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Progressive failure analysis of center-notched laminar composites in tension
No full textThis paper presents the application of the full-layerwise-theory (FLWT) in conjunction with the smeared crack-band (SCB) damage model for progressive failure analysis (PFA) of a center-notched tensile (CNT) laminar composite. The FLWT-SCB approach employs layered finite elements, enhancing computational efficiency while maintaining the accuracy of 3D finite elements. Both the initiation and modes of failure were determined using the Hashin failure criterion. The damaged lamina's response in both fiber and matrix directions was characterized by distinct bilinear strain-softening curves. To address mesh dependency, the fracture energy was scaled using a characteristic element length. A benchmark numerical study is presented to analyze the impact of specimen size on the tensile strength of center-notched laminar composites. To validate the model's effectiveness, results were compared against experimental and benchmark data from the literature, demonstrating excellent agreement. The model also revealed a weak dependency between the size of the structure and the mesh, and has a potential in analysis of bio-based composites such as CLT
Seismic Risk Assessment in School Buildings: A Comparative Study of Two Assessment Methods
Get PDFSeismic risk assessment in school buildings is critical for ensuring the safety and resilience
of educational institutions against seismic events. This paper presents a new seismic risk methodology
named MM Risk and comparative study with Adriseismic methodology used for seismic risk
assessment. The study aims to provide insights into the effectiveness and reliability of these methods
in evaluating the seismic vulnerability of school buildings. Through a comprehensive review of the
existing literature and application on a dataset of 213 schools (367 buildings), this paper evaluates the
strengths and limitations of each method in terms of accuracy, complexity, and practical applicability.
The results show that by integrating the approach of Adriseismic methodology and incorporating
extensions related to irregularities, the social risk component (number of users), and the ability to
assess different types of structures, a comprehensive and tailored methodology for assessing seismic
risk can be developed. This is important since these factors are strongly influencing the seismic risk
of schools as connected systems. Furthermore, this paper explores the implications of these findings
for improving seismic risk mitigation strategies in school buildings. MM Risk methodology places
over 70% of school buildings in the medium seismic risk category and 27% in the high seismic risk
category. On the other hand, the Adriseismic methodology is more stringent, classifying 60% of
school buildings into high and very-high risk categories. This disparity undoubtedly influences the
prioritization list for seismic risk mitigation measures. However, definitely the comparative analysis
presented in this paper offers valuable guidance for engineers, policymakers, and stakeholders
involved in the seismic retrofitting and design of school buildings, ultimately contributing to the
enhancement of seismic resilience in educational infrastructure
Experimental testing of 3d printed concrete truss girder
Get PDFIn the last few decades, the technology of 3D concrete printing (3DCP) has had a significant development. This technology has a great potential to improve efficiency in the construction industry. It can provide safer site working conditions, material savings, a reduction of construction time, and a high versatility of architectural and structural design. However, this new technology is still not fully investigated. The wider application is limited by the lack of standards and guidelines for design and production. The literature review showed that, there are only a few studies investigating structural behaviour of 3DCP structures and elements. Beams and walls with and without addition of fibers, reinforcement or cables under ultimate loads were tested. The incorporation of reinforcement in the printing process, connections between printed pieces and long-term behaviour of 3DCP elements under sustained load are opened questions. The topic of this research was an experimental testing of 3DCP truss girder. Printing of truss girder was done using a commercial, ready-to-use premix Sikacrete® 751 3D. In order to print, the printer head was moved in the Z direction to alternately place two desired path layers. A truss girder with dimensions of 87x29x12 cm, without reinforcement, was subjected to a four-point bending test up to failure. During this testing strains in two diagonals, deflection of the two bottom joints, and ultimate force were measured. Ultimate force was 30 kN and the brittle failure of tensioned bottom chord occurred. The force in tensioned diagonal was 13.45 kN and in the compressed one 36.77 kN. Additionally, three samples obtained from the top and bottom chords were tested on axial tension. The tension capacity of samples was 25.12 kN
An Introduction to the Management of Complex Software Projects
No full textA couple of years ago, a former student donated a significant amount of money to the faculty of our alma mater. The amount would today be equivalent to a total of one million dollars. This happened on the donor’s 80th birthday, when he looked back on his life, and decided to give some money to Stanford and Belgrade Universities.
After that event, the dean of the School of Electrical Engineering (at that time), who later became the rector of the entire university, together with a few other people, including one of the co-authors of this book, met to discuss what could be done on the part of the faculty to increase the probability of an event like this one happening again. The conclusion of the discussion was to form a course that would teach the students, above everything else, the skills that are crucially important in the period after graduation.
The course was first offered to students with a major in Software Engineering and Computer Engineering at the School of Electrical Engineering of the University of Belgrade and the School of Mathematics of the University of Belgrade. When the entire university heard about this course, several other schools of the same university decided to make it elective or even mandatory in their postgraduate studies; in some cases, it was even the only mandatory course of master studies. The schools that adopted the course include the School of Civil Engineering and the School of Physical Chemistry, while the same course in a reduced format was adopted by the School of Business Administration, and the School of Urban Architecture. Some of them decided that the class should include twelve hours a week dedicated to homework, with all homework assignments being mandatory. In other schools, only four homework assignments were mandatory, so the selected topics were covered both by homework and at the exam, while the remaining topics were covered only at the exam.
After the chapter that presents the teaching content for each week of the course, the authors have added chapters dedicated to special topics of importance for the success of new graduates, with special emphasis on computing
Sanacija pešačkog i drumskog mosta u Zrenjaninu
No full textThis paper describes the proposed rehabilitation measures for two bridges in Zrenjanin whose function is endangered. The Rehabilitation Project was preceded by a General Inspection of 16 bridges on the territory of the city of Zrenjanin by an expert team from the Faculty of Civil Engineering at the University of Belgrade. Based on the main inspection, it was concluded that the Pedestrian bridge over "Jezero I" and the road bridge over the DTD canal in the village of Jankov Most require rehabilitation intervention in order to enable further exploitation. The rehabilitation project of both bridges was carried out by the Faculty of Civil Engineering of the University of Belgrade in March 2024. The paper presents the damage, its cause and the proposal for rehabilitation works
Predicting Extension of Time and Increasing Contract Price in Road Infrastructure Projects Using a Sugeno Fuzzy Logic Model
No full textRoad infrastructure plays a crucial role in the development of countries, significantly
influencing economic growth, social progress, and environmental sustainability. Major infrastructure projects are frequently challenged by substantial risks and uncertainties, leading to delays, budget overruns, and compromised quality. These issues can undermine the economic viability and efficiency of projects, making effective risk management essential for minimizing negative impacts and ensuring project success. For these reasons, a study was conducted using a Sugeno fuzzy logic system applied to completed projects. The resulting model is based on 10 project characteristics and provides highly accurate predictions for Extension of Time (EoT) and Increasing Contract Price (ICP). By utilizing this model, project management can be significantly improved through more accurate forecasting of potential delays and cost overruns. The high precision of the Sugeno fuzzy logic system enables better risk assessment and proactive decision-making, allowing project managers to implement targeted strategies to mitigate risks and optimize project outcomes
Porous concrete pavement development with respect to the waste materialsand flood control
No full textIn the first two decades of the 21st century, the research of composites with the use of byproduct
materials was extensive, induced by global climate changes, disruption of the balance in the
environment, and with respect to the sustainable development concept, in the hope that there will
be a deviation from the evidently risky and self-destructive global route. The paper presents the
development of porous concrete pavement slabs, with byproduct materials as components. The
application of such slabs is a consequence of the need for improved control of water from
atmospheric precipitation, especially in urban areas. In the composition of these slabs, a spectrum of different component materials was analyzed and tested, with the byproduct material (neutral).
Component materials for porous concrete slabs included: aggregates from natural and artificial
materials (crushed aggregate and expanded clay), natural river sand, cement with additives,
water, chemical admixture and neutral. The tested physical and mechanical properties involved:
bulk density, water absorption, compressive and flexural tensile strength, load capacity, frost and
salt resistance, and wear resistance. There was a decrease in the mechanical properties and in the durability, with the increase in the content of byproduct material, but with the possibility of their improvement by partial substitution of the component materials with more suitable one
Primena testa izluživanja za procenu uticaja modifikovanih betonskih kocki na vode u okruženju
No full textZbog klimatskih promena sve je češća pojava kiša velikog intenziteta i sve kraćeg trajanja. U isto vreme, rapidna urbanizacija u našim uslovima donosi povećanje vodonepropusnosti urbanih površina. Unapređenje se očekuje u primeni savremenih sistema za kanalisanje i zbrinjavanje atmosferskih voda. Jedno od rešenja je smanjenje doticaja u kanalizacione kolektore uvođenjem polupropusne galanterije (od kaveroznih betona) za izgradnju urbanih površina (pešačkih staza, nisko opterećenih kolovoznih površina, krovova zgrada i sl.). Najvažniji parametar za modeliranje i projektovanje ovih inovativnih sistema, koji su zasnovani na interakciji porozne sredine i vode, je koeficijent filtracije pri zasićenju K sat. Za određivanje koeficijenta filtracije koriste se terenske i laboratorijske metode. Terenske metode su robusne, brze i lake za izvođenje, ali zbog velikog broja pretpostavki i nepoznavanja svih karakteristika okolnog tla njihovi rezultati su manje pouzdani od laboratorijskih metoda. Za određivanje koeficijenta filtracije K sat u laboratorijskim uslovima obično se koriste dve dobro uspostavljene metode u inženjerskoj praksi, test sa konstantnim nivoom i test sa promenjivim nivoom vode. Test sa konstantnim nivoom se primenjuje na poroznim materijalima veće propusne moći, a test sa promenjivim nivoom na poroznim materijalima je pogodniji za menje propusne materijale. Međutim, oba testa se suočavaju sa određenim ograničenjima kada se primenjuju na materijalima koji su većih dimenzija i imaju jako veliku propusnu moć. Kao rešenje ovog problema predložen je novi test vodoprovodljivosti u kojem se, usled inicijalno nametnute razlike u nivoima, voda kreće između dva međusobno povezana rezervoara prolazeći pri tom kroz uzorak poroznog materijala koji svojom vodoprovodljivošću prigušuje oscilacije nivoa u rezervoarima. Fokus ovog rada je pre svega na inoviranom postupku merenja koeficijenta filtracije i tehničkim karakteristikama aparature koja je za tu svrhu osmišljena
Numerical modelling of 1D vegetated open-channel flows
No full textAquatic and riparian vegetation affect turbulent characteristics of the flow and make the flow field
spatially inhomogeneous. Thus, the double-averaging methodology (DAM) offers a good background for the analyses of vegetated open-channel flows. Following basic DAM principles, depth-integrated double-averaged Navier-Stokes (DIDANS) equations are derived, and solved numerically using the Roe’s finite-volume based approach. This paper shows the results of testing the numerical solution of DIDANS equations. Homogeneous steady flow equations are tested against the analytical solution, and heterogeneous against a different numerical solution with a much finer grid