Analysis of space trusses by difference equations

The middle of 20^th 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 and telescope supporting systems are examples showing this tendency. With a limited, those times, computational possibilities, I undertook the research aimed on analytical solutions of mentioned structures by means of difference equations. Results, in this field, were summarized in 1973, in series of lectures, 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, 1963

A generalized micro approach to two-dimensional latticed structures ( co-author C. Ugarte) in proceedings of EMD Special Conference, Raleigh, USA, 1967

On 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 CISM Course, Springer Verlag,1976.

Mechanical problems of elastic lattice structures, in Progress in Aerospace Science, vol.15, pp 230-263 D. Kuchemann (ed.) 1974, Oxford: Pergamon Press.

Continuous structural optimization

In the last three decades, a lot of attention has been paid to structural optimization. Due to the complexity of the problems, most research has been performed under an assumption of one loading system acting on the optimized structure. It is, however, commonly known that in the most cases, structures and machines are subjected, during their service life, to several loading conditions. A number of my works was then devoted to structural optimization problems under multiple loading conditions. It was possible to accomplish this task by applying Kuhn-Tucker necessary conditions for an optimum problem, combined togathwr with Finite Element Method. The research was conducted for trusses, frames and for shape optimization of 2D bodies.

Representative publications:

Discrete structural optimization ( co-authors J.Bauer, Z. Iwanow) in Comp. Meth. Appl. Mech. Engng. Vol.51, pp. 71-78, 1985

Explicit formulation of Kuhn-Tucker necessary conditions in structural optimization (co-authors: J. Bauer and Z. Iwanow) in Computer and Structures Vol.37,No.5, pp. 753-758, 1990

Minimum weight design of structures under nonconservative forces( co-authors O. Mahrenholtz, M. Pyrz) in NATO/DFg AS1, "Optimization of Large Structural Systems",Berchtesgaden, Sept.23 Oct.4,1991,Vol.2,p.270-285

Optimal 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 variation between the manufactured structure and the intended optimum design. The differences come from technological imperfections which may cause dangerous violations of imposed constraints on performance measures. The aim of works in this subject , was aimed to give a relatively simple tool to designers, enable them to include manufacturing imperfections into their designs. The probabilistic problem 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, 1994

Manufacturing tolerance incorporated in minimum weight design of trusses(co-author J. Bauer) Engineering Optimization, 31, pp. 393-403, 1999

Manufacturing tolerances and multiple loading conditions in structural configuration optimization( co-author K. Dems), presented at 20^th ICTAM, 27August-2September, Chicago, 2000

Manufacturing 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 in excavation processes. This is mainly through control of repetitive processes, such as trenching and drilling, requiring constant attention of machine operators. The basic attention, in research, is paid to excavation along prescribed trajectories subjected to varying soil environment. The aim of research was to investigate the possibilities of controlling excavation trajectory by hydraulic module composed of a pump and load–independent valves. Other words, to investigate a system free of sensor cells mounted at the excavator attachment, combined with a feedback controller, included in the hydraulic unit of the machine.

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 in Construction vol. 1-10, 2002

Sensitivity 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

Discrete structural optimization

The engineering design of structures and machines consists often in finding the best solution among a finite number of feasible decisions. The design consists of looking for appropriate set of elements, from commercially available prefabricated parts, which is giving an optimum solution. However, with very large 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 this complex and important, from the practical point of view, problem. Four different approaches are discussed. The first one is based on controlled enumeration method. In the second approach, genetic algorithm with controlled, by stresses, mutation is proposed. The third one, is based on removing redundant material, in succeeding iterations. The fourth one deals with application of graph representation of structural volume and assumption that continuous solution constitutes lower bound of the discrete one

Representative publications:

A discrete method for lattice structures optimization ( co-authors; J. Bauer and Z. Iwanow ) in Engineering 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 Discrete Structural 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, special issue, 107-126

An effective method for discrete structural optimization ( co-authors J.Bauer, J. Zawidzka) in Engineering Computations, 17, 4, 2000, 417-426

Controlled mutation in evolutionary structural optimization (co-authors Z. Iwanow, J.Bauer) in Structural and Multidisciplinary Optimization 21, 5 , 2001, 355–360

Discrete 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

Robust Discrete Optimization for Structural Dynamics (co-author B.B³achowski) Computer Methods In Mechanics CMM-2007, £ódz-Spa³a, June 19-22, 2007

Discrete structural optimization by removing redundant material (co-author B.B³achowski) Engineering Optimization Vol. 40, No. 7, July 2008, 685-694

Graph based algorithm to large structural optimization problems (co-author B.B³achowski) 8th World Congress on Structural and Multidisciplinary Optimization (WCSMO-8), Lisboa, Portugal, June 1-5, 2009.