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1

A new geometric approach to multiobjective linear programming problems

Kaci Mustapha, Radjef Sonia

Mathematica Applicanda

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2023

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Vol. 51, no. 1

3--12

EN

This paper is a follow-up to a previous work where we developed a new geometric approach to sensitivity analysis. In this paper, we present a simple method to determine whether a given multiobjective linear programming problem (MOLPP) has an ideal solution (i.e. all of the objective functions are optimized simultaneously) without having to calculate the optimal value of each objective function. First, we divide the space of linear forms into a finite number of sets based on a fixed convex polygonal subset of R2 using an equivalency relationship. All the elements from a given equivalency class have the same optimal solution. Next, we characterize the equivalence classes of the quotient set using a geometric approach to sensitivity analysis. Finally, a numerical example is given to illustrate the method.

PL

W tym artykule przedstawiamy nową metodę rozwiązywania problemów programowania liniowego z wieloma celami (MOLPP), która eliminuje potrzebę obliczania optymalnej wartości każdej funkcji celu. Metoda ta jest kontynuacją naszych wcześniejszych prac dotyczących analizy wrażliwości, gdzie opracowaliśmy nowe podejście geometryczne. Pierwszym krokiem naszego podejścia jest podział przestrzeni form liniowych na skończoną liczbę zbiorów opartych na stałym wypukłym podzbiorze wielokąta R2. Dokonujemy tego za pomocą relacji równoważności, która zapewnia, że wszystkie elementy z danej klasy równoważności mają takie same rozwiązanie optymalne. Następnie charakteryzujemy klasy równoważności zbioru ilorazowego za pomocą podejścia geometrycznego do analizy wrażliwości. Ten krok jest kluczowy w identyfikacji rozwiązania idealnego dla MOLPP. Korzystając z tego podejścia, możemy określić, czy dana MOLPP ma rozwiązanie idealne, bez konieczności obliczania optymalnej wartości każdej funkcji celu. Jest to znacząca poprawa w stosunku do istniejących metod, ponieważ znacznie zmniejsza złożoność obliczeniową i czas wymagany do rozwiązania MOLPP. Aby zilustrować naszą metodę, przedstawiamy numeryczny przykład, który dowodzi jej skuteczności. Nasza metoda jest prosta, ale potężna i może być łatwo zastosowana do szerokiego zakresu MOLPP. Niniejsza praca przyczynia się do dziedziny optymalizacji poprzez przedstawienie nowego podejścia do rozwiązywania MOLPP, które jest wydajne, skuteczne i łatwe do zaimplementowania.

2

The Method for Assessing the Impact of Variable Coal Demand on the Efficiency of Mine Operations

Fuksa Dariusz

Inżynieria Mineralna

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2023

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no. 1

267--273

EN

The method presented in the article is based on Monte Carlo simulation and involves studying the impact of random demand fluctuations on the efficiency of mines and mine groups (companies). For random demand fluctuations, a normal distribution is assumed, and the analysis variants present-ed include: • Adopting the mean and variance values based on retrospective data, • Considering the most probable forecast error resulting from predictive formulas, • Taking into account correlated changes in demand. The results obtained are presented in the form of histograms of the degree of operational lever-age. These histograms allow for predicting how the degree of operational leverage of mines will develop, as well as estimating the direction and probability of these changes. The developed and veri-fied sensitivity analysis using real examples constitutes a useful element in rationalizing decision-making processes.

PL

Zaprezentowana w artykule metoda oparta jest na symulacji Monte Carlo i obejmuje badanie wpływu wahań losowych zapotrzebowania na efektywność kopalń oraz ich grup (spółek). Dla losowych wahań zapotrzebowania przyjęto rozkład normalny, a przedstawione warianty analizy uwzględniają: • przyjęcie wartości oczekiwanej i dyspersji według danych retrospektywnych; • przyjęcie najbardziej prawdopodobnego błędu prognozy wynikającego z formuł predykcyjnych; • uwzględnienie skorelowanych zmian zapotrzebowania. Uzyskane wyniki przedstawiono w postaci histogramów stopnia dźwigni operacyjnej. Pozwalają one przewidywać, jak będzie kształtował się stopień dźwigni operacyjnej kopalń, jak również umożliwia oszacować, w którym kierunku zmiany te będą postępować i z jakim prawdopodobieństwem. Opracowana i zweryfikowana na realnych przykładach analiza wrażliwości stanowi przydatny element racjonalizacji procesów decyzyjnych.

3

Choice of the p-norm for high level classification features pruning in modern convolutional neural networks with local sensitivity analysis

Jeczmionek Ernest, Kowalski Piotr A.

International Journal of Applied Mathematics and Computer Science

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2023

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Vol. 33, no. 4

663--672

EN

Transfer learning has surfaced as a compelling technique in machine learning, enabling the transfer of knowledge across networks. This study evaluates the efficacy of ImageNet pretrained state-of-the-art networks, including DenseNet, ResNet, and VGG, in implementing transfer learning for prepruned models on compact datasets, such as FashionMNIST, CIFAR10, and CIFAR100. The primary objective is to reduce the number of neurons while preserving high-level features. To this end, local sensitivity analysis is employed alongside p-norms and various reduction levels. This investigation discovers that VGG16, a network rich in parameters, displays resilience to high-level feature pruning. Conversely, the ResNet architectures reveal an interesting pattern of increased volatility. These observations assist in identifying an optimal combination of the norm and the reduction level for each network architecture, thus offering valuable directions for model-specific optimization. This study marks a significant advance in understanding and implementing effective pruning strategies across diverse network architectures, paving the way for future research and applications.

4

Analysis of seismic damage features of HSR CRTS III SBT simply supported bridge system

Liu Lili, Jiang Lizhong, Zhou Wangbao, Liu Xiang, Feng Yulin

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

art. no. e76, 2023

EN

In order to investigate the seismic damage features of high-speed railway (HSR) China Railway Track Slab III (CRTSIII) slab ballastless track (SBT) simply supported bridge systems, a nonlinear finite element model of HSR CRTS III SBT simply supported bridge system was established. The damage mechanisms and peak and residual displacement distribution patterns of their critical components under seismic action were investigated. In addition, the sensitivity of rail irregularity to the seismic residual deformation in such critical components was analyzed. The results indicated that midspan piers and bearings are more susceptible to failure than side span piers and bearings, and fixed bearings are more prone to failure than sliding bearings. Fastener and isolation layer deformation increases sharply on both sides of the beam joint. Rail deformation exhibits a parabolic shape that is large in the middle and small at both ends. The critical components of even-span and odd-span systems have significantly different patterns of seismic deformation distribution. Rail irregularity is mainly attributable to bearing residual deformation, pier residual deformation, and fastener residual deformation successively, and the superposition of bearing residual deformation and pier residual deformation is approximately equivalent to rail deformation. Rail irregularity is most sensitive to pier deformation, followed successively by bearing and fastener deformation.

5

A comparative study of the sensitivity analysis for systems with viscoelastic elements

Łasecka-Plura Magdalena

Archive of Mechanical Engineering

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2023

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LXX, nr 1

5--25

EN

This paper discusses the different methods used for calculating first- and second-order sensitivity: the direct differentiation method, the adjoint variables method, and the hybrid method. The solutions obtained allow determining the sensitivity of dynamic characteristics such as eigenvalues and eigenvectors, natural frequencies, and nondimensional damping ratios. The methods were applied for analyzing systems with viscoelastic damping elements, whose behavior can be described by classical and fractional rheological models. However, the derived formulas are general and can also be applied to systems with damping elements described by other models. Their advantage is a compact and easy to code form. The paper also presents a comparison of the computational costs of the discussed methods. The correctness of all the proposed methods has been illustrated with numerical examples.

6

Mathematical modeling and analysis of mycobacterium tuberculosis transmission in humans with hospitalization and reinfection

Mustapha Umar T., Idris Buhari, Musa Salihu S., Yusuf Abdullahi

Journal of Applied Mathematics and Computational Mechanics

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2022

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Vol. 21, nr 1

55--66

EN

Tuberculosis (TB), a serious public health infection that mainly affects the lungs, is caused by bacteria (Mycobacterium tuberculosis, TB). This research is designed and analyzed using a compartmental modelling approach to study the transmission dynamics of TB with different stages of infection. Qualitative analysis of the proposed model reveals that the model exhibits two equilibrium points: the disease-free equilibrium point (DFE) and the endemic equilibrium (EE). The basic reproduction number (R0 ) is determined using the next generation matrix technique, and stability analysis is carried out to show whether the disease can persist or die out in population. Further analysis of the model shows that the EE is globally asymptotically stable (GAS) when R0 > 1. With the aid of the forward sensitivity index method, we determine the most sensitive parameters of the model to control the spread of TB infection effectively. Our analysis shows that treatment (medication) and campaign awareness coupled with other key control measures, could help maintain the spread of MTB infection in human geographical boundaries.

7

Using Bayesian methods in the task of modeling the patients' pharmacoresistance development

Voronenko Mariia A., Zhunissova Ulzhalgas M., Smailova Saule S., Lytvynenko Luidmila N., Savina Nataliia B., Mulesa Pavlo P., Lytvynenko Volodymyr

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

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2022

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T. 12, nr 2

77--82

EN

In this paper, we propose a methodology for using static Bayesian networks (BN) in modeling the development of pharmacoresistance in patients with a diagnosis of epilepsy. Methods for constructing the structure of a static BN, their parametric training, validation, sensitivity analysis and “What-if” scenario analysis are considered. The model was designed in collaboration with expert doctors, as well as expert pharmacologists in the selection and quantification of input and output variables.

PL

W niniejszej pracy zaproponowano metodologię wykorzystania statycznych sieci bayesowskich (BN) w modelowaniu rozwoju farmakooporności u pacjentów z rozpoznaniem padaczki. Rozważane są metody konstruowania struktury statycznej BN, jej parametrycznego treningu, walidacji, analizy wrażliwości i analizy scenariuszy "co-jeśli". Model został zaprojektowany we współpracy z ekspertami – lekarzami, a także ekspertami – farmakologami w zakresie doboru i kwantyfikacji zmiennych wejściowych i wyjściowych.

8

Sensitivity analysis for a hybrid off-grid PV/DG/BATT system for the electrification of rural communities

Pedro Pazmiño-Zapatier, Juan Lata-García

Diagnostyka

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2022

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Vol. 23, No. 1

art. no. 2022103

EN

One of the pillars for the development of isolated communities is electricity, however the implementation of conventional networks is limited as a result of the difficulties of the terrain. This paper aims to analyze the technical-economic feasibility of implementing a hybrid off-grid solar photovoltaics (PV)/diesel generator (DG)/battery (BATT) based power system for the electrification of rural communities, using a case study in Bameno, Ecuador. The simulation and optimization of the system is done using Hybrid Optimization of Multiple Energy Resources (HOMER) software. As a result, the optimal sizing is composed of 23 kW PV modules, a DG 27 kW, 88.4 kWh storage batteries and 9.4 kW converter system, obtaining a levelized cost of energy (LCOE) of 0.359 $/kWh. After the optimization is executed, a sensitivity analysis is performed to establish the effects of the variations of solar radiation, demand, fuel, and component costs on the system. The PV/DG/BATT system is considered the best choice for fuel prices up to $0.83 per liter. For higher values the optimal system is the PV/BATT. It is also established that the LCOE is mostly affected by the cost of technological components, followed by variations in solar radiation and demand.

9

A new geometric approach for sensitivity analysis in linear programming

Kaci Mustapha, Radjef Sonia

Mathematica Applicanda

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2021

|

Vol. 49, no. 2

145--157

EN

The article presents a geometric method of sensitivity analysis in linear programming, which is a computationally practical way to study the behavior of an optimal solution to a linear programming problem. In this approach, we improve the implementation of the constraints, and then we formulate the problem of linear programming geometrically. In this way, we obtain a new, equivalent geometrical formulation of the problem for the sensitivity analysis using the concepts of affine geometry. It consists in entering the objective function coefficient vector in the polar coordinates and determining all angles for which the solution remains unchanged. The method is presented in detail and illustrated by a numerical example.

PL

W niniejszym artykule przedstawiamy nowe podejście geometryczne do analizy wrażliwości w programowaniu liniowym, które jest praktyczne obliczeniowo. Pozwala analizować zachowania optymalnego rozwi¡zania problemu programowania liniowego przy zmianach danych zadania. Najpierw ustalamy dopuszczalną dziedzinę (naprawiamy ograniczenia liniowe). Następnie geometrycznie formułujemy problem programowania liniowego. Nast¦pnie podajemy nowe równoważne sformułowanie geometryczne problemu analizy wrażliwości przy użyciu pojęć geometrii afinicznej. Piszemy wektor współczynników funkcji celu we współrzędnych biegunowych i wyznaczamy wszystkie kąty, dla których rozwiązanie pozostaje niezmienione. Proponowane podejście zostało szczegółowo przedstawione i zilustrowane przykładem liczbowym.

10

Trend of the compensation policy and tactics for the development of mineral resources in China

Wang Yiqiao, Gao Yongtao, Li Guoqing, Zhou Yu, Li Jianhui

Gospodarka Surowcami Mineralnymi

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2021

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T. 37, z. 4

29--54

EN

China has been building an ecological compensation system to eliminate the contradiction between economic development and ecological protection. Aiming at conflicts of interest in the implementation of an ecological compensation policy for China’s mineral resource development, this study established a tripartite evolutionary game model to simulate the ecological compensation scenario and determined the evolutionary stable strategy (ESS) under different scenarios; it uses numerical simulation to analyse the strategy evolution process of stakeholders and the influence of parameter changes on each strategy. The results show that there is an optimal ESS for ecological compensation for mineral resource development, which condition is C1 < Ti + F1, P < F2, C2 < R1 + R2. The initial cooperation intentions of stakeholders directly affected the final stable state. Local governments are most affected by the input cost, and mining enterprises are most affected by the supervision of the central government. Punishment can effectively restrain the behavior of local governments and mining enterprises and promote the implementation of ecological compensation systems. In addition, the higher supervision cost of the central government, the longer time it will take for the stakeholders to reach the stable state. Finally, reducing the payment amount for ecological compensation will not affect the trend in environmental improvement; in contrast, it is conducive to the preservation of enterprises’ strength, economic development and ecological environment protection. The main findings of this study can help secure coordinate between the stakeholders in conflict and jointly formulate appropriate ecological compensation policy.

PL

Artykuł dotyczy bardzo ważnego zadania, jakim jest pogodzenie celów ekonomicznych i środowiskowych w przemyśle wydobywczym Chin. Autorzy budują model uwzględniający interesy firm górniczych, samorządów i władz centralnych, wykorzystują do tego teorię gier. W ramach tych badań ustanowiono trójstronny ewolucyjny model gry do symulacji scenariusza kompensacji ekologicznej i określono strategię stabilną ewolucyjnie ESS (Evolutionary Stable Strategy) dla różnych scenariuszy; wykorzystując symulację numeryczną do analizy procesu ewolucji strategii interesariuszy oraz wpływu zmian parametrów na każdą strategię. Wyniki pokazują, że istnieje optymalny ESS dla ekologicznej kompensacji wykorzystania zasobów surowców mineralnych, którego stan to C1 < Ti + F1, P < F2, C2 < R1 + R2 (określenie parametrów podano w tabeli 2). Początkowe zamiary współpracy interesariuszy bezpośrednio wpłynęły na ostateczny stan stabilności. Samorządy lokalne są najbardziej dotknięte kosztami kapitałowymi, a przedsiębiorstwa górnicze – kosztami nadzoru rządu centralnego. Karanie może skutecznie powstrzymywać zachowania samorządów i przedsiębiorstw górniczych oraz promować wdrażanie systemów rekompensat ekologicznych. Dodatkowo, im wyższy koszt nadzoru ze strony rządu centralnego, tym dłuższy czas osiągnięcia stanu stabilnego przez interesariuszy. Wreszcie, zmniejszenie kwoty płatności na kompensację ekologiczną nie wpłynie na trend poprawy stanu środowiska, natomiast sprzyja zachowaniu siły przedsiębiorstw, rozwojowi gospodarczemu i ochronie środowiska przyrodniczego. Główne wnioski z tego badania mogą być przydatne w zapewnieniu koordynacji między zainteresowanymi stronami w konflikcie i wspólnym sformułowaniu odpowiedniej polityki kompensacji ekologicznej.

11

Koncepcja przebudowy węzła drogowego Golden Glades w Miami na Florydzie. Cz. 2, Analiza wielokryterialna, wrażliwości i przepustowości

Tkaczyk Maciej, Kowalski Karol, Dąbkowski Paweł

Drogownictwo

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2021

|

nr 4

101--113

PL

Analiza wielokryterialna jest często stosowaną metodą wyboru optymalnego rozwiązania przedsięwzięcia. W prezentowanej analizie zastosowano cztery kryteria: funkcjonalno-ruchowe, kosztowe, środowiskowe i społeczne oraz możliwości etapowania. Analiza wrażliwości jest prostą techniką analityczną pozwalającą na badanie wpływu zmiany kryteriów analizy wielokryterialnej na ostateczny wynik wyboru koncepcji. Analiza odpowiada na pytanie czy wybrany wariant przedsięwzięcia jest „stabilny”, tzn. odporny na zmianę wcześniej założonych kryteriów. Analiza przepustowości pozwala ustalić poziom swobody ruchu i wyznaczyć liczbę pasów ruchu.

EN

Multi-criteria analysis is a common method of choosing the optimal solution for specific project. Four criteria were used here: functional-utility, cost, environmental and social, and staged capabilities. Sensitivity analysis is a simple analytical technique that allows to study the impact of changing the criteria of multi-criteria analysis on the final outcome of the concept selection. It answers the question whether the chosen option of the project is “stable”, that is resistant to the change of previously established criteria. Capacity analysis allows to determine the level of service and the number of lanes.

12

Optimized multi layer perceptron artificial neural network based fault diagnosis of induction motor using vibration signals

Khoualdia Tarek, Lakehal Abdelaziz, Chelli Zoubir, Khoualdia Kais, Nessaib Karim

Diagnostyka

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2021

|

Vol. 22, No. 1

65--74

EN

Installations and the detection of their faults has become a major challenge. In order to develop a reliable approach for monitoring and diagnosis faults of these components, a test rig was mounted. In this article, a Multi Layer Perceptron (MLP) Artificial Neural Network (ANN) has been structured and optimized for online monitoring of induction motors. The input layer of our ANN used eight indicators calculated from the collected time signals and which represent the different states of the motor (Healthy, broken rotor bars, bearing fault and Misalignment) and the output layer used a codified matrix. However, based on L27 Taguchi design, the architecture for the hidden layers of our network is chosen, with the use of the LevenbergMarquardt learning algorithm. Garson's algorithm and connection weight approach showed that there's a great sensitivity of the crest factor, the kurtosis and the variance on the effectiveness of our diagnostic system. Consequently, the obtained results are capable of detecting faults in the induction motor under different operating conditions.

13

Research on stability and sensitivity of the rotating machines with overhung rotors to lateral vibrations

Szolc Tomasz, Konowrocki Robert

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2021

|

Vol. 69, nr 6

art. no. e137987

EN

The rotating machines with overhung rotors form a broad class of devices used in many types of industry. For this kind of rotor machine in the paper, there is investigated an inf luence of dynamic and static unbalance of a rotor, parallel and angular misalignments of shafts, and inner anisotropy of rigid couplings on system dynamic responses. The considerations are performed through a hybrid structural model of the machine rotor-shaft system, consisting of continuous beam finite elements and discrete oscillators. Numerical calculations are carried out for parameters characterizing a heavy blower applied in the mining industry. The main goal of the research is to assess the sensitivity of the imperfections mentioned above on excitation severity of rotor-shaft lateral vibrations and motion stability of the machine in question.

14

Sensitivity Analysis for Influence Parameters of Rail Corrugation Characteristics in Metro Straight Section

Wang Z., Lei Z.

Advances in Science and Technology. Research Journal

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2021

|

Vol. 15, no 4

110--117

EN

Based on the theory of friction self-excited vibration and the measured data of rail corrugation, the cause of rail corrugation in metro straight section was analyzed. Then, using the stochastic finite element method, the sensitivity of each parameter to rail corrugation was studied by selecting the elastic modulus E1 and density ρ1 of the wheel-rail material, the elastic modulus E2 and density ρ2 of the track slab material, the wheel-rail coefficient of friction f, the fastener vertical stiffness K and vertical damping C, the wheel-rail longitudinal relative slip s as the random parameters. The results show that under the support of Cologne egg fastener track, the characteristic frequency of friction self-excited vibration of wheel-rail system is close to the characteristic frequency of measured corrugation, indicating that the occurrence of rail corrugation is related to the friction self-excited vibration of wheel-rail system under the condition of saturated creep force. The parameter sensitivity analysis illustrates that the influence degree of each random parameter on the real part αi of complex eigenvalue is E1>ρ1>C>E2>ρ2>f>K>s in turn. E1, C and s are positively correlated with the real part αi of complex eigenvalue, while the remaining 5 parameters are negatively correlated with the real part αi of complex eigenvalue. Therefore, appropriate decrease of E1, C and s, and increase of ρ1, E2, ρ2, f and K can play a positive role in the control of rail corrugation.

15

Reliability-based safety evaluation of the BISTOON historic masonry arch bridge

Pouraminian Majid, Pourbakhshian Somayyeh, Noroozinejad Farsangi Ehsan, Berenji Sevil, Keyani Borujeni Salman, Moosavi Asl Mirhasan, Mohammad Hosseini Mehdi

Civil and Environmental Engineering Reports

|

2020

|

Vol. 30, no. 1

87--110

EN

This research examines the probabilistic safety assessment of the historic BISTOON arch bridge. Probabilistic analysis based on the Load-Resistance model was performed. The evaluation of implicit functions of load and resistance was performed by the finite element method, and the Monte-Carlo approach was used for experiment simulation. The sampling method used was Latin Hypercube. Four random variables were considered including modulus of elasticity of brick and in filled materials and the specific mass of brick and infilled materials. The normal distribution was used to express the statistical properties of the random variables. The coefficient of variation was defined as 10%. Linear behavior was assumed for the bridge materials. Three output parameters of maximum bridge displacement, maximum tensile stress, and minimum compressive stress were assigned as structural limit states. A sensitivity analysis for probabilistic analysis was performed using the Spearman ranking method. The results showed that the sensitivity of output parameters to infilled density changes is high. The results also indicated that the system probability of failure is equal to rhofsystem=1,55x10-3. The bridge safety index value obtained is betat=2.96, which is lower than the recommended target safety index. The required safety parameters for the bridge have not been met and the bridge is at the risk of failure.

16

Reliability assessment and sensitivity analysis of concrete gravity dams by considering uncertainty in reservoir water levels and dam body materials

Pouraminian Majid, Pourbakhshian Somayyeh, Noroozinejad Farsangi Ehsan

Civil and Environmental Engineering Reports

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2020

|

Vol. 30, no. 1

1--17

EN

An elaborate safety assessment of the Pine Flat (PF) concrete gravity dam (CGD) has been conducted in this paper. Structural analysis was performed by taking into account the uncertainties in the physical and mechanical properties of the dam body materials and the reservoir water level. The coefficient of variation of 5 and 10 percent and the Gaussian distribution (GAUS) are assigned to random variables (RVs). Sensitivity analysis (SA) of the RVs is done, and important parameters introduced. SA is done to identify the most influential RVs on the structural response. Also, the modulus of elasticity of concrete is the most effective parameter in response to horizontal deformation of the dam crest. The concrete density and US hydrostatic pressure height are the most effective parameters, and the Poisson's ratio is the insignificant parameter on the dam response. To be confident in the safety of the dam body under usual loading, including the dam weight and the upstream (US) hydrostatic pressure, the reliability index (RI) has been obtained by Monte Carlo simulation. The RI for the coefficients of variation of 5 and 10 percent were obtained at 4.38 and 2.47, respectively. If the dispersion of RVs is high, then the dam will be at risk of failure.

17

A Study on the Significance of the Design Parameters of Steel Plate Shear Walls Subjected to Monotonic Loading

Honarmand Saeed, Homami Peyman, Gharehbaghi Vahidreza, Noroozinejad Farsangi Ehsan

Civil and Environmental Engineering Reports

|

2020

|

Vol. 30, no. 4

142--154

EN

Steel plate shear walls (SPSWs) as a resistant system against lateral loads have a high potential for earthquake energy dissipation. Due to the uncertainties of loading, construction, and installation of SPSWs, it is vital to investigate the importance of each component and achieve higher accuracy in design and the implementation of these members. In this paper, a sensitivity analysis is carried out to determine the significance of important uncertainties. The results denoted that the most important parameters affecting the loading capacity of the SPSWs are height, thickness, length, Young's modulus of the wall material, flange, and web thickness of the column, respectively.

18

Soft computing based prediction of friction angle of clay

Dutta R. K., Gnananandarao T., Ladol S.

Archives of Materials Science and Engineering

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2020

|

Vol. 104, nr 2

58--68

EN

Purpose: This article uses soft computing-based techniques to elaborate a study on the prediction of the friction angle of clay. Design/methodology/approach: A total of 30 data points were collected from the literature to predict the friction angle of the clay. To achieve the friction angle, the independent parameters sand content, silt content, plastic limit and liquid limit were used in the soft computing techniques such as artificial neural networks, M5P model tree and multi regression analysis. Findings: The major findings from this study are that the artificial neural networks are predicting the friction angle of the clay accurately than the M5P model and multi regression analysis. The sensitivity analysis reveals that the clay content is the major influencing independent parameter to predict the friction angle of the clay followed by sand content, liquid limit and plastic limit. Research limitations/implications: The proposed expressions can used to predict the friction angle of the clay accurately but can be further improved using large data for a wider range of applications. Practical implications: The proposed equations can be used to calculate the friction angle of the clay based on sand content, silt content, plastic limit and liquid limit. Originality/value: There is no such expression available in the literature based on soft computing techniques to calculate the friction angle of the clay.

19

Searching for optimal prestressing of steel bar structures based on sensitivity analysis

Yurchenko V. V., Peleshko I. D.

Archives of Civil Engineering

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2020

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Vol. 66, nr 3

525--540

EN

The paper considers parametric optimization problems for the steel bar structures formulated as nonlinear programming ones with variable unknown cross-sectional sizes of the structural members, as well as initial prestressing forces introduced into the specified redundant members of the structure. The system of constraints covers load-bearing capacity constraints for all the design sections of the structural members subjected to all the design load combinations at ultimate limit state, as well as displacement constraints for the specified nodes of the bar system, subjected to all design load combinations at serviceability limit state. The method of the objective function gradient projection onto the active constraints surface with simultaneous correction of the constraints violations has been used to solve the parametric optimization problem. A numerical technique to determine the optimal number of the redundant members to introduce the initial prestressing forces has been offered for high-order statically indeterminate bar structures. It reduces the dimension for the design variable vector of unknown initial prestressing forces for considered optimization problems.

20

Resistance to progressive collapse performance analysis of steel open-web sandwich plate structure

Zeng W. Y., Luo J., Xiao J. C.

Archives of Civil Engineering

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2020

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Vol. 66, nr 3

281--303

EN

In order to investigate the progressive collapse performance of steel open-web sandwich plate structure, the sensitivity index and the importance coefficient of the bars are analyzed by the alternate path method. The condition that the model has perimeter supports with different parameters shows the result that: the redundancy index of structure increases at the structural edge, and the redundancy index will be reduced to changing degrees at the middle structure, when the stiffness of higher ribs increases. The redundancy index has little change, when the stiffness of lower ribs or shear keys increases. The sensitivity index of the shear keys dropped significantly, but the sensitivity index of the higher ribs and lower ribs increase, when the span to depth ratio increases. The sensitivity index of the higher ribs in L1 line increases significantly, when the span to depth ratio declines. So it is advisable to strengthen the higher ribs to avoid excessive sensitivity of ribs, when the span to depth ratio declines.