Countries world-over have thousands of critical structures and bridges which have been built decades back when strength-based designs were the order of the day. Over the years, magnitude and frequency of loadings on these have increased. Also, these structures have been exposed to environmental degradation during their service life. Hence, structural health monitoring (SHM) has attracted the attention of researchers, world over. Structural health monitoring is recommended both for vulnerable old bridges and structures as well as for new important structures. Structural health monitoring as a principle is derived from condition monitoring of machinery, where the day-to-day recordings of sound and vibration from machinery is compared and sudden changes in their features is reported for inspection and trouble-shooting. With the availability of funds for repair and retrofitting being limited, it has become imperative to rank buildings and bridges that require rehabilitation for prioritization. Visual inspection and expert judgment continues to rule the roost. Non-destructive testing techniques though have come of age and are providing excellent inputs for judgment cannot be carried out indiscriminately. They are best suited for evaluating local damage when restricted areas are investigated in detail. A few modern bridges, particularly long-span bridges have been provided with sophisticated instrumentation for health monitoring. It is necessary to identify local damages existing in normal bridges. The methodology adopted for such identification should be simple, both in terms of investigations involved and the instrumentation. Researchers have proposed various methodologies including damage identification from mode shapes, wavelet-based formulations and optimization-based damage identification and instrumentation schemes and so on. These are technically involved but may be difficult to be applied for all critical bridges, where the sheer volume of number of bridges to be investigated is enormous. Ideally, structural health monitoring has to be carried out in two stages: (a) Stage-1: Remote monitoring of global damage indicators and inference of the health of the structure. Instrumentation for this stage should be less, simple, but at critical locations to capture the global damage in a reasonable sense. (b) Stage -2: If global indicators show deviation beyond a specified threshold, then a detailed and localized instrumentation and monitoring, with controlled application of static and dynamic loads is to be carried out to infer the health of the structure and take a decision on the repair and retrofit strategies. The thesis proposes the first stage structural health monitoring methodology using natural frequencies and static deflections as damage indicators. The idea is that the stage-1 monitoring has to be done for a large number of bridges and vulnerable structures in a remote and wire-less way and a centralized control and processing unit should be able to number-crunch the in-coming data automatically and the features extracted from the data should help in determining whether any particular bridge warrants second stage detailed investigation. Hence, simple and robust strategies are required for estimating the health of the structure using some of the globally available response data. Identification methodology developed in this thesis is applicable to distributed smeared damage, which is typical of reinforced concrete structures. Simplified expressions and methodologies are proposed in the thesis and numerically and experimentally validated towards damage estimation of typical structures and elements from measured natural frequencies and static deflections. The first-order perturbation equation for a dynamical system is used to derive the relevant expressions for damage identification. The sensitivity of Eigen-value-cumvector pair to damage, modeled as reduction in flexural rigidity (EI for beams, AE for axial rods and Et 12(1 2 )3− μ for plates) is derived. The forward equation relating the changes in EI to changes in frequencies is derived for typical structural elements like simply-supported beams, plates and axial rods (along with position and extent of damage as the other controlling parameters). A distributed damage is uniquely defined with its position, extent and magnitude of EI reduction. A methodology is proposed for the inverse problem, making use of the linear relationship between the reductions in EI (in a smeared sense) to Eigen-values, such that multiple damages could be estimated using changes in natural frequencies. The methodology is applied to beams, plates and axial rods. The performance of this inverse methodology under influence of measurement errors is investigated for typical error profiles. For a discrete three dimensional structure, computationally derived sensitivity matrix is used to solve the damages in each floor levels, simulating the post-earthquake damage scenario. An artificial neural network (ANN) based Radial basis function network (RBFN) is also used to solve the multivariate interpolation problem, with appropriate training sets involving a number of pairs of damage and Eigen-value-change vectors. The acclaimed Cawley-Adams criteria (1979) states that, “the ratio of changes in natural frequencies between two modes is independent of the damage magnitude” and is governed only by the position (or location) and extent of damage. This criterion is applied to a multiple damage problem and contours with equal frequency change ratios, termed as Iso_Eigen_value_change contours are developed. Intersection of these contours for different pairs of frequencies shows the position and extent of damage. Experimental and analytical verification of damage identification methodology using Cawley-Adams criteria is successfully demonstrated. Sensitivity expressions relating the damages to changes in static deflections are derived and numerically and experimentally proved. It is seen that this process of damage identification from static deflections is prone to more errors if not cautiously exercised. Engineering and physics based intuition is adopted in setting the guidelines for efficient damage detection using static deflections. In lines of Cawley-Adams criteria for frequencies, an invariant factor based on static deflections measured at pairs of symmetrical points on a simply supported beam is developed and established. The power of the factor is such that it is governed only by the position of damage and invariant with reference to extent and magnitude of damage. Such a revelation is one step ahead of Caddemi and Morassi’s (2007) recent paper, dealing with static deflection based damage identification for concentrated damage. The invariant factor makes it an ideal candidate for base-line-free measurement, if the quality and resolution of instrumentation is good. A moving damage problem is innovatively introduced in the experiment. An attempt is made to examine wave-propagation techniques for damage identification and a guideline for modeling wave propagation as a transient dynamic problem is done. The reflected-wave response velocity (peak particle velocity) as a ratio of incident wave response is proposed as a damage indicator for an axial rod (representing an end-supported pile foundation). Suitable modifications are incorporated in the classical expressions to correct for damping and partial-enveloping of advancing wave in the damage zone. The experimental results on axial dynamic response of free-free beams suggest that vibration frequency based damage identification is a viable complementary tool to wave propagation. Wavelet-multi-resolution analysis as a feature extraction tool for damage identification is also investigated and structural slope (rotation) and curvatures are found to be the better indicators of damage coupled with wavelet analysis. An adaptive excitation scheme for maximizing the curvature at any arbitrary point of interest is also proposed. However more work is to be done to establish the efficiency of wavelets on experimentally derived parameters, where large noise-ingression may affect the analysis. The application of time-period based damage identification methodology for post-seismic damage estimation is investigated. Seismic damage is postulated by an index based on its plastic displacement excursion and the cumulative energy dissipated. Damage index is a convenient tool for decision making on immediate-occupancy, life-safety after repair and demolition of the structure. Damage sensitive soft storey structure and a weak story structure are used in the non-linear dynamic analysis and the DiPasquale-Cakmak (1987) damage index is calibrated with Park-Ang (1985) damage index. The exponent of the time-period ratio of DiPasquale-Cakmak model is modified to have consistency of damage index with Park-Ang (1985) model.

When subjected to a combination of moment and shear force, a reinforced concrete (RC) beam with either little or no transverse reinforcement can fail in shear before reaching its full flexural strength. This type of failure is sudden in nature and usually disastrous because it does not give sufficient warning prior to collapse. To prevent this type of shear failure, reinforced concrete beams are traditionally reinforced with stirrups. However, the use of stirrups is not always cost effective since it increases labor costs, and can make casting concrete difficult in situations where closely-spaced stirrups are required. The use of steel fiber reinforced concrete (SFRC) could be considered as a potential alternative to the use of traditional shear reinforcement. Concrete is very weak and brittle in tension, SFRC transforms this behaviour and improves the diagonal tension capacity of concrete and thus can result in significant enhancements in shear capacity. However, one of the drawbacks associated with SFRC is that the addition of fibers to a regular concrete mix can cause problems in workability. The use of self-consolidating concrete (SCC) is an innovative solution to this problem and can result in improved workability when fibers are added to the mix. The thesis presents the experimental results from tests on twelve slender self-consolidating fiber reinforced concrete (SCFRC) beams tested under four-point loading. The results demonstrate the combined use of SCC and steel fibers can improve the shear resistance of reinforced concrete beams, enhance crack control and can promote flexural ductility. Despite extensive research, there is a lack of accurate and reliable design guidelines for the use of SFRC in beams. This study presents a rational model which can accurately predict the shear resistance of steel fiber reinforced concrete beams. The thesis also proposes a safe and reliable equation which can be used for the shear design of SFRC beams.

Neste trabalho estudou-se o reforço de vigas T de concreto armado tanto por meio de adição de armadura longitudinal ao bordo tracionado envolvida por um material compósito (argamassa com fibras curtas de aço), quanto pela aplicação de uma capa de pequena espessura de microconcreto de alta resistência ao bordo comprimido. Para estudar as possibilidades da aplicação prática destas duas técnicas de reforço avaliou-se o comportamento das vigas reabilitadas verificando a influência: da atuação de um pré-carregamento durante a execução do reforço, das deformações diferidas diferenciais (fluência e retração) existentes entre os materiais novos e antigos e, dos mecanismos de resistência mobilizados na transmissão de esforços na junta - formada pela ligação do substrato ao concreto do reforço - ou entre as barras de aço tracionadas preexistentes e adicionadas em função da ausência de estribos envolvendo-as. Para redimensionar as peças reforçadas no bordo tracionado foram realizados ensaios complementares para identificar, dentre as várias fibras disponíveis comercialmente, qual a que proporcionaria ao material compósito, um confinamento suficiente que evitasse a ruptura prematura da viga pela tendência de deslizamento relativo entre as barras de aço tracionadas devida à ausência de estribos neste local. Para redimensionar as peças reforçadas no bordo comprimido realizou-se ensaios complementares para determinar as propriedades viscoelásticas dos materiais usados no substrato e no reforço, tornando possível estimar as descontinuidades geradas nos estados de tensão e deformação ao longo do tempo já que tais materiais são moldados e submetidos a carregamentos em idades distintas. Os resultados dos ensaios das vigas reforçadas de seção T foram analisados e comparados com previsões teóricas feitas a partir da adaptação de métodos analíticos convencionais recomendados por norma para estruturas novas, e a partir de simulações numéricas usando um programa computacional baseado no método dos elementos finitos. Do estudo realizado foi possível: comprovar a eficiência das técnicas de reforço propostas estando as peças submetidas ou não a um pré-carregamento durante a execução da intervenção, compatibilizar alguns dos conhecimentos teóricos existentes a fim de poder usá-los na análise teórica das vigas reabilitadas, além de reunir uma série de informações úteis que podem ser exploradas na definição de estratégias e procedimentos de projeto de estruturas reabilitadas semelhantes / This paper reports on the results of a study about the behavior of reinforced concrete T-beams rehabilitated using two different techniques. The first technique consists of the addition of longitudinal reinforcement embedded in a steel fiber reinforced highperformance mortar at the bottom face of the member. The second technique consists of rehabilitation by adding a thin overlay of high-strength concrete to the compression zone. The parameters analyzed to verify the possibilities of practical applications of these techniques were: the effect of a pre-loading acting on the beams during their rehabilitation, the differential time-dependent deformations (creep and shrinkage) between the new concrete and existing base, the mechanisms of resistance mobilized along the interface formed by old and new concrete or between pre-existent steel bars and added steel bars that are not involved by stirrups. Previous tests were carried out to make it possible to redesign the intervention adequately. Theses tests yield useful information about which type and volume of steel fibers need to be added to composite mortar to avoid the premature rupture of the strengthened beam caused by relative slipping between the layers of steel tensioned bars. These tests also give information about the viscoelastic properties of the materials used to manufacture the T-beams. The test results were analyzed and compared with the results of analytic models and numeric models based on the method of the finite elements. Based on this study, it can be stated that the proposed techniques are really efficient even if the beams are submitted to a pre-loading during the process of rehabilitation. Also, existing theoretical knowledge was organized to support the theoretical analysis of the rehabilitated beams, besides gathering useful information that can be explored in the definition of strategies and procedures of similar projects of rehabilitated structures

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Crack propagation in structures when subjected to fatigue loading, follows three different phases namely - short crack growth, stable crack growth and unstable crack growth. Accurate fatigue life prediction demands the consideration of every crack propagation phase rather than only the stable crack growth stage. Further, the use of existing crack growth laws in structures with small cracks under-predicts the growth rate compared to experimentally observed ones, thereby leading to an unsafe design and keeping the structure in a potentially dangerous state. In the present work, an attempt is made to establish fatigue crack propagation laws for plain concrete, reinforced concrete and concrete-concrete jointed interfaces from first principles using the concepts of dimensional analysis and self-similarity. Different crack growth laws are proposed to understand the behavior in each of the three regimes of the fatigue crack growth curve. Important crack growth characterizing material and geometrical parameters for each zone are included in the proposed analytical models. In real life applications to structures, the amplitude of cyclic loading rarely remains constant and is subjected to a wide spectrum of load amplitudes. Furthermore, the crack growth behavior changes in the presence of high amplitude load spikes within a constant amplitude history and this is incorporated in the model formulation. Using scaling laws, an improved understanding of the scaling behavior on different parameters is achieved. The models describing different regimes of crack propagation are finally unified to obtain the entire crack growth curve and compute the total fatigue life. In addition, crack growth analysis is performed for a reinforced concrete member by modifying the model derived for plain concrete in the Paris regime. Energy dissipation occurring due to shake-down phenomenon in steel reinforcement is addressed. The bond-slip mechanism which is of serious concern in reinforced concrete members is included in the study and a method is proposed for the prediction of residual moment carrying capacity as a function of relative crack depth. The application of the proposed analytical model in the computation of fatigue crack growth is demonstrated on three practical problems – beam in flexure, concrete arch bridge and a patch repaired beam. Through a sensitivity study, the influence of different parameters on the crack growth behavior is highlighted.

When subjected to a combination of moment and shear force, a reinforced concrete (RC) beam with either little or no transverse reinforcement can fail in shear before reaching its full flexural strength. This type of failure is sudden in nature and usually disastrous because it does not give sufficient warning prior to collapse. To prevent this type of shear failure, reinforced concrete beams are traditionally reinforced with stirrups. However, the use of stirrups is not always cost effective since it increases labor costs, and can make casting concrete difficult in situations where closely-spaced stirrups are required. The use of steel fiber reinforced concrete (SFRC) could be considered as a potential alternative to the use of traditional shear reinforcement. Concrete is very weak and brittle in tension, SFRC transforms this behaviour and improves the diagonal tension capacity of concrete and thus can result in significant enhancements in shear capacity. However, one of the drawbacks associated with SFRC is that the addition of fibers to a regular concrete mix can cause problems in workability. The use of self-consolidating concrete (SCC) is an innovative solution to this problem and can result in improved workability when fibers are added to the mix. The thesis presents the experimental results from tests on twelve slender self-consolidating fiber reinforced concrete (SCFRC) beams tested under four-point loading. The results demonstrate the combined use of SCC and steel fibers can improve the shear resistance of reinforced concrete beams, enhance crack control and can promote flexural ductility. Despite extensive research, there is a lack of accurate and reliable design guidelines for the use of SFRC in beams. This study presents a rational model which can accurately predict the shear resistance of steel fiber reinforced concrete beams. The thesis also proposes a safe and reliable equation which can be used for the shear design of SFRC beams.

The topic o thlis thesis is design of the structure of a bridge. The beam structure is chosen from three variants of the solution, the structure is formed by a bracket above the pillars and prepared prestressed beams. Various construction procedures have been verified and assessed for the serviceability and load-bearing limit states according to the applicable standards and regulations. Drawing documentation and static calculation are processed.

[pt] Este trabalho tem como objetivo avaliar a resistência à força cortante de vigas de concreto reforçado com barras de fibras de vidro e investigar a contribuição dos diferentes mecanismos de transferência do esforço cortante para a resistência final da viga. Um programa experimental foi conduzido, incluindo ensaios para: caracterização do material, para avaliar o efeito de pino, para avaliar o engrenamento dos agregados e, por fim, ensaios de flexão de quatro pontos em vigas. Diferentes parâmetros foram investigados, como a quantidade de barras longitudinais para o efeito de pino, dimensão máxima do agregado graúdo para engrenamento dos agregados e a presença de estribos para os ensaios de vigas. O monitoramento do desenvolvimento da fissura crítica foi realizado com auxílio de correlação de imagem digital (digital image correlation, DIC, em inglês). Os resultados mostraram que não foi evidenciada diferença no comportamento de efeito de pino e de engrenamento dos agregados através dos ensaios realizados. Para os ensaios de vigas, observou-se que todos os espécimes apresentaram ruptura por tração da diagonal crítica e, para vigas sem estribos, a ação do efeito de pino pareceu contribuir significativamente para a resistência ao cisalhamento após a fissura, quando a carga diminui e as deflexões aumentam, resultado do menor engrenamento dos agregados à medida que a fissura se abre. Foi observado que a presença de estribos aumentou em até três vezes a resistência ao cortante das vigas ensaiadas e que houve ruptura do estribo na parte da dobra. / [en] This work aims to evaluate the shear strength of reinforced concrete beams with glass fiber reinforced polymer bars and to investigate qualitatively the contribution of the different shear transfer mechanisms to the final strength of the beam. An experimental program was conducted, including material characterization, dowel action tests, push-off tests, and finally, four-point bending tests on beams. Different parameters were investigated, such as the number of longitudinal bars for dowel action effect, maximum size of the coarse aggregate for aggregate interlock and the presence of stirrups for the beam tests. The monitoring of the development of the critical crack was performed with the aid of digital image correlation (DIC). The results showed that there was no difference in the behavior of the dowel action effect and the aggregate interlock through the tests performed. For beam tests, it was observed that all the specimens exhibited a concrete diagonal tension failure and for beams without stirrups, dowel action seemed to provide significant contribution to the shear strength after the crack, when the load reduces and the deflections increases, resulting from the loss of aggregate interlock as the crack opens. It was also observed that the presence of stirrups increased up to three times the shear strength of the beams tested and that there was rupture of the stirrup at the bent region.

The scope of this diploma thesis is design and processing of the project documentation of the guesthouse along with coffee shop. The proposed object of this thesis is located in the village Čeladná next to the golf course Prosper Golf Resort Čeladná, in the location designated for mixed constructions. One of the double-storeyed, non-cellular object with roofed surface and steep roof. The object is based on the base stripes made of plain concrete and on the reinforced concrete flaps. Carrying, perihepral and dividing walls are designed on the Velox systém. The same systém was used to design roof constructions. In the rooms with excessive width are filled with reinforced concrete columns. Part of the guesthouse and second floor of the coffee shop is designed with ventilated facade with wood paneling ThermoWood. The object is divided in two parts with common entrance section. One part of the coffee shop has ability to handle capacity of 70 guests. Part of the double-storeyed coffee shop is hygienic facilities, kitchen, room for employees, warehouse and mechanical ventilation. Second part of the object is the guesthouse with flat of the manager of the guesthouse. The guesthouse consists of room with hygienic facilities for 18 people, including barrier-free room. The rooms are divided in the first floor on separate units, the rooms with hygienic facilities and the apartments in the second floor has two rooms, kitchen and hygienic facilities. For the next parts of the guesthouse is warehouse clean and dirty laundry and shared kitchen. The whole first floor is designed as barrier-free. In front of the object is the parking lot for 21 cars, which 3 of the parking places are for the cars of the disabled.

The diploma thesis processes project documentation in the stage of construction for modernization of an apartment house near the center on the street Vlhká 22 in Brno. The building is divided into four residential floors and nonresidential basement and attic. On the first floor there are two residential units and the other four residential units. The foundation structures are made of solid bricks. The vertical load-bearing and non-load-bearing structures are also made of solid bricks. Exceptionally drywall partitions. In the basement, the ceiling structures are made of brick barrel vaults, above the above-ground floors there are wooden beamed ceilings. The roof structure of the building is made of purlin system with standing stool and covering of ceramic roof tiles. Three additional housing units will be built in the attic. In the basement, the masonry will be undercut by a chain saw, partly by pressure grouting and partly by a new layer with a waterproofing layer. All wood-beamed ceilings will be replaced with prefabricated ceiling beams with aerated concrete inserts without overhead slab. The garden part of the building will be insulated with mineral wool. The roof structure will be constructed from the street side as a shed roof and in the garden part a flat roof with a gradient layer of expanded polystyrene thermal insulation and a waterproofing layer of thermoplastic poleolefin.