Analiza interakcije šipova u grupi opterećenoj horizontalnim opterećenjem proizvoljnog pravca

The analysis of pile groups subjected to horizontal loading in one of two orthogonal directions is a common problem in geotechnical engineering. However, the above analysis should sometimes be extended with the additional cases of horizontal loading, in arbitrary direction. Although the full scale experiments can provide the best insight into the above problem, they are expensive and therefore not feasible solution. Instead, numerical (i.e. finite element) analysis usually remains the ultimate tool for large scope studies. The main objective of this research is the improvement of the analysis methodology of pile group for the case of arbitrary static horizontal loading. Its influence is investigated numerically to check for the existence of the "critical" pile group configurations and soil conditions, that may lead to the failure of the foundation structure and superstructure itself. To reach the above objective, apriori sensitivity analysis of the considered problem and identification of the main problem parameters are conducted in the first phase. After that, series of complex 3D numerical models for laterally loaded pile group analysis have been generated using PLAXIS 3D. Model validation is done by the back-calculation of available experimental results. Parametric study of pile groups with various configurations under arbitrary horizontal loading is performed, with an emphasis on pile force distribution, bending response and pile group efficiency. Modelling and simulation processes and the optimization of the calculation time were improved using the originally developed codes in Python. The use of multiple computers was allowed by using the author’s scripts developed within the thesis. The above research resulted in thousands of numerical simulations, whose findings provided the improved design methodology of pile groups under arbitrary static horizontal loading.Analiza ˇsipova u grupi izloˇzenoj horizontalnom optere´cenju u nekom od dva ortogonalna pravca je uobiˇcajen problem u geotehnici. Medjutim, navedena analiza ponekad se mora proˇsiriti dodatnim sluˇcajevima horizontalnog optere´cenja, u proizvoljnom pravcu. Iako eksperimenti na realnim konstrukcijama mogu pruˇziti najbolji uvid u navedeni problem, oni predstavljaju skupo (i samim tim neizvodljivo) reˇsenje. Umesto toga, numeriˇcka analiza (npr. primenom metoda konaˇcnih elemenata) obiˇcno postaje primarni alat za studije velikog obima. Glavni cilj ovog istraˇzivanja je poboljˇsanje metodologije za analizu grupe ˇsipova za sluˇcaj proizvoljnog statiˇckog horizontalnog optere´cenja. Njegov uticaj je razmatran numeriˇcki kako bi se utvrdilo postojanje "kritiˇcne" konfiguracije ˇsipova u grupi i uslova tla, koja moˇze dovesti do loma temeljne konstrukcije i samog objekta. Radi ostvarenja gore navedenog cilja, u prvoj fazi sprovedena je uvodna analiza osetljivosti razmatranog problema i identifikacija glavnih parametara problema. Nakon toga, generisane su serije sloˇzenih 3D numeriˇckih modela za analizu boˇcno optere´cenih grupa ˇsipova u PLAXIS 3D. Validacija modela izvrˇsena je povratnim proraˇcunom na osnovu dostupnih eksperimentalnih rezultata. Sprovedena je parametarska studija boˇcno optere´cenih grupa ˇsipova razliˇcitih konfiguracija, sa akcentom na raspodelu sila u ˇsipu, odgovor ˇsipa pri savijanju i efikasnost grupe ˇsipova. Postupci modeliranja i simulacije, kao i optimizacija vremena proraˇcuna, poboljˇsani su primenom originalnih programa u Python-u. Upotreba viˇse raˇcunara za proraˇcun omogu´cena je primenom autorovih programa razvijenih u okviru ove teze. Navedeno istraˇzivanje rezultovalo je u hiljadama numeriˇckih simulacija, ˇciji su rezultati doveli do poboljˇsanja metodologije proraˇcuna ˇsipova u grupi usled proizvoljnog statiˇckog horizontalnog optere´cenja

Analysis of Interaction inside the pile group subjected to arbitrary horizontal loading

The analysis of pile groups subjected to horizontal loading in one of two orthogonal directions is a common problem in geotechnical engineering. However, the above analysis should sometimes be extended with the additional cases of horizontal loading, in arbitrary direction. Although the full scale experiments can provide the best insight into the above problem, they are expensive and therefore not feasible solution. Instead, numerical (i.e. fi nite element) analysis usually remains the ultimate tool for large scope studies. The main objective of this research is the improvement of the analysis methodology of pile group for the case of arbitrary static horizontal loading. Its influence is investigated numerically to check for the existence of the "critical" pile group con figurations and soil conditions, that may lead to the failure of the foundation structure and superstructure itself. To reach the above objective, apriori sensitivity analysis of the considered problem and identifi cation of the main problem parameters are conducted in the first phase. After that, series of complex 3D numerical models for laterally loaded pile group analysis have been generated using PLAXIS 3D. Model validation is done by the back-calculation of available experimental results. Parametric study of pile groups with various con figurations under arbitrary horizontal loading is performed, with an emphasis on pile force distribution, bending response and pile group efficiency. Modelling and simulation processes and the optimization of the calculation time were improved using the originally developed codes in Python. The use of multiple computers was allowed by using the author's scripts developed within the thesis. The above research resulted in thousands of numerical simulations, whose findings provided the improved design methodology of pile groups under arbitrary static horizontal loading

Modeliranje efikasnosti minijaturnih termoelektričnih modula

The research includes the development of a transient thermo-electric SPICE compatible model of the Wireless Sensor Network (WSN) node with aluminum core printed circuit boards. The model enables the characterization of commercial miniature thermoelectric modules (TEMs) within the node in terms of efficiency, cold boot time, dimensions and compactness of the system, as well as the minimum and maximum temperatures of application. The criteria for selecting the geometry and material of the heatsinks optimal to use with different TEMs as parts of thermoelectric systems are set. The design and optimization of voltage booster circuits for use in energy harvesting systems are presented. The analysis is based on simulations using LTspice software, numerical multiphysics simulations, and experimental measurements

EXTRACURRICULAR ACTIVITIES IN THE FUNCTION OF IMPROVING PRACTICAL SKILLS OF FUTURE STUDENTS IN THE FIELD OF ЕLECTRICAL ENGINEERING AND COMPUTING

This paper is based on the authors’ many years of experience in teaching, organizing special courses and one-day workshops for different groups of students, as well as IEEESTEC students’ project conferences. The manuscript contains a brief description and results of the implementation and evaluation of the special course “Let’s put knowledge into practical work” for grammar school students. In order to continue their study and provide students with additional knowledge, the Arduino course was designed. Since 2018, by attending the course as an extracurricular activity, students gain new knowledge in the field of electronic components and microcontroller programming. Based on the conducted analyzes and evaluations, as well as current pedagogical trends, the authors give recommendations on how to overcome problems that may arise due to a lack of practical knowledge and increase students’ self-confidence and indicate the importance of a course designed in this way for those freshmen who want to acquire some new skills and knowledge

Comparative seismic analysis of RC buildings under influence of soil-structure interaction

In this paper the effects of soil-structure interaction (SSI) on reinforced concrete (RC) buildings are analyzed. The dynamic analysis was carried out for two buildings of different heights, founded on three different types of soils, and two different types of foundation, with and without soil interaction. Ten earthquake records, chosen for Belgrade site, were used in the response spectrum analysis. The mean spectrum at the base of the soil deposit and the mean spectra at the surface of each soil types were derived. Calculation was performed using the originally coded MATLAB program, which accounts for downward and upward wave propagation. The influence of the soil layer over the bedrock on the response of the RC buildings was calculated using the commercial software SAP2000. The conclusions were carried out according to theobtained results

Electrical properties of doped BaTiO3 Ceramics

The electrical resistivity and PTCR (Positive Temperature Coefficient of Resistivity) effect doped BaTiO3 ceramics with different dopant were investigated in this paper, The content of additive in doped samples were ranged from 0.01 to 1.0 at% Er/Yb. The samples were prepared by a conventional solid state sintering procedure and sintered at 1320 °C for 4 hours. For samples doped with Er2O3 (0.01 at% Er/Yb), SEM analysis shows abnormal grain growth with the average size range between 20 μm - 40 μm. For samples doped with Yb2O3 the average size was from 30 μm - 50 μm. With increase of dopants concentration the average grain size decreases, and for samples doped with 1.0 at% Er/Yb, grain size range between 3 μm - 20 μm for samples doped with Er and between 1 μm - 10 μm for samples doped with Yb2O3. The specific electrical resistance were measured in temperature range from 25 °C to 170°C at different frequencies, ranged from 100Hz to 1MHz. To a temperature of 120 °C, resistance has a slight increase with increasing of temperature, but above this temperature the resistance rapidly increasing. The value of the specific electrical resistance decreases with increasing concentration of Er/Yb, reached the minimum at certain dopant content (0.5 at% Er/Yb), then increased rapidly with dopant content in high doping level

The Rare-Earths influences on doped BaTiO3-Ceramics Microstructure and Electric Characteristics

The influence of rare-earth additive content on microstructure and electric properties of doped BaTiO3 ceramics is investigated. The concentration of Er2O3 and Yb2O3 in the doped samples range from 0.01 to 1.0at % . The samples are prepared by the conventional solid state reaction, and sintered at 1320° and 1350°C in air atmosphere for 4 hours. SEM analysis shows that all samples are characterized by polygonal grains. The uniform and homogeneous microstructure with grain size ranged from 20 to 45μm is the main low doped samples characteristics. For the samples doped with the higher dopant concentration (0.5 and 1.0 at%) the average grains size is ranged from 5 to 10μm. Dielectric measurements are carried out as a function of temperature up to 180°C at different frequencies. The low doped samples display the high value of dielectric permittivity at room temperature. A nearly flat permittivity-temperature response is obtained in specimens with higher additive content. The Curie temperature of doped samples were ranged from 126 to 130°C. The Curie constant for all series of samples decrease with increment of dopant concentration and the lowest values is mesured from samples doped with 0.01 wt% of aditive. The obtained value of γ pointed out that the specimens have almost sharp phase transition. Also, the specific electrical resistance is measured in function of temperature at the different frequencies from 100Hz to 1MHz. With increasing additives concentration, the electrical resistance decreases to the concentration of 0.5 at% and then increases

Strategija upravljanja rizicima u osiguravajućim kompanijama

Jedan od osnovnih elemenata bez kojeg osiguranje ne postoji jeste rizik. U teoriji verovatnoće i statistici, finansijskom menadžmentu pa i investicionom menadžmentu, rizik se upotrebljava u najspecifičnijem smislu da ukaže na moguće različite ishode oko neke očekivane vrednosti. Upravljanje rizicima nešto je uže područje nego što sam naziv govori, budući da se osiguravajuće kompanije susreću s velikim brojem rizika, tj. izložene su velikom broju rizika, među kojima su i rizici kojima ne mogu upravljati. Menadžer u osiguravajućoj kompaniji je odgovoran za upravljanje svim rizicima s kojima se kompanija susreće u svom poslovanju

Conditional random fields for simulating spatial variability of geotechnical parameters in tunnelling

In times of fast urbanization, underground infrastructure has taken primacy for servicing the city development. Shield tunnel construction is facing significant challenges due to geological uncertainty and limited availability of site-specific test data. As proven by recent works, tunnel design can be done more precisely within the probabilistic frameworks by considering the soil spatial variability, rather than using conventional deterministic-based approaches. In spatial variability modelling, the problem of incomplete utilization of known borehole soil parameters within the unconditional random fields can be overcome by generating conditional random fields. This paper presents a comprehensive review of the CRF application for spatial variability assessments in tunneling in the last five years. It finds that, when applying CRF-based probabilistic approaches, parameter uncertainty is undeniably reduced, and tunnel performance assessments are improved. Since CRFs have rarely been used for tunnel performance assesment, the paper recognizes research gaps that are of great interest to be further investigated in the future

Importance of the global sensitivity analysis in development of metamodels for geotechnical back analysis

This paper investigates the use of global sensitivity analysis during the development of metamodels for back-analysis of geotechnical problems. Variance-based global sensitivity analysis was combined with Particle swarm optimization algorithm and POD-ERBF metamodel to backcalculate the hypothetic (synthetic) problem of anchor-supported excavation. PLAXIS 2D FE code was used for numerical simulations. The results of the back analysis for different sets of model parameters were compared to emphasize the importance of global sensitivity analysis before performing the back analysis and the recommendations for the robust modeling of presented geotechnical problem were given