Globaliosios sijyno optimizacijos uždaviniai

Important problem in civil engineering is obtaining optimal pile placement schemes for grillage-type foundations in order to reduce the number of piles and reactive forces arising in piles. The idealizations of problem and formulation for local and global optimization are discussed, highlighting the must for global optimization. The grillage is discretized using finite element method. Sensitivity of objective function is obtained analytically. The solution technology for a class of aforementioned problems is proposed based on the use of global optimization algorithms of package GAMS, which are implemented as ``black boxes”. Results of computational experiments are presented.Nagrinėjamas aktualus statybos inžinerijoje uždavinys: optimalios polių išdėstymo rostverkiniuose pamatuose schemos gavimas, siekiant kuo mažesnio polių skaičiaus ir kuo mažesnių atraminių reakcijų juose. Aptariami uždavinio idealizavimai, jo formulavimas lokaliajai ir globaliajai optimizacijai, parodoma globaliosios  optimizacijos reikšmė tokiems uždaviniams. Sijyno diskretizacijai taikomas baigtinių elementų metodas. Tikslo funkcijos jautrumo analizė atliekama analitiškai. Pasiūlyta tokių uždavinių sprendimo technologija, taikant globaliosios optimizacijos algoritmus kaip „juodas dėžes“; tam uždavinio sprendimo programos pritaikytos optimizacijos paketui GAMS. Pateikiamas skaitinis pavyzdys

Multi-objective global optimization of grillage-type engineering structures using advanced metaheuristics

The purpose of the paper is to present the method implemented for a global optimization of grillage-type pile foundations introducing two advanced metaheuristics: AAGA and AGADS. The suggested new optimization algorithm including the synergy of AAGA and AGADS demonstrates improved results comparing with former AGA and GADS. Compromise objective function to be minimized involves the maximum reactive force in piles and maximum bending moment in the connecting beams. The feasibility of a simple weighting technique for the objective function is proved by numerical investigation of objective function domain for several different topologies of foundations. Sizing problem of connecting beams is solved together with the optimization problem. The original finite element program was employed for solution of direct problem

Optimization of laminated bending plates

The problems of shape, material, sizing and topology optimization are formulated and solved for thin orthotropic laminated bending plate structures subjected to the in-plane as well as out-of-plane loading. A simple laminated combined finite element that comprises known elements CST for membrane part and DKT for bending part was formulated in the present study. A special numerical-analytical method for structural matrices of the element and analytical sensitivity analysis is used to cope with huge required computer resources for topology optimization. The uniform distribution of deformation energy density over the area of structure is employed as the optimality criterion in all optimization problems. The original algorithms, which may be attributed to the ESO family of algorithms, are suggested for optimization of laminae thicknesses and topology optimization. A number of numerical examples are provided. Frist Published Online: 30 Jul 201

Some insights on the optimal schemes of tall guyed masts

The article presents the technique for simultaneous topology, shape and sizing optimisation of tall guyed masts under wind loadings and self-weight using simulated annealing. The objective function is the mass of the mast structure including guys, while the set of design parameters may consist of up to 10 parameters of different nature. The constraints are assessed according to Eurocodes and include the local and global stability constraints, limitations on the slenderness in mast elements, and strength constraints. The proposed optimisation technique covers three independent parts: the optimisation algorithm, meshing pre-processor that yields computational scheme of mast depending on the design parameters, and finite element program evaluating the objective function and constraints via penalisation technique. As an example the results of optimisation of a typical 60 m tall guyed telecommunication mast with different antenna areas are presented. On the basis of these results, the authors try ascertaining the approximate optimal diapasons of geometry and topology parameters such as the width of the shaft, distance of the guy foundation from the mast axis, heights of the guy attachment levels and so on. The authors hope, this will be helpful for constructors as an initial design of mast topology, shape and element sizing

Global optimization of grillages using simulated annealing and high performance computing

The aim is to investigate ways of increasing the efficiency of grillage optimization. Following this general aim, two well‐known optimization methods, namely the Genetic Algorithm (GA) and Simulated Annealing (SA), were compared using some standard medium size (10 and 15 piles) examples. The objective function was the maximal vertical reactive force at a support. Coordinates of piles were optimization variables. SA wins and was applied to real‐life problem (55 piles) by parallel computations performed using a powerful cluster. New element is comparison of SA with GA and application of SA to a practical problem of grillage optimization. Santrauka Straipsnio tikslas ‐ ištirti galimus rostverkiniu pamatu optimizavimo būdus. Siekiant šio tikslo du gerai žinomi optimizavimo metodai ‐ genetiniai algoritmai ir atkaitinimo modeliavimo algoritmas ‐ buvo palyginti vidutinio dydžio (10 ir 15 poliu) pavyzdžiams išspresti. Tikslo funkcija imama didžiausia atraminI poliaus reakcija. Projektavimo kintamieji ‐ poliu koordinatIs. Atkaitinimo modeliavimo metodas laimi, todel jis buvo pritaikytas praktiniam uždaviniui (55 poliai) spresti. Spresti buvo naudojamas klasteris. Naujumas ‐ genetiniu algoritmu palyginimas su atkaitinimo modeliavimo metodu bei atkaitinimo modeliavimo metodo pritaikymas sprendžiant praktini uždavini. Published Published Online: 14 Oct 2010 Reikšminiai žodžiai: rostverkai, atkaitinimo modeliavimas, globalus optimizavimas, baigtiniai elementai, genetiniai algoritma

Genetic Algorithm with Modified Crossover for Grillage Optimization

Modified genetic algorithm with special phenotypes' selection and crossover operators with default specified rules is proposed in this paper thus refusing the random crossover. The suggested crossover operator enables wide distribution of genes of the best phenotypes over the whole population. During selection and crossover, the best phenotypes of the newest population and additionally the genes of the best individuals of two previous populations are involved. The effectiveness of the modified algorithm is shown numerically on the real-life global optimization problem from civil engineering - the optimal pile placement problem under grillage-type foundations. This problem is a fair indicator for global optimization algorithms since the ideal solutions are known in advance but with unknown magnitudes of design parameters. Comparison of the proposed algorithm with 6 other stochastic optimization algorithms clearly reveals its advantages: at similar accuracy level the algorithm requires less time for tuning of genetic parameters and provides narrower confidence intervals on the results than other algorithms

Global optimization of trusses with a modified genetic algorithm

In this paper, a technology enabling the optimization of the topology of truss or frame structures with genetic algorithms is presented. It has been shown that due to a huge number of possible variants the global solution of similar problems with exhaustive search algorithms is feasible only for systems possessing small numbers of d.o.f. s (usually until 10 nodes). These problems can be solved in a reasonable time by genetic algorithms. The modified genetic algorithm for optimization of topology of truss systems is suggested, where the repair of the genotype, instead of some constraint is used. The solution of numerical examples with original software illustrates the efficiency of proposed technology; the global solutions are obtained in all cases. Santrauka Straipsnyje aprašyta technologija, kuri leidžia optimizuoti strypinių sistemų (santvarų) topologiją genetiniais algoritmais. Parodyta, kad dėl milžiniško galimų variantų skaičiaus globalaus sprendinio radimas perrinkimo algoritmais tokio tipo uždaviniams yra įmanomas tik sistemoms su mažu laisvės laipsnių skaičiumi (paprastai iki 10 mazgų). Tokios klasės uždaviniai gali būti išspręsti per priimtiną laiką genetiniais algoritmais. Strypinių sistemų topologijai optimizuoti yra pasiūlytas modifikuotas genetinis algoritmas, kuriame vietoje papildomų apribojimų naudota genotipo išgryninimo operacija. Skaitinių pavyzdžių sprendimas su originalia programine įranga rodo pateiktos technologijos efektyvumą. Visais atvejais gaunamas globalus sprendinys. First Published Online: 14 Oct 2010 Reikšminiai žodžiai: genetiniai algoritmai, strypinės sistemos, globalioji optimizacija, baigtinių elementų metodas

Grading the PVC material by solving a static inverse problem with genetic algorithm

When developing hi-tech medical equipment the exact technical properties of its components must be known. Such an equipment as volumetric pump uses peristaltic mechanism compressing an intro-vein set, which is made from PVC material. Since needed mechanical properties of PVC material are not provided by its manufacturer, we aimed at finding them by solving an inverse static problem. The inverse problem appeared to be an optimization problem, therefore Genetic algorithm was chosen as an optimizer, which also let to investigate the problem landscape. In addition, a study of mechanical properties of PVC material helped to calculate optimal stiffness of the springs used in the mentioned peristaltic mechanism

Global optimization of grillages with a hybrid genetic algorithm

Aim of the article is to suggest technology for optimization of pile positions in a grillage-type foundations seeking for the minimum possible pile quantity. The objective function to be minimized is the largest reactive force that arises in any pile under the action of statical loading. When piles of the grillage have different characteristics, the alternative form of objective function may be employed: the largest difference between vertical reaction and allowable reaction at any pile. Several different allowable reactions with a given number of such piles may be intended for a grillage. The design parameters for the problem are positions of the piles. The feasible space of design parameters is determined by two constraints. First, during the optimization process piles can move only along the connecting beams. Therefore, the two-dimensional grillage is “unfolded” to a one-dimensional construct, and the supports are allowed to range through this space freely. Second, the minimum allowable distance between two adjacent piles is introduced due to the specific capacities of pile driver.The initial data for the problem are the following: the geometrical scheme of the grillage, the cross-section and material data of connecting beams, minimum possible distance between adjacent supports, characteristics of piles, and the loading data given in the form of concentrated loads or trapezoidal distributed loadings. The results of solution are the required number of piles and their positions.The entire optimization problem is solved in two steps. First, the grillage is transformed to a one-dimensional construct, and the optimizer decides about a routine solution (i.e. the positions of piles in this construct). Second, the backward transformation returns the pile positions into the two-dimensional grillage, and the “black-box” finite element program returns the corresponding objective function value. On the basis of this value the optimizer predicts the new positions of piles, etc. The finite element program idealizes the connecting beams as the beam elements and the piles – as the finite element mesh nodes with a given boundary conditions in form of vertical and rotational stiffnesses. The optimizing program is an elitist genetic algorithm or a random local search algorithm. At the beginning of problem solution the genetic algorithm is employed. In the optimization problems under consideration, the genetic algorithms usually demonstrate very fast convergence at the beginning of solution and slow non-monotonic convergence to a certain local solution point after some number of generations. When the further solution with a genetic algorithm refuses to improve the achieved answer, i.e. a certain local solution is obtained; the specific random search algorithm is used. The moment, at which the transition from genetic algorithm to the local search is optimal, is sought in the paper analyzing the experimental data. Thus, the hybrid genetic algorithm that combines the genetic algorithm itself and the local search is suggested for the optimization of grillages. Globalusis rostverkinių pamatų optimizavimas hibridiniu genetiniu algoritmu Santrauka Straipsnio tikslas – sukurti technologiją polių padėtims rostverkiniuose pamatuose optimizuoti. Siekiama minimizuoti polių skaičių rostverke. Tikslo funkcija imama didžiausia atraminė poliaus reakcija, kuri optimizavimo metu yra minimizuojama. Iš pradžių uždavinys sprendžiamas genetiniu algoritmu, o kai toliau genetinį algoritmą naudoti tampa neefektyvu, gautas rezultatas gerinamas specifiniu atsitiktinės lokalios paieškos algoritmu. Analizuodami eksperimentinius duomenis autoriai bando nustatyti momentą, kada reikia pereiti nuo genetinio algoritmo naudojimo prie lokalios paieškos algoritmo, kad geresnis rezultatas būtų pasiekiamas per kuo trumpesnį laiką. Bendrą algoritmą, sujungiantį genetinį algoritmą su lokalios paieškos algoritmu, autoriai vadina hibridiniu genetiniu algoritmu. First Published Online: 16 May 2013 Reikšminiai žodžiai: globalusis optimizavimas, genetiniai algoritmai, poliniai pamata

Identification of material properties of composite materials

Present paper describes the facilities of composite material properties identification technique using specimen vibration tests, genetic algorithms, finite elements analysis and specimen shape optimization. In identification process the elastic constants in a numerical model is updated so that the output from the numerical code fits the results from vibration testing. Main problem analysed in this paper is that Poisson's ratio is the worst determined elastic characteristic due to its low influence on specimen eigenfrequencies. It is shown that it is possible to increase its influence by choosing specific test specimen characteristics (side aspect ratio, orthotropy angle, etc.) via optimization routine. In this paper are presented test results of some experiments wherein glass‐epoxy and carbon‐epoxy material properties were identified. Kompozitinių medžiagų tamprumo identifikavimas Santrauka. Straipsnyje  aprašomas  kompozitinių  medžiagų  tamprumo  charakteristikų  identifikavimo  metodas  naudojant  bandinių  vibracinius  bandymus, genetinius algoritmus, baigtinių elementų metodą ir bandinių formos optimizavimą. Identifikavimo metu tamprumo charakteristikos skaitmeniniame modelyje  yra  atnaujinamos  tol,  kol  skaitinio  eksperimento  rezultatai  nustatytu  tikslumu  sutampa  su  vibracinio  bandymo  rezultatais.  Šio  straipsnio pagrindinis  uždavinys  yra  padidinti  Puasono  koeficiento  identifikavimo  tikslumą,  kadangi  šis,  palyginti  su  kitų  tamprumo  charakteristikų identifikavimo  tikslumas  yra  menkas  dėl  ypač  mažos  koeficiento įtakos  bandinio  tikriniams  dažniams.  Darbe  parodyta,  kad įmanoma  padidinti Puasono  koeficiento įtaką  optimizavimo  procedūromis,  pasirenkant  konkrečias  bandinio  savybes  (kraštinių  proporcijas,  ortotropijos  kampą  ir  t.t.). Pateikiami keleto stiklo ir anglies pluoštais armuotų kompozitinių medžiagų tamprumo charakteristikų identifikavimo rezultatai. Reikšminiai žodžiai: medžiagų tamprumo identifikavimas, genetinis algoritmas, formos optimizavimas, vibracijos testas. First publish online: 14 Oct 201