Textile Reinforced Concrete (TRC) with a small thickness, high tensile and compressive strength has been combined with lightweight materials to create sandwich elements. Due to the low strength of the core materials in the sandwich elements, the additional shear connector devices were suggested to improve the load capacity. However, it raised an idea of using a higher strength material core, Expanded Polystyrene Concrete (EPC), without any connector devices to create a new type of lightweight sandwich element, which can be an answer for not only developing lightweight structures but also solving environmental problems. In this thesis, this novel idea was gradually realized with a study on TRC-EPC sandwich beams. Firstly, experimental material tests on EPC showed the possibility to recycle EPS waste for EPC with a density of around 950 kg/m3. Thus, an EPC with a density of 920 kg/m3 and a compressive strength of 5.2 N/mm2 was chosen for the core to realize the concept for TRC-EPC sandwich with 18 experimental beams. Bending tests of six series with shear-to-depth-ratio (a/d) from 1.5 to 5.2 were implemented to study load responses of this type of sandwich beam. The failure moments of all the specimens were smaller than the nominal moment strength of the cross section. The load capacities of the specimens depend strongly on the ratio a/d. The calculations for the shear capacity according to standards as well as shear calculation approaches were implemented. Due to their generalized form, ACI 318-05 and EC2 offer conservative results for a/d<5.2. The dependence of the shear capacity on a/d could be better described with CEB-FIB Model Code 1990. For the beams with 1.5<a/d and a/d<2.1, Strut and Tie Model gave the most suitable results. In case a/d>2.1, ZINK’s model offered better results than the others. Besides, a new proposed equation for the shear capacity of TRC-EPC sandwich beams depending on the a/d was also suggested. In order to model the load response of the six experimental series, FEM models with ATENA developed. The models with and without a consideration of the bond between the textile and fine HSC in the TRC layer underestimated the load capacity with tolerance 26% and 28 % respectively. The tolerances for the deflections in the models with a/d>2.5 were around 22 % and 23%. Finally, an engineering model originally based on sandwich theory was developed to model the load-deflection response of this type of sandwich beams. The model could predict the displacement with tolerances from -24 % to 12 %. The load capacity of TRC-EPC sandwich beams was underestimated with a tolerance in the range of 15- 34 %. / In dieser Arbeit wurde eine neue Sandwichkonstruktion untersucht, für die Textilbeton, ein Werkstoff mit geringer Dicke und gleichzeitig hoher Zug- und Druckfestigkeit, mit leichten Kernmaterialien kombiniert wurde. Aufgrund der geringen Festigkeit der Kernmaterialien werden in vielen Sandwichkonstruktionen zusätzliche Schubverbinder benötigt, um eine ausreichende Tragfähigkeit zu erreichen. Dies führte zu der Idee, Expanded Polystyrene Concrete (EPC) als höherfestes Kernmaterial zu verwenden, das keine zusätzlichen Verbindungsmittel benötigt. Damit entsteht eine neuartige Sandwichkonstruktion, die nicht nur eine Lösung für die Entwicklung neuer leichter Strukturen ist, sondern auch für Umweltprobleme. Diese Idee wurde in dieser Arbeit durch theoretische und experimentelle Untersuchungen an Textilbeton-EPC-Sandwichbalken umgesetzt. Zunächst wurden Materialuntersuchungen an EPC durchgeführt, um nachzuweisen, dass es möglich ist, EPC mit einer Dichte von rund 950 kg/m³ mit recyceltem EPS herzustellen. Für die anschließenden Untersuchungen an 18 Sandwichbalken wurde dann ein EPC mit einer Dichte von 920 kg/m³ und einer Druckfestigkeit von 5,2 N/mm² ausgewählt. In 6 Serien von Sandwichbalken wurden 4-Punkt-Biegeversuche mit Schubschlankheiten von 1,5 bis 5,2 durchgeführt. Die Bruchmomente aller Balken waren geringer als die rechnerische Momententragfähigkeit des Querschnitts und die Tragfähigkeit war stark von der Schubschlankheit abhängig. Es wurden Berechnungen zur Schubtragfähigkeit nach den verschiedenen internationalen Normen durchgeführt. Aufgrund ihrer allgemeingültigen Form ergaben ACI 318-05 und EC2 sehr konservative Ergebnisse für Schubschlankheiten kleiner als 5,2. Die Formulierung des CEB-FIB Model Code 1990 war besser geeignet, die Abhängigkeit der Schubtragfähigkeit von der Schubschlankheit abzubilden. Für die Balken mit Schubschlankheiten a/d=1,5 bis 2,1 brachten Stabwerkmodelle ausreichend gute Ergebnisse. In Fällen mit a/d>2,1 ergab das Modell von Zink die besten Übereinstimmungen. Um die Abhängigkeit der Schubtragfähigkeit von der Schubschlankheit besser erfassen zu können, wurde eine neue Berechnungsgleichung für Textilbeton-EPC-Balken vorgeschlagen. Um das Last-Verformungsverhalten der experimentellen Untersuchungen beschreiben zu können, wurden FEM-Modelle mit der Software ATENA entwickelt. Es wurden verschiedene Modelle untersucht, die den Verbund zwischen dem textilen Gelege und dem Feinbeton unterschiedlich stark berücksichtigten. Die Tragfähigkeit der untersuchten Balken wurde mit den FEM-Modellen um ca. 26% bis 28% unterschätzt. Die Abweichungen in den berechneten Durchbiegungen betrugen für die Balken mit a/d>2,5 ca. 22% bis 23%. Abschließend wurde ein Ingenieurmodell auf Grundlage der Sandwichtheorie entwickelt, mit dem das Last-Verformungsverhalten dieser Sandwichkonstruktion gut beschrieben werden kann. Mit dem Modell ergaben sich Abweichungen von -24% bis +12% zwischen experimentellen und theoretisch ermittelten Verformungen. Die Tragfähigkeit wurde mit einer Abweichung von 15% bis 34% unterschätzt.

Application of refined ultimate state theories and use of high strength materials have resulted in longer spans and smaller depths of reinforced and prestressed concrete structures. Consequently, the condition of the limiting deflection rather than the strength requirement often is the governing design criterion. Long-term deflections might be up to 3 to 4 times larger than the short-term deflections. Such increments are caused by complex physical effects such as concrete creep, shrinkage and cracking, bond defects, etc. Long-term concrete creep and shrinkage deformations govern prestress losses. Structural analysis can be carried out either by traditional design code methods or numerical techniques. Although design code methods ensure safe design, they have significant limitations. Different techniques are used for strength, deflection, crack width and prestress loss analyses. Besides, most of the simplified approaches do not assess such factors as concrete shrinkage, cracking or tension stiffening. Based on a large number of empirical expressions and factors, they lack physical interpretation and do not reveal the actual stress-strain state of cracked structures. On the other hand, numerical techniques are universal and can take into account each physical effect. However, inadequacies made in the prediction of each effect might lead to significant inaccuracies when integral magnitudes such as deflection are to be assessed. Consequently, the predictions by the numerical... [to full text]

The research work presents the carried out investigations on the effect of the celestial bodies on the gravity field elements and the analysis was made on the Moon’s and Sun’s effect on the geodetic measurements. The results of the research are advised to be implemented for the assessment of the effect of the celestial bodies regarding the geodetic, measurements as well as when selecting the surfaces of the Earth and geoid and the system of gravity. The dissertation consists of introduction, four chapters and the summation of the results. The introduction depicts the topicality of the chosen research, determining the relevance of the investigated issue. There are described the objective of the work as well as the tasks, there is revealed the scientific novelty of the work ant etc. Chapter one deals with the review of the scientific literature. The chapter also presents the analysis of the available methods of the assessment of the Earth’s tides and their accuracies. The scientific literature was analysed extensively in terms of the effect of the celestial bodies on the Earth’s gravity field and on the issues of the geodetic measurements. The problems were indicated concerning the assessment of the effect of the celestial bodies and the tasks were specified for the research work to be investigated. Chapter 2 deals with the theoretical research. The author presents the analysis of the effect of the members of the series of the tide potential caused by the celestial bodies on... [to full text] / Disertacijoje pateikti dangaus kūnų įtakos sunkio lauko elementams tyrimai ir nagrinėjamas Mėnulio ir Saulės poveikis geodeziniams matavimams. Pagrindinis disertacijos tikslas – ištirti ir įvertinti dangaus kūnų poveikį sunkio lauko elementams ir patobulinti dangaus kūnų poveikio geodeziniams matavimams įvertinimo metodikas. Atlikto darbo rezultatus galima panaudoti vertinant dangaus kūnų poveikį geodeziniams, gravimetriniams ir geodezinės astronomijos matavimams, taip pat pasirenkant Žemės ir geoido paviršius bei sunkio sistemą, dangaus kūnų poveikio įvertinimo atžvilgiu. Disertaciją sudaro įvadas, keturi skyriai ir rezultatų apibendrinimas. Įvadiniame skyriuje pagrindžiama tiriamoji problema, apibrėžiamas problemos aktualumas, formuluojamas darbo tikslas bei uždaviniai, aprašomas mokslinis darbo naujumas, pateikiami ginamieji disertacijos teiginiai pristatomos autoriaus publikacijos ir pranešimai konferencijose, aprašoma disertacijos struktūra. Pirmasis skyrius skirtas literatūros analizei. Jame nagrinėjami esami Žemės potvynių įvertinimo metodai ir jų tikslumas. Išanalizuota mokslinė literatūra dangaus kūnų poveikio Žemės sunkio laukui ir geodeziniams matavimams klausimais. Identifikuotos problemos dangaus kūnų poveikio vertinime ir suformuluoti uždaviniai, kuriuos disertaciniame darbe tikslinga išspręsti. Antrajame disertacijos skyriuje pateiktas teorinis tyrimas. Nagrinėjamas dangaus kūno lemiamo potvynio potencialo eilutės narių poveikis sunkio lauko elementams:... [toliau žr. visą tekstą]

The influence of long-term load on the reinforced concrete beams strength-ened with a carbon fiber composite layer in the tensioned zone is considered in this dissertation. The evolution of deformations in the layers of the beams and the evolution of beam deflection is analyzed. The load carrying capacities after a long-term load action are also determined herein. The built-up-bars theory for calculation of deflections and the load carrying capacity after a long-term load action is presented in this dissertation. The thesis consists of an introduction, four main chapters, the results and conclusions and a list of used literature. The introduction describes the major objectives of the dissertation. It pre-sents the aims, the methods of research, the scientific novelty and defended pro-positions. The first chapter reviews application of carbon fiber composite polymer in strengthening structures. The influence of a long term load on concrete, polymer matrix, carbon fiber reinforced composite, strengthened concrete beams is also considered. In addition, it considers the calculation methods that evaluate the long term load influence. The second chapter is dedicated to applying of the built-up-bars theory in calculation of deflections and the load carrying capacity, including long term load action. Also, variation of concrete and carbon fiber composite contact stiff-ness is presented in this chapter. Chapter three presents the carried out experiments. It describes the experi-mental... [to full text] / Disertacijoje nagrinėjama lenkiamųjų gelžbetoninių sijų, tempiamojoje zo-noje sustiprintų anglies pluošto kompozitu, elgsena esant ilgalaikiam statinės apkrovos poveikiui. Disertacinio darbo tikslas – atlikti eksperimentinius tyrimus ir nustatyti ilgalaikės apkrovos poveikį sijos laikomajai galiai bei įlinkių vysty-muisi; apskaičiuoti sijos įlinkį pagal sudėtinių strypų teoriją įvertinant ilgalaikės statinės apkrovos poveikį bei betono ir anglies pluošto kompozito jungties stan-dumo pokytį dėl šlyties valkšnumo deformacijų prieaugio. Disertaciją sudaro: įvadas, keturi pagrindiniai skyriai, rezultatų apibendri-nimas ir išvados, naudotos literatūros sąrašas, autoriaus publikacijų disertacijos tema sąrašas. Įvadiniame skyriuje nagrinėjama tiriamoji problema ir darbo aktualumas, nurodytas tyrimų objektas, suformuluoti darbo tikslai ir uždaviniai, pateikta ty-rimų metodika, aptarta darbo svarba ir praktinė rezultatų reikšmė, pristatyti gi-namieji teiginiai. Pirmajame skyriuje atlikta literatūros apžvalga. Čia nagrinėjamas ilgalaikės apkrovos ir aplinkos poveikis anglies pluošto kompozitui, kompozito ir betono jungčiai bei gelžbetoninių sijų elgsenai. Pateikiami sustiprintų sijų elgsenos eks-perimentinių tyrimų, veikiant trumpalaike ir ilgalaike apkrova, rezultatai. Apta-riamos skaičiavimo metodikos, vertinančios ilgalaikį apkrovos poveikį. Antrajame skyriuje pateikiama skaičiavimo metodika, grindžiama sudėtinių strypų teorija. Skaičiavimo metodika skirta sijų, sustiprintų anglies... [toliau žr. visą tekstą]

This thesis investigates the performance of GFRP pretensioned concrete slabs and compares their flexural behaviour with GFRP reinforced and steel prestressed concrete slabs. A total of 12 slabs were cast in this program. The slab mid-span deflections are theoretically predicted and the results indicate that the short-term response of GFRP prestressed concrete slabs can be predicted well by the existing methods. Long-term deflection behaviour has been estimated using the Age Adjusted Effective Modulus Method by incorporating three creep and shrinkage models. A large influence of creep and shrinkage models on the theoretical determination is observed and the use of long term multipliers is not suitable for GFRP prestressed concrete members. The slabs were instrumented for long-term monitoring using strain gauges and fibre-optic sensors. It was concluded that the electrical strain gauges can be successfully used for long-term strain monitoring.

Electric Discharge Machining (EDM) is a process for eroding and removing material by transient action of electric sparks on electrically conductive materials immersed in a dielectric liquid and separated by a small gap. A spark-eroded surface is a surface with matt appearance and random distribution of overlapping craters. It is mechanically hard and stressed close to ultimate tensile strength of the material and sometimes covered with a network of micro cracks. The violent nature of the process leads a unique structure on the machined surface and generates residual stresses due mainly to the non-homogeneity of heat flow and metallurgical transformations. An extensive experimental study is presented to explore the surface and sub-surface characteristics together with the residual stresses induced by the process. Layer removal method is used to measure the residual stress profile in function of depth beneath. A finite element based model is proposed to determine residual stresses and compared with the experimental results. The residual stress pattern is found to be unchanged with respect to machining parameters. Thus, a unit amplitude shape function representing change in curvature with respect to removal depth is proposed. The proposed form is found as a special form of Gauss Distribution, which is the sum of two Gaussian peaks, with the same amplitude and pulse width but opposite center location that is represented by three constant coefficients. In each case, agreement with the proposed form is established with experimental results. Results have shown that these coefficients have a power functional dependency with respect to released energy.

The current design procedure for steel frame structures is a two-step process including an elastic analysis to determine design actions and a separate member capacity check. This design procedure is unable to trace the full range of load-deflection response and hence the failure modes of the frame structures can not be accurately predicted. In recent years, the development of advanced analysis methods has aimed at solving this problem by combining the analysis and design tasks into one step. Application of the new advanced analysis methods permits a comprehensive assessment of the actual failure modes and ultimate strengths of structural steel systems in practical design situations. One of the advanced analysis methods, the refined plastic hinge method, has shown great potential to become a practical design tool. However, at present, it is only suitable for a special class of steel frame structures that is not subject to lateral torsional buckling effects. The refined plastic hinge analysis can directly account for three types of frame failures, gradual formation of plastic hinges, column buckling and local buckling. However, this precludes most of the steel frame structures whose behaviour is governed by lateral torsional buckling. Therefore, the aim of this research is to develop a practical advanced analysis method suitable for general steel frame structures including the effects of lateral-torsional buckling. Lateral torsional buckling is a complex three dimensional instability phenomenon. Unlike the in-plane buckling of beam-columns, a closed form analytical solution is not available for lateral torsional buckling. The member capacity equations used in design specifications are derived mainly from testing of simply supported beams. Further, there has been very limited research into the behaviour and design of steel frame structures subject to lateral torsional buckling failures. Therefore in order to incorporate lateral torsional buckling effects into an advanced analysis method, a detailed study must be carried out including inelastic beam buckling failures. This thesis contains a detailed description of research on extending the scope of advanced analysis by developing methods that include the effects of lateral torsional buckling in a nonlinear analysis formulation. It has two components. Firstly, distributed plasticity models were developed using the state-of-the-art finite element analysis programs for a range of simply supported beams and rigid frame structures to investigate and fully understand their lateral torsional buckling behavioural characteristics. Nonlinear analyses were conducted to study the load-deflection response of these structures under lateral torsional buckling influences. It was found that the behaviour of simply supported beams and members in rigid frame structures is significantly different. In real frame structures, the connection details are a decisive factor in terms of ultimate frame capacities. Accounting for the connection rigidities in a simplified advanced analysis method is very difficult, but is most critical. Generally, the finite element analysis results of simply supported beams agree very well with the predictions of the current Australian steel structures design code AS4100, but the capacities of rigid frame structures can be significantly higher compared with Australian code predictions. The second part of the thesis concerns the development of a two dimensional refined plastic hinge analysis which is capable of considering lateral torsional buckling effects. The formulation of the new method is based on the observations from the distributed plasticity analyses of both simply supported beams and rigid frame structures. The lateral torsional buckling effects are taken into account implicitly using a flexural stiffness reduction factor in the stiffness matrix formulation based on the member capacities specified by AS4100. Due to the lack of suitable alternatives, concepts of moment modification and effective length factors are still used for determining the member capacities. The effects of connection rigidities and restraints from adjacent members are handled by using appropriate effective length factors in the analysis. Compared with the benchmark solutions for simply supported beams, the new refined plastic hinge analysis is very accurate. For rigid frame structures, the new method is generally more conservative than the finite element models. The accuracy of the new method relies on the user's judgement of beam segment restraints. Overall, the design capacities in the new method are superior to those in the current design procedure, especially for frame structures with less slender members. The new refined plastic hinge analysis is now able to capture four types of failure modes, plastic hinge formation, column buckling, local buckling and lateral torsional buckling. With the inclusion of lateral torsional buckling mode as proposed in this thesis, advanced analysis is one step closer to being used for general design practice.

The operating motion of a ground compactor uses high power vibrations to improve mechanical properties of a compacted ground. This motion gives a good base for the vibration analysis with an aid of Signal Processing. In this thesis, the motion of a bottom plate in a compactor is of the main interest. The thesis concerns usage of two main spectral analyzing tools, Power Spectrum estimators and Power Spectral Density estimators, presenting advantages and disadvantages in the application of a vibration analysis. Moreover, an influence of two window applications, a Flattop window, and a Hanning window, is described in relation to both analyzing approaches. The results present problems that occur when a vibration with a present modulated frequency is analyzed and how a Power Spectral Density estimator arise in a more consistent estimate over analyzed vibration spectrum. What is more, an Ordinary Deflection Shapes for a simplified bottom plate model, under different motion excitations, are presented at the end of this thesis, giving a better view of the operational motion of an analyzed system.

abstract: Distributed inference has applications in a wide range of fields such as source localization, target detection, environment monitoring, and healthcare. In this dissertation, distributed inference schemes which use bounded transmit power are considered. The performance of the proposed schemes are studied for a variety of inference problems. In the first part of the dissertation, a distributed detection scheme where the sensors transmit with constant modulus signals over a Gaussian multiple access channel is considered. The deflection coefficient of the proposed scheme is shown to depend on the characteristic function of the sensing noise, and the error exponent for the system is derived using large deviation theory. Optimization of the deflection coefficient and error exponent are considered with respect to a transmission phase parameter for a variety of sensing noise distributions including impulsive ones. The proposed scheme is also favorably compared with existing amplify-and-forward (AF) and detect-and-forward (DF) schemes. The effect of fading is shown to be detrimental to the detection performance and simulations are provided to corroborate the analytical results. The second part of the dissertation studies a distributed inference scheme which uses bounded transmission functions over a Gaussian multiple access channel. The conditions on the transmission functions under which consistent estimation and reliable detection are possible is characterized. For the distributed estimation problem, an estimation scheme that uses bounded transmission functions is proved to be strongly consistent provided that the variance of the noise samples are bounded and that the transmission function is one-to-one. The proposed estimation scheme is compared with the amplify and forward technique and its robustness to impulsive sensing noise distributions is highlighted. It is also shown that bounded transmissions suffer from inconsistent estimates if the sensing noise variance goes to infinity. For the distributed detection problem, similar results are obtained by studying the deflection coefficient. Simulations corroborate our analytical results. In the third part of this dissertation, the problem of estimating the average of samples distributed at the nodes of a sensor network is considered. A distributed average consensus algorithm in which every sensor transmits with bounded peak power is proposed. In the presence of communication noise, it is shown that the nodes reach consensus asymptotically to a finite random variable whose expectation is the desired sample average of the initial observations with a variance that depends on the step size of the algorithm and the variance of the communication noise. The asymptotic performance is characterized by deriving the asymptotic covariance matrix using results from stochastic approximation theory. It is shown that using bounded transmissions results in slower convergence compared to the linear consensus algorithm based on the Laplacian heuristic. Simulations corroborate our analytical findings. Finally, a robust distributed average consensus algorithm in which every sensor performs a nonlinear processing at the receiver is proposed. It is shown that non-linearity at the receiver nodes makes the algorithm robust to a wide range of channel noise distributions including the impulsive ones. It is shown that the nodes reach consensus asymptotically and similar results are obtained as in the case of transmit non-linearity. Simulations corroborate our analytical findings and highlight the robustness of the proposed algorithm. / Dissertation/Thesis / Ph.D. Electrical Engineering 2013

Embora sejam reconhecidas diversas vantagens na adição de fibras curtas de aço ao concreto (CRFA), em especial o ganho de tenacidade, pouco se sabe a respeito da fluência desses materiais compostos. Este trabalho teve como objetivo principal investigar o potencial e as dificuldades inerentes de um método de avaliação experimental da fluência pelo ensaio de vigas, como possível alternativa aos ensaios de compressão axial já consagrados. Ao mesmo tempo, considerando a nova tendência de exploração de compósitos híbridos - formados por fibras de diferentes características, de modo a obter respostas adequadas aos processos de micro e macrofissuração - tomou-se como objeto de estudo experimental um conjunto de modelos e corpos-de-prova de CRFA comum e de CRFA híbrido, este formado pela combinação de fibras de aço de diferentes comprimentos, umas mais longas e outras mais curtas. Para caracterização dos materiais, foram efetuados ensaios para determinação das principais propriedades mecânicas de interesse em distintas idades. As proporções da mistura adotada neste programa experimental foram baseadas em dados de estudos anteriores, que suscitaram investigações mais detalhadas. Entretanto, neste particular programa de ensaios, a adição das fibras, principalmente as mais curtas, acarretou maior teor de ar incorporado ao compósito, o que penalizou o seu desempenho em alguns aspectos. Os resultados desses ensaios demonstraram pouca influência das fibras sobre as propriedades de resistência à compressão, módulo de elasticidade e resistência à tração por compressão diametral. Quanto à fluência, o desempenho do CRFA e do compósito híbrido foi inferior ao da matriz. Por outro lado, notou-se maior restrição à retração do concreto com a adição de fibras. Na análise dos resultados experimentais, o estudo das flechas diferidas foi efetuado pelas correspondentes deformações, para interpretação do fenômeno por meio das curvas de fluência específica. O ajuste de resultados experimentais para curvas de fluência específica demonstrou que a fluência em vigas, apesar de apresentar - comparativamente aos modelos teóricos fundamentados em ensaios de compressão - maior taxa inicial, maiores coeficientes de fluência e estabilização aparentemente mais rápida, pode ser representada por modelos teóricos semelhantes aos usuais. As curvas de tendência determinadas para a matriz foram comparadas com aquelas derivadas de expressões dadas por normas técnicas (NBR 6118:2003 e ACI209:1982), assim como com as obtidas em simulações numéricas efetuadas como software DIANA®. A fluência também foi avaliada experimentalmente em vigas entalhadas, submetidas apenas à ação do peso-próprio, sendo estes ensaios também simulados por meio de modelagem numérica e aplicação de conceitos da mecânica da fratura. Os resultados analisados permitem dizer que há possibilidade de avaliar a fluência pela metodologia estudada, o que oferece um método alternativo para avaliação experimental da fluência. Nesta pesquisa, avaliou-se também a alteração de rigidez das vigas ensaiadas em decorrência dos efeitos do tempo, por meio de ensaios dinâmicos de vibração livre, segundo a ASTM C-215:1991a. / Despite of the well known advantages of steel fiber addition to concrete (SFRC), especially the toughness improvement, only a few number of studies has been developed about creep on these composites. The main purpose of this research is to investigate the feasibility and inherent difficulties related to a particular creep evaluation method. This method is based on beam test results and their analysis by fracture mechanics theory. It is intended to become an alternative method instead of the usual creep analysis of axial compression test results. At the same time, looking at the development of hybrid composites - made of distinct kind of fibers to obtain the best responses for micro and macrocracking - an experimental program was performed. Specimens molded with plain concrete, ordinary SFRC and hybrid SFRC were tested in flexure, the last one made of an association of short and large steel fibers. Characterization tests were performed to obtain the main mechanical properties of these materials at several ages. The mixture proportions were based in previous studies, where good performance characteristics were observed in hybrid composites. Nevertheless, in this particular test series, the addition of shorter steel fibers resulted in high air contents, what probably caused the decrease of the composite\'s performance in some aspects. The test results displayed low influence of the fiber addition on mechanical properties such compression strength, modulus of elasticity and tensile strength. Creep performance showed to be worse in the SFRC and hybrid composites than in plain concrete matrix. However, the reinforcement with steel fibers improved the shrinkage restrain. The analysis of the long-term beam deflections was made by finding the corresponding strains in the sections. Afterwards, specific creep functions were obtained by regression methods. The experimental creep functions were compared to the existing ones in literature and design codes. Despite of some differences, such as higher initial creep rate, higher creep coefficients and faster stabilization, it may be concluded that these functions represented quite well the phenomenon. Also experimental functions for plain concrete showed good results when compared to creep prediction model given by design codes, such as the Brazilian NBR 6118:2003 and ACI 209:1982. Comparison with numerical modeling results also gave satisfactory results. Creep in flexure was also evaluated by means of notched beam tests, where the sustained load was performed only by the beam self-weight. The test results were analyzed by numerical modeling and application of fracture mechanic concepts. The overall results showed the feasibility of creep assessing by the beam test method, which can be, after further detailed test series, a good alternative method instead of axial compression tests. Also dynamic free vibration tests were performed, according to ASTM C-215:1991 recommendations, to investigate the beam stiffness loss due to long term loading effects. These tests showed that modal analysis can be a helpful method in the tests, since it does not introduce damages in the test specimens.