1. Optimal design and competitive spans of timber floor joists based on multi-parametric MINLP optimizationPrimož Jelušič, Stojan Kravanja, 2022, original scientific article Abstract: 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.
Keywords: structural optimization, cost optimization, discrete optimization, mixed-integer nonlinear programming, MINLP, timber floor joists
Published in DKUM: 12.03.2025; Views: 0; Downloads: 1
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2. Optimal positioning of mobile cranes on construction sites using nonlinear programming with discontinuous derivativesMatjaž Hozjan, Uroš Klanšek, 2023, original scientific article Abstract: Mobile cranes represent conventional construction machinery that is indispensable for the erection of most prefabricated buildings, especially those containing heavy components. However, it is also common knowledge that the engagement of these machines has a significant influence on the environment, various social aspects of the construction process, and its economic benefits. Optimal positioning of the mobile crane on the construction site, primarily driven by the contractor’s interest to perform assembly operations with expensive machinery as effectively as possible, considerably reduces not only the costs of engaging such a machine but indirectly also its negative impacts on construction sustainability. This paper discusses an exact nonlinear model for the optimization task. The optimization model consists of a cost objective function that is subject to various duration and positioning constraints for the mobile crane, including bounds on its degrees of freedom of movement and stop positions. Because the model formulation includes discontinuous and non-smooth expressions, nonlinear programming with discontinuous derivatives (DNLP) was employed to ensure the optimal solution was reached. The model provides the mobile crane operator with exact key information that enables the complete and optimal assembly of the building structure under consideration. Additionally, the information gained on the optimal distribution of the mobile crane rental period to assembly operations allows for a detailed duration analysis of the entire process of building structure erection, which can be used for its further improvement. An application example is given in this study to demonstrate the advantages of the proposed approach.
Keywords: construction sustainability, mobile crane, nonlinear programming with discontinuous derivatives, optimization, positioning
Published in DKUM: 18.12.2023; Views: 403; Downloads: 27
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3. A practical method for the optimal design of continuous footing using ant-colony optimizationBoonchai Ukritchon, Suraparb Keawsawasvong, 2016, original scientific article Abstract: The objective of this paper is to present a practical method for the optimal design of a continuous footing subjected to vertical and horizontal loads. The design problem of finding the optimal size of footing as well as the minimum steel reinforcement is formulated in a nonlinear minimization form. The continuous footing is subjected to the vertical and horizontal loads acting on the top of the column. There are four design variables in the design problem, i.e., the width of the footing, the thickness of the footing, the soil-embedment depth, and the amount of steel reinforcement. The required geotechnical constraints include the bearing capacity, overturning, as well as global sliding and local sliding at the footing corners. Short-term stability and long-term stability are considered simultaneously in the same formulation. The structural constraints are enforced to control the shear force and bending moment within the section resistance. The formulation of the problem’s constraints leads to the nonlinear programming, whose objective function is to minimize the total cost of the footing material, including the concrete and steel reinforcement. The optimal solution is solved using the ant-colony optimization algorithm MIDACO. The proposed optimization method is demonstrated through the actual design of the footing for supporting a large machine moving on rails.
Keywords: optimal design, footing, stability, nonlinear programming, ant-colony optimization
Published in DKUM: 18.06.2018; Views: 1480; Downloads: 94
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4. The anchored pile wall optimization using NLP approachHelena Vrecl-Kojc, 2005, original scientific article Abstract: The type of a retaining structure as well as the structure configuration mainly depends on geological conditions. If geological, urban and other data allow an alternative, the costs should also be considered as an important factor. In geotechnical practise, pile walls are especially used in excavations, in the erection of traffic facilities and in the sanitation of landslides. This paper is aimed at presenting economical differences between cantilever and anchoring pile walls and the impact of different parameters on costs. The optimization method, which uses mathematical programming, gives an optimal solution to geometry, self-manufacturing costs, and other characteristics of the structure in a uniform optimization process. This paper presents the optimization process using the nonlinear programming (NLP) approach for the anchored pile wall. The application presented only serves to confirm the effectiveness of the proposed optimization method. Therefore, the retaining structure is situated in homogeneous non-cohesive soil at three different soil friction angles of 35°, 30° and 25°. The generalized analytical method, the USA method, which was first introduced by Bowles [3], isused in the application. The analysis of the results shows the impact of parameters, the main controlling factors, configuration geometry and savings. The optimal results allowed from 18 up to 47 per cent savings compared to the cantilever pile wall depending on ground and structure input data and the excavation depth.
Keywords: civil engineering, optimum design, retaining structures, USA analytical method, nonlinear programming
Published in DKUM: 16.05.2018; Views: 1419; Downloads: 78
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5. Mixed-integer nonlinear programming based optimal time scheduling of construction projects under nonconvex costsRok Cajzek, Uroš Klanšek, 2016, original scientific article Abstract: 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.
Keywords: extreme environments, construction management, discrete optimization, mixed-integer nonlinear programming, nonconvex costs, time scheduling
Published in DKUM: 12.07.2017; Views: 1577; Downloads: 422
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6. Cost optimal project schedulingUroš Klanšek, Mirko Pšunder, 2008, original scientific article Abstract: This paper presents the cost optimal project scheduling. The optimization was performed by the nonlinear programming approach, NLP The nonlinear total project cost objective function is subjected to the rigorous system of the activity preceden- ce relationship constraints, the activity duration constraints and the project duration constraints. The set of activity precedence relationship constraints was defined to comprise Finish-to-Start, Start-to-Start, Start-to-Finish and Finish-to-Finish precedence relationships between activities. The activity duration constraints determine relationships between minimum, maximum and possible duration of the project activities. The project duration constraints define the maximum feasible project duration. A numerical example is presented at the end of the paper in order to present the applicability of the proposed approach.
Keywords: project management, scheduling, optimization, nonlinear programming, NLP
Published in DKUM: 10.07.2015; Views: 1863; Downloads: 422
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7. Estimation of solid solubilities in supercritical carbon dioxide: Peng-Robinson adjustable binary parameters in the near critical regionMojca Škerget, Zorka Novak-Pintarič, Željko Knez, Zdravko Kravanja, 2002, original scientific article Abstract: The density dependence of the binary parameters of the Peng-Robinson equation of state in near the critical region was examined. Published solubility data of eight compounds in pure CO2 have been fitted to the Peng-Robinson equation in combination with one and two parameters van der Waals mixing rules and in combination with the three parameter density dependent mixing rule of Mohamed and Holder. A systematic study has been done to determine the influence of different terms in the mixing rules. In order to obtain density dependence, binary parameters were calculated for each isotherm at particular experimental point separately in the way to equalise experimental and calculated solubility data. The system was formulated as an equation-oriented model and solved by means of a nonlinear programming optimisation algorithm. For all compounds the binary interaction parameters thus obtained were found to vary strongly with pressure in the range from 75 bar to approximately 150 bar, i.e. near the critical end point (CEP) of the low temperature branch of the three phase solid-liquid-gas (SLG) curve. At higher pressures, the parameter is practically independent on pressure. In general, for the systems investigated, kij increases linearly with increasing density and reaches a constant value at higher densities in the range from 700 to 800 kg/m3, depending on the system under investigation.
Keywords: solid liquid equilibria, equation of state, mixing rules, binary parameters, near critical region, nonlinear programming, thermodynamic model, supercritical fluids, CO2, solubility
Published in DKUM: 01.06.2012; Views: 2331; Downloads: 121
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8. A strategy for MINLP synthesis of flexible and operable processesZorka Novak-Pintarič, Zdravko Kravanja, 2004, original scientific article Abstract: Abstract This paper presents a sequential two-stage strategy for the stochastic synthesis of chemical processes in which flexibility and static operability (the ability to adjust manipulated variables) are taken into account. In the first stage, the optimal flexible structure and optimal oversizing of the process units are determined in order to assure feasibility of design for a fixed degree of flexibility. In the second stage, the structural alternatives and additional manipulative variables are included in the mathematical model in order to introduce additional degrees of freedom for efficient control. The expected value of the objective function is approximated in both stages by a novel method, which relies on optimization at the central basic point (CBP). The latter is determined by a simple set-up procedure based on calculations of the objective functionćs conditional expectations for uncertain parameters. The feasibility is assured by simultaneous consideration of critical vertices. The important feature of the proposed stochastic model is that its size depends mainly on the number of design variables and not on the number of uncertain parameters. The strategy is illustrated by two examples for heat exchanger network synthesis.
Keywords: chemical processing, process synthesis, MINLP, mixed integer nonlinear programming, flexibility, operability, controllability, steady state model
Published in DKUM: 01.06.2012; Views: 2622; Downloads: 99
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9. An integrated strategy for the hierarchical multilevel MINLP synthesis of overall process flowsheets using the combined synthesis/analysis approachNataša Iršič Bedenik, Bojan Pahor, Zdravko Kravanja, 2004, original scientific article Abstract: This paper describes an integrated strategy for a hierarchical multilevel mixed-integer nonlinear programming (MINLP) synthesis of overall process schemes using a combined synthesis/analysis approach. The synthesis is carried out by multilevel-hierarchical MINLP optimization of the flexible superstructure, whilst the analysis is performed in the economic attainable region (EAR). The role of the MINLP synthesis step is to obtain a feasible and optimal solution of the multi-D process problem, and the role of the subsequent EAR analysis step is to verify the MINLP solution and in the feedback loop to propose any profitable superstructure modifications for the next MINLP. The main objective of the integrated synthesis is to exploit the interactions between the reactor network, separator network and the remaining part of the heat/energy integrated process scheme.
Keywords: multilevel MINLP, MINLP synthesis, attainable region, economic attainable region, concentration attainable region, continous stirred tank reactor, plug flow reactor, recycle reactor, nonlinear programming, mixed integer nonlinear programme
Published in DKUM: 01.06.2012; Views: 2805; Downloads: 112
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10. MINLP optimization of a single-storey industrial steel buildingTomaž Žula, Zdravko Kravanja, Stojan Kravanja, 2008, original scientific article Abstract: The paper presents the topology and standard sizes optimization of a single-storey industrial steel building, made from standard hot rolled I sections. The structure consists of main portal frames, connected with purlins. The structural optimization is performed by the Mixed-Integer Non-linear programming approach (MINLP). The MINLP performs a discrete topology and standard dimension optimization simultaneously with continuous parameters. Since the discrete/continuous optimization problem of the industrial building is non-convex and highly non-linear, the Modified Outer- Approximation/Equality-Relaxation (OA/ER) algorithm has been used for the optimization. Alongside the optimum structure mass, the optimum topology with the optimum number of portal frames and purlins as well as all standard cross-section sizes have been obtained. The paper includes the theoretical basis and a practical example with the results of the optimization.
Keywords: civil engineering, topology optimization, sizing optimization, nonlinear programming, MINLP
Published in DKUM: 31.05.2012; Views: 2545; Downloads: 70
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