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1
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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Al-Tamimi, Adnan. "Fibre-reinforced connections in precast concrete flat slabs." Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367112.
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Trygstad, Steinar. "Structural Behaviour of Post Tensioned Concrete Structures : Flat Slab. Slabs on Ground." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2001. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-114.
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In this investigation strength and structural behaviour of prestressed concrete is studied with one full scale test of one flat slab, 16000 mm x 19000 mm, and three slabs on ground each 4000 mm x 4000 mm with thickness 150 mm. The flat slab was constructed and tested in Aalesund. This slab has nine circular columns as support, each with diameter 450 mm. Thickness of this test slab was 230 mm and there were two spans in each direction, 2 x 9000 mm in x-direction and 2 x 7500 mm in y-direction from centre to centre column. The slab was reinforced with twenty tendons in the middle column strip in y-direction and eight tendons in both outer column strips. In x-direction tendons were distributed with 340 mm distance. There were also ordinary reinforcement bars in the slab. Strain gauges were welded to this reinforcement, which together with the deflection measurements gives a good indication of deformation and strains in the structure.
At a live load of 6.5 kN/m2 shear failure around the central column occurred: The shear capacity calculated after NS 3473 and EuroCode2 was passed with 58 and 69 %, respectively. Time dependent and non-linear FE analyses were performed with the program system DIANA. Although calculated and measured results partly agree well, the test show that this type of structure is complicated to analyse by non-linear FEM.
Prestressed slabs on ground have no tradition in Norway. In this test one reinforced and two prestressed slabs on ground were tested and compared to give a basis for a better solution for slabs on ground. This test was done in the laboratory at Norwegian University of Science and Technology in Trondheim. The first slab is reinforced with 8 mm bars in both directions distributed at a distance of 150 mm in top and bottom. Slab two and three are prestressed with 100 mm2 tendons located in the middle of slab thickness, and distributed at a distance of 630 mm in slab two and 930 mm in slab three. Strain gauges were glued to the reinforcement in slab one and at top and bottom surface of all three slabs. In slab two and three there were four load cells on the tendons.
Each slab were loaded with three different load cases, in the centre of slab, at the edge and finally in the corner. This test shows that stiffness of sub-base is one of the most important parameters when calculating slabs on ground. Deflection and crack load level depends of this parameter. Since the finish of slabs on ground is important, it can be more interesting to find the load level when cracks start, than deflection for the slab. It is shown in this test that crack load level was higher in prestressed slabs than in reinforced slab. There was no crack in the top surface with load in the centre, but strain gauges in the bottom surface indicate that crack starts at a load of 28 kN in the reinforced slab, and 45 kN in the prestressed slabs. Load at the edge give a crack load of 30 kN in reinforced slab, 45 kN and 60 kN in prestressed slabs. The last load case gives crack load of 30 kN in reinforced slab, 107 kN and 75 kN in prestressed slabs. As for the flat slab, FE analyses were performed for all of the three slabs on ground, and analyses shows that a good understanding of parameters like stiffness of sub-base and tension softening model, is needed for correct result of the analyses.
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Melo, Guilherme Sales S. de A. "Behaviour of reinforced concrete flat slabs after local failure." Thesis, University of Westminster, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304732.
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Samadian, Fariborz. "Investigation of shear reinforcement for reinforced concrete flat slabs." Thesis, University of Westminster, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362692.
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Cloete, Renier. "A simplified finite element model for time-dependent deflections of flat slabs." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-05302005-123208/.
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Gomes, Ronaldo Barros. "Punching resistance of reinforced concrete flat slabs with shear reinforcement." Thesis, University of Westminster, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303158.
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Smith, Holly Kate Mcleod. "Punching shear of flat reinforced-concrete slabs under fire conditions." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/20962.
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This thesis examines punching shear response of reinforced-concrete flat slabs under fire conditions. The shear behaviour of concrete in fire is relatively poorly understood compared to its flexural response. Failures such as the Gretzenbach car park failure in Switzerland (2004) have prompted concerns over the punching shear capacity of flat slabs in fire. The shear behaviour of reinforced-concrete in fire depends on degradation of the individual material properties with temperature, their interaction, and more recently recognised, the effects of restrained thermal expansion. Through experimental testing this thesis aims to build a foundation understanding of the punching shear behaviour of flat reinforced-concrete slabs in fire conditions. A series of shear blocks, tested after exposure to elevated temperature (realistic fire temperature), were used to develop an understanding of the effects of elevated temperature on the shear transfer performance of reinforced-concrete. These tests allowed the complex interplay of shear-carrying mechanisms at ambient temperature to be extended to the case of post-elevated temperature. Fifteen slab-column punching shear specimens were tested under both applied load and extreme heating. In particular, the effects of restrained thermal expansion were experimentally investigated by altering the support conditions of the slab-column specimens. A purpose-built restraint frame allowed the boundary support conditions to be either fully restrained or unrestrained. This experimental series is the only series to have tested restrained specimens at elevated temperatures, though previous researchers have simulated the thermal restraint effects and reported the importance of restrained thermal expansion and curvature on the behaviour of punching shear. Parameters of slab thickness and reinforcement ratio were also varied to investigate their respective impacts on punching shear behaviour at elevated temperature. The thicker 100 mm reinforced slabs failed in punching shear, whereas the 50 mm and 75 mm thick slabs failed in flexure-shear mechanisms and the unreinforced slabs failed in flexure. Clear behavioural differences were observed between specimens with different support conditions. Unrestrained 100 mm thick slabs under sustained load failed soon after heating began, whereas none of the corresponding restrained specimens failed during heating. One restrained, heavily reinforced specimen failed during cooling, whilst under sustained load. This is the first recorded punching shear failure during the cooling phase of an elevated temperature test and may also be the first recorded test specimen ever to have failed during the cooling phase of an elevated temperature test. This failure highlights the unknown and potentially unsafe behaviour of structures during the cooling phase. Further structural investigation of the cooling behaviour of concrete flat slabs after exposure to fire, needs to be undertaken. Most of the specimens’ central deflection was away from the heat source (in the direction of loading) during the whole test, irrespective of support condition. The test setup was assessed to investigate the unusual slab-column deflection away from the heat source, however the complex behaviour observed during the tests cannot currently be explained. It is assumed that the degradation in concrete properties and non-linear material behaviour dominates over the thermal expansion of the slabs. Quantitative and qualitative comparisons are presented, though the quantitative data is impacted by size effect, non-repeatable heating application between tests and jack friction influences on specimens with low capacities. Eurocode 2 punching shear prescriptive elevated temperature design, extends the ambient temperature equation for elevated temperature use, by degrading the temperature-dependant parameters by factors. Support conditions are not considered, with the code specifically telling the designer not to consider in-plane thermal expansion effects, therefore consequently ignoring the premature punching shear failure that can occur. Furthermore, the ambient temperature equation is based on the regression of available experimental data at the time and does not consider the reinforcement as a shear transfer mechanism. The experimental capacities of the 100 mm thick, reinforced slabs that failed in pure punching shear mechanism were similar to the Eurocode 2 punching shear prescriptive design capacity, when directly compared. The unrestrained support condition was shown to be consistently, not conservatively predicted by Eurocode 2, whereas the restrained support condition capacities were conservatively predicted. It is comforting to know that the Eurocode 2 design predicts the restrained supported slabs conservatively, as real buildings are more likely to have supports closer to the restrained condition rather than the unrestrained support condition. A sensitivity analysis of the Eurocode 2 prescriptive design equation shows it is highly sensitive to the concrete strength degradation and not the variable, cp, which was used to make a support condition comparison in this thesis. This indicates how the Eurocode 2 equation for punching shear capacity lacks in its consideration of whole structural behaviour. The Critical Shear Crack Theory has been proposed as the background to a harmonised shear design approach, called Model Code 2010. The Critical Shear Crack Theory was safe in predicting the experimental punching shear capacities. There were large variances for the 100 mm thick slabs, however they are consistent with the original model comparison to test data. An expansion of the Critical Shear Crack Theory for elevated temperature requires further validation with experimental restrained thermal expansion tests, such as those presented in this thesis. Finally, a digital image correlation technique has been proven to be a reliable method to measure structural displacements of concrete at elevated temperatures. Digital image correlation allowed the crack locations and slab rotation angles to be visualized throughout testing. No other measurement techniques are able to provide similar versatility in fire testing such as that presented herein.
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Kamaraldin, Khaled. "Punching shear and moment transfer in reinforced concrete flat slabs." Thesis, University of Westminster, 1990. https://westminsterresearch.westminster.ac.uk/item/94vwq/punching-shear-and-moment-transfer-in-reinforced-concrete-flat-slabs.
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Michels, Julien [Verfasser]. "Bearing Capacity of Steel Fiber Reinforced Concrete Flat Slabs / Julien Michels." Aachen : Shaker, 2010. http://d-nb.info/1104047403/34.
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Sha'at, Emad. "Punching shear strength of reinforced concrete flat slabs at edge columns." Thesis, Queen's University Belfast, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261880.
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CUBAS, MARIA VANESSA LA TORRE. "NUMERICAL ANALYSIS OF THE BEHAVIOR OF FLAT SLABS PRESTRESSED CONCRETE FLOORS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2012. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=20465@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Lajes lisas de concreto protendido com cordoalhas engraxadas não aderentes têm sido empregadas em pavimentos de edificações com frequência nos últimos anos. Essa solução estrutural é ideal quando se tem uma distribuição regular dos pilares. Além disso, sabe-se que lajes de concreto protendido oferecem vantagens técnicas sobre a solução tradicional em concreto armado, principalmente para vencer vãos maiores e onde muitas vezes se exigem seções mais esbeltas. O objetivo desta dissertação é estabelecer critérios práticos para o projeto de lajes lisas protendidas, maciças ou nervuradas, visando ao atendimento dos critérios relativos ao estado limite de utilização. Com este propósito, um estudo paramétrico foi realizado no qual foram analisados as tensões nas regiões de introdução das forças de protensão e a influência da rigidez dos pilares na retenção da protensão. A investigação foi conduzida por meio de modelagens em elementos finitos, empregando elementos do tipo casca para as lajes e elementos tipo viga para os pilares. No caso das lajes nervuradas, suas mesas foram representadas por elementos casca e as nervuras por elementos viga levando em conta a excentricidade entre seus centros geométricos.
Concrete flat slabs prestressed with unbounded greased strands have been used in building floors over the last years. This structural solution is ideal when the columns are regularly distributed. In addition, it is known that prestressed floors have some technical advantages when compared to the traditional solution in reinforced concrete, mainly in cases of large spans and when lighter elements are required. The objective of the present work is to propose practical criteria for the design of flat slab prestressed concrete floors, for the cases of uniform thickness slabs and waffle slabs, aiming at complying with serviceability limit state. A parametric study was carried out to analyze the stress distribution in prestressing load introduction zones and the influence of the columns in retaining prestressing loads. The investigation was conducted using finite element models in which shell and frame elements were used to represent the slabs and the columns. For the case of waffle slabs, flanges and webs were modeled with shell and frame elements, respectively, taking into consideration the eccentricity between these two elements.
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Jarrat, Robert. "Construction in in-situ cast flat slabs using steel fibre reinforced concrete." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/17861.
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Thesis (MScEng)--Stellenbosch University, 2011.ENGLISH ABSTRACT: Fibre reinforced concrete (FRC) transforms concrete from a characteristically brittle material to one with a post-crack tensile residual capacity. Its application in industry has varied over the past of which the tensile properties have generally been used in the form of crack mitigation. More recently, the introduction of steel fibres has broadened this scope to structural applications in which the resisting tensile stresses that develop within a steel FRC (SFRC) element can be rather significant. This thesis reviews the existing practices and design models associated with SFRC and the suitability of its implementation as the sole form of reinforcement in in-situ cast flat slab systems. As a material SFRC is dependent on a number of factors which include the fibre type and volume, fibre distributions, element size, as well as the support and applied load conditions. Thus, its performance can be considered rather variable in comparison to conventional concrete should the incorrect practices be implemented. In order to adequately define the material characteristics, it is necessary to use test procedures that accurately reflect on the intended structural application. As a result a number of test procedures have been developed. In addition to this, the post-crack material performance is associated with a non-linear behaviour. This attribute makes the design of structural SFRC elements rather difficult. In an attempt to simplify this, existing design models define stress-strain or stress-crack width relations in which assumptions are made regarding the cross-sectional stress distribution at specified load states. This thesis takes on two parts in defining the suitability of SFRC as the sole form of reinforcement in flat slab systems. The first is a theoretical investigation regarding the micro and macro scale material performance of SFRC, the practices that exist in defining the material properties and its application in structural systems (particularly suspended slab systems), and a breakdown of the existing design models applicable to strain softening deflection hardening SFRC materials. The second part is an experimental program in which the fresh state and hardened state material properties of specified SFRC mix designs defined through flow and beam testing respectively. These properties are then implemented in the design and construction of full scale flexural and punching shear test slabs in an attempt to verify the theory applied. The investigation reveals that the use of SFRC significantly improves the ductility of concrete systems in the post-crack state through fibre crack bridging. This ductility can result in deflection hardening of flat slab systems in which the redistribution of stresses increases the load carrying capacity once cracking has taken place. However, the performance of large scale test specimens is significantly influenced by the construction practices implemented in which the material variability increases as a result of non-uniform fibre distributions. The results indicate that the load prediction models applied have potential to adequately predict the ultimate failure loads of SFRC flat slab systems but however cannot account for possible non-uniform fibre distributions which could result in premature failure of the system.
AFRIKAANSE OPSOMMING: Vesel versterkte beton (VVB) verander beton van die kenmerkende uiters bros material na ‘n material met ‘n residuele post-kraak trekkapasiteit. Die toepassing daarvan in die bedryf het in die verlede gewissel en die trek eienskappe is oor die algemeen gebruik vir kraak vermindering. Meer onlangs het die bekenstelling van staal vesel hierdie omvang verbreed na die strukturele toepassings waar trekspannings wat ‘n VVB element kan weerstaan noemenswaardig kan wees. Hierdie tesis ondersoek bestaande praktyke en ontwerpmodelle met die oog op staalvesel versterkte beton (SVVB) en die geskiktheid van die implementering daarvan as die enigste vorm van bekisting in in-situ gegiete plat blad stelsels. As ‘n materiaal, is SVVB afhanklik van ‘n aantal faktore wat die tipe vesel en volume, vesel verspreiding, element grootte, sowel as die randvoorwaardes tipe aangewende las insluit. As gevolg hiervan, kan die gedrag van SVVB, wat korrek geïmplimenteer word, as redelik varieerbaar beskou word wanneer dit met konvensionele beton vergelyk word. Ten einde die materiaaleienskappe voldoende te definieer, is dit noodsaaklik dat prosedures wat die strukturele toepassing akuraat voorstel, getoets word en daarom is ‘n aantal toets prosedures ontwikkel. Verder het die post-kraak materiaalgedrag ‘n nie-lineêre verband wat struktuurontwerp met SVVB redelik moeilik maak. Om dit te vereenvoudig, definieer bestaande ontwerpmodelle spanning-vervorming of spanning-kraakwydte verhoudings waarin aannames gemaak word ten opsigte van die spanningsverdeling oor ‘n snit, gegewe sekere lastoestande. Hierdie studie bestaan uit twee dele wat die geskiktheid van SVVB as die enigste vorm van bikisting in plat blad stelsels definieer. Die eerste deel bestaan uit ‘n teoretiese ondersoek wat handel oor die mikro- en makro-skaal materiaalgedrag van SVVB, die praktyke wat bestaan om die materiaaleienskappe en toepassing in strukturele sisteme (spesifiek opgelegde blad stelsels) te definieer, en ‘n uiteensetting van die bestaande ontwerpmodelle wat van toepassing is vir defleksie as gevolg van vervormingsversagting wat SVVB material verhard. Die tweede deel bestaan uit ‘n eksperimentele program waarin die materiaaleienskappe van gespesifiseerde SVVB meng-ontwerpe in die vars toestand en in die verharde toestand gedefinieer word deur middel van vloei- en balktoetse onderskeidelik. Hierdie eienskappe word dan toegepas vir die ontwerp en konstruksie van volskaalse buig- en ponsskuif toetsblaaie ten einde die modelle en teorie wat toegepas is, te bevestig. Die ondersoek toon dat die gebruik van SVVB die duktiliteit van beton sisteme noemenswaardig verbeter in die post-kraak toestand deur kraak oorbrugging. Hierdie duktiliteit kan defleksie verharding van plat blad stelsels veroorsaak waarin die herverdeling van spannings, nadat kraking plaasgevind het, die lasdraende kapasiteit verhoog. Die gedrag van die grootskaalse toetsmonsters word egter noemenswaardig beïnvloed deur die konstruksiemetodes wat geïmplementeer word waarin die materialveranderlikheid toeneem as ‘n gevolg van nie-uniforme vesel verdelings. Die resultate dui daarop dat die modelle wat toegepas is om die laste te voorspel, die potensiaal het om die grens falingslas van SVVB plat blad stelsel voldoende te voorspel, maar neem nie moontlike nie-uniforme veselverdelings wat kan lei tot vroeë faling van die stelsel in ag nie.
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Al, Ajami Abdulhamid. "Punching shear of concrete flat slabs reinforced with fibre reinforced polymer bars." Thesis, University of Bradford, 2018. http://hdl.handle.net/10454/16864.
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Fibre reinforcement polymers (FRP) are non-corrodible materials used instead of
conventional steel and have been approved to be an effective way to overcome
corrosion problems. FRP, in most cases, can have a higher tensile strength, but
a lower tensile modulus of elasticity compared to that of conventional steel bars.
This study aimed to examine flat slab specimens reinforced with glass fibre
reinforced polymer (GFRP) and steel bar materials for punching shear behaviour.
Six full-scale two-way slab specimens were constructed and tested under
concentric load up to failure. One of the main objectives is to study the effect of
reinforcement spacing with the same reinforcement ratio on the punching shear
strength. In addition, two other parameters were considered, namely, slab depth,
and compressive strength of concrete.
The punching shear provisions of two code of practises CSA S806 (Canadian
Standards 2012) and JSCE (JSCE et al. 1997) reasonably predicted the load
capacity of GFRP reinforced concrete flat slab, whereas, ACI 440 (ACI
Committee 440 2015) showed very conservative load capacity prediction.
On the other hand, a dynamic explicit solver in nonlinear finite element (FE)
modelling is used to analyse a connection of column to concrete flat slabs
reinforced with GFRP bars in terms of ultimate punching load. All FE modelling was performed in 3D with the appropriate adoption of element size and mesh.
The numerical and experimental results were compared in order to evaluate the
developed FE, aiming to predict the behaviour of punching shear in the concrete
flat slab. In addition, a parametric study was created to explore the behaviour of
GFRP reinforced concrete flat slab with three parameters, namely, concrete
strength, shear load perimeter to effective depth ratio, and, flexural reinforcement
ratio. It was concluded that the developed models could accurately capture the
behaviour of GFRP reinforced concrete flat slabs subjected to a concentrated
load.
Artificial Neural Networks (ANN) is used in this research to predict punching
shear strength, and the results were shown to match more closely with the
experimental results. A parametric study was performed to investigate the effects
of five parameters on punching shear capacity of GFRP reinforced concrete flat
slab. The parametric investigation revealed that the effective depth has the most
substantial impact on the load carrying capacity of the punching shear followed
by reinforcement ratio, column perimeter, the compressive strength of the
concrete, and, the elastic modulus of the reinforcement.
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Jalal, Pasha, and Jose Andres Perez. "Punching shear in concrete flat slabs supported on slender edge steel columns." Thesis, KTH, Betongbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-278546.
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Punching shear is a failure mechanism caused by concentrated loads, creating a crack pattern that resembles a cone shape or piece of pie starting from the top surface of the slab and prolongs downwards. When the total shear force is greater than the shear resistance of the slab, it may eventually lead to punching shear failure. It can be visualized as the column punches through the slab. Punching shear is very brittle and occurs all of a sudden. It is believed that the slab is subjected to hogging moments over the column in both directions, i.e. parallel and perpendicular to the free edge. Non-linear finite element analyses (NLFEA) has been used to study the cracking and failure mechanism for the reinforced slab. It is a slab over the edge support without clamping stiffness, therefore simulating the slab shear mechanism over a slender steel column is carried out in this study. The analyses has been performed using the software ATENA 3D Engineering developed by Červenka Consulting. Since the symmetry has been taken into account over an edge column, only one half of the cross-section has been modeled, with a symmetry line passing vertically through the slab and column. It can be summarized that the failure encountered around the column has a conical shape crack pattern similar to the ones encountered when punching shear occurs. However, it is important to note that this failure is not due to classic punching shear, but instead due to shear cracks developing around the column in both directions, both parallel and perpendicular to the free-edge. Three models (C1, C2, and C3) are studied to evaluate the impact that the length of the lower leg of the c-bar reinforcement has during failure. As mentioned earlier above, the crack propagation during punching shear begins from the upper surface of the slab and prolongs downwards diagonally towards the bottom of the slab and adjacent to the column. However, the crack propagation in the strip perpendicular to the free edge in all three models initiate from the bottom and propagate upwards. It can be concluded that the length reduction of the lower leg of the c-bars as a consequence reduced the shear strength capacity of the slab around the steel-plate. The reason for this is due to a reduction in maximum peak load when the lower leg of the c-bars were reduced. Consequently, this leads to a decrease in shear strength capacity of the slab and an earlier failure, where the inner-span was not able to take additional loads which could have led to greater deflections.Genomstansning är en brottmekanism orsakad av koncentrerade laster, vilket skapar ett sprickmönster i likhet med en konfrom ellet en bit av paj som börjar från den övre ytan av plattan och förlängs nedåt. När den totala skjuvkraften är större än skjuvmotståndet i plattan , kan det så småningom leda till ett genomstansningsbrott. Det kan visualiseras som att pelaren stansar eller slår igenom plattan. Genomstansning är ett mycket sprött brott och inträffar helt plötsligt. Det antas att plattan utsätts för negativt moment ovanför pelaren i båda riktningarna, d.v.s såväl parallellt som vinkelrät mot den fria kanten. Icke-linjära finita elementanalyser (NLFEA) har använts för att studera sprickbildnings och brottmekanismen för den förstärkta plattan. Det är en platta över kantstödet utan någon fast inspänd styvhet, därför simuleras skjuvmekanismen för plattan över en slank stålpelare i denna studie. Analyserna har utförts med programvaran ATENA 3D Engineering som utvecklats av Červenka Consulting. Eftersom hänsyn har tagits till symmetrin över en kantpelare har endast halva tvärsnittet modellerats, med en symmetrilinje som går vertikalt genom plattan och pelaren. Det kan sammanfattas att brottet som påträffas runt pelaren har en konisk form med ett sprickamönster som liknar de som påträffas vid genomstansning. Det är dock viktigt att notera att detta brott inte orsakats av klassisk genomstansning, utan istället på grund av skjuvsprickor som utvecklast runt pelaren i båda riktningarna, såväl parallellt som vinkelrät mot den fria kanten. Som det tidigare nämnts ovanför börjar sprickan vid genomstansning från plattans övre yta och förlängs nedåt diagonalt mot bottenplattan och intill pelaren. Sprickmönstret i remsan vinkelrät mot den fria kanten i alla tre modellerna (C1, C2 och C3) initierar dock från botten och sprids uppåt. Slutsatsen kan dras att längdminskningen av c-stängernas underben minskade skjuvhållfastheten hos betongplattan runt pelaren. Anledningen till detta beror på en minskning av maximal toppbelastning när c-stängernas underben reducerades. Följaktligen leder detta till en minskning av skjuvhållfastheten och ett tidigare brott, där den inre spännvidden inte kunda ta ytterligare belastningar som kunde ha lett till större nedböjningar.
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Hossain, Tahsin Reza. "Numerical modelling of deflections of reinforced concrete flat slabs under service loads." Thesis, Imperial College London, 1999. http://hdl.handle.net/10044/1/7243.
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Broms, Carl Erik. "Concrete flat slabs and footings : Design method for punching and detailing for ductility." Doctoral thesis, KTH, Brobyggnad inkl stålbyggnad, 2005. http://innopac.lib.kth.se/search/.
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Thesis (Ph.D.)--Royal Institute of Technology (Stockholm, Sweden), 2005."ISRN KTH/BKN/B-80-SE." "Dept. of Civil and Architectural Engineering, Division of Structural Design and Bridges, Royal Institute of Technology, Stockholm. " Includes bibliographical references. Available from the Royal Institute of Technology (Sweden) Library as a .pdf document http://www.lib.kth.se/main/eng/
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Ngekpe, B. E. "Punching shear failure of reinforced concrete flat slabs supported on steel edge column." Thesis, Coventry University, 2016. http://curve.coventry.ac.uk/open/items/5f0f9112-1838-448f-a245-cacc0bc3a9f5/1.
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This study examines punching shear failure at edge supported flat slab. Due to the significant dearth of research on punching shear at edge steel column, this study focuses on the design and performance of a novel shearhead system proposed for edge connection. By considering multi-stage processes and parameters that influence punching shear failure, both numerical and experimental studies were adopted. Firstly linear finite element analysis was employed to study the relationship between the continuous structure and the representative specimen; in order to support decisions on boundary conditions that create the similitude. A nonlinear (NLFEA) model was proposed where various concrete material constitutive models were compared and contrasted. The Total Strain crack model was adopted on the ground that it accounts for the tensile strength of cracked concrete which was ignored in previous theoretical model that lead to poor prediction of punching shear. By considering the appropriate material constitutive model for concrete and steel, material parameters, appropriate modelling scheme capable of predicting punching shear was formulated. The adopted modelling scheme was validated using previous research work. Numerical results reveal that punching shear is influenced most significantly by concrete tensile strength, fracture energy. The shearhead assembly was design with using ACI318-05 and Newzealand codes recommendations with some modifications. These are only codes that provide design guidance on shearhead. Experimental and numerical results show that the shearhead contributes appreciably to punching shear capacity of the edge connection. Various design codes on punching shear were compared; Eurocode 2 provides a good prediction of punching shear at edge support; which correlate well with experimental result. Hence, it was adopted to propose an equation for punching shear for edge connection with shearheads. Most importantly, appropriate design guidance and analytical equation have been proposed for shearhead connection. The design guidance and equation would enable practising Engineers to design shearheads without going through the rigor of experimental or numerical investigation. This study has contributed appreciably to the applicability of steel column in flat slab construction.
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Baskaran, Kathirgamanathan. "Flexural behaviour of reinforced concrete flat slabs supported on non-rectangular column grid." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615995.
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Grira, Mongi. "A critical review of the symmetric punching shear of reinforced concrete flat slabs." Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/6038.
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An experimental investigation on model slabs and on a 1/3 scale composite bridge deck showed that the ultimate punching shear load depends on the shape of the loaded area, the compressive strength of concrete, the flexural reinforcement ratio and on the arrangement of steel bars. Punching failure follows the formation of an inclined failure surface from the edge of the loaded area to the opposite slab face running through the effective depth at a mean angle of 22 to 30 degrees. A study of the application of the yield line theory proves that flexure theory alone is not recommended to treat local failure because of the violent and nonductile nature of punching shear failure. An explanation of the application of the strut and tie model to symmetric punching shear is given to provide a base for future experimental programs and the development of this approach. The mechanism of symmetric punching of slabs without shear reinforcement is described based on observations from tests. An empirical equation to determine the ultimate punching load of flat slabs is proposed. It is concluded that the proposed equation can predict the ultimate punching shear loads of flat slabs with confidence similar to Kinnunen and Nylander's model. Present North American codes should be updated to express the state of present day knowledge, particularly with the inclusion of the influence of the flexural reinforcement. (Abstract shortened by UMI.)
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Aalto, Jonatan, and Elisabeth Neuman. "Comparison of Punching Shear Design Provisions for Flat Slabs." Thesis, KTH, Betongbyggnad, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-215631.
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Abstract A new generation of EN 1992-1-1 (2004) also known as Eurocode 2 is under development and currently there is a set of proposed provisions regarding section 6.4 about punching shear, PT1prEN 1992-1-1(2017). It was of interest to compare the proposal with the current punching shear design provisions. The aim of this master thesis was to compare the punching shear resistance obtained in accordance with both design codes. Furthermore the eect of some parameters on the resistance was to be compared. It was also of interest to evaluate the userfriendliness of the proposal. In order to meet the aim, a case study of a real at slab with drop panels was performed together with a parametric study of a pure ctive at slab. The parametric study was performed for inner, edge and corner columns in the cases prestressed, without and with shear reinforcement. It was concluded that the distance av from the column axis to the contra exural location has a big in uence on the punching shear resistance. The factor ddg considering concrete type and aggregate properties also has a big impact on the resistance. The simplied estimation of av according to 6.4.3(2) in PT1prEN 1992-1-1 (2017) may be inaccurate in some cases. The length b0 of the control perimeter has a larger eect on the resistance in EN 1992-1-1 (2004) than in PT1prEN 1992-1-1 (2017). In PT1prEN 1992-1-1 (2017), studs located outside the second row has no impact on the resistance. The tensioning force in a prestressed at slab has a larger in uence on the resistance in PT1prEN 1992-1-1 (2017) than in EN 1992-1-1 (2004). Furthermore, the reinforcement ratio is increased by the tendons, and thus aect the resistance in PT1prEN 1992-1-1 (2017). Clearer provisions for the denition of the support strip bs for corners and ends of walls are needed in PT1prEN 1992-1-1 (2017). It may be questionable if the reduction of the perimeter for a large supported area in accordance with 6.4.2(4) in PT1prEN 1992-1-1 (2017) underestimates the resistance v in some cases. Considering the work-load with PT1prEN 1992-1-1 (2017), more parameters are included. However, they may not require that much eort to obtain. Keywords: Punching shear, resistance, concrete, at slab, design provisions, Eurocode 2, case study, parametric study, shear reinforcement, prestressed vi
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Vosoughian, Saeed. "The effect of pre-stressing location on punching shear capacity of concrete flat slabs." Thesis, KTH, Betongbyggnad, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-263243.
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Implementing pre-stressing cables is a viable option aiming at controlling deformation and cracking of concrete flat slabs in serviceability limit state. The pre-stressing cables also contribute to punching shear capacity of the slab when they are located in vicinity of the column. The positive influence of pre-stressing cables on punching capacity of the concrete slabs is mainly due to the vertical component of inclined cables, compressive in-plane stresses and counter acting bending moments near the support region. The method presented in Eurocode 2 to determine the punching capacity of the pre-stressed concrete flat slabs considers the in-plane compressive stresses but totally neglects the effect of counter acting moments. The effect of vertical forces introduced by inclined cables is only considered when they are within the distance 2d from the face of the column. This area is called basic control area in the Eurocode 2. In this master thesis nonlinear finite element analysis is carried out to study the effect of pre-stressing cables on punching shear capacity of concrete slabs respecting the distance of cables from the face of the column. To attain this objective, the concrete damage plasticity model is implemented to model the concrete. The results indicate that until the distance of 6d from the face of the column the contribution of pre-stressing cables in punching shear capacity of slabs is significant. Furthermore, comparing the numerical results with the punching shear capacity of slabs predicted by Eurocode 2 reveals that Eurocode tremendously underestimates the punching shear capacity when the cables are located outside the basic control area.
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Murray, Karl Anthony. "An investigation of the behaviour of reinforced concrete flat slabs in the vicinity of edge columns." Thesis, Queen's University Belfast, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343022.
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Thuresson, Sofia. "Parametric optimization of reinforced concrete slabs subjected to punching shear." Thesis, KTH, Betongbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-279466.
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The construction industry is currently developing and evolving towards more automated and optimized processes in the project design phase. One reason for this development is that computational power is becoming a more precise and accessible tool and its applications are multiplying daily. Complex structural engineering problems are typically time-consuming with large scale calculations, resulting in a limited number of evaluated solutions. Quality solutions are based on engineering experience, assumptions and previous knowledge of the subject.The use of parametric design within a structural design problem is a way of coping with complex solutions. Its methodology strips down each problem to basic solvable parameters, allowing the structure to be controlled and recombined to achieve an optimal solution.This thesis introduces the concept of parametric design and optimization in structural engineering practice, explaining how the software application works and presenting a case study carried out to evaluate the result. In this thesis a parametric model was built using the Dynamo software to handle a design process involving a common structural engineering problem. The structural problem investigated is a reinforced concrete slab supported by a centre column that is exposed to punching shear failure. The results provided are used for comparisons and as indicators of whether a more effective and better design has been achieved. Such indicators included less materials and therefore less financial cost and/or fewer environmental impacts, while maintaining the structural strength. A parametric model allows the user to easily modify and adapt any type of structure modification, making it the perfect tool to apply to an optimization process.The purpose of this thesis was to find a more effective way to solve a complex problem and to increase the number of solutions and evaluations of the problem compared to a more conventional method. The focus was to develop a parametric model of a reinforced concrete slab subjected to punching shear, which would be able to implement optimization in terms of time spent on the project and therefore also the cost of the structure and environmental impact.The result of this case study suggests a great potential for cost savings. The created parametric model proved in its current state to be a useful and helpful tool for the designer of reinforced concrete slab subjected to punching shear. The result showed several solutions that meet both the economical and the punching shear failure goals and which were optimized using the parametrical model. Many solutions were provided and evaluated beyond what could have been done in a project using a conventional method. For a structure of this type, a parametric strategy will help the engineer to achieve more optimal solutions.Just nu utvecklas Byggbranschen mot mer automatiserade och optimerade processer i projektdesignfasen. Denna utveckling beror till stor del på teknikutveckling i form av bättre datorprogram och tillgänglighet för dessa. Traditionellt sett löses komplexa konstruktionsproblem med hjälp av tidskrävande och storskaliga beräkningar, vilka sedan resulterar i ett begränsat antal utvärderade lösningar. Kvalitets lösningar bygger då på teknisk erfarenhet, antaganden och tidigare kunskaper inom ämnet.Användning av parametrisk design inom ett konstruktionsproblem är ett sätt att hantera komplexa lösningar. Dess metod avgränsar varje problem ner till ett antal lösbara parametrar, vilket gör att strukturen kan kontrolleras och rekombineras för att uppnå en optimal lösning.Denna avhandling introducerar begreppet parametrisk design och optimering i konstruktionsteknik, den förklarar hur programvaran fungerar och presenterar en fallstudie som genomförts för att utvärdera resultatet. I denna avhandling byggdes en parametrisk modell med hjälp av programvaran Dynamo för att hantera en designprocess av ett vanligt konstruktionsproblem. Det strukturella problemet som undersökts är en armerad betongplatta som stöds av en mittpelare, utsatt för genomstansning. Resultaten används för att utvärdera om en bättre design med avseende på materialanvändning har uppnåtts. Minimering av materialanvändning anses vara en bra parameter att undersöka eftersom det ger lägre kostnader och/eller lägre miljöpåverkan, detta undersöks under förutsättning att konstruktionens hållfasthet bibehålls. En parametrisk modell gör det möjligt för användaren att enkelt modifiera en konstruktionslösning med avseende på olika parametrar. Detta gör det till det perfekta verktyget att tillämpa en optimeringsprocess på.Syftet med denna avhandling var att hitta ett mer effektivt sätt att lösa ett komplext problem och att multiplicera antalet lösningar och utvärderingar av problemet jämfört med en mer konventionell metod. Fokus var att utveckla en parametrisk modell av en armerad betongplatta utsatt för genomstansning, som kommer att kunna genomföra optimering med avseende på tid som spenderas på projektet och därmed också kostnaden för konstruktionen och miljöpåverkan.Resultatet av denna fallstudie tyder på att det finns en stor möjlighet till kostnadsbesparingar och anses därför vara ett mycket hjälpsamt verktyg för en konstruktör. Resultatet visade flera lösningar som uppfyllde de konstruktionsmässiga kraven samtidigt som de gav en lägre materialanvändning tack vare optimeringen. Många lösningar tillhandahölls och utvärderades utöver vad som kunde ha gjorts i ett projekt med en konventionell metod. En parametrisk strategi kommer att hjälpa ingenjören att optimera lösningen för en konstruktion av denna typ.
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Cicolin, Luiz Antonio Betin. "Estabilidade em edifícios de concreto armado com pavimentos em lajes planas." Universidade Federal de São Carlos, 2007. https://repositorio.ufscar.br/handle/ufscar/4622.
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Previous issue date: 2007-08-24This present work covers possible manners of evaluating steel concrete frames designed for multiple flooring buildings as far as instability and necessity of second order efforts are concerned. Starting from single floor projects with simple flat slab frame, models with different numbers of floors are considered. The models do not use large rigidity elements such as staircases and lift shafts. The modeling used in this piece adopts simplified criteria for vertical action dimensioning, forming frames with flat slab layers taken as low height beams. These models are evaluated. Based on the results, the work analyzes the application validity of criteria to dismiss consideration of the NBR6118:2003 code presented second order global effort, and compares this against the P-∆ process utilization. Results both with and without inverted beams at the periphery are compared.
O presente trabalho aborda maneiras possíveis de avaliar estruturas de concreto armado destinadas a edifícios de múltiplos pavimentos quanto à instabilidade e necessidade de considerações de esforços de segunda ordem. A partir de plantas simples de estruturas em lajes planas, são considerados modelos com diferentes números de pavimentos. Os modelos não utilizam elementos de grande rigidez, como poços de elevadores e escadas. A modelagem utilizada adota os critérios simplificados para dimensionamento às ações verticais, formando pórticos com faixas de lajes admitidas como vigas de pequena altura. Estes modelos são avaliados. A partir dos resultados, analisa- se a validade a aplicação dos critérios para dispensa de consideração dos esforços globais de segunda ordem apresentados na NBR6118:2003, e se compara com a utilização do processo P-∆. São comparados resultados para estruturas com e sem utilização de vigas invertidas na periferia.
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Vargas, Elioth Neyl Zambrana. "Punção em lajes-cogumelo de concreto de alta resistência reforçado com fibras de aço." Universidade de São Paulo, 1997. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-25052018-175031/.
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Neste trabalho investiga-se o comportamento resistente de lajes-cogumelo de concreto armado, analisando-se as possibilidades de melhoria de desempenho com relação ao fenômeno de punção, pelo emprego de concreto de alta resistência, pelo reforço com fibras de aço e pelo uso de armaduras transversais de combate à punção, através de ensaios de modelos de lajes-cogumelo quadradas que representam a ligação laje-pilar para o caso do pilar interno. Apresenta-se também uma revisão de conhecimentos sobre as lajes-cogumelo, o seu comportamento estrutural com ênfase no fenômeno da punção, e os principais conceitos sobre os concretos de alta resistência e os compósitos constituídos de matriz de cimento reforçada com fibras. Doze modelos de laje-cogumelo foram ensaiados com diferentes combinações de concreto de alta resistência, concreto de resistência convencional, armadura transversal e volume de fibras (0%, 0,75% e 1,5%). Um acréscimo significativo de resistência à punção foi observado, devido ao uso de concreto de alta resistência e à adição de fibras. A combinação de concreto de alta resistência com 1,5% de volume de fibras e armadura transversal proporcionaram o dobro de aumento na resistência à punção em relação ao modelo de concreto convencional sem armadura transversal e sem adição de fibras. A adição de fibras é a suposta responsável por cerca de 50% de acréscimo de resistência e o aumento da ductilidade. Outras comparações incluindo as previsões teóricas (Texto Base da NB1/94, CEB/90, AGI 318/89 e EUROCODE N.2) são comentadas.This work investigates the behavior of reinforced concrete flat slabs, analysing the possibility of performance improvement, in relation to punching shear phenomenon, regarding to the use of high strength concrete, the addition of steel fibres and the use of transversal steel reinforcement against punching shear, through tests of flat slab square models that represent the slab-column connection, for the case of an interior column. lt introduce a revision of knowledge of flat slabs, their structural behavior with emphasis on the punching shear phenomenon, and the main concepts about high strength concretes and the composites made of cement matrix reinforced with fibres. Twelve flat slab models were tested in different combinations of high strength concrete, ordinary strength, shear reinforcement and steel fibre volume fraction (0%, 0,75% e 1,5%). A significant increase in the punching shear strength was observed, either due to the use of high strength and the addition of steel fibres. The combination of high strength concrete with 1,5% fibre volume fraction and shear reinforcement provide twice the punching shear resistance of an ordinary concrete strength model without shear reinforcement and without fibre. Fibre addition is supposed to be responsible by about 50% of the resistance improvement and the increase of ductility. Other comparisons including theoretical previsions (Texto Base da NB1/94, CEB/90, ACI 318/89 e EUROCODE N.2) are commented.
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OLIVEIRA, Diorgenes Carvalho de. "Punção em lajes lisas de concreto armado com furo adjacente ao pilar e transferência de momento." Universidade Federal de Goiás, 2011. http://repositorio.bc.ufg.br/tede/handle/tde/661.
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Previous issue date: 2011-06-17The structural behavior and the ultimate punching shear resistance of internal reinforced concrete flat slab-column connections, with one hole adjacent to the column, with or without flexural moment transfer of the slab to the column was investigated. Main variables were: the existence whether or not hole, flexural reinforcement layout and ratio, the direction and sense of the moment transferred and the eccentricity of the load (M (moment transferred to column) / V (shear)) ratio at the connection - 0,50 m or 0,25 m. Seven internal slab-column joining were tested and ultimate loads, cracking, deflections, concrete and reinforcement strains were analyzed. The existence of hole adjacent to the smaller column dimension, the hole dimension, flexural reinforcement rate and placing, the variation of relation Mu/Vu in function of the load, and, than, of eccentricity of the load, influenced the slabs behavior and rupture load. These influences were quantified. Test results were compared with the estimations from CEB-FIP/MC1990, EC2/2004, ACI-318:2005 and NBR 6118:2003. ACI and EC2 presented most conservative estimates, although have presented some non conservative estimates. Brazilian NBR, even though being partly based in EC2, presented smaller conservative estimates and more non conservative estimates. A modification on all codes is proposed for taking in account the moment caused by the eccentricity at the critical perimeter for slabs with holes.
São investigados o comportamento estrutural e a resistência última à punção de ligações laje-pilar de regiões internas das lajes lisas, com um furo adjacente ao pilar, e com ou sem transferência de momento fletor da laje ao pilar. As principais variáveis foram: a existência ou não de furo, a taxa e a distribuição da armadura de flexão, a direção e o sentido do momento transferido e a excentricidade de carga (relação M(momento transferido ao pilar)/V(força cortante)) na ligação, igual a 0,50 m ou 0,25 m. Foram ensaiadas 7 (sete) ligações internas laje-pilar e analisados os resultados das cargas últimas, fissuração, deslocamento vertical, deformações das armaduras de flexão e do concreto. A existência de furo adjacente ao menor lado do pilar, a taxa e a distribuição da armadura de flexão, a variação da relação Mu/Vu em função do carregamento, e, por conseguinte, da excentricidade, influenciaram o comportamento e a carga de ruptura das lajes. Essas influências foram quantificadas. Os resultados experimentais foram comparados com os estimados pelas normas: CEB-FIP/MC1990, EC2/2004, ACI-318:2005 e NBR 6118:2003. O ACI e o EC2 apresentaram estimativas mais conservadoras, embora tenham apresentado algumas estimativas contra a segurança. A NBR 6118:2003, apesar de baseada em parte no EC2, apresentou estimativas menos conservadoras e com um número maior de estimativas contra a segurança. Recomenda-se que todas as normas passem a considerar o momento causado pela excentricidade do perímetro crítico em lajes com furos e, neste sentido, foram apresentadas propostas de modificações para todas as normas estudadas.
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Navarro, Menargues Miguel. "Estudio numérico parametrizado del punzonamiento en losas de hormigón armado. Evaluación del refuerzo estructural." Doctoral thesis, Universidad de Alicante, 2018. http://hdl.handle.net/10045/83429.
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En el presente trabajo se aborda la tesis “Estudio paramétrico con FEM del refuerzo a punzonamiento de losas de hormigón armado”. Se trata de todo lo relacionado con el fenómeno resistente de punzonamiento en estructuras, especialmente en forjados construidos mediante hormigón armado. Se trata de cuatro apartados bien diferenciados. En este, el primero, se desarrolla la síntesis de la tesis, donde se marcan unos objetivos, seguido de una explicación detallada y descripción de este fenómeno mediante su estado del arte, que abarca el grueso de éste primer apartado, en el cual se describen, entre otros aspectos, las diferentes patologías producidas por el punzonamiento y casos de sucesos catastróficos que provocaron, la historia de los forjados y los principales estudios llevados a cabo sobre este fenómeno, y acabando con las principales resultados y conclusiones de la tesis. Después, el segundo y tercer apartado contienen los artículos publicados y no publicados, respectivamente, por capítulos. Por último, se desarrollan las conclusiones en el último y cuarto apartado.
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Avilla, Junior Jovair. "Contribuição ao projeto e execução de lajes lisas nervuradas pré-fabricadas com vigotas treliçadas." Universidade Federal de São Carlos, 2010. https://repositorio.ufscar.br/handle/ufscar/4656.
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Previous issue date: 2010-02-18The big surge in use of systems for flat slabs gave up the search for freedom in the definition and organization of architectural interior spaces in buildings. The design and construction of buildings on flat slabs, which allow great mobility in defining the internal space of the building and reducing its height. The slabs with prefabricated trussed beams using forms lost in blocks of expanded polystyrene (EPS) or removable forms, brought new perspectives to the design of flat slabs, allowing greater spans with low deadweight. The precast elements are lightweight, easy handling, transport and assembly, and require the use of molds and special equipment and requires little bracing. Computer programs have emerged in recent years provide more refined calculations that predict the behavior of the structure in service with greater precision. This way the designers have increased security in systems design less common as flat slabs ribbed, without internal beams, capitals and even edge beams. In Brazil the predominant culture in the design and implementation of flat slabs is given by the system option molded on site. The objectives of this study are: to seek answers to the prevailing cultural behavior, and to compare their advantages and disadvantages when compared with cast on site, presenting the normative regulations and simplified calculation method according to ABNT NBR 6118:2003, provide subsidies for the project and implementation of flat slabs with ribbed prefabricated trussed beams, provide a calculation method for the infinitely rigid diaphragm; present a real case study as a comparison of costs.
O grande impulso na utilização dos sistemas de lajes lisas deu-se pela busca de liberdade na definição e organização arquitetônica de espaços internos em edifícios. O projeto e execução de edificações em lajes lisas, permitem grande mobilidade na definição do espaço interno do edifício e na redução da sua altura final. As lajes pré-fabricadas com vigotas treliçadas que utilizam fôrmas perdidas em blocos de Poliestireno Expandido (EPS) ou fôrmas removíveis trouxeram novas perspectivas ao projeto de lajes lisas, permitindo vãos maiores com baixo peso próprio. Os elementos pré-moldados são leves, de fácil manuseio, transporte e montagem, dispensam o uso de fôrmas e equipamentos especiais e requerem pouco escoramento. Programas computacionais surgidos nos últimos anos propiciam cálculos mais refinados que permitem prever o comportamento em serviço da estrutura com maior precisão. Dessa maneira, os projetistas têm maior segurança no projeto de sistemas menos usuais, como lajes lisas nervuradas, sem vigas internas, capitéis e até mesmo vigas de borda. No Brasil, a cultura predominante no projeto e execução de lajes lisas se dá pela opção do sistema moldado no local. Nestes termos, os objetivos do presente trabalho são: buscar respostas para o comportamento cultural predominante; comparar suas vantagens e desvantagens em relação aos sistemas moldados no local; apresentar as regulamentações normativas e o método de cálculo simplificado segundo a ABNT NBR 6118:2003; fornecer subsídios para o projeto e execução das lajes lisas nervuradas pré-fabricadas com vigotas treliçadas; apresentar um método de cálculo para o diafragma infinitamente rígido e apresentar um estudo de caso real como comparativo de custos.
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RODRIGUES, David Rosa. "Comparação experimental entre tipos de armadura de cisalhamento para combate à punção em lajes cogumelo de concreto armado: Stud rails e Double headed studs." Universidade Federal de Goiás, 2009. http://repositorio.bc.ufg.br/tede/handle/tde/683.
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Previous issue date: 2009-09-29This research presents the results of an experimental comparison between the types of shear reinforcement "stud rails" and "double headed studs" to combat the punching shear of a reinforced concrete flat slabs. It also presents a comparison of experimental results with those provided under the ACI 318/2005, CEB-FIP MC/1990, EUROCODE 2/2004 and NBR 6118:2003. The motivation was to investigate the efficiency of these shear reinforcement for the differences between them. It was tested six slabs of concrete to concentric load, with dimensions of 2400 mm x 2400 mm x 150 mm. It was concreted a column of section 500 mm x 200 mm to 850 mm total height next to the slab. The main variables were the type of shear reinforcement "stud rails" x "double headed studs, the "studs" diameter and the shear reinforcement area per layer. The slabs were tested until the failure. It was monitored the deflection, reinforcement deformation of bending and shear. All slabs failed by punching with internal surface rupture. The experimental results after being compared with the expected standard in each individual calculation showed conservative values. Slabs of Group 1 with "stud rails" presented failed loads greater than those in Group 2 with "double headed studs. Codes/standards 318/2005 ACI, CEB-FIP MC/1990, EUROCODE 2 / 2004 and NBR 6118:2003 safely predict the failed loads of all slabs. The base of the shear reinforcement type "stud rails" moving inside the column may have reduced the failed load of the slab L3. Shear reinforcement type stud rails it is easer of assembly and play than the type double headed studs .
Esta pesquisa apresenta os resultados de uma comparação experimental entre os tipos de armadura de cisalhamento stud rails e double headed studs para combate à punção em lajes cogumelo de concreto armado. Apresenta, também, uma comparação dos resultados experimentais com os previstos segundo o ACI 318/2005, CEB-FIP MC/1990, EUROCODE 2/2004 e a NBR 6118:2003. A motivação foi investigar a eficiência destas armaduras de cisalhamento a procura de diferenças entre elas. Foram ensaiadas seis lajes maciças de concreto armado à punção centrada, com dimensões 2400 mm x 2400 mm x 150 mm. Foi concretado junto à laje um pilar de seção 500 mm x 200 mm com altura total 850 mm. As principais variáveis foram o tipo de armadura de cisalhamento: stud rails x double headed studs , o diâmetro dos studs e a área de armadura de cisalhamento por camada. As lajes foram ensaiadas até a ruptura. Foram monitoradas as flechas, deformações da armadura de flexão e cisalhamento. Todas as lajes romperam por punção com superfície de ruptura interna. Os resultados experimentais após serem comparados com os esperados segundo cada norma de cálculo apresentaram valores conservadores. As lajes do Grupo 1 com stud rails apresentaram cargas de ruptura maiores que as do Grupo 2 com double headed studs . Os códigos/normas ACI 318/2005, CEB-FIP MC/1990, EUROCODE 2/2004 e a NBR 6118:2003 previram com segurança as cargas de ruptura de todas as lajes. A base da armadura de cisalhamento tipo stud rails avançando dentro do pilar pode ter reduzido a carga de ruptura da Laje L3. A armadura de cisalhamento tipo stud rails apresenta maior facilidade de montagem e execução que a tipo double headed studs .
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Hrbáček, Adam. "Knihovna Nymburk." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265537.
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Topic of my diploma thesis is creating design documentation on level of detailed design, Library of Nymburk. Project contains engineering reports, realization drawings, thermal assessment, fire safety assessment, static ceiling evaluation, simplified foundation design and design of staircases. Projected building has three above ground floors and one partial basement. Structural system vertical is made of mansory walls, based in basement on drilled piles and in first upper floor on strip foundations. Staircases are made of cast-in-place reinforce concrete same for ceiling slabs and joist slabs. Roof structure is warm flat roof. Project was designed in computer programs: ArchiCAD 19, IdeaSTATICA7, WDLS 5, Svoboda software and vizualization done in Lumion 3D.
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Russell, Justin. "Progressive collapse of reinforced concrete flat slab structures." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/28991/.
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In 1968 a relatively small gas exposition on the 18th floor of the Ronan Point tower building resulted in the partial collapse of the structure. This event highlighted that progress collapse may occur to structures under an accidental loading event. Other events, including the bombing of the Murrah federal building in 1993 in Oklahoma, have resulted in the common design requirement that a structure be capable of surviving the removal of a load bearing element. This approach, often referred to as the sudden column loss scenario, effectively ignores the cause of the damage and focuses on the structure’s response afterwards. The refinement of the analysis varies, with options to include the nonlinear and dynamic behaviours associated with extreme events, or to use simplified linear and static models with factors included to account for the full behaviour. Previous research into progressive collapse has highlighted that providing ductility in the connections, and avoiding brittle failures, is important in ensuring the structure maintains integrity after a column loss event. However, the majority of this work has been focused on the behaviour of steel and Reinforced Concrete (RC) frame structures. As flat slab construction is a popular method for many structures, due to the flexibility it offers for layouts and its low storey heights, it is an important to consider flat slab behaviour in more detail. Furthermore, slab elements behave differently to frame structures due to the Alternative Load Paths (ALPs) that can develop after a column loss via two-dimensional bending mechanisms. Additionally, punching shear failure is a known issue due to the thin section depths. This work addresses the issue of the response of RC flat slab structures after a sudden column loss. As previous case studies have demonstrated that brittle failures may lead to progressive collapse of such structures, a complete understanding of the response is required. The nonlinear behaviour of a slab structure, due to both material and geometric factors, is investigated to determine the additional capacity available beyond the usual design limits. Additionally, the dynamic factors involved, primarily due to inertial effects, are also considered. To achieve this, experimental and numerical studies were conducted. A series of 1/3 scale models of slab substructures were constructed to replicate column loss events. Two types of tests were conducted, a static push down test with a support removed and a sudden dynamic column removal case. Displacements, strains and support reactions were recorded throughout, along with cracking patterns. For the dynamic tests a high speed camera was used to obtain the deflection response in the short time period after removal and to observe the formation of cracks. Comparisons between the two cases allowed determination of the dynamic effects on the response of the system. The experimental programme was then replicated using a Finite Element (FE) model. The results taken from the experimental case were used to validate the material and modelling assumptions made during the numerical simulations. This validated model was finally used to investigate a wider range of variables and assess the response of typical structural arrangements, with particular focus on the nonlinear and dynamic factors involved after a sudden column loss. The experimental and numeral investigations demonstrated that after the loss of a column, flat slab structures can maintain integrity due to a change in the load paths away from the removal location. Although in some cases a large amount of flexural damage to the concrete and reinforcement occurred, such effects did not lead to complete failure. However, during the experimental programme some punching shear failures occurred, usually at the corner column locations. From the numerical analysis, shear forces of over twice the fully supported condition occurred as a result of removing a column, which may exceed the designed capacity. Comparisons between a static and dynamic analysis provides information into a suitable Dynamic Amplification Factor (DAF) for use with simplified modelling approaches. Based on the range of structures considered, the maximum increase in deflections as a result of a sudden removal was 1.62 times the static case, this is less than the commonly used factor of 2.0. Additionally, this factor reduces as the nonlinearity increases due to further damage, with a smallest DAF calculated at 1.39. This factor can be reduced further if the column is not removed instantaneously. Finally, the material strengthening effect, due to high strain rates, was considered with the conclusion that as such effects only make a limited increase in the capacity of the slab and may be conservatively ignored. In conclusion, RC flat slab structures are capable of resisting progressive collapse after the loss of a column. This is primarily due to their ability to develop ALPs. However, while flexural damage is usually fairly minimal, progressive punching shear failure is a critical design condition as it may result in a complete collapse. Furthermore, the inertial effects involved after a sudden removal can increase the damage sustained, although current design methods may be over conservative.
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Jurka, František. "Bytový dům, Brno - Židenice." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227838.
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Subject of this diploma thesis is desing dokumentation of apartment house. Documentation contains all requisites according to valid regulations. House is designed as detached basement house with one underground floor and five aboveground floors. Object is based on reinforced concrete foundation pads. House is roofed with a flat roof. House contains 18 dwelling units with balconies or terraces. In object is solved parking in underground floor. Vertical load-bearing structure is made of clay blocks. Floors are made of cast-in-place reinforced concrete. Underground floor load-bearing structure is reinforced concrete frame. House is insulated with contact thermal insulation. Mechanical resistence and stability, health protection, healthy live conditions and enviroment, fire security, safety in use of building, energy savings and thermal protection is ensured.
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Subally, Pavel. "Univerzitní knihovna." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240253.
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The content of this diploma project is to design an university library in the city of Brno, Czech Republic. The object is designed as multistory building with underground stories included. The design is created based on requests brought by the investor and includes architectural, constructional and technological proposes for the building. The aim is to create not only a modern cultural and educational center but also a place of entertainment and relax for students of Vysoké Učení Technické. During the design it is taken in an account the request of having the auditorium and lecture rooms available for public, also.
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Hradský, Peter. "Polyfunkční dům." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226343.
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Multifunctional buliding is designed as a alone standing new buliding in the cadastral area of Žilina on a private plot no. 4518, Alexandra Street Rudnaya. The buidling is situated in the older part of city build in the sixties with the dominanting residental houses. Type of the multipurpose building is dominant with a residental function. The building totaly contains four apartment units. In the ground floor are offices, spaces of surgeries and access to housing and accessories. Each function has a separate entrance, which is designed for handicapped. In the basemnt of the building are designed in a common garage, basement and substation for heating domestic hot water and heating all function in the building. Enterence in to garage is designed from the east side od street Juraja Sklenara. The building is covered wich flat, monotube roof. The building has got rectangular shape which one outlet on the southeast side. Attic roof is 10,75 meters above the ground.
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Tran, David, and Sebastian Correa. "Inverkan av placering av spännkablar pågenomstansningskapacitet hos armeradebetongplattor." Thesis, KTH, Byggteknik och design, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-233187.
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På grund av bostadsbristen de senaste åren har byggbranschen varit tvungen att möta den höga efterfrågan på bostäder. Ett sätt att underlätta det tryck som skapats på grund av den höga efterfrågan är att rekonstruera byggnader avsedda för annan användning än bostäder till bostadshus. Ett problem som har uppstått vid ombyggnation av till exempel ett kontorshus som består av spännarmerade pelardäck, är känsligheten för nya hål som krävs för nya installationer som går igenom de efterspända bjälklagen (bestående av betongplattor). Problematiken består av att håltagningar som vanligtvis är lokaliserade nära pelarna måste göras på ett större avstånd från pelaren på grund av de spännkablar som går över och nära plattans pelaranslutning. Efterspända kablar är normalt sett belägna över plattans pelaranslutning enligt dagens dimensioneringsnormer för att bidra till plattornas genomstansningskapacitet.I detta examensarbete undersöktes det om det finns vetenskapligt stöd för att flytta kablarna till en längre distans från pelaren (än vad normerna rekommenderar) med hänsyn till genomstansningskapaciteten, och därmed förenkla vid en potentiell ombyggnation.Huvudsyftet med arbetet var att med hjälp av en litteraturstudie samt beräkningar jämföra ett experiment som utförts av Ghassem Hassanzadeh och Håkan Sundquist vid KTH 1997- 1998 (som visade att kablar på ett längre avstånd från pelaren ger ett visst bidrag till betongplattans genomstansningskapacitet) med dagens normer samt nyare studier. Dagens dimensioneringsnormer inkluderar inte bidraget till kapaciteten när spännkablarna placeras utanför det så kallade grundkontrollsnittet (området som undersöks vid dimensionering enligt normerna).Ett annat syfte med detta examensarbete var att studera och uppdatera de beräknade resultaten (enligt dåtidens normer) från studien. Denna rapport uppdaterar studien genom att undersöka rådande normernas beräknade resultat samt jämföra med liknande tester från andra forskare. Dimensioneringsnormerna som undersöktes var Eurokod 2, ACI 318 och MC2010Som del av litteraturstudien redovisas även en liknande försökserie från Portugal av A. Pinho Ramos, Valter J.G. Lúcio & Duarte M.V Faria samt en sammanställning av olika försök som genomfördes i Schweiz av Clément T, Ramos A.P, Fernández Ruiz M, Muttoni A. Sammanställning i Schweiz beräknade genomstansningskapaciteten för 74 olika plattor där plattorna från försöket vid KTH finns med. Den här studien tyder på att dagens dimensioneringsnormer har en säkerhetsmarginal vid approximationer (vid både normalfall och vid flytt av kablar), men att det fortfarande saknas tillräckliga belägg för att rättfärdiga en flytt av spännkablar.Rapporten är skriven för CBI Betonginstitutet där G. Hassanzadeh har varit handledare.
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Bai, Jong-Wha. "Seismic fragility and retrofitting for a reinforced concrete flat-slab structure." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/521.
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The effectiveness of seismic retrofitting applied to enhance seismic performance was assessed for a five-story reinforced concrete (RC) flat-slab building structure in the central United States. In addition to this, an assessment of seismic fragility that relates the probability of exceeding a performance level to the earthquake intensity was conducted. The response of the structure was predicted using nonlinear static and dynamic analyses with synthetic ground motion records for the central U.S. region. In addition, two analytical approaches for nonlinear response analysis were compared. FEMA 356 (ASCE 2000) criteria were used to evaluate the seismic performance of the case study building. Two approaches of FEMA 356 were used for seismic evaluation: global-level and member-level using three performance levels (Immediate Occupancy, Life Safety and Collapse Prevention). In addition to these limit states, punching shear drift limits were also considered to establish an upper bound drift capacity limit for collapse prevention. Based on the seismic evaluation results, three possible retrofit techniques were applied to improve the seismic performance of the structure, including addition of shear walls, addition of RC column jackets, and confinement of the column plastic hinge zones using externally bonded steel plates. Finally, fragility relationships were developed for the existing and retrofitted structure using several performance levels. Fragility curves for the retrofitted structure were compared with those for the unretrofitted structure. For various performance levels to assess the fragility curves, FEMA global drift limits were compared with the drift limits based on the FEMA member-level criteria. In addition to this, performance levels which were based on additional quantitative limits were also considered and compared with FEMA drift limits.
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Eder, Martin A. "Inelastic behaviour of hybrid steel/concrete column-to-flat slab assemblages." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/7017.
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The use of tubular columns in conjunction with reinforced concrete flat slabs provides structurally efficient solutions which avoid undesirable failure modes such as those associated with shear. This thesis is concerned with the development of a tubular column-to- flat slab connection system that enables reliable performance under seismic loading conditions. During this research a novel detail which features a gap around the column is proposed and developed; hence only the structural steel shearhead establishes the connection. The exposed parts of the shear arms (fuses) are designed to yield prior to punching shear failure, in a way that utilises the favourable features of steel in terms of the response to seismically induced loads. The proposed connection could serve as a primary lateral resisting system within all building configurations in regions of low to moderate seismicity or as a secondary system in areas of signi cant seismicity. In order to provide validation for the proposed details as well as associated numerical and design procedures, a purpose-built rig which is suitable for large scale testing of structural sub assemblages under combined gravity and uniaxial lateral loading, has been designed and constructed, and subsequently employed for a number of tests. Test results and numerical analyses are presented with respect to a conventional con guration, as well as for the proposed, partially embedded connection. The latter is shown to offer enhanced ductility compared with traditional forms. The results are used to demonstrate the favourable inelastic performance of the proposed detail in terms of ductility, low degradation effects and increased energy dissipation capabilities. Complementary small scale slab panel tests are also used to further optimise the composite behaviour of the proposed detail. Additionally, a closed form solution based on plastic limit analysis which can serve as a basis for a simplified design approach is proposed. Finally, the main findings from the experimental and analytical investigations are highlighted, and recommendations for future research are outlined.
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Sharifi, Haki. "Strength of edge column-slab connections of post-tensioned concrete flat plates." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0010/MQ32558.pdf.
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AlHarras, Omar. "Seismic behaviour and nonlinear modeling of reinforced concrete flat slab-column connections." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54469.
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The contemporary structural design practice of tall buildings typically incorporates a lateral force resisting system, along with a gravity system that often includes reinforced concrete flat slabs. A major challenge with the design of this system is ensuring adequate strength and deformation capacities of the flat slab-column connections, especially when the structure is prone to strong seismic excitations. When a flat slab-column connection is subjected to a combination of gravity and lateral loads, failure may occur in multiple modes. Comprehensive literature reviews of the experimental studies and the analytical models related to reinforced concrete flat slabs, and flat slab-column connections are presented in Chapters 2 and 3, respectively.
The existing nonlinear models that are currently available in literature were developed as assessment tools for old flat-plate structures. Thus, they are not capable of capturing the hysteretic behaviour of ductile flat slab-column connections with shear reinforcement. In Chapter 4, a new nonlinear model for flat slab-column connections is proposed. Utilizing the proposed model allows detecting potential failures due to all the possible modes of failure. The model was verified and calibrated using data from actual experimental studies.
Chapter 5 investigates the effects of flat slabs on the global seismic response of typical high-rise concrete shear wall buildings. Two analytical case studies were conducted using a prototype building designed in Vancouver, Canada. The results from nonlinear dynamic analyses confirmed that including flat slabs in the analysis models of tall buildings is important to obtain accurate estimates of the structural responses and seismic demands. A concise summary of the research outcomes is presented in Chapter 6.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Subedi, Shobha K. "Load Rating of Flat Slab Bridges Without Plans." Youngstown State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1471608754.
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Deaton, James B. "A Finite Element Approach to Reinforced Concrete Slab Design." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7188.
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The objective of this study was the development of a procedure in GT STRUDL to design reinforced concrete flat plate systems based on the results of finite element analysis.
The current state-of-practice of reinforced concrete flat plate design was reviewed, including the ACI direct design and equivalent frame techniques, the yield line method, and the strip design method. The principles of these methods along with a critical evaluation of their applicability and limitations were presented as motivation for a finite element based design procedure. Additionally, the current state-of-the-art of flat plate design based on finite element results was presented, along with various flat plate modeling techniques. Design methodologies studied included the Wood and Armer approach, based on element stress resultants, and the resultant force approach, based on element forces.
A flat plate design procedure based on the element force approach was embodied in the DESIGN SLAB command, which was implemented in GT STRUDL. The DESIGN SLAB command provides the user the ability to design a slab section by specifying a cut definition and several optional design parameters. The procedure determines all nodes and elements along the cut, computes the resultant moment design envelope acting on the cross-section, and designs the slab for flexure in accordance with provisions of ACI 318-02.
Design examples presented include single-panel flat plate systems with various support conditions as well as multi-panel systems with regular and irregular column spacing. These examples allowed for critical comparison with results from experimental studies and currently applied design methods in order to determine the applicability of the implemented procedure. The DESIGN SLAB command was shown to produce design moments in agreement with experimental data as well as conventional design techniques for regular configurations. The examples additionally showed that when cuts were not oriented orthogonally to the directions of principle bending, resulting designs based on element forces could significantly under-reinforce the cross-section due to significant torsional effects.
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Samad, Shahab. "Engineering properties of binary cement concretes and their effect on punching shear of flat slabs." Thesis, Kingston University, 2013. http://eprints.kingston.ac.uk/26572/.
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Concrete is the most important building material in the world due to the fact that it is versatile and gives architectural freedom. For sustainable construction solutions concrete is the material of choice if the embodied CO2 content is considered. In concrete, cement is the main constituent and due to the limit on the availability of natural minerals used, the energy released and the CO2 emissions produced during its manufacture, it can be partially replaced using industrial by-products e.g. Pulverised Fuel Ash (PFA), Ground Granulated Blast furnace Slag (GGBS) and silica fume. The effects of the partial replacement of cement with these industrial by products on fresh and hardened properties of concrete cured under summer and winter environments are established and compared with the Portland cement (PC) concrete. Early age strength of concrete containing GGBS and PFA is less than the PC concrete, which would prevent its use in the in the post tensioned concrete and in fast-track construction, where early removal of formwork, or early application of load to the structure are the main requirements. For this reason, and due to the demand of high strength concrete in construction, for its improved durability properties, concrete containing GGBS and PFA was produced by keeping the water/cement ratio low and a superplasticiser was used to achieve the required workability. At low water/cement ratio, concrete containing GGBS up to 50 % and PFA Lip to 30 % can achieve the required early age strength for the removal of formwork if cured properly. At the age of 28 days, the flexural strength and modulus of elasticity of concrete in which PC is partially replaced with GGBS and PFA are increased in comparison to where this is not carried out. For practical applications of the sustainable concrete mixes in structural concrete production and due to the limited data availability on punching shear strength, concrete containing GGBS and PFA in flat slab specimens were tested for this property. In flat slabs without beams, the design criteria is often the resistance against punching shear failure at the column/slab connection. Punching failure is the separation of the portion of the slab surrounding the column from the rest and is a brittle failure. Experimental punching shear results are compared to the estimates of BS 8110, BS EN1992-1-1 and ACI 318 and it was found that the estimates of ACI318 and BS 8110, ignoring the partial safety factors, are close to the experimental results and the estimates of BS EN 1992-1-1 are over conservative. Based on the test results of punching shear resistance of flat slabs, and the materials used, it is concluded that concrete containing GGBS up to 50 % and PFA up to 30 % can be used in flat slabs without any special design requirements and the design rules given in different codes of practice can be used without modifications. It is evaluated that for a concrete, designed for characteristic strength of 30 MPa, a reduction of 152 kg/m3 of CO2 and 0.65 GJ/m30f energy consumption can be achieved by replacing PC with 50 % GGBS and a reduction of 62.5 kg/m3 of C02 and 0.27 GJ/m3 of energy can be achieved by using 30 % PFA concrete.
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Yan, Ping Yu. "Behaviour of shearhead system between flat reinforced concrete slab and steel tubular column." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/behaviour-of-shearhead-system-between-flat-reinforced-concrete-slab-and-steel-tubular-column(7a3b5496-ca58-4a85-8028-3f64ad0eeddd).html.
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This thesis presents the results of an experimental, numerical and analytical study to develop a design method to calculate punching shear resistance for a new shearhead system between tubular steel column and reinforced concrete flat slab. This shearhead system enables two of the most popular structural systems, i.e. reinforced concrete flat slab floor and steel tubular column, to be used to produce efficient structures of low cost and short construction time. This research investigates slabs without and with a service hole adjacent to the column. The new shearhead system should not only possess sufficient punching shear resistance, but should also be efficient for construction. The main methodology for this project was based on numerical finite element simulations verified by two full scale tests. These two tests were carried out in the University of Manchester's Structural Testing Laboratory. The two specimens had the same slab size, thickness and reinforcement ratio, but differed in the column shape (rectangular or circular), central reinforcement arrangement (continuous or discontinuous), shearhead position in the slab thickness and shearhead fabrication arrangement. Recorded load-deflection and load-strain relationships, crack development and critical perimeter were used for detailed validation of using the commercial finite element software ABAQUS. The validated ABAQUS model was used to conduct a comprehensive parametric study to investigate the effects of a number of design parameters, including the effect of varied column size, shearhead arm length, shearhead arm cross section, shearhead arm angle, amount of flexural reinforcement, slab thickness, shearhead positions and hole positions. The main conclusion from the parametric study was that the shearhead system could be treated as an enlarged column in normal flat slab structure. The parametric study enabled pressure distribution below the shearhead arms to be approximated for checking whether the shearhead arms would be sufficient for the enlarged column assumption to be valid. The parametric study results were also used to determine the effective depth of the flat slab and critical punching shear perimeter of the slab with and without a service hole.Using the enlarged column assumption, the punching shear resistance of all structures used in the parametric study were re-calculated using Eurocode 2 (EC2), British stand 8110 (BS8110) and American Concrete Institute code 318 (ACI 318). Comparison of calculation results using these three design methods indicates that both EC2 and BS8110 predicted very close value which reached very good agreement with the ABAQUS simulation (normally within 10%). Among these three design methods, ACI 318 was the only code that explicitly considered shearhead system. ACI 318 was not able to predict the slab critical perimeter length with good accuracy, however, its prediction of slab punching shear resistance achieved reasonably good agreement with numerical analysis results and were on the safe side. Based on these studies, a design method for calculating punching resistance of the proposed shearhead system between reinforced concrete flat slab and steel tubular column has been developed in this thesis.
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Milani, Alexandre Caio. "Análise de lajes planas protendidas pelo método dos elementos finitos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2006. http://hdl.handle.net/10183/10608.
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Na construção civil atual, existe uma tendência de crescimento da automatização do projeto, visando o desenvolvimento de soluções personalizadas a fim de fugir das indesejadas repetições arquitetônicas. Dentro desta tendência, as lajes planas protendidas proporcionam grande flexibilidade de layout, maior rapidez na execução da estrutura e diminuição do número de pilares, proporcionando ganhos de área útil. Um dos principais esquemas estruturais adotados para representar lajes planas protendidas é a laje lisa, com ou sem engrossamento na região dos pilares. As lajes lisas apresentam vantagens em relação às demais (nervuradas e outras), sobretudo do ponto de vista da facilidade de execução. Esta dissertação apresenta um modelo numérico para o cálculo de lajes planas lisas protendidas via Método dos Elementos Finitos.O elemento finito empregado, isoparamétrico com 8 nós, possui 5 graus de liberdade por nó: os 3 graus de liberdade referentes a teoria de Flexão de Placas de Reissner-Mindlin e os 2 graus de liberdade relativo ao Estado Plano de Tensões. A protensão é considerada através do Método de Equilíbrio de Cargas (criado por T. Y. Lin e utilizado por AALAMI (1990)), que consiste na transformação dos esforços devido aos cabos protendidos em um conjunto de cargas equivalentes. Também é proposto um modelo de cálculo para determinação da posição do cabo de protensão em elevação e das perdas imediatas da força de protensão (perdas por atrito e recuo das ancoragens). São analisadas as tensões de serviço, para verificação da deformação, e as tensões últimas a que a laje protendida pode estar submetida, para o dimensionamento das armaduras ativa e passiva.There is a recent trend, in Civil Engineering, toward automatized projects, aiming at the development of personal solutions, avoiding undesirable design repetitions. As an example, pre-tensioned plane plates give great layout flexibility, faster structural execution and reduction of the number and cross section of pillars, resulting in gains in the net area of the construction. One of the most common structures used as pre-tensioned plates is the flat slab, with or without enlargements near the pillars. The flat slab have advantages related to others (ribbed and others) mainly regarding its easier execution. These work presents a numerical model to calculate pre-tensioned flat slab by the Finite Element Method. The finite element used, isoparametric with 8 nodes, has 5 degrees of freedom per node: 3 degree of freedom regarding the Reissner-Mindlin´s plate bending theory and the 2 remaining regarding the plane stress state. The pre-tension is considered through the Load Equilibrium Method (created by T. Y. Lin and used AALAMI (1990)). The method consists in the transformation of loads due to pre-tensioned cables in one assemble of equivalent loads. Also, it is proposed a calculus model to determine the pre-tensioned cable elevation and the instantaneous losses of the pre-tensioned forces (losses by friction and partial retreat of the anchorage). The stress and deformation in service are analyzed as well as the ultimate stresses of the pre-tensioned plate can be subjected are verified, in order to design active and passive reinforcements.
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OLIVEIRA, Túlio Pessoa Souto Maior. "Utilização de capitéis para aumento de resistência à punção em Lajes de concreto armado." Universidade Federal de Pernambuco, 2015. https://repositorio.ufpe.br/handle/123456789/17673.
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CNPq
Em lajes de concreto armado sem vigas, apoiadas em pilares, a resistência à punção torna-se um ponto crítico para seu dimensionamento. Até recentemente, os modelos mecânicos para se calcular a resistência à punção das lajes de concreto armado, eram muito complexos, sem praticidade para se aplicar em projetos. O dimensionameto à punção na maioria das normas são baseados em resultados experimentais sem uma modelação física. Uma das formas de se aumentar a resistência à punção é a utilização de capitéis. Para esse trabalho foi definido a utilização de capitéis curtos. As poucas informações sobre a utilização de capitéis curtos deixam os engenheiros receosos quanto a sua utilização. O objetivo desse trabalho é elucidar mais um pouco sobre esse tipo de solução para combate à punção. É apresentado como a litetura aborda a utilização dos capitéis curtos e como a sua utilização e suas dimensões são orientadas. Também é apresentado como os métodos normativos, ACI- 318/2014, NBR 6118/2014 e FIB MODEL CODE 2010 abordam a sua utilização e dimensionamento. É selecionado um caso de uma laje submetida à punção e feito o seu dimensionamento segundo os três métodos já mencionados. Também é feita uma comparação com os resultados experimentais obtidos na literatura, os quais são poucos, com os três métodos já citados.
In flat plates without beams, supported directly on columns, punching shear strength becomes critical in design. Until recently mechanically based models for punching shear computation in reinforced concrete slabs were too complex for routine design work. Punching shear strength checks are basically empirical for most design codes, without a mechanical model basis. A possible alternative to enhance punching shear capacity is to locally increase slab thickness through shear caps or drop panels. In this work, the shear cap option is studied in detail. Due to lack of information, designers are generally wary of the usage of shear caps. This work aims at gaining a better understanding of this type of solution for punching shear strengthening. A literature review is presented on shear cap usage as well as guidance with respect to its geometry. Also presented are design check procedures according to ACI-318/2014, NBR 6118/2014 and FIB MODEL CODE 2010. A case study of a slab subjected to punching shear is selected and its design reviewed according to the three abovementioned codes. Punching shear capacity of shear caps of the very few experimental results are compared with the presented verification procedures.
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Ulaeto, Nsikak. "Progressive collapse analysis of reinforced concrete flat slab structures considering post-punching and dynamic response." Thesis, University of Surrey, 2018. http://epubs.surrey.ac.uk/850029/.
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Flat slabs are reinforced concrete slabs supported directly on columns without beams. Flat slabs are commonly used for construction of medium-rise office buildings and car parking structures due to their ease of construction, reduced story height and ease of routing of services. Load concentrations can be significant at edge and corner columns as well as around internal columns, making the slab-column connections susceptible to punching shear failure. Most reported occurrences of progressive collapse in flat slab structures have had punching shear failure as an initial local failure. Some of these collapses progressed horizontally through punching of adjoining connections due to gravity load redistribution, dynamic effects and excessive slab deformation. In many cases, failure also progressed vertically due to impact of falling slabs on lower lying ones. Design rules specified in codes and building regulations to prevent progressive collapse are not suitable for application to flat slab structures due to the development of failure mechanisms, such as punching shear and compressive membrane action at small deformations; and post-punching shear and tensile membrane action at large deformations. The influence of these mechanisms, and their interaction, on the response of flat slab systems during progressive collapse is not fully understood. Knowledge on influence of the dynamic nature of progressive collapse in flat slab system response is also not fully established. Existing numerical and analytical approaches for assessment of progressive collapse in flat slab structures either limits response assessment to failure at the first connection or neglects one or more mechanisms. Hence, they can provide unrealistic predictions of damage after local failure, little knowledge on the collapse progression and the contributions of neglected mechanisms to overall system response. In this thesis, numerical and analytical models were developed and validated for the prediction of the post-punching shear capacity of isolated slab specimens, using tests reported in literature. Results of numerical modelling of punching shear strength, residual shear strength after punching and post-punching shear strength in isolated slab specimens agreed with those of tests. Results of residual shear strength after punching and post-punching shear strength obtained analytically were also in agreement with test results. A numerical approach was developed for the assessment of progressive collapse of flat slab systems. The flat slab system model considered compressive membrane action, tensile membrane action, gravity load redistribution and damage propagation. These mechanisms were not considered in the isolated slab specimens. Results of numerical flat slab system analysis provided a good understanding of the gravity load redistribution after the sudden loss of an internal column, the contribution of compressive membrane action prior to the punching shear failure, tensile membrane and post-punching shear actions after punching shear failure of connections. The transition and interaction between these mechanisms were also investigated. Analytical slab-column subsystem and flat slab system models were also developed. Both models provided results which agreed with those obtained through dynamic finite element analysis. Results from the analytical flat system model confirmed the contribution of compressive membrane action in the resistance of progressive collapse through the confinement of the slab area around the slab-column connections and the reduction of slab deformation around the slab-column connections. Both numerical and analytical flat slab system approaches showed that for cases of slabs with sufficient integrity reinforcement and no punching shear reinforcement, punching shear failure of adjoining connections would occur though the progressive collapse could be arrested with sufficient area of integrity reinforcement. Required areas of integrity reinforcement calculated using code formulae were found to be insufficient in cases of sudden loss of an internal column since they do not account for dynamic amplifications of gravity loads and possible reductions in post-punching capacity at the connections due to geometric and load asymmetry. It was generally concluded that integrity reinforcement is effective for arresting progressive collapse (vertical collapse propagation) in flat slab systems if designed with the consideration of dynamic loading, geometric and load asymmetry developed after the occurrence an initial local failure. However, provision of integrity reinforcement for robustness does not arrest the horizontal propagation of damage after an initial punching shear failure of adjacent connections. Therefore, it is concluded that a more effective design approach for robustness is increasing the strength and deformation capacity of flat slab connections (using punching shear reinforcement).
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Yu, Junlong. "Development of a new connection between steel tubular column and concrete flat slab using shear studs." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/development-of-a-new-connection-between-steel-tubular-column-and-concrete-flat-slab-using-shear-studs(ad03f86d-5f15-4ed9-92e3-7a9b011393a5).html.
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This thesis presents the results of experimental, numerical and analytical studies to investigate two shear connection systems to provide punching shear resistance between flat slabs and steel tubes. Shear connector system 1 relies purely on welded shear studs around the steel tube section and shear connector system 2 incorporates welded shear studs, steel plate and bent-up rebars. The aim of this research is to develop a simple shear connection system that can allow two of the most popular structural systems, reinforced concrete flat slab and steel tubular column to achieve construction efficiency and to reduce construction cost. For each shear connection system, physical tests were carried out to provide experimental data to validate relevant ABAQUS numerical finite element simulation models. These tests were carried out in the University of Manchester's Structural Testing Laboratory. The validated numerical simulation models were used to perform extensive numerical parametric studies to investigate the effects of changing different design parameters of these two shear connection systems, so as to develop a thorough understanding of their punching shear behaviour and to provide comprehensive data for development of analytical methods for design. For shear connection system 1, the experimental and numerical studies have investigated the effects on punching shear behaviour and resistance of different design variables including concrete depth above the shear stud, concrete compressive strength, concrete tensile strength, shear stud dimensions (length and diameter), and reinforcement. The concrete capacity method (CCD) was modified to develop an accurate analytical method. However, this shear connection system is unlikely to be able to provide sufficient slab punching shear resistance for practical applications. For shear connection system 2, two full scale column-slab assemblies were carried out, one representing interior position column and one for corner position column. The numerical parametric study investigated the effects of different design parameters including flat slab depth, concrete grade, bent-up rebar design, shear stud dimensions (length and diameter) and steel tube size. An analytical design method was developed to calculate the capacities of shear studs, bent-up rebars and slab punching shear resistance as an enlarged column. Shear connection system 2 is simple to construct in practice. For this system, it is easy to prevent shear stud failure and bent-up rebar failure so that the system behaves as an enlarged column for calculating punching shear resistance of the slab. The punching shear resistance of the enlarged column can be calculated using the design method in EN 1992-1-1 (CEN, 2004a), and has been demonstrated to be sufficient for practical applications in flat slab construction.
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Aldwaik, Mais M. "Cost Optimization of Reinforced Concrete Highrise Building Structures." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1574738135695095.
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Silva, Carolina Ribeiro da. "Punção em lajes de concreto armado com furo e transferência de momento: comparação de normas." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3144/tde-12032018-085200/.
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O crescente uso de lajes sem vigas (lisa com ou sem capitel) como solução estrutural de edificações, justificado por questões econômicas e construtivas, têm destacado a importância do estudo desses elementos estruturais. Já as desvantagens desse sistema estrutural estão associadas às altas tensões geradas na região próxima dos pilares, originando o fenômeno de punção. As normas atuais especificam uma seção íntegra resistente para dimensionamento à punção, entretanto, devido principalmente à passagem de instalações hidráulicas e elétricas através dos pavimentos, é necessária a execução de furações, em alguns casos muito próximas ao contorno dos pilares, o que implica diretamente na redução dessa seção e da resistência das lajes. Portanto, são necessários modelos de cálculo específicos para isso. A NBR 6118 tem critérios para esse problema, mas são antigos e precisam ser modernizados. Assim, comparando os dados experimentais de algumas pesquisas com as cargas últimas estimadas para normas vigentes (fib MC2010:2013, EC2:2004, ACI-318:2014 e NBR 6118:2014), este trabalho teve como objetivo identificar limitações das normas estudadas e verificar a eventual possibilidade de melhorias. Com base nos resultados observados foi proposta uma alteração para a NBR 6118: 2014 no cálculo da punção para lajes lisas com furo(s) na região do pilar, de modo que seja considerado no dimensionamento o momento gerado pela excentricidade do perímetro crítico devido à presença de furo(s) na laje.The increasing use of flat slabs (slabs without beams with or without drop panel) as a structural solution of buildings, justified by economic and constructive issues, has highlighted the importance of the study of these structural elements. The disadvantages of this structural system are associated with high stresses generated in the region near of the columns, causing the punching shear phenomenon. The current standards specify a resistant section for punching shear design, however, due mainly to the passage of hydraulic and electric installations through the floors, it is necessary to execute holes, in some cases very close to the boundaries of the columns, which reduces this section and the slab strength. Therefore, it is necessary to specify calculation models for that. The NBR 6118 has criteria for this problem, nonetheless it is old and needs to be modernized. Comparing experimental data from some researches, with the estimated ultimate loads for current standards (fib MC2010: 2013, EC2: 2004, ACI-318: 2014 and NBR 6118: 2014), this work had as objective to identify limitations of the standards studied and verify possible improvements. Based on the observed results, it was proposed a modification for NBR 6118: 2014 in the design of the punching shear of flat slabs with hole(s) near of the column, considering the moment caused by the eccentricity of the critical perimeter due to the presence of hole(s) in the slab.