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Huang, Haibin. "Study of reinforced concrete building demolition methods and code requirements." Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5167.
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Thesis (M.S.)--West Virginia University, 2007.Title from document title page. Document formatted into pages; contains vii, 64 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 58-59).
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Alameddine, Fadel 1964. "FLEXURAL STIFFNESS OF CIRCULAR REINFORCED CONCRETE COLUMNS (SLENDERNESS, ACI CODE, LOAD, DESIGN)." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/276368.
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Al-Chatti, Qusay. "Decision tree based seismic retrofit selection for non-code conforming reinforced concrete buildings." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43564.
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Pacific Earthquake Engineering Research (PEER) Center has developed a comprehensive framework for quantitative assessment of performance level of structures. The framework relies on integrated work of four consecutive stages to provide probabilistic description of system level performance in terms of repair cost, downtime, casualties, deaths or any other parameter of interest to engineers and stakeholders. This is for the purpose of communicating behaviour of facility under earthquake in term of identified damage states and expected economic losses, thus treats possible disconnection between engineers and stakeholders on the desired performance target for the facility.
Key objective of this dissertation is to present simplified version of the PEER framework to conduct earthquake-related financial loss studies for structures in a computationally efficient manner. The presented framework is utilized in this investigation to examine and compare efficiency of alternative seismic strengthening technique to control earthquake-induced monetary losses of a non-ductile hotel building, representative of 1960s construction. The framework integrates knowledge obtained by analyzing seismic environment at building site, investigation of structural demand, and quantifying levels of structural damage and consequential financial losses. Damage measures are computed, by generating fragility models, to link structural response directly to monetary losses. Seismic-induced economic losses are predicted by converting fragility information (i.e. damage probabilities) into financial losses utilizing inventory and monetary losses data of HAZUS-MH. The economic losses computed in this investigation included direct costs, such as construction cost of retrofit, and repair and replacement cost of the facility. In addition, indirect costs, such as losses due damage of building content and business interruption, as well as consequential losses, such as job and housing losses were also considered. Finally, decision tree model was implemented, as a final component of the framework, to establish a decision-assisting platform that enables transparent comparison and selection of the best retrofit option to reduce owner’s susceptibility for financial losses.
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Eigelaar, Estee M. "Deflections of reinforced concrete flat slabs." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/2389.
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Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010.ENGLISH SUMMARY: It is found that the serviceability limit state often governs the design of slender reinforced concrete members. Slender flexural members often have a percentage tension reinforcement less than 1.0% and an applied bending moment just above the point of first cracking. For such members, the available methods to evaluate the serviceability conditions produce inadequate and unrealistic results. The evaluation of the serviceability of a slender member includes the calculation of the predicted deflection, either by empirical hand-calculation or analysing a finite element model, and the verification using the span-to-effective-depth ratio. The focus of the study is on flat slab structures. It investigates the different deflection prediction methods and the span-to-effective-depth ratio verifications from various design standards. These design standards include the ACI 318 (2002), the SABS 0100-1 (2000), the EC2 (2004) and the BS 8110 (1997). The background to the methods, as well as the parameters which influences the deflection development for lightly reinforced members, are investigated in order to define the limitations of the methods. As a result of the investigation of the deflection calculation methods, an Alternative Approach is suggested and included in the comparisons of the various methods. The deflection prediction methods and the span/effective depth verification procedures are accurately formulated to predict the serviceability behaviour of beams. Additional approaches had to be used to apply these methods to a two-dimensional plane such as that of a flat slab structure. The different deflection prediction methods and the span/effective depth verification methods are calculated and compared to the recorded data of seven experimental flat slab specimens as performed by others. A study by Gilbert and Guo (2005) accurately recorded the flexural behaviour of flat slab specimens under uniformly distributed loads for test periods up to 750 days. The methods to evaluate the serviceability of a slender member were also applied to slab examples designed using South African standards. The study concludes by suggesting a suitable deflection prediction method for different parameter (limitation) categories with which a slender member can comply to. The typical span/effective depth ratio trend is also presented as the percentage tension reinforcement for a slender member changes. It is observed that the empirical hand-calculation methods present more reliable results than those of the finite element models. The empirical hand-calculation methods are accurate depending on the precision to which the slab was constructed relative to the actual slab design. The comparison of the deflection methods with South African case studies identified the role played by construction procedures, material parameters and loading history on slab behaviour.
AFRIKAANSE OPSOMMING: Die diensbaarheidstoestand is in baie gevalle die bepalende faktor vir die ontwerp van slank gewapende beton elemente bepaal. Slank elemente, soos lig bewapende buigbare beton elemente, het gewoonlik ‘n persentasie trekbewapening van minder as 1.0% en ‘n aangewende buigmoment net wat net groter is as die punt waar kraking voorkom. Die metodes beskikbaar om die diensbaarheid van sulke elemente te evalueer gee onvoldoende en onrealistiese resultate. Die evaluering van die elemente in die diensbaarheidstoestand sluit in die bepaling van defleksies deur berekening of die analise van ‘n eindige element model, en die gebruik van die span/effektiewe diepte metode. Die fokus van die studie is platbladstrukture. Die doel van die studie is om die verskillende metodes vir die bereking van defleksie asook die verifikasie volgens span/effektiewe diepte metodes van die verskillende ontwerp standaarde te ondersoek. Die ontwerp standaarde sluit die ACI 318 (2002), SABS 0100-1 (2000), EC2 (2004) en die BS 8110 (1997) in. Die agtergrond van hierdie metodes is ondersoek asook die parameters wat ‘n rol speel, sodat die beperkings van die metodes geidentifiseer kan word. As ‘n gevolg van die ondersoek na die beperkings van die metodes, is ‘n Alternatiewe Benadering voorgestel. Die Alternatiewe Benadering is saam met die metodes van die ontwerpstandaarde gebruik om die verskille tussen die metodes te evalueer. Die defleksievoorspelling en die span/effektiewe diepte verifikasie metodes is korrek geformuleer om die diensbaarheid van balke te evalueer. Ander benaderings was nodig om die diensbaarheid van blad blaaie te toets. Die onderskeie defleksievoorspelling en span/effektiewe diepte metodes is bereken vir sewe eksperimentele plat blaaie soos uitgevoer deur ander navorsers. Gilbert and Guo (2005) het ‘n studie uitgevoer waar die buigingsgedrag van die sewe plat blaaie, met ‘n uniforme verspreide las vir ‘n toetsperiode van tot 750 dae, akkuraat genoteer is. Die metodes om die diensbaarheid van ‘n slank element te toets, was ook op Suid-Afrikaanse blad voorbeelde getoets. Dit was gedoen om die Suid- Afrikaanse ontwerp van ligte bewapende beton elemente te evalueer. Die gevolgetrekkings stel ‘n gepaste defleksie metode vir ‘n slank element vir verskillende beperking kategorië voor. Dit is ook verduidelik hoe die tipiese span/effektiewe diepte verhouding met die persentasie trek bewapening vir ‘n slank element verander. Dit is bevind dat die imperiese handmetodes om defleksies te bereken, meer betroubaar as die eindige element modelle se resultate is. Die imperiese handberekening metodes is akkuraat relatief tot hoe akkuraat die blad konstruksie tot die blad ontwerp voltooi is. ‘n Vergelyking van defleksieberekening met Suid-Afrikaanse gevallestudies het die belangrikheid van konstruksieprosedures, materiallparamteres and belastingsgeskiedenis geïdentifiseer.
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Sudre, Gustavo. "Characterizing the Spatiotemporal Neural Representation of Concrete Nouns Across Paradigms." Research Showcase @ CMU, 2012. http://repository.cmu.edu/dissertations/315.
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Most of the work investigating the representation of concrete nouns in the brain has focused on the locations that code the information. We present a model to study the contributions of perceptual and semantic features to the neural code representing concepts over time and space. The model is evaluated using magnetoencephalography data from different paradigms and not only corroborates previous findings regarding a distributed code, but provides further details about how the encoding of different subcomponents varies in the space-time spectrum. The model also successfully generalizes to novel concepts that it has never seen during training, which argues for the combination of specific properties in forming the meaning of concrete nouns in the brain. The results across paradigms are in agreement when the main differences among the experiments (namely, the number of repetitions of the stimulus, the task the subjects performed, and the type of stimulus provided) were taken into consideration. More specifically, these results suggest that features specific to the physical properties of the stimuli, such as word length and right-diagonalness, are encoded in posterior regions of the brain in the first hundreds of milliseconds after stimulus onset. Then, properties inherent to the nouns, such as is it alive? and can you pick it up?, are represented in the signal starting at about 250 ms, focusing on more anterior parts of the cortex. The code for these different features was found to be distributed over time and space, and it was common for several regions to simultaneously code for a particular property. Moreover, most anterior regions were found to code for multiple features, and a complex temporal profile could be observed for the majority of properties. For example, some features inherent to the nouns were encoded earlier than others, and the extent of time in which these properties could be decoded varied greatly among them. These findings complement much of the work previously described in the literature, and offer new insights about the temporal aspects of the neural encoding of concrete nouns. This model provides a spatiotemporal signature of the representation of objects in the brain. Paired with data from carefully-designed paradigms, the model is an important tool with which to analyze the commonalities of the neural code across stimulus modalities and tasks performed by the subjects.
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Kabir, Md Rashedul. "Critical seismic performance assessment of concrete bridge piers designed following Canadian Highway Bridge Design Code." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/63369.
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Performance-based design (PBD) method is gradually taking over the traditional force-based design (FBD) for designing bridges in North America. Considering the importance of bridge structures in the transportation network, quantitative performance criteria were adopted in Canadian Highway Bridge Design Code (CHBDC) in 2014 and a supplement to CHBDC 2014 was published in 2016. In this study, a lifeline bridge pier is designed following the FBD method from CHBDC 2010 and PBD approach following CHBDC 2014 and the supplement to CHBDC 2014 to understand the impression of changes in bridge design codes. The dominating performance criteria in the new supplement to CHBDC 2014 for a lifeline bridge is the maintenance of repairable damage at a seismic event of 975 years return period. The performances of the designed bridge piers are assessed using 20 near-fault ground motions through incremental dynamic analysis. Fragility curves for the bridge piers are plotted to perform the seismic vulnerability analysis of the bridge piers designed following three different alternatives. A lifeline bridge pier is also designed following PBD from CHBDC 2014 using different ASTM grade steel of varying strength and fracture elongation in combination with different concrete strength. Performances of the designed bridge piers are evaluated for site-specific ground motion suits. Moreover, the impact of changing reinforcement strength on the designed bridge piers' seismic behavior is checked by fragility analysis. PBD from the supplement to CHBDC 2014 shows the highest damage probability. Whereas, the FBD from CHBDC 2010 and the PBD from CHBDC 2014 substantially reduce the risk of damage and improve the performance of the bridge pier. Practicing high strength steel reinforcement (HSR) in PBD of bridge piers can reduce the required percentage of reinforcement by 50% compared to conventionally used Grade 60 reinforcement. Construction difficulties can be avoided due to less congestion of rebars and cost of construction can be cut down without compromising the seismic performance. Damage vulnerability related to longitudinal steel strain reduces remarkably, and the collapse performance decreases when HSR are practiced in the design of bridge piers. Incorporation of high strength concrete can marginally improve the collapse performance.Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate
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Isabell, Eriksson, and Niklas Karlsson. "Non-Linear Assessment of a Concrete Bridge Slab Loaded to Failure." Thesis, KTH, Betongbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-188900.
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This thesis covers an investigation regarding the failure in the bridge slab of Gruvvägsbron, which was the result of the full scale test that the bridge was subjected to prior to demolition. Using the non-linear finite element software ATENA 3D, a model of the bridge was assembled, with the purpose to attempt to reenact the test procedure and realistically capture the failure load and behaviour. This in order to be able to conclude what kind of failure that occurred. The initial part of this thesis presents a summary of a conducted literature study, which aims to give deeper knowledge regarding the linear shear and punching shear phenomena and their respective failure mechanisms, and how they are applied on bridge slabs. Furthermore, the shear capacity of the bridge was calculated according to current design codes. A parameter study was conducted on the model, which initially showed a over-stiff response. The aim of this was to study the influence of key variables on the outcome of the analysis, and hopefully get closer to the failure load acquired inthe experiment. From the studied parameters, it was observed that a combined reduction of the tensile strength and fracture energy, together with a low fixed crack coefficient had the largest influence on the outcome of the analysis. It was also observed that the location of the failure and failing load was dependant on how the loading was applied to the model, i.e. via load control or deformation control. The final model failed at a load which surpassed the actual failure load by 10.5%. The mode of failure obtained in all the analyses were the result of a large shear crack propagating from the edges of the loading plate, through the slab to the slab/girder-intersection. This indicates that the type of failure that occurred was primarily due to a linear shear mechanism with a secondary punching effect. The design values calculated by keeping with the current codes resulted in too conservative values when compared to the obtained failure load from the experiment. This proves the difficulty in regarding the internal force distribution in slab struc-tures as well as the shear carrying width, which from the analysis were found to be larger than that obtained from the code.Denna uppsats behandlar en utredning gällande brottet i plattan på Gruvvägsbron, som var resultatet av det fullskaletest som bron utsattes för innan rivning. Med hjälp av den icke-linjära finita element-programvaran ATENA 3D skapades en modell avbron, med syfte att på ett realistiskt sätt försöka återskapa experimentet och fånga brons verkliga beteende. Detta för att således kunna dra slutsatser angående brottets natur. Den första delen av denna uppsats innehåller en sammanfattning av en utförd litteraturstudie, som ämnar ge en ökad förståelse angående fenomenen skjuvning och genomstansning, tillsammans med olika brottmekanismer relaterade till dessa. Vidare har brons motstånd mot skjuv- och genomstansningbrott beräknats enligt rådande normer. En parameterstudie utfördes på modellen, då den ursprungligen uppvisade ett överstyvt beteende. Syftet med detta var att studera nyckelparametrars påverkan på analysens resultat, och eventuellt komma närmare den verkliga brottlasten i experimentet. Av de studerade parametrarna observerades att en samtida reduktion av draghållfasthet och brottenergi, samt ett lågt värde på den så kallade "fixedcrack"-koefficienten gav störst inverkan på resultatet. Vidare observerades att brottets lokalisering och brottlasten var beroende av hur lasten påfördes modellen, dvs genom last- eller deformationsstyrning. Den slutgiltiga modellen gick till brott vid en last som översteg den verkliga brottlasten med 10.5%. Brottet som skedde var i samtliga analyser resultatet av en skjuvspricka som sträckte sig från kanten av lastplattan, genom plattan, ner till mötet mellan platta och balk. Detta indikerar att den typ av brott som skedde var ett primärt skjuvbrott med en sekundär stanseffekt. Lastvärdena beräknade enligt rådande normer tycks vara för konservativa, om jämförelse görs med lasten som uppnåddes i experimentet. Detta visar på svårigheten i att bedöma den inre kraftspridningen i plattor, och även dess skjuvbärande bredd, då analysen visade att denna var betydligt större än vad som ges i koden.
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Saleh, N., Ashraf F. Ashour, and Therese Sheehan. "Bond between glass fibre reinforced polymer bars and high - strength concrete." ElSevier, 2019. http://hdl.handle.net/10454/17246.
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YesIn this study, bond properties of glass fibre reinforced polymer (GFRP) bars embedded in high-strength concrete (HSC) were experimentally investigated using a pull-out test. The experimental program consisted of testing 84 pull-out specimens prepared according to ACI 440.3R-12 standard. The testing of the specimens was carried out considering bar diameter (9.5, 12.7 and 15.9 mm), embedment length (2.5, 5, 7.5 and 10 times bar diameter) and surface configuration (helical wrapping with slight sand coating (HW-SC) and sand coating (SC)) as the main parameters. Twelve pull-out specimens reinforced with 16 mm steel bar were also tested for comparison purposes. Most of the specimens failed by a pull-out mode. Visual inspection of the tested specimens reinforced with GFRP (HW-SC) bars showed that the pull-out failure was due to the damage of outer bar surface, whilst the detachment of the sand coating was responsible for the bond failure of GFRP (SC) reinforced specimens. The bond stress – slip behaviour of GFRP (HW-SC) bars is different from that of GFRP (SC) bars and it was also found that GFRP (SC) bars gave a better bond performance than GFRP (HW-SC) bars. It was observed that the reduction rate of bond strength of both GFRP types with increasing the bar diameter and the embedment length was reduced in the case of high-strength concrete. Bond strength predictions obtained from ACI-440.1R, CSAeS806, CSA-S6 and JSCE design codes were compared with the experimental results. Overall, all design guidelines were conservative in predicting bond strength of both GFRP bars in HSC and ACI predictions were closer to the tested results than other codes.
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Duzce, Zeynep. "Performance Evaluation Of Existing Medium Rise Reinforced Concrete Buildings According To 2006 Turkish Seismic Rehabilitation Code." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607834/index.pdf.
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Linear elastic and nonlinear analysis procedures of 2006 Turkish Seismic Rehabilitation Code are applied to medium rise reinforced concrete buildings. In this study, four storey residential buildings are designed according to the 1998 and 1975 Turkish Seismic Design Codes, and the analysis procedures are verified on these case studies. In addition to these buildings, the analysis procedures are tested on an existing school building before and after retrofitting.
The assessment procedures employed in the 2006 Turkish Seismic Rehabilitation Code are based on linear elastic analysis (equivalent lateral load method, mode superposition method)non-linear analysis (pushover analysis with equivalent lateral load method and mode superposition method) and non-linear time history analysis. In this study, linear elastic analysis with equivalent lateral loads and non-linear static analysis (pushover analysis) with equivalent lateral loads are investigated comparatively. SAP2000 software is used for pushover analysis
however the plastic rotation values obtained from SAP2000 are not used directly but defined according to the code procedures. Post-elastic rotations at yielding sections are transferred to Excel and the corresponding strains are calculated from these rotations by Excel Macro. These strains are compared with strain limits described in the 2006 Turkish Seismic Rehabilitation Code to obtain the member performances. In the linear elastic procedure, structural analysis is performed also by SAP2000 to obtain the demand values, whereas the capacity values are calculated by another Excel Macro. With these demand and capacity values, corresponding demand to capacity ratios are calculated and compared with demand to capacity ratio limits described in 2006 Turkish Seismic Rehabilitation Code to obtain the member performances. Global performances of the buildings are estimated from the member performances and from the inter-storey drifts for both two methods. The results are compared to each other, and critically evaluated.
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Rahman, Muhammad Mostafijur. "Seismic Design of Reinforced Concrete Buildings Using Bangladesh National Building Code (BNBC 1993) and Comparison with Other Codes (ASCE 7-10 And IS 1893-2002)." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin150487859306952.
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Trindade, Yasmin Teixeira. "Numerical modeling of the post-cracking behavior of SFRC and its application on design of beams according to fib Model Code 2010." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3144/tde-07022019-090223/.
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A finite element model with discrete and explicit representation of steel fibers is applied for modeling the post-cracking behavior of Steel Fiber Reinforced Concrete (SFRC) in order to contribute on the design of beams with combined reinforcement of steel fibers and rebars (RC-SFRC beams). In this numerical approach, concrete and fibers are initially discretized in finite elements in an independent way, avoiding high computational costs due to conforming meshes. Then, coupling finite elements are introduced to describe the concrete-fiber interaction. The steel fibers are discretized using truss finite elements and their behavior described by an elastoplastic constitutive model. The position of each fiber is defined into the specimen by an uniform isotropic random distribution using as reference the concrete finite element mesh. Concrete and concrete-fiber interface are represented using three and fournoded triangular finite elements, respectively, and their behavior represented by appropriate continuum damage models integrated using an implicit-explicit scheme to enhance the robustness and to reduce the expense of computation. Firstly, the numerical tool is applied in the simulation of three-point bending tests according to EN 14651 to verify its ability to obtain the performance parameters of SFRC and for calibrating the material parameters that describe the concrete-fiber interface. Secondly, both numerical and experimental performance parameters of SFRC are used on the design of RC-SFRC beams according to fib Model Code 2010 to study their influence on the amount of bending and shear reinforcements required. Thirdly, the RC-SFRC beams designed are numerically simulated and the results are compared to the designed ones in terms of crack width, mean crack spacing, deflection and ultimate and service loads. Finally, the numerical results of small scale beams are compared to the experimental and the fib Model Code 2010 predictions to study the capability of the numerical tool to simulate the behavior of structural members. The results demonstrated that computational simulations with an appropriated approach to represent the composite may be an important tool to contribute to better understanding its behavior, extrapolating the conditions considered in laboratory and contributing on the design of SFRC structural members.Um modelo em elementos finitos com representação discreta e explícita de fibras de aço é utilizado para modelar o comportamento pós-fissuração do Concreto Reforçado com Fibras de Aço (CRFA) com objetivo de contribuir para o dimensionamento de vigas com reforço combinado de fibras e armadura convencional (vigas de CACRFA). Na abordagem numérica utilizada para modelagem de CRFA o concreto e as fibras são inicialmente discretizados em elementos finitos de forma independente, evitando altos custos computacionais devido às malhas conformes. Então, elementos finitos de acoplamento são introduzidos para descrever a interação concreto-fibra. As fibras de aço são discretizadas utilizando elementos finitos de treliça e seu comportamento é descrito por um modelo constitutivo elastoplástico Um algoritmo para distribuição isotrópica randômica é utilizado para gerar e distribuir fibras de aço com base na malha de elementos finitos do concreto. O concreto e a interface concreto-fibra são representados utilizando elementos finitos triangulares de três e quatro nós, respectivamente, e seus comportamentos representados por uma modelos apropriados de dano contínuo integrados utilizando um esquema implícito-explícito com objetivo de aumentar a robustez a reduzir o custo computacional. Primeiramente, a ferramenta numérica é aplicada na simulação de ensaios de flexão de três pontos de acordo com EN 14651 para verificar sua capacidade de obter os parâmetros de desempenho do CRFA e para calibrar os parâmetros do material que descrevem a interface concreto-fibra. Em segundo lugar, os parâmetros de desempenho numéricos e experimentais do CRFA são usados no vigas de CA-CRFA de acordo com o fib Model Code 2010, a fim de estudar sua influência na quantidade de armadura de flexão e cisalhamento necessárias. Em terceiro lugar, as vigas de CA-CRFA são numericamente simuladas e os resultados são comparados com os dimensionados em termos de largura de fissura, espaçamento médio entre fissuras, flecha e cargas últimas e de serviço. Finalmente, os resultados numéricos de vigas de pequena escala são comparados com aqueles obtidos experimentalmente e pelo fib Model Code 2010 para estudar a capacidade da ferramenta numérica em simular o comportamento de elementos estruturais. Os resultados demonstraram que a utilização de simulações computacionais com uma abordagem apropriada para representar o compósito podem ser uma importante ferramenta para contribuir para um melhor entendimento do seu comportamento, extrapolando as condições consideradas em laboratório e contribuindo para o dimensionamento de elementos estruturais de CRFA.
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Kazaz, Ilker. "Dynamic Characteristics And Performance Assessment Of Reinforced Concrete Structural Walls." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611712/index.pdf.
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The analytical tools used in displacement based design and assessment procedures require accurate strain limits to define the performance levels. Additionally, recently proposed changes to modeling and acceptance criteria in seismic regulations for both flexure and shear dominated reinforced concrete structural walls proves that a comprehensive study is required for improved limit state definitions and their corresponding values. This is due to limitations in the experimental setups, such that most previous tests used a single actuator at the top of the wall, which does not reflect the actual loading condition, and infeasibility of performing tests of walls of actual size in actual structural configuration. This study utilizes a well calibrated finite element modeling tool to investigate the relationship between the global drift, section rotation and curvature, and local concrete and steel strains at the extreme fiber of rectangular structural walls. Functions defining more exact limits of modeling parameters and acceptance criteria for rectangular reinforced concrete walls were developed. This way a strict evaluation of the requirements embedded in the Turkish Seismic Code and other design guidelines has become possible. Several other aspects of performance evaluation of structural walls were studied also. Accurate finite element modeling strategies and analytical models of wall and frame-wall systems were developed for seismic response calculations. The models are able to calculate both the static and dynamic characteristics of wall type buildings efficiently. Seismic responses of wall type buildings characterized with increasing wall area in the plan were analyzed under design spectrum compatible normal ground motions.
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Lima, Juliana Soares. "Verificações da punção e da estabilidade global em edifícios de concreto: desenvolvimento e aplicação de recomendações normativas." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-12082016-121356/.
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Neste trabalho, são estudas as verificações da punção global segundo a revisão da NBR 6118. A partir da análise dos fenômenos físicos e com base nos estudos teóricos realizados, são feitas sugestões para serem contornadas algumas omissões da Norma. Também são propostas complementação que facilitem o entendimento das novas recomendações e, ainda, modificações que melhorem seus resultados. Sugerem-se métodos simplificados relacionados à punção excêntrica, e propõem-se algumas alterações quanto ao uso do γz como coeficiente majorador na avaliação da estabilidade global. Observa-se que as verificações, apesar de mais trabalhosas, apresentam melhorias significativas em relação à NBR 6118 (1978), mostrando-se mais detalhadas e eficientes. Ainda assim, considera-se importante a introdução de algumas complementações, como aquelas sugeridas neste trabalho.This work presents an overview of the requirements for punching shear and global stability of buildings in the draft Brazilian Code for concrete structures. Suggestions are made for fulfilling some omissions of the Code, based on theoretical studies and physical phenomena analysis. Some complements and changes are also proposed to facilitate the understanding of the new recommendations and to improve their results. Simplified methods related to the eccentric punching and modifications in the use of γz as a first order effects magnifier are suggested. It is concluded that the new provisions are more detailed and efficient, presenting significant improvements on both topics, especially when compared to NBR 6118 (1978). Nevertheless, it is considered important the introduction of some complements, as those suggested in this work.
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Tan, Mustafa Tumer. "Seismic Strengthening Of A Mid-rise Reinforced Concrete Frame Using Cfrps: An Application From Real Life." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610562/index.pdf.
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SEISMIC STRENGTHENING OF A
MID-RISE REINFORCED CONCRETE FRAME
USING CFRPs: AN APPLICATION FROM REAL LIFE
Tan, Mustafa Tümer M.S., Department Of Civil Engineering Supervisor: Prof. Dr. Gü
ney Ö
zcebe Co-Supervisor: Assoc. Prof. Dr. BariS Binici May 2009, 162 pages FRP retrofitting allows the utilization of brick infill walls as lateral load resisting elements. This practical retrofit scheme is a strong alternative to strengthen low to mid-rise deficient reinforced concrete (RC) structures in Turkey. The advantages of the FRP applications, to name a few, are the speed of construction and elimination of the need for building evacuation during construction. In this retrofit scheme, infill walls are adopted to the existing frame system by using FRP tension ties anchored the boundary frame using FRP dowels. Results of experiments have previously shown that FRP strengthened infill walls can enhance lateral load carrying capacity and reduce damage by limiting interstory drift deformations. In previous, analytical studies, a detailed mathematical model and a simplified version of the model for compression struts and tension ties was proposed and verified by comparing model estimations with test results. In this study, an existing 9-storey deficient RC building located in Antakya was chosen to design and apply a hybrid strengthening scheme with FRPs and reduced number of shear walls. Linear elastic analysis procedure was utilized (force based assessment technique) along with the rules of Mode Superposition Method for the reftrofit design. FRP retrofit scheme was employed using the simplified model and design was conducted such that life safety performance criterion is satisfied employing elastic spectrum with 10% probability of exceedance in 50 years according to the Turkish Earthquake Code 2007. Further analytical studies are performed by using Modal Pushover and Nonlinear Time-History Analyses. At the end of these nonlinear analyses, performance check is performed according to Turkish Earthquake Code 2007, using the strains resulting from the sum of yield and plastic rotations at demand in the critical sections. CFRP retrofitting works started at October 2008 and finished at December 2008 for the building mentioned in this study. Eccentric reinforced concrete shearwall installation is still being undertaken. All construction business is carried out without evacuation of the building occupants. This project is one of the first examples of its kind in Turkey. Keywords: CFRP, Carbon Fiber Reinforced Polymers, Masonry Infill Walls, Reinforced Concrete Infill Walls, Mid-Rise Deficient Structures, Turkish Earthquake Code 2007, Modal Pushover Analysis, Nonlinear Time History Analysis, Linear Elastic Building Assessment
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Shaikh, Adnan Muzaffar. "Study of the fracture behavior of concrete by the development and application of the nonlinear finite element code incorporating the composite damage mechanics theory for brittle materials." Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1435225.
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Idir, Achour. "Justification du coefficient de comportement sismique des structures en béton armé par des approches statiques équivalentes." Châtenay-Malabry, Ecole centrale de Paris, 1997. http://www.theses.fr/1997ECAP0508.
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Le calcul des constructions vis-à-vis du séisme en prenant en compte la réponse élastique linéaire conduit le plus souvent à des dimensionnements qui ne vont pas dans le sens de l'économie. Afin de permettre à l'ingénieur de tenir compte des différentes non linéarités, la plupart des règlements modernes (règles françaises PS92, règles européennes EC8, etc. ) ont préconisé de réduire les forces issues d'un calcul élastique linéaire par un coefficient appelé : coefficient de comportement. Un logiciel d'évaluation automatique de ce coefficient a été établi, selon la méthode préconisée par les règles ps92, basée sur les critères d'égalité de déplacement et d'énergie. Dans sa phase actuelle, le logiciel traite des structures planes isostatiques encastrées à la base (type brochette). Un calcul statique équivalent est effectue. On recherche de façon itérative la valeur du coefficient de comportement qui satisfait à l'un ou l'autre des critères précédents. A chaque étape de calcul, on dimensionne le ferraillage correspondant à la valeur du coefficient de comportement Q. En plus de cette option, il est possible d'imposer un ferraillage donné et de vérifier la valeur de Q correspondante. D'autres options complémentaires, utiles au niveau de la recherche, ont été introduites. Des exemples de bâtiments à murs en béton armé et d'une pile de pont ont été traités et les valeurs du coefficient de comportement obtenues sont comparées à celles issues d'un calcul dynamique effectue à l'aide d'un programme établi antérieurement au CEBTP et à celles préconisées par les règles PS92. Le calcul statique équivalent donne des valeurs de Q dont les tendances confirment les résultats des calculs dynamiques non-linéaires. Les valeurs forfaitaires réglementaires sont soit trop sévères soit pas assez: la tendance est gouvernée par plusieurs paramètres (période, pourcentage d'armatures, contrainte moyenne de compression,). Dans la plupart des calculs, la convergence du calcul est obtenue avec un nombre d'itérations relativement bas
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Santos, Andreilton de Paula. "Análise da continuidade em lajes alveolares: estudo teórico e experimental." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-18122014-100018/.
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A maioria dos edifícios de concreto pré-moldado, construídos no Brasil e no exterior, é constituída por lajes alveolares. Este trabalho considera o estudo da continuidade dessas lajes. No cálculo desses elementos, a prática comum é considerá-los como simplesmente apoiados. Para melhorar o desempenho, é possível promover a continuidade nos apoios intermediários. Isso pode ser feito colocando armadura na região tracionada da ligação, no interior da capa, ou através de barras concretadas dentro dos alvéolos. O objetivo deste trabalho é investigar o comportamento de pavimentos formados por lajes alveolares com continuidade, com armadura na capa. Para isso, foi realizado um estudo envolvendo análise teórica e experimental em três modelos. Esses modelos, em escala real, foram submetidos a um carregamento transversal, distribuído de forma linear. Os estudos teóricos consideraram uma simulação numérica com elementos de viga e a fórmula de Branson para descrever o comportamento não linear físico do material. Além disso, foram avaliadas as expressões dos principais códigos nacionais e internacionais, no que diz respeito à ruptura por cisalhamento da seção transversal e da interface laje-capa. Os resultados da análise experimental indicaram que o modelo 1 rompeu por cisalhamento da seção transversal, com o mecanismo de tração diagonal do concreto. O modelo 2 apresentou ruptura por cisalhamento da interface. No modelo 3, a ruptura foi por flexão. O comportamento dos modelos ensaiados foi governado pela fissuração da capa na região de momento negativo. A análise teórica com elementos de barra representou de forma satisfatória o comportamento dos modelos ensaiados. As únicas formulações que apresentaram resultados coerentes com os três ensaios foram: EUROCODE 2:2004, para o cálculo da resistência ao cisalhamento da interface, e FIB MODEL CODE 2010, para o cálculo da resistência ao cisalhamento da seção transversal. Conclui-se que a continuidade melhora o desempenho das lajes alveolares, uma vez que reduz os deslocamentos no meio do vão e aumenta a capacidade de carga.Most buildings of precast concrete built in Brazil and abroad consist of hollow core slabs. This paper considers the study of the continuity of these slabs. In design of these elements the common practice is to consider them as simply supported. To improve the performance it is possible to promote the continuity in the intermediate supports. This can be done by placing reinforcement in the tensioned region of the connection, inside the topping, or by bars concreted inside the voids. The aim of this work is to investigate the behavior of hollow core floors with continuity, with reinforcement in the topping. For this, a study involving theoretical and experimental analysis was conducted in three models. The full-scale models were subjected to a transverse loading distributed linearly. The theoretical studies have considered a numerical simulation with beam elements and the Branson formula to describe the physical nonlinear behavior of the material. Furthermore, the specifications of the major Brazilian and international codes were evaluated, with respect to failure by shear of the cross section and the slab-topping interface. The results of the experimental analysis indicated that the model 1 failed by shear of the cross section with the mechanism of diagonal tension of the concrete. Model 2 presented shear failure of the interface. In model 3, the failure was by flexure. The behavior of the tested models was ruled by cracking of the topping in region of negative bending moment. Theoretical analysis with beam elements represented satisfactorily the behavior of the tested models. The only formulations that presented consistent results with the three tests were: EUROCODE 2:2004, to calculate the shear strength of the interface, and FIB MODEL CODE 2010, for calculating of the shear strength of the cross section. It is concluded that the continuity improves the performance of the hollow core slabs, as it reduces the displacements at mid-span and increases the bearing capacity.
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Venieri, Valeria. "Shape modelling and design of a new sleeper for the "Shift2Rail Project"." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
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Il ricerca condotta rientra all' interno di un progetto europeo noto come il nome di “Shift2rail”. Shift2Rail è la prima iniziativa ferroviaria europea nata con l’intento di perseguire innovazioni e soluzioni guidate dal mercato, al fine di sviluppare nuove e avanzate tecnologie capaci di poter essere concorrenti all’ interno del mercato dei prodotti ferroviari. Shift2Rail promuove la competitività dell'industria ferroviaria europea e risponderà alle mutevoli esigenze di trasporto dell'UE.
Lo studio condotto in questa tesi, accoglie l’idea fino ad oggi non ancora messa in pratica, di concentrarsi sul miglioramento di un elemento in particolare della sezione ferroviaria, lo sleeper o traversina. L’obiettivo della tesi proposta è quello di investigare una nuova forma di sleeper con migliori capacità resistenti, supportato da un codice numerico in Matlab, capace di dimostrare la sua validità, passando attraverso un’ampia analisi del comportamento dell’elemento all’interfaccia sleeper/ballast.
La ricerca effettuata si pone quindi solo come punto di partenza e non di arrivo per una nuova area di ricerca che in futuro produrrà risultati stupefacenti.
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Liu, Fangzhou. "Dynamic analysis of hollow core concrete floors." Licentiate thesis, KTH, Bro- och stålbyggnad, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-224778.
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Lucena, Júlio César Tavares de. "Concreto reforçado com fibras de polipropileno: estudo de caso para aplicação em painel alveolar de parede fina." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-30032017-104705/.
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Essa pesquisa apresenta um estudo da composição de concreto reforçado com fibras de polipropileno e objetiva avaliar seu comportamento estrutural em um tipo de painel alveolar de parede fina. A adição de alto teor de fibras de polipropileno ao concreto modifica algumas de suas propriedades mecânicas, conferindo ao compósito maior resistência à tração, resistência à flexão, resistência ao impacto e tenacidade. Inicialmente foram realizados ensaios de caracterização do compósito, sendo eles: consistência, resistência à compressão axial, módulo de elasticidade, resistência à tração por compressão diametral, resistência à tração na flexão e tenacidade. Estudou-se o comportamento de todas essas propriedades mecânicas para os teores de fibras de polipropileno de 0, 1 e 2% em volume de concreto. Com intuito de estudar o comportamento mecânico dos painéis alveolares de parede fina pela adição de fibras, foram realizados ensaios de carga concentrada e flexão. Este estudo foi realizado para os teores de fibra de 0 e 2%. Foram produzidos dois tipos de corpos de prova, ambos com seção transversal de 300 mm x 140 mm, e comprimentos de 600 mm e 1200 mm, para cada teor de fibra e respectivamente para os ensaios de carga concentrada e flexão. Para os ensaios de caracterização, não houve indícios de resultados significantes da adição dos teores de fibras 1 e 2% para a resistência à compressão e módulo de elasticidade. Já os ensaios de consistência, resistência à tração e tenacidade, apresentaram resultados expressivos, principalmente para o teor de fibra de 2%. Para os ensaios nos corpos de prova no painel quanto à carga concentrada, observou-se aproximadamente dez vezes maior capacidade de carga, cinco vezes maior capacidade de deslocamento e sete vezes maior resistência à punção. Os ensaios à flexão no painel apresentaram tensões resistentes pouco menores para os corpos de prova do painel contendo 2% de fibras. Conclui-se então que as propriedades do material cimentício com elevado teor de fibras são apropriadas para aplicação em painéis alveolares de parede fina. No entanto, é necessário melhorar a trabalhabilidade da mistura, pois devido às pequenas espessuras das paredes do painel, o adensamento do material não foi realizado de forma satisfatória.This research presents a study on the composition of polypropylene fiber reinforced concrete and intents to evaluate its structural behavior in a type of thin-walled hollow core panel. The addition of high content of polypropylene fibers to the concrete modifies some of its mechanical properties, giving the composite greater split tensile strength, flexural strength, impact strength and toughness. Firstly, characterization tests of the composite were performed: consistency, compressive strength, modulus of elasticity, split tensile strength, flexural tensile strength and toughness. It was studied the behavior of all these mechanical properties for the contents of polypropylene fibers of 0,1 and 2% by volume of concrete. In order to study the mechanical behavior of the thin-walled hollow core panels by the addition of fibers, were performed concentrated load and flexural tests. This study was performed for fiber contents of 0 and 2%. Two types of specimens were produced, both with a cross section of 300 mm x 140 mm, and lengths of 600 mm and 1200 mm, for each fiber content and to be tested respectively for the concentrated load and flexural tests. For the characterization tests, there was no evidence of significant results arising on the addition of the fiber contents 1 and 2% for the compressive strength and modulus of elasticity. The tests of consistency, tensile strength and toughness presented significant results, especially for the fiber content of 2%. The flexural tests on the panel showed slightly lower tensile strengths for specimens containing 2% fibers. It is then concluded that the properties of the high fiber cementitious material are suitable for application in thin-walled alveolar panels. However, it is necessary to improve the workability of the composite, because due to the small thicknesses of the panel walls, a satisfactorily consolidation of the material has not been achieved.
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Sun, Yaojun. "Heat transfer in molten core/concrete interaction systems." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/17105.
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Reis, João Felipe Araujo [UNESP]. "Determinação de parâmetros reológicos de concretos através do ensaio de abatimento de tronco de cone modificado: estudo de caso." Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/94495.
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reis_jfa_me_ilha.pdf: 4095503 bytes, checksum: 7b68949931b17d9ea9723fac44c2e518 (MD5)As propriedades reológicas do concreto no seu estado fresco são importantes principalmente no período em que o material é lançado nas fôrmas e podem ser determinadas em qualquer momento durante o período de indução da hidratação do cimento. Entretanto, o uso da reologia para estudar a taxa de fluidez ou trabalhabilidade do concreto não é muito comum. Geralmente, o abatimento de tronco de cone é o único parâmetro medido e, mesmo em laboratório, os estudos raramente fornecem informações adicionais sobre o comportamento ao escoamento desses materiais. O ensaio do tronco de cone modificado proposto de LARRARD permite avaliar a tensão crítica e a viscosidade plástica do concreto, de maneira simples e sem grandes custos, uma vez que reômetros de laboratórios são aparelhos sofisticados e relativamente com custos elevados. Este estudo avalia a tensão de escoamento e a viscosidade plástica obtida pelo teste de abatimento de tronco de cone modificado para dois tipos distintos de concreto, a saber: o concreto fresco convencional e o concreto de alto desempenho (CAD), elaborados com cimento CPV ARI-Plus. E também foi realizado correlações entre o ensaio de abatimento de tronco de cone modificado e o ensaio de reometria clássica. Os resultados obtidos mostraram-se bastante satisfatórios para o cálculo da tensão e da viscosidade dos concretos avaliados.
The concrete rheological properties in fresh state are mainly important in the period that the material is thrown in the molds and it can be certain in any moment during the induction period of the cement hydration. However, the use of the rheology to study the fluidity rate or concrete workability is not very common. Usually, the slump is just an unique measured parameter and, even in laboratory, the studies rarely supply additional information about the flow behavior of those materials. The slump modified test proposed by LARRARD it allows to evaluate the critical tension and concrete plastic viscosity so simply and without significant costs, because rheometers of the laboratories are very sophisticated and relatively expensive apparels. This study evaluates the yield stress and the viscosity obtained by the slump modified test for two different types of concrete, like to: the conventional fresh concrete and the concrete of high acting (CAD), elaborated with cement CPV ARIPlus. And it was done to test the correlation between slump modified test and test classical rheometer. For the concretes of high performed starting from the specific line the addictive volume addition superplastificante was varied obtaining initial slumps that varied between 100mm and 260mm. The initial results obtained have proved very satisfactory in tension and viscosity calculus of the evaluated concretes.
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Falah, Nabil. "The interaction of steel tube and concrete core in concrete filled steel tube columns." Aachen Shaker, 2010. http://d-nb.info/1003886949/04.
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Filho, José Orlando Vieira. "Avaliação da resistência à compressão do concreto através de testemunhos extraídos: contribuição à estimativa do coeficiente de correção devido aos efeitos do broqueamento." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/3/3146/tde-26102007-144854/.
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Esta pesquisa experimental destina-se à avaliação da resistência à compressão do concreto na estrutura através da análise das resistências de corpos-de-prova padrão moldados fc(M), denominada potencial e de testemunhos extraídos da estrutura fc(E), denominada efetiva objetivando quantificar o coeficiente de correção devido aos efeitos do broqueamento na extração - nesta tese considerado como a relação entre elas R(M/E) = fc(M)/fc(E) - a ser aplicado à resistência dos testemunhos de mesmas dimensões dos corpos-de-prova. Admitindo-se que a resistência dos testemunhos representa a resistência do concreto na estrutura, esta relação R(M/E) corresponde a parcela yc2 do coeficiente normativo de ponderação da resistência do concreto yc. A norma brasileira NBR 6118:2003 - Projeto de Estruturas de Concreto - Procedimento, para o caso de não-conformidade na aceitação do concreto, indica a extração de testemunhos segundo a NBR 7680:1983. Admite, neste caso de extração, dividir o valor de yc por 1,1 nas avaliações estruturais no estado limite último. Em sua versão anterior de 1978 e registrada como NBR 6118:1980 recomendava que os resultados dos testemunhos fossem corrigidos em virtude dos efeitos do broqueamento, sem, no entanto, especificar o coeficiente para a correção referida, sugerindo que os resultados fossem majorados em 10% ou 15%, dependendo da amostragem, por se tratar da resistência do concreto na própria estrutura. A NBR 6118:2003 estabelece para o coeficiente yc o valor de 1,4 sem especificar valor para a parcela yc2. O CEB igualmente recomenda 1,4 para o yc citando o valor de 1,10 para o yc2. Especificamente quanto à correção devida aos danos causados pela extração aos testemunhos, o ACI 214 4R-2003 indica o coeficiente de 1,06 para ser multiplicado pela resistência dos testemunhos nas avaliações estruturais. Trabalhando-se com corpos-de-prova padrão curados úmidos e com testemunhos extraídos de blocos tanto curados úmidos quanto curados ao ar buscou-se avaliar esse coeficiente referente aos danos causados pela extração. Utilizaram-se ainda corpos-de-prova padrão curados ao ar para comparação de resultados. No presente estudo procurou-se também verificar a viabilidade da utilização de testemunhos de diâmetros inferiores aos de 15cm e 10cm normalmente previstos na normalização nacional e internacional, extraindo-se, além daqueles, testemunhos de 7,5cm; 5,0cm e do diminuto diâmetro de 2,5cm; que podem vir a facilitar e agilizar as avaliações de estruturas acabadas. Permitem ainda evitar cortes de armaduras, reduzir custos, possibilitar a obtenção da relação altura/diâmetro igual a 2 e ainda o aumento significativo da amostragem. No programa de ensaios desenvolvido foram estudados concretos produzidos por central dosadora que atende à Região Metropolitana do Recife, em quatro níveis de resistência à compressão aos 28 dias, respectivamente de 20Mpa, 50Mpa e 70MPa e amostragem suplementar de 65MPa, para rupturas também aos 90 dias de idade. Foram realizados também ensaios esclerométricos, ultrassônicos e de massa específica aparente do concreto como subsídios aos ensaios de resistências à compressão. Após análise estatística chegou-se a um valor final promédio para o coeficiente de correção dos efeitos de broqueamento R(M/E) de 1,07; demonstrando-se ainda por correlações ao nível de significância de 1% a viabilidade da utilização dos testemunhos de diâmetros 7,5cm; 5,0cm e do minitestemunho de 2,5cm na avaliação de estruturas acabadas.The present research aims to evaluate concrete\'s compressive strength in the structure through the analysis of the strength of cast concrete specimens fc(M), hereafter called \"potential\", and that of concrete cores extracted from the structure fc(E), hereafter called \"effective\". The objective was to quantify the coefficient to correct for drilling effects during core extraction - in the present work taken as the ratio R(M/E)=fc(M)/fc(E) - to be applied to the strength of cores with the same dimensions as the specimens. By assuming that the strength of the cores represents the strength of concrete within the structure, R(M/E) corresponds to the term yc2 of the normative coefficient of concrete strength yc. Brazilian Standard NBR 6118:2003 - Procedures for the Design of Concrete Structures - whenever non-conformity in concrete acceptance arises, indicates the extraction of cores in accordance with Standard NBR 7680:1983. It accepts, in this case, that yc be divided by 1.1 in structural evaluations at the ultimate limit state. Former versions of Standard 6118:1980 recommended that core results be corrected due to drilling effects, but made no mention to the correction coefficient itself, merely suggesting that results were increased in 10 to 15 %, depending on the sampling, because it is dealing with the strength of concrete in the structure. NBR 6118:2003 establishes a figure of 1.4 for yc without specifying any value for yc2. The European Concrete Committee (CEB) also recommends a figure of 1.4 for yc, mentioning a figure of 1.1 for yc2. With regard to the corrections due to the damage caused by core extraction, ACI 214 4R-2003 proposes a coefficient of 1.06 to be multiplied by core strength in structural evaluations. By working with wet-cured standard cast specimens and with cores extracted from concrete blocks - either wet-cured or air-cured - an attempt was made to assess this coefficient related to the damage caused by drilling. Standard air-cured cast specimens were used to verify the results. The present study also managed to verify the feasibility of using cores with diameter smaller than those nationally and internationally adopted (15 and 10 cm), namely, 7.5cm, 5.0cm and 2.5cm, which can potentially speed up the evaluation of finished structures. Smaller diameters also decrease the risk of reinforcement damage, lead to lower costs and allow that height: diameter ratios of 2:1 be obtained, thus increasing sampling. During the test programme developed for the present investigation concretes produced by one of the main suppliers in Recife\'s Metropolitan Region were studied, at four compressive strength levels at 28 days: 20, 50 and 70MPa, with a supplementary sampling at 65MPa, for rupture tests at 90 days. Sclerometric, ultrasound and apparent density tests were also performed, as further subsidies to compressive strength tests. The application of statistical analysis led to a final average figure of 1.07 for yc2. The feasibility of using cores with diameters of 7.5, 5.0 and even 2.5 cm was also established at a significance level of 1%.
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Massucato, Carlos Jose. "Utilização de escoria de alto-forno a carvão vegetal como adição no concreto." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258498.
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Orientador: Vladimir Antonio PaulonDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
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Resumo: Este estudo teve como objetivo principal avaliar propriedades oriundas da adição de escória de alto-forno à carvão vegetal, do concreto no estado fresco e endurecido, produzido com cimentos que já utilizam em sua composição a escória de alto-forno. Com a determinação da quantidade de escória de alto-forno pelo método de dissolução seletiva, foi possível adicionar escória de alto-forno no concreto até os limites estabelecidos na especificação do cimento de alto-forno (CPIII) pela NBR 5735 (ABNT, 1991) e conhecer o efeito na resistência mecânica, módulo de elasticidade, abatimento, incorporação de ar, tempo de pega e exsudação, em traços de concreto sem adição e com adição de escória de alto-forno à carvão vegetal e à coque. As indústrias de cimento utilizam, em sua maioria, escórias provenientes dos altos-fornos à coque. Entretanto, o tratamento adequado nas escórias de alto-forno à carvão vegetal pode ampliar o consumo deste produto como adição mineral diretamente nas centrais de concreto, com a vantagem de ser uma fonte renovável de energia e eliminar este resíduo que se acumula nas usinas siderúrgicas. O estudo comprovou que, a utilização da escória de alto-forno à carvão vegetal como adição, não provoca alterações nas propriedades do concreto no estado fresco, em comparação com a escória de alto-forno à coque. A resistência à compressão com adição da escória de alto-forno à carvão vegetal aumentou em até 5% em idades superiores a 60 dias em comparação com o concreto sem adição de escória
Abstract: This study had the main purpose to evaluate properties of fresh and hardened concrete in with slag addition of blast furnace from charcoal in concrete produced with cements that already use in its composition the blast furnace slag. With the determination of the amount of slag of blast furnace by the selective method of dissolution, it was possible to add slag of blast furnace in concrete up to the limits established by NBR 5735 (ABNT, 1991) and to know the effect in concrete resistance, modulus of elasticity, slump test, air entrained concrete, setting of the cement and bleeding, in the mix proportions of concrete with and without slag addition of blast furnace from charcoal and coke. The cement industries use in its majority slag from coke deriving from blast furnace. However, the suitable treatment in slag of blast furnace from charcoal can extend the consumption of this product as mineral addition directly in the concrete plant, with the advantage of being a renewable source of energy and to eliminate this residue that accumulates in the siderurgical plants. The study proved that the use of the slag of blast furnace from charcoal as addition in concrete presented the same properties of fresh concrete compared with the slag of blast furnace with coke. The compressive strength increased in 5% at superior ages at 60th day in comparison without slag addition
Mestrado
Edificações
Mestre em Engenharia Civil
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Schurr, Dennis Patrick. "Monitoring damage in concrete using diffuse ultrasonic coda wave interferometry." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37237.
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The prevalence of concrete and cement-based materials in the civil infrastructure
plus the risk of failure makes structural health monitoring an important issue in the
understanding of the complete life cycle of civil structures. Correspondingly, the
field of nondestructive evaluation (NDE) has been maturing and now concentrates
on the detection of flaws and defects, as well as material damage in early stages of
degradation.
This defect detection is typically usually done by looking at the impulse response
of the medium in question such as a cement-based material. The impulse response
of a solid can be used to image a complex medium. Classically, the waveform is
obtained by an active setup: an ultrasonic signal is generated at one location and
recorded at another location. The waveform obtained from imaging can be used to
quantitatively characterize the medium, for example by calculating the material's
diffusivity coefficient or dissipation rate.
In recent years, a different monitoring technique has been developed in seismology
to measure the velocity of different kinds of waves, the Coda Wave Interferometry
(CWI). In this CWI technique, the main focus is given to the late part of the recorded
waveform, the coda. CWI is now successfully used in seismology and acoustics.
In the current research, CWI is applied on concrete in different damage states
to develop basic knowledge of the behavior of the wave velocity, and how it can be
used to characterize cement-based materials. By comparing two impulse responses,
the relative velocity change between the two impulse responses is used to characterize
damage. Because of the stress-dependency of the velocity change, the calculations can also be used to directly calculate the Murnaghan's and Lam´e's coefficients. The
newer technique of CWI is applied - the Stretching Technique (ST) [27]. The first goal
of this research is to establish the viability of using CWI in cement-based materials.
Next, we use the ST in the application of stress as we compress concrete samples for
the detection of thermal damage, ASR-damage and mechanical softening.
27
Kilic, Arif Nesimi 1963. "A transient model for decomposition and ablation of concrete during a molten core/concrete interaction." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/277892.
Full textAbstract:
A simple approximation for predicting the concrete erosion rate and depth is derived based on heat balance integral method for conduction with the time dependent boundary conditions. The problem is considered a four-region model including separate, moving heat sinks at the boundaries due to endothermic decomposition reactions. Polynomial temperature profiles are assumed and the results are compared to previous experimental data and other analytical solutions. Since the technique provides an approximate temperature distribution on the average, it does not give the real temperature evaluation but provides a simple prediction of the erosion rates in terms of the parameters that are important during the physical phenomena. Because of its simplicity and reliability, the model might be useful of the larger molten core/concrete interaction models.
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Paine, Kevin Andrew. "Steel fibre reinforced concrete for prestressed hollow core slabs." Thesis, University of Nottingham, 1998. http://eprints.nottingham.ac.uk/11095/.
Full textAbstract:
An investigation of prestressed concrete containing steel fibres as secondary reinforcement to improve performance in shear, flexure and bond is reported. Emphasis is placed on the use of steel fibres in prestresssed extruded hollow core slabs, since these common precast elements have intrinsic difficulty in incorporating traditional secondary reinforcement due to their unique shape and manufacturing method. Two separate studies were carried out. The first study involved laboratory investigations into the bond between fibre reinforced concrete (FRC) and the prestressing strand, and the shear behaviour of laboratory-cast prestressed fibre reinforced concrete (PFRC) beams. The second part involved the factory production of fibre reinforced hollow core slabs in co-operation with a local manufacturer. The fibre reinforced hollow core slabs were subjected to conventional full-width shear tests, concentrated load shear tests, and to transverse flexure. For all laboratory cast elements, cubes, cylinders and prisms were cast to investigate compressive, tensile and flexural properties, respectively. Two types of steel fibre were investigated: hooked-end steel fibres at fibre volume fractions (Vf) of 0.5%, 1.0% and 1.5%; and amorphous metal fibres at Vf‘s of 0.28% and 0.56%. The trial production of fibre reinforced hollow core slabs necessitated the investigation of the effect of steel fibres on the extrusion manufacturing process. It was shown that fibre reinforced hollow core slabs could be adequately compacted with only slight increases in mixing water. Fibres were found to distribute randomly throughout the cross-section. However, the rotation of the augers affected the orientation of fibres, with fibres tending to align vertically in the web. It was shown that the addition of steel fibres to prestressed concrete has a negative effect on the bond between matrix and tendon, leading to longer transfer lengths. The effect of the increase in transfer length was to reduce cracking shear strengths by 4%. Shear tests showed that the incorporation of steel fibres could increase shear strength by as much as 45% for Vf = 1.5%. This increase in shear strength, known as the fibre contribution, was shown to be due to fibres bridging across the crack and an increased compressive resistance due to fibres arresting the propagation of cracks into the compressive zone. A semi-empirical equation for shear strength of PFRC elements is developed. It is given in two forms, one compatible with the present equations for prestressed concrete given in BS 8110 and Eurocode 2, and a second form compatible with that advocated for fibres in reinforced concrete. The equation makes use of equivalent flexural strength which is recognised as the most useful material property for design of FRC. The equation was found to give good correlation with the shear strength of single web beams cast both in the laboratory and under factory conditions. However, a overall strength reduction factor is required for full-width hollow core slabs to account for uneven load distribution and inconsistent web widths. This is consistent with tests on plain hollow core slabs found in the literature.
29
Bartulíková, Radka. "Vliv provzdušnění a ošetřování na vývoj modulu pružnosti betonu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-225737.
Full textAbstract:
Master's thesis deals with influence of various factors on the concrete compressive strength and modulus of elasticity. This work concentrates mainly on the influence of early curing and air entrainment of concrete. One part of this work is the evaluation of laboratory measurement, which was carried out on cubes of standard and norm prisms. The development of elastic moduli was monitored in time to 730 days of age with respect to air entrainment and curing conditions. The second part of the experiment deals with a comparison of theoretical creep curves depending on the value of the modulus of elasticity based on different standards. Again, the air entrainment effect and influence of initial conditions are reflected.
30
Falah, Nabil [Verfasser]. "The Interaction of Steel Tube and Concrete Core in Concrete-Filled Steel Tube Columns / Nabil Falah." Aachen : Shaker, 2010. http://d-nb.info/1104047292/34.
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Marmash, Basem Ezzat. "The properties of recycled precast concrete hollow core slabs for use as replacement aggregate in concrete." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/13501/.
Full textAbstract:
The dumping cost of wasted concrete including the rejected units in precast concrete plants is expected to keep rising as the production increases. The waste material from precast concrete hollow core floors (hcu) is high grade and uncontaminated material. This research work was carried out to investigate mainly the strength and other engineering properties of high strength concrete made with recycled concrete aggregate derived from rejected hcu. Three major categories (based on a questionnaire) were investigated: (i) Type of crushers and the crushing method, (ii) The properties of RCA output from these crushers, (iii) The performance of fresh and hardened concrete, including prestressed concrete, with these RCA. The input material for the crushers was from the same origin of disposed hcu's. The waste concrete was crushed to -14 mm using three different types of crushers - the cone, impact and jaw crushers. The recycled material was separated into fractions of 14 mm, 10 mm and - 5 mm, and tested for physical and mechanical properties relevant to use in concrete. Concrete was then made using zero (control mix), 20% and 50% replacement of recycled coarse (RCCA), recycled fine (RCFA) and mixed (RCCA+RCFA) aggregates. All three crushers produced acceptable shape and strength of RCCA. Some properties are competitive to that of natural limestone aggregate. RCFA was much coarser than river gravel and just complied with the British Standard coarse grading limits. The impact crusher performed best with regard to most aggregate properties, e. g. flakiness, strength and water absorption, but has a disadvantage in producing a large amount of fine-to-coarse RCA. Concerning shape and strength, RCA showed similar properties, and in some cases better, than the conventional limestone aggregate. The water absorption for RCA is 3 to 4 times greater than the natural aggregates. For that reason an extra amount of water (called free water) will be added to the mix to compensate the water absorptions for aggregates. Some proportions of this extra added water may not be absorbed by the aggregates and will float to interrupt the design W/C ratio and caused it to increase. The slump value of fresh concrete made with RCA varied widely depending on the percentage and type of replacement, and the type of crusher. The compaction factor of fresh concrete made with RCA was more consistent and logical. Compressive strength of concrete made with RCA were generally within ±5 N/mm2 of the control. For tensile strength, RCA showed similar performance to that of natural limestone. The SS density of concrete with RCA is lower than that of the control concrete and is lower if the replacement percentages increase. Using RCFA causes higher bleeding rate and considerably reduces density and strength, and the severity increases as the replacements of RCFA increases. Using natural limestone aggregates with RCFA will minimize this poor behaviour and maintain the strength to certain extent. However joining RCCA with RCFA will not limit the poor behaviour and is not recommended. For bonding reinforcing bars most methods indicated that high replacement (100%) of CA cause some reduction in bond strength. In pretensioning wires the RCA concrete had a better performance in bond but some reduction was still reported. Prestressed X-shape beams were used to assess the effects of using of RCA on the performance of hollow core slabs. For 20% RCCA replacements, the prestressing loss, deflection and X-beam flexure crack failure were similar to the standard X-beam, at least and within the design limit. However at higher replacements (50%) some deterioration starts to reveal and the effects are even greater when using a combination of RCCA and RCFA.
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Sandoval, Gersson Fernando Barreto. "Desempenho do concreto poroso com agregados sustentáveis." Universidade Estadual de Londrina. Centro de Tecnologia e Urbanismo. Programa de Pós-Graduação em Engenharia de Edificações e Saneamento, 2014. http://www.bibliotecadigital.uel.br/document/?code=vtls000197929.
Full textAbstract:
A impermeabilização dos solos devido a urbanização vem sendo um dos grandes problemas da atualidade já que leva a uma mudança radical do ciclo hidrológico. Além disso, contribui para as enchentes, hidroplanagem e proliferação de doenças. Dessa forma o estudo de novos materiais é muito importante na tentativa de dar resposta a este tipo de problema. O presente trabalho tem por objetivo avaliar o desempenho mecânico e hidraúlico do concreto poroso com agregados sustentáveis. Os agregados escolhidos como referência nesta pesquisa foram agregados de basalto. Os agregados sustentáveis escolhidos foram: agregados graúdos de escória siderúrgica, resíduo de contrução civil (RCC) cerâmico e, finalmente, resíduo de contrução civil (RCC) de bloco de concreto de alvenaria estrutural. O traço, em massa, utilizado nas misturas de concreto poroso foi 1:3,26, com um consumo de cimento aproximado de 420 kg/m3, relação a/c igual a 0,34, sem uso de aditivos químicos ou adições minerais. Foram avaliadas resistência à compressão, à flexo-tração, vazios, permeabilidade e desgaste. No caso da permeabilidade foram utilizados dois tipos de ensaios: de carga constante e de carga variavél. Os resultados obtidos mostram que os agregados siderúrgicos apresentam o melhor comportamento mecânico, com valores de resistência à compressão e flexo-tração na ordem de 10,0 e 2,9 MPa, respectivamente. Verificou-se que para a resistência à compressão o parâmetro mais relevante foi a natureza do agregado e não a granulometria. Já na flexo-tração o parâmetro que mais impactou no desempenho foi a porcentagem de finos. Para o desempenho hidraúlico o parâmetro preponderante foi a porcentagem de vazios, que neste trabalho ocorreu com RCC cerâmico apresentando 27% de vazios, e permeabilidade de 15,2 mm/s. Desta forma, verificou-se que a utilização de agregados sustentáveis é uma alternativa viável na produção de concreto poroso.Nowadays, one of the major problems related to urbanization process is soil sealing, it leads to a radical change on the hydraulic cycle It also contributes to floods, aquaplaning and outbreaks of diseases. In this sense, study of new materials became important in the attempt to solve these issues. The objective of the present work is to evaluate the mechanical and hydraulic performance of pervious concrete with sustainable aggregates. Basaltic aggregates were chosen as reference in this research. Slag aggregates, recycled ceramic and construction blocks waste aggregates were chosen as sustainable aggregates. Mixture design, in mass, of pervious concrete used was 1:3.26 with an approximate consumption of 420 kg/m3, water cement ratio of 0.34, without any additives or admixtures. Compressive and flexural strengths, voids (%), water permeability and abrasion were analyzed. In the case of permeability, two methods were used: falling and constant head permeameter. The results showed the slag aggregates with the best mechanical behavior, presenting compressive and flexo-traction strength in the order of 10.10 and 2.92 MPa, respectively. It was observed that for compressive strength the most important parameter is the nature of the aggregate and not granulometry. However, the percentage of fines had a great influence on the flexural strength. Regarding permeability, the predominant parameter was the percentage of voids, and recycle ceramic waste aggregates, with around 27 % of voids, presented the best results in the order of 15.2mm/s. In this sense, the usage of sustainable aggregates is a viable alternative in the production of pervious concrete.
33
Lindwall, Caroline, and Jonas Wester. "Modelling Lateral Stability of Prefabricated Concrete Structures." Thesis, KTH, Betongbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-188586.
Full textAbstract:
Stability calculations of prefabricated concrete structures with help of FEM-tools demand knowledge about how the elements are related to each other. This thesis concerns how joints between building elements affect the results when modelling prefabricated concrete structures, with demarcation to joints between hollow core (HC) slabs and between solid wall elements. The thesis also covers how the properties of the floor can be adjusted to account for the effects of the joints without modelling every single element. The work started by measuring the deflection of 10 HC-slabs jointed together and loaded in-plane acting as a deep beam, in a FE-model made with Robot™, from Autodesk®. The joints between the HC-elements were modelled either rigid or elastic, and the cross-section and the length of the HC-elements were varied. The linear elastic stiffness between the HC-elements was obtained from the literature as 0.05 (GN/m)/m. The results showed that a changed cross-section geometry gave greater differences in deformation than a changed length. The in-plane shear modulus was then adjusted for the HC-elements in the rigid cases until the same deflection was achieved as for the elastic cases. The result showed that the shear modulus in average for the different cross-section geometries and lengths had to be reduced with a factor of 0.1 to account for the joints. Based on the geometry of a castellated joint between prefabricated solid concrete walls, a calculation model was developed for its linear elastic stiffness. The result was a stiffness of 1.86 (GN/m)/m. To verify the calculated stiffness, a FE-model was developed consisting of a 30m high wall, loaded horizontally in-plane and with one or two vertical joints where the stiffness was applied. The deflection and the reaction forces were noted and the result from the calculated stiffness was compared to other stiffnesses and assessed reasonable. The reaction forces were shown to depend on the stiffness of the joint. The reduced in-plane shear modulus of the HC-elements and the calculated stiffness of the wall joints were then used in a FE-model of a 10-storey building stabilised by two units. The vertical reaction forces were analysed and the results showed 0.02 % difference in the reaction forces in the stabilising units when consideration of the joints between the HC-elements were taken into account and 0.09 % when the vertical joints in the shear wall were taken into account. The results for the wall joint differed from the results when only the wall was modelled. This was thought to be a result of that the floors counteract the shear deformations in the wall joints. The influence of the floor joints was not significant for the building considered in this thesis, but for buildings with non-continuous configuration of the stiffness in the shear walls the outcome may be another, in these cases the reduction factor may be useful.Vid stabilitetsberäkningar av prefabricerade betongstommar med hjälp av FEM-verktyg ställs krav på kunskap om hur elementen förhåller sig till varandra. Detta arbete berör hur fogar mellan byggnadselement påverkar modellering av prefabricerade betongstommar med avgränsning till fogar mellan håldäckselement och mellan solida väggelement. Arbetet berör även en studie i hur ett bjälklags egenskaper kan justeras så att fogarnas effekt kan tillvaratas utan att modellera varje enskilt håldäckselement. Arbetet inleddes med att utböjningen analyserades hos 10 st ihopskarvade håldäckselement, lastade i dess plan likt en hög balk, i en FE-modell skapad i programmet Robot™, från Autodesk®. Fogarna mellan håldäcken modellerades som antingen rigida eller elastiska och håldäckens tvärsnittsgeometri och längd varierades under testet. Den linjära styvheten mellan håldäcken togs från litteraturen som 0.05 (GN/m)/m. Resultatet visade att ändrad tvärsnittsgeometri gav större skillnader för deformationen än varierad längd på håldäcken. Håldäckens skjuvmodul justerades sedan i dess plan för de rigida testen tills dess att de uppnådde samma utböjning som de elastiska. Resultatet visade att skjuvmodulen behövdes reduceras med en faktor 0.1, i medeltal för de olika tvärsnittsgeometrierna och håldäckslängderna. Utefter geometrin på en fog med förtagningar mellan prefabricerade väggar togs en beräkningsmodell fram för den linjärelastiska styvheten i väggfogarna. Resultatet blev en styvhet på 1.86 (GN/m)/m. För att verifiera den beräknade styvheten togs en FE-modell fram bestående av en 30m hög vägg lastad horisontellt i dess plan med en eller två vertikala fogar där en linjär styvhet applicerades. Utböjningen samt reaktionskrafterna noterades, resultatet för den uträknade linjära styvheten jämfördes med andra styvheter och bedömdes utifrån detta vara rimlig. Reaktionskrafterna visade sig vara beroende av styvheten på fogen. Den sänkta skjuvmodulen för håldäcken och den beräknade linjära elasticiteten för väggarna användes sedan i en FE-modell av en 10-våningsbyggnad med två stabiliserande enheter där de vertikala reaktionskrafterna analyserades. Resultatet visade att endast 0.02 procentenheter skiljer reaktionskrafterna i de stabiliserande enheterna då hänsyn tas till fogarna mellan håldäcken och 0.09 procentenheter då hänsyn tas till fogarna mellan väggarna. Resultatet skiljer sig från när endast väggen modellerades, vilket tros bero på att bjälklaget hjälper till att motverka deformationer i väggfogarna. Fogen mellan bjälklagselementen tros kunna ha större inverkan på en byggnad med stabiliserande enheter som drastiskt ändrar styvhet från ett plan till ett annat, i dessa fall kan den framtagna reduktionsfaktorn vara av nytta.
34
Bary, Benoît. "Étude du couplage hydraulique-mécanique dans le béton endommagé." Cachan, Ecole normale supérieure, 1996. http://www.theses.fr/1996DENS0022.
Full textAbstract:
Les travaux effectues dans le cadre de la thèse portent sur l'étude du couplage hydromécanique dans le béton, avec pour objectif une application au calcul prédictif du comportement des barrages. L'approche proposée est basée sur la mécanique des milieux poreux saturés couplée à la mécanique de l'endommagement anisotrope. Sont ainsi pris en compte les transferts de fluide sous pression, les phénomènes de dégradation orientée de la matrice, et les répercussions de cet endommagement sur les paramètres de couplage hydromécaniques. Une procédure expérimentale autorisant le pilotage simultané de la pression interstitielle et des contraintes va permettre l'identification des paramètres introduits dans le modèle. Les évolutions de ces paramètres sont alors simulées et comparées à d'autres approches proposées pour ce type de problème. L'implantation numérique du modèle ainsi identifié est réalisée dans le code de calcul par éléments finis Castem 2000. Une méthode de régularisation du problème de localisation des déformations est mise en œuvre avec succès pour le modèle d'endommagement. Une simulation d'un essai de fissuration hydraulique sur une structure pré-entaillée est alors effectuée, et prouve que le caractère dégradable des paramètres hydromécaniques influence fortement la réponse post-pic. On procède ensuite a la simulation du comportement d'un barrage poids soumis a une crue. Les résultats produits permettent de retrouver les principaux aspects mis en évidence sur ouvrages réels
35
Fichant, Stéphanie. "Endommagement et anisotropie induite du béton de structures : modélisations approchées." Cachan, Ecole normale supérieure, 1996. http://www.theses.fr/1996DENS0015.
Full textAbstract:
Les modèles d'endommagement ont fait l'objet de nombreuses études ces dernières années. En effet, une fois implantes dans un code de calcul, ils permettent de prédire l'état d'endommagement d'une structure sous chargement. Ces modèles peuvent se décliner en une version isotrope ou anisotrope. Dans ce document, nous nous sommes attaches à construire une classe de modèles allant du modèle d'endommagement isotrope à celui anisotrope (le plus général possible). Ce modèle reproduit certaines caractéristiques physiques observées expérimentalement sur les matériaux adoucissants tel que le béton. La méthode de décomposition de l'endommagement sur des microplans permet de décliner le même type de modèle en une version isotrope et une version anisotrope. Cette méthode est basée sur l'établissement des lois de comportement sur les microplans. Afin de voir l'influence de l'anisotropie induite par endommagement sur le comportement mécanique du béton, notre modèle a été implante dans un code éléments finis puis teste sur des exemples précis de la littérature.
36
Manatakos, Kyriakos. "Behaviour and design of reinforced concrete core-slab-frame structures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ30330.pdf.
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Manatakos, Kyriakos 1960. "Behaviour and design of reinforced concrete core-slab-frame structures." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=42088.
Full textAbstract:
This dissertation examines the response and design of reinforced concrete core-slab-frame structures subjected to monotonically increasing earthquake and gravity loads throughout the entire load range until failure, presenting findings from three separate studies by Manatakos and Mirza (1995) continuing the M. Eng. thesis research by Manatakos (1989). A typical building is selected consisting of a central core substructure composed of elevator, staircase and infilled slab cores, with coupling and lintel beams, and surrounding slabs joining to a frame substructure composed of slab-band girders, slabs and columns.Stage 1 concentrates on the elastic response and Stage 3 examines the nonlinear response of the core-slab-frame structure considering the effects of cracking and crushing of concrete, strain-hardening of the reinforcement, and tension-stiffening. Analyses involve three-dimensional elastic and nonlinear finite element modeling techniques of the structure to investigate the contribution and influence of the various structural components. The structural response is examined for the deformations, the concentrated reinforcement strains and concrete stresses in the cores, the force and stress distributions in the structural members, and the failure mode.
Stage 2 focuses on the design and detailing of the core-slab-frame structure following seismic provisions of building code requirements for reinforced concrete structures where applicable as given in the CSA Standard CAN3-A23.3-MS4 (1984), the ACI Standard ACI 318M-83 (1983) and the New Zealand Standard NZS3101 (1982). Assumptions made in the conventional design procedures and any shortcomings encountered are examined. Suitable design procedures and reinforcement details are suggested where no provisions exist in the codes.
Findings demonstrate complex three-dimensional interaction among the cores, beams, slabs and frames in resisting the lateral and gravity loads, and show considerable strength, ductility and energy absorption capability of the structure. Critical areas for design include the joints and junctions near the vicinity of core wall-slab-beams ends and corners. Plastic hinging extends over the lower 2.5% to 33% height of the structure with the majority of inelastic action and damage concentrated in the bottom 10% to 15% height, predicting an ultimate load of 3.4 to 5.9 times the design earthquake load with top drifts of the structure between 750 mm to 1375 mm.
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Lam, Dennis. "Composite steel beams using precast concrete hollow core floor slabs." Thesis, University of Nottingham, 1998. http://eprints.nottingham.ac.uk/11350/.
Full textAbstract:
The main aim of this thesis is to develop an insight into the behaviour of composite floors that utilise steel beams acting in combination with precast concrete hollow core floor slabs and to produce design recommendations for use by industry for this type of construction. Full scale bending tests of proprietary precast prestressed concrete hollow core unit floor slabs attached through 19mm diameter headed shear studs to steel Universal Beams (UB) have been carried out to determine the increased strength and stiffness when composite action is considered. The results show the bending strength of the composite beam to be twice that of the bare steel beam, and its flexural stiffness to be more than trebled. In addition to the beam tests, isolated push-off tests and horizontal eccentric compression tests were used to study the horizontal interface shear resistance of the headed studs and the strength of the slab, respectively. Maximum resistances were compared with the predictions of the Eurcode EC4, and a reduction formula for the precast effect derived. In addition to the experimental investigations, finite element (FE) studies were also conducted using the FE package ABAQUS to extend the scope of the experimental work. Results show a 2-dimensional plane stress analysis to be sufficiently accurate, providing the correct material input data obtained from isolated push-off and compression tests are used. The FE model for the composite beam was designed and validated using the full scale beam tests. A parametric study, involving 45 analyses, was carried out to cover the full range of UB sizes and floor depths used in practice. From the finite element work, design charts are formulated which may be used to simplify the design rules. Given the results of this work, a full interaction composite beam design may be carried out using the proposed design equations. The results show that precast slabs may be used compositely with steel UB's in order to increase both flexural strength and stiffness at virtually no extra cost, except for the headed shear studs. The failure mode is ductile, and may be controlled by the correct use of small quantities of transverse reinforcement and insitu infill concrete.
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Mohammed, Anwer Sabah Mohammed. "Seismic Behavior of Screen Grid Core Insulated Concrete Form Walls." PDXScholar, 2019. https://pdxscholar.library.pdx.edu/open_access_etds/4810.
Full textAbstract:
The use of the insulated concrete form (ICF) walls in residential buildings has increased over the past few decades. Much research has been conducted to evaluate the lateral strength of these walls by applying monotonic and cyclic loadings. In the current study, full-scale shake table experiments were employed to evaluate the in-plane behavior of four screen grid insulated concrete form (SGICF) walls. The first two wall specimens utilized dry fit insulated form blocks made from recycled expanded polystyrene granules that were bonded together with cement. When stacked, the cavities in the blocks formed a grid of cores that are evenly spaced vertically and horizontally. The walls consisted of four circular vertical cores and five circular horizontal cores reinforced with a single rebar placed nominally in the center of each core. The rest of the wall specimens were newly suggested pattern of SGICF walls, which consisted of three circular vertical cores and five circular horizontal cores. Two rebars were placed in each vertical core, and a single rebar was placed nominally in the center of each horizontal core.
Each wall was built on top of a foundation block that was designed such that failure would occur within the walls themselves. For each type of SGICF walls, steel fiber-reinforced concrete was used in one of the walls to evaluate the effect on failure modes, drift capacity, and shear strength. The results showed that the use of fiber-reinforced concrete in the cores of the SGICF walls that were built out of ICF blocks had not significantly improved the drift capacity, and had exhibited lower strengths than the wall with conventional concrete. These outcomes were mainly attributed to voids in the cores that had resulted despite similarities in workability of the concrete mixes and in techniques used to place the concrete in the walls. On the other hand, the use of the steel fiber-reinforced concrete in the cores of the newly suggested pattern of SGICF wall and the two rebars in the vertical cores had improved the drift ductility of the wall by about 63%.
The evaluation of the steel fiber-concrete was conducted at the component levels of the SGICF walls. Six simply supported reinforced concrete beams (3 ft. long) were tested in a three-point bending configuration by applying a cyclic loading protocol. Results showed that the steel fiber-concrete did not improve the lateral strength and the drift capacity. Steel fiber dose played an essential role in this investigation.
Analytical approaches were used to estimate the initial stiffness and the lateral strength of the SGICF walls. None of the approaches managed to provide an acceptable estimation of the initial stiffness. Meanwhile, the summation of individual vertical core plastic moment capacity and the ACI equation for the minimum shear strength of the concrete methods were successful in estimating the in-plane lateral strengths. Finally, a computer model was created to predict the lateral in-plane behavior of the SGICF walls. Results showed that the computer model provided good estimations for the peak lateral strength and the initial stiffness.
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Gao, Shanshan, and 高珊珊. "Coring process monitoring for strength of grout, concrete and rock in laboratory testing." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45530361.
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Woods, Lisa Joy. "The significance of negative bending moments in the seismic performance of hollow-core flooring." Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2008. http://hdl.handle.net/10092/2042.
Full textAbstract:
Hollow-core flooring units are designed as simply supported members. However, frequently in construction, continuity is established between the units and supporting structure by the addition of insitu topping concrete and steel reinforcement. This change in structural form can result in negative bending moments and axial forces being induced in the floor by seismic and other structural actions. Significant negative moments are induced by load combinations that include the effects of seismic forces due to vertical ground motion. The focus of this research was two failure mechanisms possible under these loading conditions, a flexural failure and a shear failure. Both failure mechanisms were investigated analytically and experimentally.
A brittle flexural failure was observed experimentally in a sub assembly test that contained starter bars and mesh reinforcement in the insitu topping concrete. The failure occurred at loads lower than those predicted using standard flexural theory. It appears that, due to the prestressing and low reinforcement ratio of the topping concrete, the assumption that plane sections remain plane is not appropriate for this situation. It is proposed that a strain concentration factor be introduced to account for the effects of tension stiffening. This factor improves the correlation between observed and predicted flexural strength.
The second failure mode investigated was a flexure shear failure in a negative moment zone. Flexural cracks reduce the shear strength of a reinforced concrete member. Analytical predictions suggest that some hollow-core floor details could be prone to this type of brittle failure. A flexure shear failure was not observed experimentally; however, this does not eliminate the possibility of this failure mode.
A summary of other failure mechanisms possible in hollow-core flooring is also presented. All failure modes should to be considered as part of establishing a hierarchy of failure in the design or retrofit of hollow-core floors.
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Smith, William Peter Younger. "Relating concrete cube, core and cylinder compressive strengths that are cast, cured, prepared and tested in laboratory conditions." Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/26895.
Full textAbstract:
In practice, concrete is initially tested for compressive strength by casting a cube/cylinder, which is left to cure in favourable conditions until the date of testing. The results obtained from such tests can give a consultant guidance on the material's properties such as estimated porosity, density and compressive strength. These tests are known as control and conformity tests. Supplementary tests may be needed if the control test fails or further investigation must be done to the concrete. These tests are done by drilling core specimens out of the in-situ concrete and applying the necessary tests. These results are used to verify conformity with specifications set out by the engineer. The outcome of such a test is extremely important as it is often used as the basis to decide the integrity of the structure. Although important, in-situ compressive strength remains as one of the least understood concrete properties due to the difficulty in relating and interpreting the results. Furthermore, there is no reliable universal relationship between compressive strength of cores and; moulded cubes and cylinders. A comprehensive literature and experimental study was attempted to relate standard cube and core compressive strength, as well as, cylinder and core strengths to identify the factors that may affect the analysis and interpretation of results. An experimental program was set out to relate the compressive strength of cubes, cores and cylinders, with a length/diameter ratio of 1.0. All specimens were cast, cured, prepared and tested in the University of Cape Town, New Engineering Building (NEB) laboratory according to South African National Standards. Twelve concrete mixes were designed using two concrete strengths (30 and 50 MPa), three maximum aggregate sizes (9.2, 19.2 and 26.5 mm) and two aggregate types, namely greywacke and quartzitic sandstone. An additional two mixes of high strength concrete were created (60 and 75 MPa) using 19.2mm greywacke aggregate. The compressive tests involved a 100 mm cube, three diameter cylinders (70, 100 and 150 mm) and four core diameter sizes (50, 70, 100 and 150 mm). All core specimens were drilled from beams that were cast. A total of 520 specimens were tested during this study. An analysis of variance (ANOVA) was applied to all the results to identify if the compressive strengths were statistically significantly different. The compressive strength and statistical results indicate that 100 mm cubes and 100 mm diameter cores have statistically similar compressive strengths. The diameter of the core and cylinder influenced the compressive strength. It was found, as the diameter size decreased the strength increased for core specimens and the opposite was found for the cylinder. Both findings were inconsistent with literature. However, as the core and cylinder diameters increased to a size larger than 100 mm, the compressive strengths were statistically similar. With respect to the maximum aggregate size, the strength was influenced in correspondence with the diameter size. As the core diameter decreased and the maximum aggregate size increased, the compressive strength increased. Whereas, the opposite was found with the cylinders. The strength level further determined the influence that the coarse aggregate type had on the compressive strength. At the 30 MPa strength level, the aggregate types produced statistically similar strength. At the 50 MPa strength level, the sandstone produced a statistically higher compressive strength compared to the greywacke aggregate. Finally, as the strength level increased over 50 MPa there was no significant difference between the mean compressive strength of cubes and cores. It was concluded, owing to the controlled environment that the all specimens were cast, cured, prepared and tested; as well as the similarity in the geometric size, statistically comparable compressive strengths were obtained for cubes and cores.
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Gouasmia, Abdelhacine. "Seismic response of reinforced concrete structures designed using North American building codes." Thesis, University of Ottawa (Canada), 1987. http://hdl.handle.net/10393/5467.
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Vicente, Osni. "Estudo sobre o comportamento elétrico do concreto utilizado em sistemas de aterramento estrutural." Universidade Estadual de Londrina. Centro de Tecnologia e Urbanismo. Programa de Pós-Graduação em Engenharia Elétrica, 2010. http://www.bibliotecadigital.uel.br/document/?code=vtls000166151.
Full textAbstract:
Diante das solicitaçãoes exigentes de uma descarga atmosférica, o sistema de aterramento por estruturas de concreto armado tem sido reconhecido, quando bem executado, um excelente método de proteção para edificações. Embora existam muitos estudos na área, pouco se tem falado, no entanto, sobre a influência da composição do concreto em seu comportamento elétrico. Uma vez que a corrente de descarga necessariamente passa pelo concreto como meio condutor antes de dissipar-se no solo, o conhecimento de suas características nas condições reais de uma construção usual nos fornece uma informação importante sobre a segurança da instalação e a integridade do concreto. Neste trabalho procura-se levantar relações entre a resistência elétrica, a umidade e o traço do concreto encontrado normalmente em construção civil. Diversos corpos de prova (CP) são levados a ensaios em alta e baixa tensão com o objetivo de determinar uma relação entre a impedância em AT (e também a resistência em BT) com as diferentes proporções de água/cimento dentro de cada traço e condição de umidade especificados. O trabalho também apresenta uma metodologia de ensaio com relação à preparação e manipulação dos corpos de prova de concreto, utilizando as recomendações práticas da área de construção civil, trazendo uma experiência e um conjunto de critérios pouco explorados pelos engenheiros eletricistas na área de aterramentos. Os resultados mostram que é possí?vel controlar as variáveis envolvidas na confecção dos CP para obter maior homogeneidade nos valores de massa seca, massa úmida saturada e resistividade elétrica. Os testes mostram ainda a importância de utilizar um alto teor de umidade nos CP, uma vez que o trabalho se dirige ao concreto de elementos de fundação. O estudo não garante a integridade do concreto úmido quando atravessado por correntes de descargas atmosféricas, mas fornece indícios de que sua utilização é segura para aterramentos estruturais e abre perspectivas para novos estudos.Given the exacting demands of a lightning strike, the grounding system for reinforced concrete structures has been recognized, when properly executed, as an excellent method for protecting buildings. Although there are many studies in the area, little has been said, however, about the influence of the composition of concrete on its electrical behavior. Since the discharge current necessarily passes through the concrete as conductive medium before dissipating into the soil, the knowledge of its characteristics in real conditions of an usual construction provides us with important information about the safe installation and integrity of the concrete. In this study we aimed to raise relations between electrical resistance, moisture and trace normally found in concrete construction. Several tests are carried out with samples at high and low voltage with the intention of seeking a relationship between the impedance at high voltage (and also resistance to low voltage) with different water/cement ratios within each trait and each specified condition of moisture. The work also includes a chapter on the testing methodology regarding the preparation and handling of test samples of concrete, using the practical recommendations of the construction area, bringing an experience and a set of criteria rarely explored by electrical engineers in the area of groundings. The results show that it is possible to control the variables involved in the production of CP to achieve greater uniformity in the values of dry weight, wet saturated weight and electrical resistivity. The tests also show the importance of using a high moisture content in CP, since the work is directed to the concrete foundation elements. The study does not guarantee the integrity of the wet concrete when crossed by currents of lightning strikes, but provides evidence that their use is safe for structural grounds and opens perspectives for further studies.
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Lin, Yi-de, and 林宜德. "Seismic Fragility Analysis of Reinforced Concrete Structure－Considering Different Seismic Code." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/81019109032735501770.
Full textAbstract:
碩士國立中央大學
土木工程研究所
95
Taiwan locates on high seismicity pacific ring of fire. It is also one of high felt earthquake occurring zone. Due to earthquakes cause damages to life and properties, damage assessment of structures is the most important part of earthquake loss assessment. For providing a rational and reliable result of structural loss, fragility curves of structures must be established. In this thesis, finite element models for vary floors of RC structures of different building code phase are modeled. SAP2000 is utilized to perform non-linear dynamic analyses. Responses of structures when earthquakes occur are simulated. Maximum story drift of each simulation result is defined as the damage parameter. Damage state of structure can be identified through damage parameter which is correspondent to threshold of damage state. After establishments of reliable seismic fragility curves of RC structures, damage assessment of structures of building code decade can be performed to predict losses after earthquakes happening. Risk management mechanisms can be set up via assessment above. After a real earthquake happening, quick assessment can be performed, and result of assessment could be a guide to prevention and rescue of earthquake hazard.
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Shen, Chin-Hung, and 沈錦鴻. "Application of neural networks and ACI code in pozzolanic concrete mix design." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/whjp54.
Full textAbstract:
碩士國立交通大學
土木工程系所
101
Concrete is the most widely used materials in civil engineering. Concrete is a high variability of material owing to composed with a variety of different materials. Since the mix proportioning of concrete are added pozzolanic and chemical admixtures, it became more difficult to control the properties of concrete. The purpose of this study is to establish a computer-aided system for concrete mix design. First, actual data in reference or laboratory are collected to establish a real mix proportioning of concrete database. A supervised neural network (ANN) model is then employed to establish the prediction models of strength and slump of concretes. Following, based on ACI code, a practical database of mix proportioning of concrete is produced. For verifying the correction of generated data, the strength and slump of concrete are yielded via ANN prediction models. 12 different mix designs are also verified via cylinder test in laboratory. Finally, a classification system is utilized to categorize data into 360 clusters based on strength of concrete, pozzolanic admixtures replacement rate, and materials costs. Simulation results reveal that based on these grouped 360 clusters, the proposed concrete mix computer-aided design system can provide engineering acceptable solutions (mix design) as users acquiesced required strength of concrete, pozzolanic admixtures replacement rate, and materials costs.
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Gullapalli, Anusha Scanlon Andrew. "ACI 318 Code provisions for deflection control of two-way concrete slabs." 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4459/index.html.
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(13146967), Grace Kurniawati Santoso. "Evaluation of capacity reduction factors for the design of reinforced concrete structural elements case study: Indonesia." Thesis, 2002. https://figshare.com/articles/thesis/Evaluation_of_capacity_reduction_factors_for_the_design_of_reinforced_concrete_structural_elements_case_study_Indonesia/20366616.
Full textAbstract:
Although there has been many changes in the development of the safety provisions for the Indonesian codes of practice since 1971, most of the changes have either been compromised or combined with the corresponding codes of the developed countries. For example, the current Indonesian concrete code (SKSNI) has adopted many factors from the American Concrete Institute (ACI 318) code, the British Standard (BSI,1985) code, the Architectural Institute of Japan (AIJ,1994) code and the Dutch code (GBV, 1985).
Comments amongst the practicing engineers as the end user on the existing code often refer to the inconsistencies of the code provisions and the field practices in Indonesia. As Indonesia is a country with an unbalanced distribution of skills and knowledge between the main island Java and other islands, providing an unified national standard without referring to the regional practices adversely affects the safety levels. This thesis attempts to demonstrate the inconsistencies in the provisions of the current Indonesian concrete code (SKSNI T-15, 1991) and the field practices in the main island Java. An extensive probability analysis has been carried out based on the statistical field data collected from several projects and material testing institutions for the demonstration of the aims of the thesis. From the probabilistic analyses of the statistical data, load and resistance factors for some important structural actions (viz, flexure, compression, flexural shear and punching shear) have been evaluated and compared with the provisions of the SKSNI, ACI 318 and AS 3600-1988. Gravity load (dead and live loads) and lateral load (dead, live and earthquake loads) combinations have been considered in the evaluation of the load and resistance factors for the selected structural actions. The thesis proposes the evaluated load and resistance factors as rational provisions reflecting the field practices of the Java island and recommendations that similar studies be carried out to reflect the regional practices in the safety provisions of the Indonesian concrete code.
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Mahroug, Mohamed E. M., Ashraf F. Ashour, and Dennis Lam. "Experimental response and code modelling of continuous concrete slabs reinforced with BFRP bars." 2014. http://hdl.handle.net/10454/5914.
Full textAbstract:
This paper presents test results and code predictions of four continuously and two simply supported concrete slabs reinforced with basalt fibre reinforced polymer (BFRP) bars. One continuously supported steel reinforced concrete slab was also tested for comparison purposes. All slabs tested were 500 mm in width and 150 mm in depth. The simply supported slabs had a span of 2000 mm, whereas the continuous slabs had two equal spans, each of 2000 mm. Different combinations of under and over BFRP reinforcement at the top and bottom layers of slabs were investigated.
The continuously supported BFRP reinforced concrete slabs exhibited larger deflections and wider cracks than the counterpart reinforced with steel. Furthermore, the over reinforced BFRP reinforced concrete slab at the top and bottom layers showed the highest load capacity and the least deflection of all BFRP slabs tested. All continuous BFRP reinforced concrete slabs failed owing to combined shear and flexure at the middle support region. ISIS-M03-07 and CSA S806-06 design guidelines reasonably predicted the deflection of the BFRP slabs tested. However, ACI 440-1R-06 underestimated the BFRP slab deflections and overestimated the moment capacities at mid-span and over support sections.
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Yang, Keun-Hyeok, Ashraf F. Ashour, and J.-K. Song. "Shear capacity of reinforced concrete beams using neural network." 2007. http://hdl.handle.net/10454/959.
Full textAbstract:
NoOptimum multi-layered feed-forward neural network (NN) models using a resilient back-propagation algorithm and early stopping technique are built to predict the shear capacity of reinforced concrete deep and slender beams. The input layer neurons represent geometrical and material properties of reinforced concrete beams and the output layer produces the beam shear capacity. Training, validation and testing of the developed neural network have been achieved using 50%, 25%, and 25%, respectively, of a comprehensive database compiled from 631 deep and 549 slender beam specimens. The predictions obtained from the developed neural network models are in much better agreement with test results than those determined from shear provisions of different codes, such as KBCS, ACI 318-05, and EC2. The mean and standard deviation of the ratio between predicted using the neural network models and measured shear capacities are 1.02 and 0.18, respectively, for deep beams, and 1.04 and 0.17, respectively, for slender beams. In addition, the influence of different parameters on the shear capacity of reinforced concrete beams predicted by the developed neural network shows consistent agreement with those experimentally observed.