1. Optimal design and competitive spans of timber floor joists based on multi-parametric MINLP optimizationPrimož Jelušič, Stojan Kravanja, 2022, izvirni znanstveni članek Opis: This study investigates the optimization of the design of timber floor joists, taking into
account the self-manufacturing costs and the discrete sizes of the structure. This non-linear and
discrete class of optimization problem was solved with the multi-parametric mixed-integer non-linear
programming (MINLP). An MINLP optimization model was developed. In the model, an accurate
objective function of the material and labor costs of the structure was subjected to design, strength,
vibration and deflection (in)equality constraints, defined according to Eurocode regulations. The
optimal design of timber floor joists was investigated for different floor systems, different materials
(sawn wood and glulam), different load sharing systems, different vertical imposed loads, different
spans, and different alternatives of discrete cross-sections. For the above parameters, 380 individual
MINLP optimizations were performed. Based on the results obtained, a recommended optimal
design for timber floor joists was developed. Engineers can select from the recommendations the
optimal design system for a given imposed load and span of the structure. Economically suitable
spans for timber floor joists structures were found. The current knowledge of competitive spans for
timber floor joists is extended based on cost optimization and Eurocode standards.
Ključne besede: structural optimization, cost optimization, discrete optimization, mixed-integer nonlinear programming, MINLP, timber floor joists
Objavljeno v DKUM: 12.03.2025; Ogledov: 0; Prenosov: 0
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2. The MINLP approach to topology, shape and discrete sizing optimization of trussesSimon Šilih, Zdravko Kravanja, Stojan Kravanja, 2022, izvirni znanstveni članek Opis: The paper presents the Mixed-Integer Non-linear Programming (MINLP) approach to the
synthesis of trusses. The solution of continuous/discrete non-convex and non-linear optimization
problems is discussed with respect to the simultaneous topology, shape and discrete sizing optimization of trusses. A truss MINLP superstructure of different topology and design alternatives
has been generated, and a special MINLP model formulation for trusses has been developed. In the
optimization model, a mass objective function of the structure has been defined and subjected to
design, load and dimensioning constraints. The MINLP problems are solved using the Modified
Outer-Approximation/Equality-Relaxation (OA/ER) algorithm. Multi-level MINLP strategies are introduced to accelerate the convergence of the algorithm. The Modified Two-Phase and the Sequential
Two-Phase MINLP strategies are proposed in order to solve highly combinatorial topology, shape
and discrete sizing optimization problems. The importance of local buckling constraints on topology
optimization is also discussed. Some simple numerical examples are shown at the end of the paper to
demonstrate the suitability and efficiency of the proposed method.
Ključne besede: structural synthesis, topology optimization, discrete sizing optimization, mixed-integer non-linear programming, MINLP, modified OA/ER algorithm, multi-level MINLP strategies, steel structures, trusses
Objavljeno v DKUM: 11.03.2025; Ogledov: 0; Prenosov: 2
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3. Innovative approaches to wear reduction in horizontal powder screw conveyors : a design of experiments-guided numerical studyMarko Motaln, Tone Lerher, 2024, izvirni znanstveni članek Opis: Numerical simulations play a vital role in the modern engineering industry, especially when faced with interconnected challenges such as particle interactions and the structural integrity of conveyor systems. This article focuses on the handling of materials and emphasizes the importance of using parametric numerical analysis to improve efficiency, reduce wear, and enhance the structural integrity of horizontal screw conveyors. Through the utilization of the Design of Experiments, we systematically investigated critical parameters such as screw pitch, clearance, wear, rotational velocity, and additional structural factors. This examination was carried out within a well-defined parametric framework, utilizing a combination of software tools provided by the Ansys suite and Minitab. The findings demonstrate the effectiveness of the Design of Experiments analysis in achieving improved performance and provide valuable insights for engineers and researchers involved in the design of conveyor systems. Furthermore, this comprehensive approach clarifies how conveyor systems respond to changes in parameters and highlights the complex interaction between transported particles and the conveyor system. We present a detailed analysis that clarifies the complex relationships and dependencies among different parameters, providing engineers and researchers with valuable insights. By understanding the interactions of these factors, the methodology provides not only results but also a strategic framework for advancing conveyor system design and engineering practices.
Ključne besede: discrete element method, design optimization, horizontal screw conveyors, parametric study, conveying equipment, bulk handling, bulk solids, abrasive wear, screw conveyor, FEA, performance analysis
Objavljeno v DKUM: 09.04.2024; Ogledov: 275; Prenosov: 50
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4. Discrete optimization with fuzzy constraintsPrimož Jelušič, Bojan Žlender, 2017, izvirni znanstveni članek Opis: The primary benefit of fuzzy systems theory is to approximate system behavior where analytic functions or numerical relations do not exist. In this paper, heuristic fuzzy rules were used with the intention of improving the performance of optimization models, introducing experiential rules acquired from experts and utilizing recommendations. The aim of this paper was to define soft constraints using an adaptive network-based fuzzy inference system (ANFIS). This newly-developed soft constraint was applied to discrete optimization for obtaining optimal solutions. Even though the computational model is based on advanced computational technologies including fuzzy logic, neural networks and discrete optimization, it can be used to solve real-world problems of great interest for design engineers. The proposed computational model was used to find the minimum weight solutions for simply-supported laterally-restrained beams.
Ključne besede: uncertainty, discrete optimization, neuro-fuzzy technique, structural optimization
Objavljeno v DKUM: 09.08.2017; Ogledov: 1474; Prenosov: 380
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5. On vulnerability measures of networksRija Erveš, Darja Rupnik Poklukar, Janez Žerovnik, 2013, objavljeni znanstveni prispevek na konferenci Opis: As links and nodes of interconnection networks are exposed to failures, one of the most important features of a practical networks design is fault tolerance. Vulnerability measures of communication networks are discussed including the connectivities, fault diameters, and measures based on Hosoya- Wiener polynomial. An upper bound for the edge fault diameter of product graphs is proved.
Ključne besede: discrete optimization, communication network, vulnerability
Objavljeno v DKUM: 21.07.2017; Ogledov: 1112; Prenosov: 115
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6. Mixed-integer nonlinear programming based optimal time scheduling of construction projects under nonconvex costsRok Cajzek, Uroš Klanšek, 2016, izvirni znanstveni članek Opis: Optimal project scheduling under nonconvex time-cost relations represents a challenging problem in construction management. The nonconvex time-cost relations may appear in a construction project when several different duration options are available for its activities due to alternative technological processes enabled for their realization or wide accessibility of production resources. The source of nonconvexity of the project scheduling optimization problem can also be the project penalty- or bonus-duration relations arranged within the construction contract. The aim of this paper is to present the mixed-integer nonlinear programming (MINLP) based optimal time scheduling of construction projects under nonconvex costs. For this purpose, the MINLP model was developed and applied. A numerical example from literature and an example of construction project time-cost trade-off analysis under practical nonconvex penalty function are given in the paper to demonstrate advantages of MINLP optimization. The example from literature first presented the capability of the MINLP approach to obtain the optimal solution for difficult, highly combinatorial nonconvex discrete project scheduling problem. Thereupon, the following example revealed that the optimal project time-cost curve may take very nonuniform shape on account of discrete nature of activity direct cost options and nonconvex relation between project duration and total cost. In this way, the presented study intends to provide practitioners with new information from the field of optimization techniques for project scheduling as well as an alternative view on performance of total cost when project duration is changed.
Ključne besede: extreme environments, construction management, discrete optimization, mixed-integer nonlinear programming, nonconvex costs, time scheduling
Objavljeno v DKUM: 12.07.2017; Ogledov: 1577; Prenosov: 420
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7. Chinese postman problem with priorities (high cost of delays)Tomaž Kramberger, Janez Žerovnik, 2008, objavljeni znanstveni prispevek na konferenci Opis: Several real-world problems, such as street sweeping, mail delivery, solid waste collection, salt gritting and snow plowing can be modeled as Chinese postman problems with some additional constraints. In the paper we present a formal definition of the special case of CPP problem where a subset of priority nodes are given that must be visited as soon as possible, i.e. the cost of delays is much bigger than the cost of additional edges traversed. A heuristical algorithm is proposed which gives near optimal feasible solutions.
Ključne besede: combinatorial optimization, discrete optimization
Objavljeno v DKUM: 05.06.2012; Ogledov: 1658; Prenosov: 48
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8. The multilevel MINLP optimization approach to structural synthesis: the simultaneous topology, material, standard and rounded dimension optimizationStojan Kravanja, Simon Šilih, Zdravko Kravanja, 2005, izvirni znanstveni članek Opis: The paper describes the simultaneous topology, material, standard and rounded dimension optimization of mechanical structures, performed by the Mixed-Integer Non-linear Programming (MINLP) approach. Beside the generation of an MINLP mechanical superstructure, the development of a general multilevel MINLP formulation for a mechanical superstructure is presented. The consideration of the discrete materials as well as standard and particularly rounded dimensions in structural synthesis significantly increases the combinatorics of the discrete optimization, which as a result may become too difficult to solve. A Linked Multilevel Hierarchical Strategy (LMHS) has been introduced for the solving of such large combinatorial problems. In order to decrease the effect of non-convexities, the Modified Outer-Approximation/Equality-Relaxation (OA/ER) algorithm has been applied. Four numerical examples of different complexities are presented to illustrate the proposed multilevel MINLP optimization approach: the optimization of two steel trusses, a composite I beam and a hydraulic steel roller gate Intake gate, erected in Aswan II, Egypt.
Ključne besede: structural optimization, structural synthesis, MINLP, topology opitmization, material optimization, discrete variable optimization, multilevel MINLP strategy, truss, composite beam, roller gate
Objavljeno v DKUM: 01.06.2012; Ogledov: 2803; Prenosov: 109
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