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A practical method for the optimal design of continuous footing using ant-colony optimization
Boonchai Ukritchon, Suraparb Keawsawasvong, 2016, izvirni znanstveni članek

Opis: 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.
Ključne besede: optimal design, footing, stability, nonlinear programming, ant-colony optimization
Objavljeno: 18.06.2018; Ogledov: 494; Prenosov: 38
.pdf Celotno besedilo (446,51 KB)
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A stability assessment of coastal cliffs using digital imagery
Igor Ružić, Čedomir Benac, Ivan Marović, Suzana Ilić, 2015, izvirni znanstveni članek

Opis: The investigated area around the Stara Baška settlement (the island of Krk, NE channel part of the Adriatic Sea) is in a delicate geodynamic balance. Marine erosion is quite prominent and the recorded cliff retreat between 1966 and 2004 was from 4 to 5 metres. The cliff slopes are formed in talus breccias. Strong waves and formations of wave-cut notches are the main causes of the cliff’s instability. The secondary causes are the weathering and erosion of the soil and rocks on the cliff. The slump of the cliff slope can occur in a rock mass with higher strength parameters, where the notches are cut a few metres inward into the toe of the cliff slope. A combined method for the stability analysis of the coastal cliffs was tested; this incorporates the cantilever-beam model and the structure-from-motion (SfM) photogrammetry. This method can provide highly detailed 3D geometrical data of the cliff, which can then be used in the calculations of the stability model. This is particularly important in a stability analysis of lithologically heterogeneous rocks such as breccias with varied geometry, which cannot be easily replaced by a rectangular surface. The simple and useful SfM method overcomes the limitations of traditional surveys in estimating the cliff overhang surface and the notch length.
Ključne besede: marine erosion, cliff stability, SfM photogrammetry, Krk island, Adriatic sea
Objavljeno: 15.06.2018; Ogledov: 624; Prenosov: 43
.pdf Celotno besedilo (865,75 KB)
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Lessons learnt from field tests in some potentially unstable slopes in Switzerland
Sarah Springman, Armin Askarinejad, Francesca Casini, Sven Friedel, Peter Kinzler, Philipp Teysseire, Andrea Thielen, 2012, izvirni znanstveni članek

Opis: Rain-induced slope instability is a significant natural hazard in Switzerland, Slovenia and elsewhere in Europe. This contribution was prepared especially for the 12th Šuklje Symposium, and recognises that landslides occur both in mountain regions as well as in lowland regions during and following extreme-rainfall conditions. The Institute (and Professorship) for Geotechnical Engineering at the Swiss Federal Institute of Technology (ETH Zürich) has been engaged over several years in projects concerned with the characterisation, monitoring and modelling behaviour of slopes in mainly granular porous media across the full range of altitudes in Switzerland. A link is made to the doyen of the Šuklje day and then three case histories are presented and discussed to demonstrate the principal reactions to seasonal rainfall. A small slip was released in two of these cases and the “triggering” factors have been investigated and are discussed in this contribution. It transpires that the mode of inslope drainage influences the way in which the ground saturates and hence the volume of the potentially unstable ground. Simple stability analyses using limit equilibrium and soil parameters that have been amended to account for unsaturated soil behaviour were found to function well for slopes in largely granular media.
Ključne besede: rain-induced landslides, slope stability, case histories, monitoring, characterisation, modelling
Objavljeno: 13.06.2018; Ogledov: 409; Prenosov: 43
.pdf Celotno besedilo (1,79 MB)
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Non-linear finite-element modelling of room and pillar mine workings including the strain-softening behaviour of the rock mass
Salim Bensehamdi, Abdelbaki Seriani, 2008, izvirni znanstveni članek

Opis: A two-dimensional model adopting post-failure criteria was used to simulate the behaviour of the rock mass and the development of yield zones around room and pillar mine workings. The model conformed to the strain-softening behaviour of the rock mass and accounted for its post-failure residual strength. The structural-stability-analysis approach accounted for the main features of the mine structures’ yield produced during loading through changes in the rock material’s stiffness and the subsequent evolution of the stresses. A comprehensive parametric analysis was performed and the inevitable effect of the interaction of the roof, pillar and floor on the overall stability limit of the mine was investigated. The numerical results clearly showed that the finite-element linear models could not realistically represent the true behaviour of the mine structure. However, they clearly demonstrated the limitations of the finite-element linear solutions in representing the true behaviour of the mine structure, particularly when the rock-mass structure is relatively weak, and that a non-linear approach was justified.
Ključne besede: non-linear FE analysis, yielding, plastic zones, room and pillar mining, residual strength, stability assessment
Objavljeno: 05.06.2018; Ogledov: 379; Prenosov: 41
.pdf Celotno besedilo (651,93 KB)
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A 3D nonlinear dynamic analysis of a rock-fill dam based on IZIIS software
Violeta Mircevska, Vladimir Bickovski, Mihail Garevski, 2007, izvirni znanstveni članek

Opis: This paper treats the 3D nonlinear dynamic behavior of a rock-fill dam based on the Mohr-Coulomb failure criterion. The dam is situated in a steep, narrow, “V-shaped” rigid canyon. The concept of a massless rock foundation is treated, for which a certain part of the rock is included in the model. The dam-rock interface was modeled by contact elements, which allowed certain relative displacements between the two media of different stiffnesses. The generation of the 3D mathematical model was related to the topology of the terrain, and the nonlinear dynamic response was based on the "step-by-step" linear-acceleration direct-integration method, making use of the Wilson-θ method. The convergence process was in accordance with the Newton-Raphson method. First, the initial static effective stresses existing in the conditions of the established stationary filtration through the clayey core were defined. The analysis was based on an original FE program for the static and dynamic analyses of rock-fill dams, as well as a FE program for the solution of the stationary filtration process through the clayey core. The dynamic response of the 3D model of the dam was defined for the effect of harmonic excitations. Dynamic analyses in the linear and nonlinear domains were performed for the purpose of comparing the results. The time histories of the linear and nonlinear responses were defined for selected sections and nodes of the model, the tension cut-off zones, the plastic deformations, and the stress-shear strain relationships. The coefficient against the sliding of the potential sliding surfaces was also defined. It can be concluded that 3D analyses as well as a nonlinear material treatment of the soils built in the dam are imperative for a proper assessment of the stability of rock-fill dams situated in narrow canyons.
Ključne besede: automatic generation of 3D model, rock-fill dam, nonlinear dynamic analysis, elastic perfectly plastic criterion, tension cutoff, cracking zones, plastic deformations, stability
Objavljeno: 18.05.2018; Ogledov: 897; Prenosov: 59
.pdf Celotno besedilo (923,69 KB)
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Organization in finance prepared by stohastic differential equations with additive and nonlinear models and continuous optimization
Pakize Taylan, Gerhard-Wilhelm Weber, 2008, izvirni znanstveni članek

Opis: A central element in organization of financal means by a person, a company or societal group consists in the constitution, analysis and optimization of portfolios. This requests the time-depending modeling of processes. Likewise many processes in nature, technology and economy, financial processes suffer from stochastic fluctuations. Therefore, we consider stochastic differential equations (Kloeden, Platen and Schurz, 1994) since in reality, especially, in the financial sector, many processes are affected with noise. As a drawback, these equations are hard to represent by a computer and hard to resolve. In our paper, we express them in simplified manner of approximation by both a discretization and additive models based on splines. Our parameter estimation refers to the linearly involved spline coefficients as prepared in (Taylan and Weber, 2007) and the partially nonlinearly involved probabilistic parameters. We construct a penalized residual sum of square for this model and face occuring nonlinearities by Gauss-Newton's and Levenberg-Marquardt's method on determining the iteration step. We also investigate when the related minimization program can be written as a Tikhonov regularization problem (sometimes called ridge regression), and we treat it using continuous optimization techniques. In particular, we prepare access to the elegant framework of conic quadratic programming. These convex optimation problems are very well-structured, herewith resembling linear programs and, hence, permitting the use of interior point methods (Nesterov and Nemirovskii, 1993).
Ključne besede: stochastic differential equations, regression, statistical learning, parameter estimation, splines, Gauss-Newton method, Levenberg-Marquardt's method, smoothing, stability, penalty methods, Tikhonov regularization, continuous optimization, conic quadratic programming
Objavljeno: 10.01.2018; Ogledov: 502; Prenosov: 57
.pdf Celotno besedilo (364,34 KB)
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Exploring approaches how to measure a lean process
Christer Österman, Anders Fundin, 2014, izvirni znanstveni članek

Opis: Purpose:The purpose of the research is to explore a practical method of measuring the implementation of lean in a process. The method will be based on examining the abilities of a group. At this scale the ability to work standardized and solve problems is important. These two abilities are dependent of each other and are fundamental for the group's ability to create a stable result. In this context the method of standardized work (SW) is define to be the methods used in a process to generate stable results. Problem solving (PS) is defined as the methods used to return a process to a condition where SW is possible. Methodology /approach: The research is conducted in a multiple case study in four large global manufacturing companies. The order of the data collection is: Firstly, interviews with the individuals that are centrally responsible for overall implementation of lean in the organization. Secondly, observe the implementation of SW and PS at the group level. In total 7 groups have been studied and 19 respondents interviewed. Findings: Results show that the central definition of the methods for standardized work does not by itself have a direct impact on success of implementation of SW at group level. The method of SW where similar on a general level in the different cases, but with varying levels of implementation at group level was applied. Results also show that key factors for a successful implementation of standardized work on group level are: Ownership of the process, Direct connection to result of process, Correct workload and Leader demand. Methods of PS at group level where dissimilar despite a superficially similar approach. The evaluation method used was successful in providing comparable results between the cases. Research limitations: A limitation of this research is within the scale of the measurement, as it only examines the group level. The research is further limited to four companies and seven groups. Originality/value of paper: This paper aims to fill a gap in the established measurement methods of lean, as it examines the abilities of SW and PS at the group level of a process. These abilities are often referred to as essential in lean theory. However, there has been little scholarly work in defining the methods of SW and PS or the key factors affecting the methods at an operational level.
Ključne besede: lean, performance measures, problem solving, standardized work, stability
Objavljeno: 30.11.2017; Ogledov: 518; Prenosov: 268
.pdf Celotno besedilo (428,73 KB)
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Model of determining the stability of retail deposits with higher outflow rates
Aleksandra Murks Bašič, 2015, izvirni znanstveni članek

Opis: Retail deposits are treated as one of the cheapest and most stable funding sources for banks, especially for those with high volumes of retail deposits. A bank defines three main categories of retail deposits that are subject to different outflow rates for the purpose of liquidity coverage requirements in reporting and compliance. The outflow rates for the first two main groups are 5% and 10% respectively, but for the third main group the bank calculates its own outflow rates. We analyzed the latter in this paper. Each bank should assign retail deposits to one of the three categories based on the number and type of predetermined risk factors. Risk factors are divided into two groups according to the degree of risk. The paper first describes the legislative framework, followed by the method of calculating higher outflow rates for retail deposits according to the historical movements and the expected volatility assessment in the situation of stress conditions. At the end of the paper, we briefly provide the future treatment of retail deposits with higher outflow rates.
Ključne besede: retail deposits, stability, transactional account, LCR, deposit guarantee scheme, depositors, higher outflow rates, Basel III
Objavljeno: 14.11.2017; Ogledov: 725; Prenosov: 103
.pdf Celotno besedilo (366,09 KB)
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Analytical and numerical factor of safety (uls) calculations on reinforced embankments
Tadej Vidnar, 2017, magistrsko delo

Opis: This thesis deals with factor of safety calculations on geogrid reinforced embankments carried out by commonly used limit equilibrium (LEM) and finite element methods (FEM). The study utilize LEM based software SLIDE and FEM based software PHASE2. The main difference between these two approaches is that the LEM methods are based on the static of equilibrium whereas FEM methods utilise the stress strain relationship. Unlike to LEM, numerical analysis also computes displacements. For practical example of a geogrid reinforced embankment the factor of safeta (FoS) is calculated. Reinforced soil structures are nowadays utilized for a lot of civil engineering applications. Traditionally, the design of geogrid reinforced soil is performed using analytical methods (LEM). Unfortunately, these methods missing the fundamental physics of stress-strain relationship and are therefore not able to compute a realistic stress distribution. In first step of the analysis the FoS is carried out with analytical approach. The most rigorous LEM methods, Bishop’s, Spencer’s and Morgenstern-Price are selected and the FoS for circular and polygonal slip surface is calculated. In second step of the analysis the FoS is carried out with numerical approach. Shear strength reduction (SSR) procedure was performed to determine the critical strength reduction factor (SRF) which represents the FoS of slope.
Ključne besede: civil engineering, finite element method (FEM), limit equilibrium method (LEM), embankments, slope stability, bearing capacity failure, geosynthetics, geogrids, shear strains
Objavljeno: 27.09.2017; Ogledov: 609; Prenosov: 124
.pdf Celotno besedilo (17,05 MB)

Tracking without concessions?
Danilo Šuster, 2013, izvirni znanstveni članek

Opis: In the first, shorter part of the paper I point out some problems and potential misunderstandings connected with B. Berčić's treatment of Nozick's sensitivity condition for knowledge. In the second part of the paper I offer the condition of modal stability or limited sensitivity as a revision of Nozickian conditions for non-accidental connection between our belief and the truth of our belief. "When it is seriously possible for you to falsely believe that p", that is a goodreason for denying that you know that p. Sensitivity within limits requires that we consider more possible worlds (all within a sphere of serious or relevant possibilities) than classical sensitivity, but not the worlds outside this sphere. The idea of modal stability combines robustness (benefits of safety) with responsiveness to facts (benefits of sensitivity).
Ključne besede: modal epistemology, modal stability, safety, sensitivity
Objavljeno: 02.08.2017; Ogledov: 539; Prenosov: 57
.pdf Celotno besedilo (331,79 KB)
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