
loadingsystem acting on the optimized structure. I t is, however,
commonly known that in the most cases,structures and machines are
subjected, during their service life, to several loading
conditions. A numberof my works was then devoted to structural
optimization problems under multiple loading conditions. Itwas
possible to accomplish this task by applying Kuhn-Tucker necessary
conditions for an optimumproblem, combined togathwr with Finite
Element Method. The research was conducted for trusses,frames and
for shape optimization of 2D bodies.
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Representative publications:
Discrete structural optimization ( co-authors J.Bauer, Z.
Iwanow) in Comp. Meth. Appl. Mech. Engng.Vol.51, pp. 71-78,
1985Explicit formulation of Kuhn-Tucker necessary conditions in
structural optimization (co-authors: J. Bauerand Z. Iwanow) in
Computer and Structures Vol.37,No.5, pp. 753-758, 1990Minimum
weight design of structures under nonconservative forces(
co-authors O. Mahrenholtz, M.
Pyrz) in NATO/DFg AS1, "Optimization of Large Structural
Systems",Berchtesgaden, Sept.23Oct.4,1991,Vol.2,p.270-285Optimal
design of a truss configuration under multiloading conditions (
co-author K. Dems), in Struct.Opt., Vol. 9, 3/4 , pp. 262-265,
1995.Shape optimization of 2D elastic structures using adaptive
grids ( co-author J. Zawidzka) in Engng.Trans. Vol. 43, 1-2, pp137-
150, 1995.Shape optimization of a 2D body subjected to several
loading conditions (co-author K. Dems), in Eng.Opt., Vol. 29, pp.
293-311, 1997.2D shape optimization with static and dynamic
constraints ( co-author K. Dems) in Eng.Opt., Vol. 30,3/4,
pp.201-207, 1998.
Manufacturing tolerances in structural optimization
Application of structural optimization is often limited by
designers concern about possible variationbetween the
manufactured structure and the intended optimum design. The
differences come fromtechnological imperfections which may cause
dangerous violations of imposed constraints onperformance measures.
The aim of works in this subject , was aimed to give a relatively
simple tool todesigners, enable them to include manufacturing
imperfections into their designs. The probabilisticproblem was
brought to a deterministic one, however, assuring the solution on a
safe side.
Representative publications:
Structural optimization with sensitivity constraints(co-author
J. Bauer) in Comput. Struct. Vol. 52, pp.121-125, 1994Manufacturing
tolerance incorporated in minimum weight design of
trusses(co-author J. Bauer)Engineering Optimization, 31, pp.
393-403, 1999Manufacturing tolerances and multiple loading
conditions in structural configuration optimization( co-author K.
Dems), presented at 20th ICTAM, 27August-2September, Chicago,
2000Manufacturing tolerances of fiber orientation in optimization
of laminated plates (co- author J. Latalski),in Engng. Opt.
2003.
Controlled excavation processes
Recently, there are increasing possibilities for enhancement of
a large spectrum of human efforts inexcavation processes. This is
mainly through control of repetitive processes, such as trenching
anddrilling, requiring constant attention of machine operators. The
basic attention, in research, is paid toexcavation along prescribed
trajectories subjected to varying soil environment. The aim of
research wasto investigate the possibilities of controlling
excavation trajectory by hydraulic module composed of apump and
load independent valves. Other words, to investigate a system free
of sensor cells mountedat the excavator attachment, combined with a
feedback controller, included in the hydraulic unit of
themachine.
Representative publications:
Multi-arm mechanism design minimizing hinge reaction between
arms ( co-authors: J. Bauer, Z.Iwanow, J. Putresza) in Mech. Mach.
Theory Vol. 30, No. pp. 829-836, 1995.Load-independent control of a
hydraulic excavation ( co-authors E.Budny, M.Chłosta) in Automation
inConstruction vol. 1-10, 2002Sensitivity of the bucket motion in
controlled excavation (co-author M. Chłosta) in ANC 8
th Int. Topical
Meeting on Robotics and Remote Systems, 1999,CD
Proceedings.Optimal control of an excavator bucket positioning
(co-authors E.Budny, M. Chłosta) in Proc. of 19
th Int.
Symp. On Automation and robotics in Construction, National
Institute of Standards and Technology,USA,23-25 Sept.2002
