Modeling of localized deformation in high and ultra-high performance fiber reinforced cementitious composites

Doctor of PhilosophyDepartment of Civil EngineeringDunja PericA low ratio between the compressive strength of concrete and its cost makes concrete one of the most widely used construction materials in civil engineering. Despite of a very good response to compressive stress, concrete exhibits a low tensile strength and limited tensile strain capacity. Adding short discrete fibers to a cementitious matrix can significantly improve its performance under tensile stress, thus ultimately exhibiting a ductile behavior. Nevertheless, in spite of their beneficial properties fiber reinforced cementitious composites remain underutilized in engineering practice. One of the main reasons for this is a lack of an adequate characterization of the tensile behavior as well as a lack of analysis methods that would allow engineers to incorporate fiber reinforced structural concrete elements into their design. Therefore, this dissertation has four key objectives: 1) to computationally model a stress-strain response of high performance fiber reinforced cementitious composites in uniaxial tension and uniaxial compression prior to macro-crack localization, 2) to develop and perform a diagnostic strain localization analysis for high performance fiber reinforced cementitious composites, the results of which can characterize effects of fibers on failure precursors, 3) to devise and perform an experimental program for characterization of ultra-high performance fiber reinforced cementitious composites, and 4) to characterize a full-fledged behavior including stress-strain and stress-crack opening displacement responses of ultra-high performance fiber reinforced cementitious composites in uniaxial tension. To quantify effects of fibers on onset of strain localization in fiber reinforced cementitious composites a combined computational/analytical models have been developed. To this end, linear-elastic multi-directional fibers were embedded into a cementitious matrix. The resulting composite was described by different types of two-invariant non-associated Drucker-Prager plasticity models. In order to investigate effects of a shape of a yield surface and hardening type linear and nonlinear yield surfaces, and linear and nonlinear hardening rules were considered. Diagnostic strain localization analyses were conducted for several plane stress uniaxial tension and uniaxial compression tests on non-reinforced cementitious composites as well as on high performance fiber-reinforced cementitious composites. It was found that presence of fibers delayed the inception of strain localization in all tests on fiber-reinforced composites. Furthermore, presence of fibers exerted a more significant effect on the strain localization direction and mode in uniaxial compression than in uniaxial tension. The main objective of experimental program was to facilitate characterization of the post-cracking tensile behavior of ultra-high performance fiber reinforced cementitious composites. To this end, five different mixes of fiber-reinforced cementitious composites were cast, whereby volumetric fiber content, fiber shape and water to binder ratio were the experimental variables. Two testing methods were adopted, a direct uniaxial tension test and four-point prism bending test. Two different post-cracking behaviors were observed in direct tension tests, softening and strain hardening accompanied with multiple cracking. On the other hand, the response from prism bending tests was less scattered. Several different inverse analyses were carried out to predict stress-strain and stress-crack opening displacement responses in uniaxial tension based on the prism bending tests. The analyses resulted in worthy correlations with the experimental data, thus suggesting that the prism bending test is a viable alternative to a much more challenging to perform direct tension test for ultra-high performance fiber reinforced composites

Monitoring steel fibre orientation in self-compacting cementitious composite slabs during pouring with dynamic X-ray radiography

This paper presents a new technique based on dynamic X-ray radiography that can be used to assess fibre orientation during pouring of steel fibre reinforced cementitious composites. Synthetic examples were used to assess the suitability and robustness of the technique, which was shown to provide reliable measurements of fibre orientation even when the signal-to-noise ratio is relatively high. A study was then carried out on the effect of formwork aspect ratio, time/duration of pouring, and rebar placement on the fibre orientation while pouring self-compacting cementitious composite slabs. Results demonstrated the ability of the technique in monitoring the movements of fibres while pouring, and the strong effect of the flow in inducing preferential fibre alignment within the slabs. Fibre orientation was found to vary progressively over time and could take about half of the duration of pouring to fully stabilise.University of Sydney - Sydney Research Accelerator (SOAR) programm

THE INFLUENCE OF THE BRAND OF FOOD PRODUCTS ON CONSUMER BEHAVIOR

Uspjeh tvrtke na tržištu ovisi o tome kako su proizvode i usluge prihvatili potrošači. Proizvodi i usluge usmjereni su funkcionalno i prema zadovoljavanju potreba, a ako nude dodatne vrijednosti, izazivaju želje, pozitivne asocijacije i osjećaje, stvaraju emocionalnu vezu s potrošačima, tek onda imaju uvjet da to bude prihvaćena marka. Izgradnja jake marke izazov je i prigoda za menadžment. Rastom njezine vrijednosti i vrijednosti tvrtke stvaraju se konkurentske prednosti nužne za daljnji opstanak i razvoj. Markom se stvaraju odnosi s potrošačima i oni je valoriziraju prema tome kako procjenjuju njezinu razlikovnost te relevantnost za sebe iz čega stvaraju emocionalne veze i lojalnost.The success of a company in the market depends on how products and services are accepted by consumers. Products and services are focused on functional and satisfying needs, and if they offer additional value, generate desires, positive associations and feelings, create an emotional connection with consumers, only then have the condition that it be accepted. Building a strong brand is also a challenge for management. With the growth of the brand value and the value of the company, the competitive advantages are necessary for further survival and development. Marks are creating relationships with consumers and they are valorizing how they estimate its distinctiveness and relevance to oneself, creating emotional relationships and loyalties

Global challenges and foreign direct investment in the second decade of the 21st century

Izravna inozemna ulaganja predstavljaju najznačajniji oblik ekonomskih aktivnosti. S obzirom na njihov značaj, utječu na sve oblike međunarodnih transakcija. Izravna inozemna ulaganja sastavnica su međunarodnog kretanja kapitala i imaju veliku ulogu u razvitku svjetskog gospodarstva. Problem istraživanja krije se u tome kako se na današnjem visokokonkurentnom, globaliziranom tržištu izravna inozemna ulaganja susreću s mnogobrojnim izazovima. Cilj je istraživanja ustanoviti utjecaj inozemnih izravnih ulaganja na razvoj zemlje. Svrha je istraživanja ustanoviti ulogu i važnost izravnih inozemnih ulaganja, te istražiti s kojim su se izazovima susrela izravna inozemna ulaganja.Foreign direct investment is the most important form of economic activity. Given their importance, they affect all forms of international transactions. Foreign direct investment is a component of international capital movements and plays a major role in the development of the world economy. The problem with research lies in how foreign direct investment faces many challenges in today’s highly competitive, globalized market. The aim of the research is to establish the impact of foreign direct investment on the country's development. The purpose of the research is to establish the role and importance of foreign direct investment, and to investigate the challenges faced by foreign direct investment

DALMATIAN WILD PLANTS

Na području Dalmacije postoji oko 3 500 svojti samoniklog bilja, što ju svrstava među najbogatije florističke regije u Europi. Zanimljiva je činjenica da mnoge biljke pripadaju gotovo svim kategorijama: od aromatičnog i začinskog bilja, preko ljekovitog i medonosnog pa sve do ukrasnog. Samoniklo bilje je u prošlosti imalo ključnu ulogu u prehranjivanju stanovnika Dalmacije ali i Hrvatske, pogotovo u ratno doba i doba oskudice. Također se samoniklo bilje koristilo u narodnoj medicini, a u novije vrijeme znanstvena istraživanja su potvrdila njihova ljekovita svojstva za liječenje od raznih bolesti. Danas, osim u medicinske svrhe samoniklo bilje ima sve veći odjek u gastronomiji. Tako se od samoniklog bilja mogu praviti razne delicije, od hladnih i toplih predjela, pa sve do slastica. Samoniklo bilje ima veliki potencijal za razvoj ruralnog turizma, koji nažalost nije u potpunost iskorišten. Tradicionalni proizvodi napravljeni od samoniklog bilja poput mirisnih sapuna i balzama, eteričnih ulja, tradicionalnih kolača i alkoholnih pića samo su dio turističke ponude ruralnog turizma. Najveći i trajni suvenir o nekoj turističkoj destinaciji je ipak zadovoljstvo turista koji se mjeri ponovnim povratkom.In the area of Dalmatia, there are about 3 500 species of wild plants which puts it among one of the richest floristic region in Europe. Interesting is the fact that many plants belong to almost all categories of aromatic and seasoning herbs and medicinal through to ornamental. Wild plants in the past had a key role of feeding the population of Dalmatian and Croatian, especially in times of war and times of scarcity. Also, the wild plants are used in traditional medicine, in more recent times scientific studies have confirmed their medical properties for the treatment of various diseases. Today, except for medical purposes wild plants have increasing resonance in gastronomy. Also from wild plants can make a different specialties from hot and cold appetizers to desserts. Wild plants have great potential for the development of rural tourism, which unfortunately are not used properly. Traditional products made from wild plants such as scented soaps and balsam, essential oils, traditional cakes and alcoholic drinks are just part of tourist offer of rural tourism. But the greatest and permanent souvenir of all is the satisfaction of tourists which is measured by returning

WOMEN SENTENCED TO PRISON - PHENOMENOLOGICAL AND ETIOLOGICAL ANALYSIS

Nakon povijesnog pregleda položaja žena u društvu te odnosa društva prema ženi, analizirana je stopa kriminaliteta žena te se u diplomskom radu nadalje provodi analiza kriminoloških karakteristika žena koje su zbog određenih kaznenih djela lišene slobode u kaznionicama Republike Hrvatske. Analizirana je težina njihovih kaznenih djela te se u radu promišlja na koji način se provodi psihološka pomoć ženama u kaznionicama. Čitatelju rada približavaju se penološki programi u kaznionicama, proces resocijalizacije i pita se što društvo može učiniti kako bi se ojačali preventivni programi i smanjio rizik od najtežeg kriminalnog ponašanja žena. Želimo društvo u kojemu žene ne bi bile ni u kakvim diskriminatornim odnosima prema muškarcima ili marginalizirane unutar bilo kojih društvenih procesa, društvo u kojemu se ženama pruža pomoć i briga u okviru institucija. U zaključku su predložene i neke konkretne mjere.After a historical review of the position of women in society and the attitude of society towards women, the crime rate of women was analyzed. Furthermore, the thesis contains a special chapter dedicated to the criminological characteristic of incarcerated women in the penitentiary of the Republic of Croatia for certain criminal offenses. The gravity of the crimes is analyzed, and it is considered how psychological assistance is carried out in penitentiaries. A special attention is given to penological programs in penitentiaries, and to the process of resocialization. A discussion is opened about what we can do as a society to raise the quality of the social position of women to strengthen preventive programs and reduce the risk of the most severe criminal behavior of women. We want a society where women will not be in any discriminatory relationship with men or marginalized within any social processes, a society in which women receive help and care by institutions, a society in which women are protected. In conclusion, some concrete measures are proposed

Global challenges and foreign direct investment in the second decade of the 21st century

Izravna inozemna ulaganja predstavljaju najznačajniji oblik ekonomskih aktivnosti. S obzirom na njihov značaj, utječu na sve oblike međunarodnih transakcija. Izravna inozemna ulaganja sastavnica su međunarodnog kretanja kapitala i imaju veliku ulogu u razvitku svjetskog gospodarstva. Problem istraživanja krije se u tome kako se na današnjem visokokonkurentnom, globaliziranom tržištu izravna inozemna ulaganja susreću s mnogobrojnim izazovima. Cilj je istraživanja ustanoviti utjecaj inozemnih izravnih ulaganja na razvoj zemlje. Svrha je istraživanja ustanoviti ulogu i važnost izravnih inozemnih ulaganja, te istražiti s kojim su se izazovima susrela izravna inozemna ulaganja.Foreign direct investment is the most important form of economic activity. Given their importance, they affect all forms of international transactions. Foreign direct investment is a component of international capital movements and plays a major role in the development of the world economy. The problem with research lies in how foreign direct investment faces many challenges in today’s highly competitive, globalized market. The aim of the research is to establish the impact of foreign direct investment on the country's development. The purpose of the research is to establish the role and importance of foreign direct investment, and to investigate the challenges faced by foreign direct investment

Study on Shear Strength of Xanthan Gum-Amended Soil

When construction work is planned on soil with inadequate shear strength, its engineering properties need to be improved. Chemical stabilization is one of the solutions for soil strength improvement. Currently, the most common additive that is used for chemical soil improvement is cement. Cement is an effective solution, but it has several negative effects on the environment. Therefore, the urges for environment-friendly solutions that can replace cement and show good potential for sustainable engineering are rising. One of the promising environment-friendly solutions is the use of biopolymers. Therefore, the main aim of the present study was to investigate the effect of the biopolymer xanthan gum on the strength of different types of soil. Xanthan gum was mixed with three different types of soil: sand, clay, and silty sand. The strength of treated and non-treated soil was experimentally investigated by performing unconfined compression, direct shear, and triaxial tests. From the results, it was observed that xanthan gum significantly increased the strength of each soil, which shows its major potential for the future of sustainable engineering

Desiccation Cracking Behavior of Sustainable and Environmentally Friendly Reinforced Cohesive Soils

Desiccation cracking of cohesive soils is the development of cracks on the soil surface as a result of a reduction in water content. The formation of desiccation cracks on the cohesive soil surface has an undesirable impact on the mechanical, hydrological, and physicochemical soil properties. Therefore, the main aim of this study is to experimentally and numerically investigate eco-friendly soil improvement additives and their effect on the desiccation cracking behavior of soils. Improvement of soil crack resistance was experimentally studied by conducting desiccation cracking tests on kaolin clay. Biopolymer xanthan gum and recycled carpet fibers were studied as potential sustainable soil improvement additives. In addition, image processing was conducted to describe the effect of an additive on the geometrical characteristics of crack patterns. The results show that the soil improvement additives generally enhanced the soil strength and reduced cracking. Furthermore, a hydro-mechanical model was developed to predict the moisture transfer and onset of desiccation cracks in plain and amended kaolin clays. Data obtained show that the inception of the desiccation cracking and radial displacements were delayed in the improved soil specimens, which is in agreement with the experimental data

Sustainable Improvement of the Crack Resistance of Cohesive Soils

Desiccation cracking of cohesive soils is the development of cracks on the soil surface as a result of a reduction in the soil moisture content. The decrease in soil surface area owing to the desiccation of cohesive soils has an undesirable impact on the mechanical, hydrological, thermal, and physico-chemical properties. Many efforts have been made to improve the desiccation crack resistance of cohesive soils, but the current solutions raise a number of environmental issues, increasing the demand for sustainable soil improvement alternatives. Therefore, the main objective of this study is to investigate novel eco-friendly soil improvement techniques, such as recycled carpet fibers and a gelatin-based bioplastic, and their effect on desiccation cracking in cohesive soils. The improvement of soil crack resistance was studied by conducting desiccation cracking tests on plain and improved soils. In addition, image processing was conducted to quantitatively describe the effect of soil improvement type on the geometrical characteristics of crack patterns. Each soil improvement technique enhanced the soil strength and reduced cracking at room temperature, at an elevated temperature, and when subjecting to cyclic wetting and drying. The addition of bioplastics proved to be the most effective solution, thus demonstrating a viable option to advance future sustainable engineering practices