Lateral load carrying capacities of reinforced concrete structures which are designed by considering only gravity loads or according to outdated earthquake codes can be insufficient. The most important problem for these buildings is the limited ductility of the frame elements. How to evaluate the performance of an existing structure and to what level to strengthen it had been major concerns for structural engineers. Recent earthquakes which occurred in the Marmara Region in the last decade have increased the number of seismic assessment projects drastically. However, there was no special guideline or code dealing with the assessment of existing buildings. In order to have uniformity in assessment projects, a new chapter has been included in the revised Turkish Earthquake Code (2006). In this study, the existing and retrofitted conditions of a reinforced concrete building were assessed comparatively by employing linear and nonlinear assessment procedures according to different seismic rehabilitation codes. The study was carried out on a six storey reinforced concrete telephone exchange building. Although there was no damage in the structure due to the recent earthquakes that occurred in the Marmara Region, the building was assessed and retrofitted in 2001 by using equivalent lateral load analysis results. The results of linear and nonlinear assessment procedures performed in the scope of this thesis, were also compared with the assessment results of this previous study. In the nonlinear assessment procedures, pushover analysis results were used. In addition to comparison of the assessment procedures, efficiency of a widely used approximate pushover method was also investigated.

Most of the older reinforced concrete (RC) buildings have columns that are deficient when the current code requirements are considered. Therefore, performance of the columns determines the performance of the structure under the effects of earthquake induced lateral loads. It is recognized that no provision is proposed in TEC2007 to estimate the failure type called flexure-shear. Behavior of columns having probability of failing in flexure-shear failure mode is mostly underestimated by TEC2007 procedures. In addition, failure type classification of columns performed according to the linear and nonlinear procedures of TEC2007 needs to be examined with respect to the test results to cover all failure types including flexure-shear failure in order to lead the engineers develop economical and realistic retrofit solutions. In this study, different methods are explored to obtain reliable estimates for the performance of code deficient shear critical RC columns. Special considerations are given to Axial-Shear-Flexure interaction (ASFI) approach due to its mechanical background. After examination of different approaches, ASFI method with proposed modifications was selected as the most reliable model and lateral load-displacement analyses were performed on a database of shear critical columns. Findings were compared with the estimations of the nonlinear procedure given in Turkish Earthquake Code (TEC2007) for database columns. In addition, drift capacity equations and simplified safe drift capacity equations are proposed in light of statistical studies on the selected column specimens. In the last part of the study, performance evaluation of columns according to nonlinear procedures of FEMA 356, TEC2007, ASCE/SEI 41 update supplement, and EUROCODE 8 were conducted.

Fundações profundas, quando solicitadas ao carregamento lateral, são regidas por três critérios de projeto: resistência última do solo, carga última do elemento estrutural e deflexão máxima. Esses critérios atuam em conjunto e é necessário que sejam analisados dessa forma, visto que a falha de um deles é capaz de acarretar o colapso de todo sistema. No que tange à resistência do solo, metodologias de capacidade de carga existentes traduzem o comportamento de solos granulares e coesivos. Dada a particularidade da atuação de solos residuais na mecânica dos solos, não há uma metodologia abrangente para estacas sujeitas a solicitação de carregamento lateral nesse tipo de solo, o qual apresenta comportamento intermediário e estrutura levemente cimentada. Em vista disso, o presente trabalho propõe um método de estimativa de capacidade de carga para estacas carregadas horizontalmente, quando inseridas em solo residual e em casos em que as mesmas apresentam topo locado em superfície de solo tratado. Dessa forma, dados de provas de carga lateral pré-existentes e ensaios de laboratório executados ao longo da pesquisa serviram como base para a proposição do método, fundamentado no comportamento do material quando solicitado ao carregamento lateral Ensaios de resistência à compressão simples, compressão oedométrica, compressão isotrópica e ensaios triaxiais com medidas de módulo cisalhante demonstram que há um ponto em que se dá a quebra da estrutura cimentada do solo, passando o mesmo a se apresentar num arranjo desestruturado, refletido em maiores deformações. Uma relação linear é capaz de equacionar a capacidade de carga, tanto para estacas inseridas em solo residual quanto para estacas executadas em solo com camada superficial melhorada. Essa relação é estabelecida entre a carga de ruptura das estacas ensaiadas e a área de solo adjacente à mesma, mobilizada pelo carregamento. Os resultados demonstram que a capacidade de carga das estacas estudadas é regida pela tensão de plastificação do material. O equacionamento proposto possibilita a obtenção da carga de ruptura com base em ensaios simples e de fácil execução, tal como o ensaio de resistência à compressão simples que estabelece relação direta com a tensão de plastificação do solo estudado. / Deep foundations, when requested to lateral loading, are governed by three design criteria: ultimate soil strength, piles’ ultimate load, and maximum deflection. These criteria act together and must be analyzed in this way, since the failure of one of them is capable of causing the collapse of the entire system. Regarding soil resistance, the current bearing capacity methodologies describe the behavior of granular and cohesive soils. Given the particular behavior of the residual soils in the soil mechanics, there is no comprehensive methodology for piles subject to lateral loads and inserted in this soil type, which presents an intermediate behavior and a lightly cemented structure. Thus, the present work proposes an estimated bearing capacity for crosswise loaded piles, when inserted in residual soil and in soil with the top layer cemented. So, data from preexisting lateral loading tests and laboratory tests, performed during the research, served as a basis for the proposition of the method, based on the behavior of the material when requested to lateral loading Unconfined compression tests, oedometer consolidation tests, isotropic compression, and triaxial tests with measures of shear modulus demonstrate that there is a point where the soil's cemented structure breaks down, presenting itself in a destructured arrangement, reflected by larger strains. A linear relationship is capable of equating the bearing capacity for both, piles inserted in residual soil and piles carried out in soil with improved surface layer. This relationship is established between the rupture load of the piles tested and the area of soil adjacent to it mobilized by the loading. The results shows that the piles' bearing capacity is governed by the yield stress of the material. The proposed equation makes it possible to obtain the rupture load based on simple and easy tests, such as the unconfined compression test that establishes a direct relationship with the yield stress of the studied soil.

Made available in DSpace on 2015-05-08T14:59:33Z (GMT). No. of bitstreams: 1 parte1.pdf: 2316235 bytes, checksum: 0033949f9aa3743186479e5db2794978 (MD5) Previous issue date: 2011-03-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In large span footbridges, it has been observed that pedestrian traffic can induce low frequency oscillations. The proximity between the natural frequencies of the structure and the frequencies of the excitation can result in the occurrence of resonance phenomenon, causing difficulties to use the structure for fear of its collapse on the part of users. Notably, the increased amplitude of the vibration, in the lateral direction that have been induced by crowds of pedestrians were brought to attention by the behavior of some footbridges that presented excessive vibration in this direction such as the Millennium Bridge in London, Solferino Bridge in Paris, among others. The lateral movement can cause alteration on the movement of the center of gravity of the pedestrian during the crossing and thus discomfort to transit on it. On the other hand, the lateral movement of the structure can induce synchronization between pedestrians and the structure s own move, resulting in amplification of vibrations, a phenomenon identified in the literature by lock-in. However, research on the relationship between frequency and amplitude of motion of the structure and percentage of synchronization that this motion induces on the pedestrians are incipient, which hampers the development of mathematical models to analyze the phenomenon. To investigate this phenomenon, we developed a control system using fuzzy logic to control a pneumatic system excitation applied in a prototype footbridge built in the laboratory. The system was conceived to provide oscillatory movement, with control of frequency and amplitude. Results showed that pedestrians tend to synchronize with the footbridge, causing the lock-in effect in the lateral direction, when the footbridge lateral oscillation approaches by half of the pedestrian pacing rate in vertical direction. / Em passarelas de grande vão, vêm sendo observado que o tráfego de pedestres pode induzir oscilações de baixas frequências. A proximidade entre as frequências naturais da estrutura e as frequências de excitação pode resultar na ocorrência do fenômeno de ressonância, ocasionando dificuldades de uso da estrutura por receio de seu colapso por parte dos usuários. Notadamente, o aumento da amplitude das vibrações, na direção lateral, induzidas por multidões de pedestres, chamou à atenção pelo comportamento de várias passarelas que apresentaram vibrações excessivas nesta direção, tais como a Millennium Bridge, em Londres; Solferino Bridge em Paris; entre outras. O efeito do movimento lateral da passarela ocasiona alteração do movimento do centro de gravidade do pedestre durante seu percurso sobre a mesma e, desta forma, desconforto ao transitar sobre ela. Por outro lado, tal efeito pode induzir uma sincronização entre o caminhar dos pedestres na estrutura e o próprio movimento da estrutura, resultando em amplificação das vibrações, um fenômeno identificado na literatura por lock-in. Entretanto, investigações sobre a relação entre amplitudes e frequências do movimento da estrutura e percentual de sincronização que tal movimento induz nos pedestres são incipientes, o que dificulta o desenvolvimento de modelos matemáticos para analisar o fenômeno. Para investigação desse fenômeno, foi desenvolvido um sistema de controle, utilizando lógica fuzzy, para controlar um sistema pneumático de excitação aplicado em um protótipo de passarela construído em laboratório. Assim, tal sistema deve proporcionar a atuação de uma força oscilatória na passarela, com frequência e amplitude controladas. Os resultados da investigação mostraram que os pedestres tendem a sincronizar-se com a passarela, provocando o efeito lock-in na direção lateral, quando a passarela oscila lateralmente próximo da metade do valor da taxa de passo do pedestre na direção vertical.

Fundações profundas, quando solicitadas ao carregamento lateral, são regidas por três critérios de projeto: resistência última do solo, carga última do elemento estrutural e deflexão máxima. Esses critérios atuam em conjunto e é necessário que sejam analisados dessa forma, visto que a falha de um deles é capaz de acarretar o colapso de todo sistema. No que tange à resistência do solo, metodologias de capacidade de carga existentes traduzem o comportamento de solos granulares e coesivos. Dada a particularidade da atuação de solos residuais na mecânica dos solos, não há uma metodologia abrangente para estacas sujeitas a solicitação de carregamento lateral nesse tipo de solo, o qual apresenta comportamento intermediário e estrutura levemente cimentada. Em vista disso, o presente trabalho propõe um método de estimativa de capacidade de carga para estacas carregadas horizontalmente, quando inseridas em solo residual e em casos em que as mesmas apresentam topo locado em superfície de solo tratado. Dessa forma, dados de provas de carga lateral pré-existentes e ensaios de laboratório executados ao longo da pesquisa serviram como base para a proposição do método, fundamentado no comportamento do material quando solicitado ao carregamento lateral Ensaios de resistência à compressão simples, compressão oedométrica, compressão isotrópica e ensaios triaxiais com medidas de módulo cisalhante demonstram que há um ponto em que se dá a quebra da estrutura cimentada do solo, passando o mesmo a se apresentar num arranjo desestruturado, refletido em maiores deformações. Uma relação linear é capaz de equacionar a capacidade de carga, tanto para estacas inseridas em solo residual quanto para estacas executadas em solo com camada superficial melhorada. Essa relação é estabelecida entre a carga de ruptura das estacas ensaiadas e a área de solo adjacente à mesma, mobilizada pelo carregamento. Os resultados demonstram que a capacidade de carga das estacas estudadas é regida pela tensão de plastificação do material. O equacionamento proposto possibilita a obtenção da carga de ruptura com base em ensaios simples e de fácil execução, tal como o ensaio de resistência à compressão simples que estabelece relação direta com a tensão de plastificação do solo estudado. / Deep foundations, when requested to lateral loading, are governed by three design criteria: ultimate soil strength, piles’ ultimate load, and maximum deflection. These criteria act together and must be analyzed in this way, since the failure of one of them is capable of causing the collapse of the entire system. Regarding soil resistance, the current bearing capacity methodologies describe the behavior of granular and cohesive soils. Given the particular behavior of the residual soils in the soil mechanics, there is no comprehensive methodology for piles subject to lateral loads and inserted in this soil type, which presents an intermediate behavior and a lightly cemented structure. Thus, the present work proposes an estimated bearing capacity for crosswise loaded piles, when inserted in residual soil and in soil with the top layer cemented. So, data from preexisting lateral loading tests and laboratory tests, performed during the research, served as a basis for the proposition of the method, based on the behavior of the material when requested to lateral loading Unconfined compression tests, oedometer consolidation tests, isotropic compression, and triaxial tests with measures of shear modulus demonstrate that there is a point where the soil's cemented structure breaks down, presenting itself in a destructured arrangement, reflected by larger strains. A linear relationship is capable of equating the bearing capacity for both, piles inserted in residual soil and piles carried out in soil with improved surface layer. This relationship is established between the rupture load of the piles tested and the area of soil adjacent to it mobilized by the loading. The results shows that the piles' bearing capacity is governed by the yield stress of the material. The proposed equation makes it possible to obtain the rupture load based on simple and easy tests, such as the unconfined compression test that establishes a direct relationship with the yield stress of the studied soil.

Although it is well established that spacing of piles within a pile group influences the lateral load resistance of that group, additional research is needed to better understand trends for large pile groups (greater than three rows) and for groups in sand. A 15-pile group in a 3x5 configuration situated in sand was laterally loaded and data were collected to derive p-multipliers. A single pile separate from the 15-pile group was loaded for comparison. Results were compared to those of a similar test in clays. The load resisted by the single pile was greater than the average load resisted by each pile in the pile group. While the loads resisted by the first row of piles (i.e. the only row deflected away from all other rows of piles) were approximately equal to that resisted by the single pile, following rows resisted increasingly less load up through the fourth row. The fifth row consistently resisted more than the fourth row. The pile group in sand resisted much higher loads than did the pile group in clay. Maximum bending moments appeared largest in first row piles. For all deflection levels, first row moments seemed slightly smaller than those measured in the single pile. Maximum bending moments for the second through fifth rows appeared consistently lower than those of the first row at the same deflection. First row moments achieved in the group in sand appeared larger than those achieved in the group in clay at the same deflections, while bending moments normalized by associated loads appeared nearly equal regardless of soil type. Group effects became more influential at higher deflections, manifest by lower stiffness per pile. The single pile test was modeled using LPILE Plus, version 4.0. Soil parameters in LPILE were adjusted until a good match between measured and computed responses was obtained. This refined soil profile was then used to model the 15-pile group in GROUP, version 4.0. User-defined p-multipliers were selected to match GROUP calculated results with actual measured results. For the first loading cycle, p-multipliers were found to be 1.0, 0.5, 0.35, 0.3, and 0.4 for the first through fifth rows, respectively. For the tenth loading, p-multipliers were found to be 1.0, 0.6, 0.4, 0.37, and 0.4 for the first through fifth rows, respectively. Design curves suggested by Rollins et al. (2005) appear appropriate for Rows 1 and 2 while curves specified by AASHTO (2000) appear appropriate for subsequent rows.

Motivated by the structure of the normal surface stress of the extended Hertzian approach [1] given due to terms of the form r^2n*(a^2-r^2)^(1/2) (n=0, 2, 4, 6…) it seems attractive to evaluate the complete elastic field also for shear loadings of this form. The reason for this lays in the demand for analytical tools for the description of mixed loading conditions as they appear for example in scratch experiments. [1] N. Schwarzer, "Elastic Surface Deformation due to Indenters with Arbitrary symmetry of revolution", J. Phys. D: Appl. Phys., 37 (2004) 2761-2772

Masters Research - Master of Philospohy (MPhil) / It has been shown that masonry material properties, in particular, unit flexural bond strength (ft), vary significantly throughout masonry structures, despite the fact that often only one type of brick and mortar are used. Unit flexural bond strength was previously identified as one of the most important material parameters contributing to the strength of clay brick unreinforced masonry (URM) walls in flexure. It was the objectives of this research, in the context of clay brick URM walls subject to vertical bending, to examine how unit flexural bond strength varied spatially in a clay brick URM wall, determine a best fit probability distribution function which can describe expected variability in unit flexural bond strength and determine how this variability and other factors affect wall behaviour and failure load using 3D non-linear finite element analysis (FEA). It was hoped that modelling a full sized clay brick URM wall subject to vertical bending using a 3D non-linear FEA model would more accurately predict wall failure load (compared to current analytical methods) and allow the examination of crack pattern development as the wall progresses to failure upon being laterally loaded. The first part of the research project was to conduct an experimental program to examine unit-to-unit spatial strength correlation within six full sized clay brick URM walls and to characterise a unit flexural bond strength probability distribution. It was observed that although weak correlation in unit flexural bond strength exists in some courses and between courses, these locations were difficult to predict and didn����t follow any particular pattern relating to for example, mortar batch. Therefore, although somewhat counter-intuitive, the results indicate that statistically significant correlation between adjacent unit flexural bond strengths is not likely to be observed. It was also observed that clay brick wall unit flexural bond strengths obtained for all of the walls tested best fit a truncated Normal probability distribution. Strength of the brick/mortar interface appeared to be governed by factors relating to workmanship (and therefore mortar quality and moisture content), weather (which can affect material characteristics like brick suction rate) and inherent material variability. It would appear that brick suction rate can significantly affect the overall strength of a URM wall. v Stochastic analysis was conducted for walls with and without uncorrelated spatial variability in unit flexural bond strength and associated tensile fracture energy (GfI ). It was found that the TNO DIANA 9.2 FEA package could be used to implement spatial variability of various material parameters and reasonably accurately model failure of clay brick URM walls in vertical bending. From the non-linear FEA model development stage, it was observed that because the brick/mortar bond has significantly more strength capacity in compression, it appears that the lateral load resistance of the wall comes from a combination of the ability of the brick/mortar bond to tensile soften while providing significant compressive resistance at the compressive edge. It was found for a spatial stochastic analysis with spatial variability in bond strength (referred to from now on as a spatial stochastic analysis), with COVs of 0.1, 0.3 and 0.5, that COV of wall failure loads were relatively small, being 0.02, 0.04 and 0.06 respectively. For the non-spatially varying stochastic analysis with fully correlated bond strength (now referred to as non-spatial stochastic analysis), with COVs of 0.1, 0.3 and 0.5, COV of wall failure loads were 0.07, 0.20 and 0.32 respectively. For the spatial stochastic analysis, it was found that with a bond strength COV increase from 0.1 to 0.5 the mean wall failure load dropped from 2.25 kPa to 2.0 kPa (an 11% reduction). Despite the relatively small drop in magnitude of the mean wall failure load with increase in bond strength COV, the mean wall failure loads were statistically different to one another. For the non-spatial stochastic analysis, mean failure load stayed relatively constant at 2.24-2.25 kPa. These results could be explained by examining the 3D wall progression to failure. For walls with spatial variability in bond strength, it is expected that wall failure load COVs would be smaller because those walls would consistently be composed of smaller valued bond strengths which would consistently contribute to weakness in the wall. For the non-spatial wall simulations, this effect would not occur as failure load is determined by one uniform weak or strong bond strength. It was proposed that failure of a clay brick URM wall is not governed by one course only cracking, but rather, instability in the wall is governed by several courses in the vicinity of locations of large bending moment. It was shown that various current stochastic approximations which employ a unit failure hypotheses in combination with a linear/elastic approximation for first cracking load all underestimated wall capacity significantly. The reason for this is suggested as being vi because all hypotheses only assume failure is governed by one course and linear/elastic theory only considers the tensile capacity of a joint and neglects strength capacity available as a result of joint tension softening and the resistance to failure provided by compressive strength on the compression side of the wall. The hypotheses also don’t take into consideration factors which affect overall wall bond strength mean which result from influences such as workmanship, weather and material variability factors, such as (for example), variation in brick suction rate due to weather conditions which can make the overall strength of the wall stronger or weaker. Based upon a comparison in wall failure load COV for the spatial and non-spatial stochastic wall analysis results, a more realistic approach for future modelling attempts of spatial variability in masonry material properties is suggested. This would address the issue of external factors such as workmanship and weather on the overall strength of the wall, as well as the inherent bond strength variability due to material variability. For walls with spatial variability in bond strength, upon examination of numerous wall simulation results, several crack patterns were witnessed and are discussed.

The governing set of regulations for structural engineering in Sweden used to be Boverket, BKR. However in the beginning of the 21st century a changeover to new regulations, the Eurocodes, started. The transition was completed in year 2011 when the Eurocodes became the mandatory design work policy for all countries within the European Union. The Eurocodes were implemented to simplify and remove potential barriers to trade that may exist when countries have different design rules.  Since the changeover it has been important for all construction companies to update their knowledge base and their design software. When comparing the two calculation processes they seem similar, but there are a couple of differences worth noting.  With the new regulations, engineers will find that the process when designing joints in timber structures has changed.  What used to be a fairly easy and straight forward calculation procedure has now become tedious and time consuming. The objective of this degree project is to present a product, a dimensioning tool that will help structural engineers when computing lateral load carrying joints in timber structures. The degree project is made up of two parts where the first part is the written report describing the background and theory behind load carrying computations. The second part of the project is the actual dimensioning tool which includes several worksheets in Microsoft Excel. The program treats single and double shear connections of the following: Nail joints Screw joints Steel plates (thick and thin types)  The user can edit the following parameters: Type of plate/ number of shears Strength class of timber members Member and plate size Type of fastener Diameter of fastener Length of fastener Yield moment of fastener kmod and partial factors for design load carrying capacity The dimensioning tool was created and developed in collaboration with structural engineers at the company Byggteknik AB. By request, a results documentation sheet was developed with intended use for project presentations and project reviews.

No description available.