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Zanjir, Ahmad Mohamed Rifat. "Vulnerability of Buildings with Flat Plates and Flat Slabs to Progressive Collapse." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/22824.
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The investigation of progressive collapse of buildings has been of special interests during the last decade. The aim of this study is to assess the influence of selected design parameters on the vulnerability of structures with flat plates or flat slabs to progressive collapse triggered by the severe damage or failure of a column as a result of accidental or maliciously intended terrorist activity. The variables of frames with two-way slab systems investigated include: the number of stories in buildings (low-, medium- and high-rise buildings), span ratio (the ratio of span lengths in two orthogonal directions), span length for square panels, as well as the effect of having flat plates compared to flat slabs detailed either as ordinary gravity load carrying systems or by following the seismic detailing requirements of the Canadian practice as per CSA A23.3-04.
The linear-elastic static analysis method, outlined in the General Services Administration (GSA) guidelines of the US, was employed to conduct a parametric investigation to assess the significance of the design variables considered on progressive collapse potentials of buildings. This involved the computation of demand/capacity ratios (DCR) Higher DCRs were obtained for buildings with increased number of stories and span ratios, while the change in span lengths did not show a clear trend. Also, flat slabs were less vulnerable, and experienced smaller DCRs, than flat plates. Buildings detailed according to the seismic provisions of CSA A23.3-04 were less vulnerable than those detailed without these provisions. However, both slabs with non-seismic and seismic detailing required improvements in terms of the percentage of top and bottom reinforcement and bar lengths, depending on the slab type and the design parameters considered.
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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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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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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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Redl, Erin. "Post-punching response of flat plate slab-column connections." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40840.
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The post-punching failure response of reinforced concrete flat plate slab-column connections is investigated. The first part of this thesis discusses previous research on the tensile membrane action of reinforced concrete slabs and the use of structural integrity reinforcement to prevent progressive collapse after punching failure of slab-column connections. The second part of this thesis describes the design of a flat plate slab system that is the basis for slab-column connection test specimens. Two specimens were constructed and tested to determine punching failure resistance and post-punching failure resistance. The parameter investigated was the detailing of structural integrity reinforcement. Observations from testing contributed to the understanding of the post-punching resisting mechanism that developed. Three failure modes observed during testing were the yielding of reinforcing steel, concrete failure similar to the breakout of embedments, and pullout bond failure. The test results were compared to the predicted resistance of structural integrity reinforcement by CSA A23.3-04 (2004). The test specimens achieved 98% and 104% of the predicted resistance. Test results were also used to evaluate the equation proposed by Melo and Regan (1998) for concrete failure similar to the breakout of embedments, and the equation was found to underestimate the post-punching resistance of flat plate slab-column connections.La réponse après-poinçonnement d’assemblages dalle-poteau de béton armé a été étudiée. Cette thèse constitue de deux parties dont la première discute les recherches précédentes sur l’effet des membranes en traction en plus de l’utilisation d’armature d’intégrité structurale de façon à éviter l’effondrement progressif après avoir subit un poinçonnement en cisaillement d’assemblage dalle-poteau. La deuxième partie décrit la conception d’un système formant d’une dalle plate qui sera la base des modèles d’assemblage dalle-poteau de cette recherche. Deux modèles ont été construits et testés à déterminer la résistance de poinçonnement en cisaillement et la résistance après-poinçonnement pour étudier le paramètre d’armature d’intégrité structurale.Les résultats expérimentaux obtenus ont contribués aux connaissances du mécanisme de résistance après-poinçonnement et trois modes de rupture ont été observés : le fluage de l’acier, la rupture du béton similaire aux brisures des ancrages, et l’échec du lien de retirement. Les résultats ont été comparés aux prédictions de la résistance d’armature intégrité structurale du CSA A23.3-04 (2004) et les modèles conçus ont obtenus 98% et 104% de la résistance prévue. De plus, ses résultats ont été utilisés pour évaluer l’équation proposée par Melo et Regan (1998) pour la rupture du béton similaire aux brisures des ancrages et cette équation a été déterminée à sous-estimer la résistance après-poinçonnement des assemblages dalle-poteau.
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Alfonso, Lazaro. "Crack control in toppings for precast flat slab bridge deck construction." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010294.
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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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Paudel, Binod. "Determining Material and Geometric Properties of Flat Slab Bridges Without Plans." Youngstown State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1471358453.
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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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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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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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Lindstrand, Klas, and Axel Simonsson. "Optimization Workflow for Flat Slab Systems : Using Parametric Design with Visual programming." Thesis, KTH, Mekanik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-230892.
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The advancement of IT and technology has enabled the development of boundary breaking tools such as Parametric design and visual programming. Structural engineering has the potential to take the advantage of this development, by implementing visual programming which with the combination of optimization algorithms can explore design proposals. This opens up new possibilities to work closer with architects in the early stages of projects to create bolder architectural and structural designs. The task of the master thesis was to create a workflow using parametric design with visual programming and including an optimization algorithm. In the workflow, an optimization process should perform structural analysis and optimization operations to find suboptimal flat slab system designs. The idea was that the workflow should be implemented in the early stages of the structural design process, where an architectural model is used as a boundary to generate suboptimal flat slab systems based on user input. Thereafter, the different generated solutions need to be evaluated and verified by an engineer before proceeding further to the final design. The result obtained from the workflow was that an optimized flat slab system with column placements could be created through an optimization process with input data including geometry, loads and element properties. This led to an approach which exploited the capabilities of using parametric design and visual programming for structural design. This meant that, the user could alter the optimization process to narrow down the generated solutions to find the optimal flat slab system based on the requirements of the project. The results of the structural analysis in the workflow was not fully satisfactory, meaning it could not be used for final design without verification. The conclusion was that parametric design in combination with visual programming and optimization algorithms could generate multiple alternative designs. These alternatives could be used as inspiration for engineers to create new structural solutions in the early stages.Framsteg inom IT och teknologi har möjliggjort utveckling av banbrytande verktyg som parametrisk design med visuell programmering. Konstruktörer har möjligheten att utnyttja denna utveckling genom att implementera visuell programmering, vilket i kombination med optimeringsalgoritmer kan generera alternativa konstruktionslösningar. Detta teknikskifte möjliggör ett närmare samarbete med arkitekter i tidiga skeden vilket kan resultera i mer vågade konstruktioner och arkitektur. Syftet med examensarbetet var att skapa ett arbetsflöde som utnyttjade parametrisk design och optimering i en visuell programmeringsmiljö som kunde utföra strukturanalys och optimering, vilket genererade optimala pelardäck med oväntade pelarplaceringar. Idén med detta var att arbetsflödet kunde implementeras i tidiga skeden med arkitekter, när den kan användas för att generera optimala pelardäck baserade på användarens indata. Därefter behöver de genererade lösningarna utvärderas och verifieras av en ingenjör, innan man fortsätter till nästa skede. Resultatet från arbetsflödet är att ett optimerat pelardäck med oväntade pelarplaceringar skapas genom en optimeringsprocess med indata innehållande geometri, laster, randvillkor och materialegenskaper. Detta arbetsflöde leder till ett angreppssätt som utnyttjar möjligheterna med parametrisk design och visuell programmering. Detta innebär att användaren kan påverka optimeringsprocessen för att smalna av resultatet för att hitta optimerade pelardäck baserade på projektets krav. Resultaten från strukturanalysen i arbetsflödet är inte helt tillförlitliga, vilket innebär att resultaten behöver verifieras. Sammanfattningsvis kan parametrisk design i kombination med visuell programmering och optimeringsalgoritmer skapa en mångfald av lösningar. Dessa alternativ kan inspirera ingenjörer att skapa nya konstruktionslösningar i tidiga skeden.
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Jensen, Stine Maria F. "Numerical Investigation of a Post-tensioned Flat Slab with Steel Fibre Reinforcement." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bygg, anlegg og transport, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-24262.
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This study consists of a numerical investigation of a post-tensioned flat slab without conventional longitudinal reinforcement; only steel fibres were employed to ensure sufficient ductility and shear capacity of the slab. Results were taken from a reported experiment conducted on a full scale steel-fibre reinforced flat slab (0.38 % fibre content) which was tested until failure, undergoing a ductile bending failure at a load of 6.5 kN/m2. A nonlinear finite element analysis was employed to study the experiment, including the ultimate state. A parametric study was performed using the numerical model to investigate the influence of the tensile behaviour of steel fibre-reinforced concrete (SFRC) the response of the structure. The model proved to be relatively sensitive to changes in the tensile behaviour, but the differences were not prominent until entering the nonlinear area of the load-displacement curve. A constant curve with tensile stress equal to the residual tensile strength of the SFRC provided a robust numerical model and results on the conservative side. Including a peak stress with a multilinear tensile curve provided a less stable analysis but more accurate results, however the model behaviour was stiffer than the experiment, providing too small deformations at failure. Nevertheless, the numerical model was able to display the ductile bending failure mode and moment redistribution.
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Lynner, Colton, Megan L. Anderson, Daniel E. Portner, Susan L. Beck, and Hersh Gilbert. "Mantle flow through a tear in the Nazca slab inferred from shear wave splitting." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/625357.
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A tear in the subducting Nazca slab is located between the end of the Pampean flat slab and normally subducting oceanic lithosphere. Tomographic studies suggest mantle material flows through this opening. The best way to probe this hypothesis is through observations of seismic anisotropy, such as shear wave splitting. We examine patterns of shear wave splitting using data from two seismic deployments in Argentina that lay updip of the slab tear. We observe a simple pattern of plate-motion-parallel fast splitting directions, indicative of plate-motion-parallel mantle flow, beneath the majority of the stations. Our observed splitting contrasts previous observations to the north and south of the flat slab region. Since plate-motion-parallel splitting occurs only coincidentally with the slab tear, we propose mantle material flows through the opening resulting in Nazca plate-motion-parallel flow in both the subslab mantle and mantle wedge.
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Sudarsana, I. Ketut. "Punching shear in edge and corner column slab connections of flat plate structures." Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/6326.
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The behavior and strength of edge and corner column slab connections of flat plate structures subjected to shear force only, moment only as well as combined shear force and moment were investigated. A two bay by two bay flat plate structure (nine columns) and eight isolated edge column slab connections were constructed and tested to failure. After the tests of the four edge column connections of the continuous slab were completed, the edge connections were repaired using two types of concretes (normal concrete and CAB expansive concrete) and tested to failure. Interaction diagrams between shear force and unbalanced moment at edge column slab connections based on building code provisions (ACI 318-99, CSA A23.3-94 and CEB-FIP MC90) and three alternative approaches (Regan's approach, the Truss Model and the Strip Model) proposed in the literature are examined using the results of the present experimental work. Interaction diagrams for corner connections calculated using Regan's approach and the building code provisions are compared with the experimental results. The shear strength of edge and corner connections is calculated according to ACI 318-99, CSA A23.3-85, BS8110-85, CEB-FIP MC90 and the alternative approaches of Regan, Sherif, Gardner, Elgabry, the Truss Model and the Strip Model. All alternative approach predictions of shear strength of edge connections, except Sheril's, are conservative. The average ratio of measured shear strength to calculated shear strength ranges from 0.90 to 1.30 with coefficients of variation (COV) ranging from 0.18 to 0.40. Gardner's approach, that considered a linear shear stress distribution as in ACI 318-99, with a critical shear section taken at the column perimeter or perimeter of loaded area gives the most conservative and the least scatter of the test results compared with the other proposed approaches. The measured shear strengths of the corner connections are compared to the calculated shear strengths based on the building code provisions and five alternative approaches available in the literature (i.e. Ingvarsson's, Regan's, Zaghlool's, Gardner's and Desayi's approach). On the basis of the present test results, the effects of load eccentricity (M/V) and reinforcement ratio (rho avg) on shear strength of edge column slab connections are investigated. The reduction in shear capacity of edge connections due to the increase in M/V ratios approximates a logarithmic function. The effect of the reinforcement ratio on the shear strength of the present tests on the edge and corner connections calculated using the North American codes is not obvious. However, tests by Zaghlool (1973) and Regan (1981) show that the shear strength increased with an increase in reinforcement ratio. The strength and stiffness of repaired edge connections were investigated using the four, previously failed, edge connections of the continuous slab specimen. Connections repaired using normal concrete can have similar strength and stiffness as the original connections. However, the connections repaired using the CAH expansive concrete exhibited less strength and stiffness compared to the original edge connections.
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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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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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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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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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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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Scott, Brandt E. "Structural Control of Thermal Fluid Circulation and Geochemistry in a Flat-Slab Subduction Zone, Peru." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7469.
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Hot spring geochemistry from the Peruvian Andes provide insight on how faults, or fractures in the Earth's crust, are capable of influencing fluid circulation. Faults can either promote or inhibit fluid flow and the goal of this study is test the role of a major fault, such as the Cordillera Blanca detachment, as a channel for transporting deep fluids to the surface. Hot springs are abundant in the Cordillera Blanca and Huayhuash ranges in Peru, and several springs issue along the Cordillera Blanca detachment, making this region an ideal setting for our study. To test the role of the Cordillera Blanca detachment, hot springs were sampled along the trace of the fault (Group 1), the western edge of the Cordillera Blanca (Group 2), the eastern side of the Cordillera Blanca (Group 3), and in the Cordillera Huayhuash (Group 4). Water and dissolved gas samples were collected from a total of 25 springs and then analyzed for an array of geochemical parameters. Distinct fluid chemistries from Groups 1 and 2 suggest that the Cordillera Blanca detachment and adjacent minor faults to the west intersect at depth and provide a preferential flow path for deep fluid circulation. Understanding the influence of faults on fluid flow is essential for many disciplines (e.g. oil exploration, hydrology), and this work demonstrates that fluid geochemistry is an excellent tool for assessing the role of faults on fluid distribution.
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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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Anderson, Megan Louise. "Seismic Anisotropy, Intermediate-Depth Earthquakes, and Mantle Flow in the Chile-Argentina Flat-Slab Subduction Zone." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1257%5F1%5Fm.pdf&type=application/pdf.
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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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Porter, Ryan Charles. "Broadband Seismological Imaging of Flat-Slab Subduction and its Long-Term Impact on Lithospheric Structure and Processes." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/205469.
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In subduction zones, the dip of the downgoing oceanic lithosphere has a profound impact on the nature and extent of deformation as well as the generation of melt. In ~10% of subduction zones, the downgoing slab assumes a low-angle, or horizontal geometry, referred to as flat-slab subduction. The focus of this work is to better understand both the driving forces and impacts of flat-slab subduction on the Earth's lithosphere and asthenosphere. This is accomplished by focusing on three areas impacted by flat-slab subduction. The first area is the Pampean region of central Argentina and Chile, a modern flat-slab subduction zone. In this region, we invert Rayleigh-wave-dispersion data to produce a 3D shear velocity model. The flat slab is visible within the upper mantle as a high-velocity body containing low-velocity pockets that dissipate inboard from the trench. We interpret these velocities in the context of slab hydration and argue that the subducting Nazca plate is initially hydrated at the trench and dewaters as it subducts. The second area is southern California, which was impacted by Laramide flat-slab subduction. In this area, we use receiver functions to locate and parameterize anisotropy within the crust. Results show a persistent NE-SW oriented layer of lower crustal anisotropy. We conclude that this layer consists of schists that were emplaced during Laramide flat-slab subduction and have remained largely intact since. The final component of this work is a study of the Colorado Plateau in which we use ambient-noise tomography and receiver functions to study lithospheric structure. Results show fast crust, a complicated Moho and intact Laramide features throughout the crust beneath the Colorado Plateau while slower crust with a sharp Moho is observed along its margins. Based on these observations, published tomographic data and the volcanic and uplift history of the region, we argue that delamination of the lower crust has occurred beneath the Marysvale volcanic field. This process was driven by the gravitational instability of a dense mafic root that formed during mid-Tertiary magmatism related to the rollback of the Farallon flat slab.
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Wagner, Lara Suzanne. "Investigations of Upper Mantle Structure using Broadband Seismology." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1204%5F1%5Fm.pdf&type=application/pdf.
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ElGendy, Mohammed. "Punching shear behaviour of slab-column edge connections reinforced with fibre-reinforced polymer (FRP) composite bars." Canadian Society of Civil Engineering, 2014. http://hdl.handle.net/1993/24092.
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The use of fibre reinforced polymer (FRP) composites as an alternate to steel has proved to be an effective solution to the corrosion problem. However, FRP bars have low axial and transverse stiffness compared to steel bars which results in a lower shear capacity of FRP reinforced concrete (RC) elements compared to steel-RC elements.
Flat plate systems are commonly used to take advantages of the absence of beams. They, however, are susceptible to punching shear failure where the column suddenly punches through the slab.
An experimental program was conducted to investigate the punching shear behaviour of slab-column edge connections. Nine isolated full-scale slab-column edge connections were constructed and tested to failure. One connection was reinforced with steel flexural reinforcement, six with GFRP flexural reinforcement and two with GFRP flexural and shear reinforcement. The parameters investigated were the flexural reinforcement type and ratio, the moment-to-shear ratio and the shear reinforcement spacing.
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Lim, Boon Tiong. "Punching shear capacity of flat slab-column junctions (a study by 3-D non-linear finite element analysis)." Thesis, University of Glasgow, 1997. http://theses.gla.ac.uk/1708/.
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This thesis presents a study of punching shear capacity of flat slab-column junctions. A three dimensional non-linear finite element program based on 20 node isoparametric solid element was used for the investigation. The non-linear 3-D elastic isotropic model proposed by Motsovos was used to describe the behaviour of concrete before cracking or crushing. After cracking, a yield criteria for 2-D model similar to Kupfer-Hilsdorf was used and concrete was assumed to be anisotropic. No softening in compression is assumed. Smeared crack approach with simple tension stiffening and shear retention equations were employed to mimic the post-cracking behaviour of concrete. Reinforcing bars were represented by one dimensional element embedded in the solid elements and for both tension and compression, linear elastic-plastic behaviour is assumed. A comparison was first made between the predictions of slab behaviour using Kotsovos' model (In-house program) and plasticity based model used in the commercial package ABAQUS. From this it was concluded that Kotsovos' concrete model is a good model for the three dimensional analysis of the punching shear problem but the ABAQUS model was unsuitable. In order to achieve an accurate and economical solution for the non-linear analysis, a parametric study was carried out to choose a suitable analytical model. After having chosen the "best" concrete model, over 175 slabs from different sources were analysed using a constant set parameters. The analysis includes various types connections (interior, edge and corner) with and without shear reinforcement, subjected to shear force alone or to a combination of shear force and unbalanced moment. These slabs cover most of the factors affecting punching shear strength, such as slab thickness, flexural reinforcement ratios, concrete strength, and column size. This study also includes the effect of in-plane restraint on punching shear strength of slabs.
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Diao, Mengzhu. "Punching and Post-Punching Shear Behaviour of Interior RC Slab-Column Joints with Inplane Constraints." Thesis, Griffith University, 2021. http://hdl.handle.net/10072/404856.
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A reinforced concrete (RC) flat plate is a type of structural system widely used in the construction of about 80-90% of residential high-rise buildings in Australia and similarly overseas. Flat plate construction is however prone to punching shear failure at slab-column joints which may trigger a catastrophic progressive collapse of the entire structure.
In a flat plate structure, unbalanced moments at the slab-column joints are unavoidable. These bending moments are commonly caused by asymmetric loading, unequal spans or horizontal forces like wind or earthquake. The existence of unbalanced moments could increase the vulnerability of a flat plate structure to punching shear failure. In addition, the load originally resisted by a potentially damaged column will be transferred to the adjacent joints, at which a large additional shear stress and unbalanced bending moment will be generated, eventually leading to more complex mechanical performance and failure mechanism of the joints. Limited collapse-resistant design guidelines are available for this type of structure. Moreover, its punching shear and post-punching failure mechanisms in the context of a progressive collapse are still in need of in-depth study.
To investigate the punching and post-punching shear mechanisms of slab-column joints subjected to concentric loading (with balanced moments), previous static tests on four slab-column joint specimens with slab in-plane restraints have been analysed. The effects of different punching directions (upward punching and downward punching) and embedded beams on the post-punching performance of the joints were studied. Furthermore, a 3D nonlinear finite element modelling approach for concentrically loaded joints was developed using software LS-DYNA and verified against the test results. Based on the numerical study, the contributions of the concrete and reinforcement in resisting the collapse of the slab-column joints were evaluated.
To investigate the mechanical behaviour and resistance of slab-column joints subjected to eccentric loading (with unbalanced moments), experimental tests were performed on seven 1/3-scaled interior slab-column joint specimens with appropriate in-plane restraints.
In order to achieve different levels of eccentricities of loading, a special device was designed, through which an upward monotonic asymmetric loading scheme could be implemented. The overall load-displacement responses, crack propagations and strain developments were recorded and analysed. The damage and failure modes at different loading stages were examined and the influence of unbalanced moments, slab thickness and reinforcement ratio on the punching and post-punching shear behaviours of the slab-column joints with in-plane restraints were also explored. In addition, the results from eccentric loading tests were compared with those of the concentric loading tests and the differences between the two were highlighted.
Numerically, a 3D nonlinear finite element modelling approach was established to investigate the punching and post-punching shear behaviours of eccentrically loaded joint specimens. Appropriate selection of different element types, bond-slip relationships, loadings and boundary conditions and element erosion ensured the accuracy of the proposed model. The displacement-controlled quasi-static upward loading scheme was implemented in the numerical models by applying a thermo elastic material to the elements representing the loading device. The proposed numerical models were validated against experimental results, in terms of overall responses, crack patterns and failure modes. Good agreement was obtained, which confirmed the accuracy and reliability of the proposed models. Moreover, parametric studies were performed to investigate the effect of lateral boundary restraints, different levels of eccentricity and the strengthening methods on the punching and post-punching shear behaviours of the slab-column joints.
Finally, to analytically investigate the post-punching responses of the slab-column joints with in-plane restraints, mechanical models and analytical solutions were proposed for the joints subjected to either concentric or eccentric loading. The analytical solutions developed for calculating the post-punching resistance were based on the interactions between the reinforcement and concrete, satisfying the compatibility of deformation and equilibrium relationships. The analytical solutions were validated against all the tested specimens, including concentrically and eccentrically loaded joints. Furthermore, the contribution of the tensile and integrity reinforcement to the overall post-punching capacity were quantified.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
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Rodríguez, Montecinos María Pía. "Cenozoic uplift and exhumation above the southern part of the flat slab subduction segment of Chile (28.5-32°S)." Tesis, Universidad de Chile, 2013. http://www.repositorio.uchile.cl/handle/2250/115404.
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Doctora en Ciencias, Mención GeologíaEn esta tesis se incluyen los resultados y conclusiones de un estudio de geomorfología tectónica en los Andes del Norte Chico de Chile (28,5-32°S) orientado a reconstruir la evolución del relieve desde el Neógeno en esta región. Los periodos de alzamiento principales son determinados a través del análisis geomorfológico de paleosuperficies, la geocronología de U-Pb circón en niveles volcánicos sobreyacientes y la isotopía cosmogénica. A su vez, las variaciones espaciales y temporales en la exhumación son determinadas al combinar la termocronología de trazas de fisión en apatito (AFT) y de (U-Th)/ He en apatito (AHe) con geocronología de U-Pb circón a ambos lados del frente topográfico que separa la Cordillera de la Costa de la Cordillera Frontal. Las rocas mesozoicas de la Cordillera de la Costa presentan edades AFT entre ~ 60 y 40 Ma y edades AHe alrededor de 30 Ma, mientras que las rocas Paleozoicas y Cenozoicas de la Cordillera Frontal presentan edades AFT y AHe entre ~ 40 y 8 Ma y ~ 20 y 6 Ma, respectivamente. El modelamiento termal de los datos termocronológicos indica que la Cordillera de la Costa fue exhumada de manera acelerada entre ~ 65-50 Ma y fue escasamente exhumada desde ~ 45 Ma hasta, al menos, ~ 30 Ma. La exhumación acelerada entre ~ 65-50 Ma se correlaciona con eventos tectónicos compresivos del Mesozoico Tardío al Cenozoico Temprano. Al norte de 31°S, los modelos termales indican que la exhumación comenzó antes de ~ 30 Ma al pie del frente topográfico. En este sector la exhumación fue continua hasta los 20 Ma, mientras que hacia el este, episodios de exhumación acelerada tuvieron lugar ~ 22-18 Ma y ~ 7 Ma. La exhumación Oligocena se correlaciona con la denudación de una cadena montañosa Eocena ubicada a lo largo del eje de la Cordillera Frontal, mientras que los episodios de exhumación durante el Mioceno Temprano y Tardío se correlacionan con la inversión tectónica progresiva de una cuenca extensional de intra-arco que se desarrolló durante el Oligoceno a lo largo del actual límite de Chile y Argentina. Al sur de los 31°S, el frente topográfico se habría desarrollado con posterioridad, comenzando con un episodio de exhumación acelerada entre los 22-16 Ma al pie del frente topográfico y extendiéndose hasta el Mioceno Tardío hacia el este. La exhumación acelerada a 22-16 Ma en esta área se correlaciona con la inversión de la cuenca extensional de Abanico, desarrollada entre el Eoceno y el Oligoceno al sur de 32°S. Antes del Mioceno Temprano, una extensa pediplanicie cercana al nivel del mar dominaba el paisaje de la actual Cordillera de la Costa. Al norte de los 31°S, esta superficie se desarrolló al pie de un relieve Eoceno reconocido por la termocronología, mientras que al sur de los 31°S lo hizo al oeste del cordón magmático Eoceno. El desarrollo de esta pediplanicie es consistente con la escasa exhumación sufrida por la Cordillera de la Costa durante el Eoceno-Oligoceno Tardío como indican los datos termocronológicos. La pediplanicie fue dislocada durante el Mioceno Temprano generando el alzamiento de ~ 1,1 km de la Cordillera de la Costa oriental respecto de la Cordillera de la Costa occidental. Posteriormente, durante el Mioceno Tardío, tanto la Cordillera de la Costa oriental como la occidental fueron alzadas ~ 1,2 km. Una nueva superficie de bajo relieve formada por plataformas de abrasión marina a lo largo de la costa y por strath terraces y pedimentos al interior de los valles principales se desarrolló entre el Pleistoceno Temprano y Medio en la Cordillera de la Costa occidental y finalmente se alzó ~ 150 m post-500 ka. Los principales eventos de alzamiento y/o exhumación acelerada identificados para el Mioceno Temprano, el Mioceno Tardío y el Pleistoceno Medio se correlacionan con episodios de incremento de la deformación contraccional reconocidos ampliamente a lo largo de los Andes Centrales, que habrían comenzado después del quiebre de la placa de Farallón en las placas de Nazca y Cocos a los 25 Ma.
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Linkimer, Abarca Lepolt. "Lithospheric Structure of the Pampean Flat Slab (Latitude 30-33S) and Northern Costa Rica (Latitude 9-11N) Subduction Zones." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202730.
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The Pampean flat slab subduction in west-central Argentina (latitude 30-33S) and the steeply dipping Northern Costa Rica subduction zone (latitude 9-11N) show significant along-trench variations in both the subducting and overriding plates. This dissertation contains the results of three seismological studies using broadband instruments conducted in these subduction zones, with the aim of understanding the structure of the lithosphere and the correlation between the variability observed in the downgoing and the overriding plates. In the Costa Rica region, by analyzing teleseismic receiver functions we investigate the variability in the hydration state of the subducting Cocos Plate and the nature of three distinct crustal terranes within the overriding Caribbean Plate: the Nicoya and Chorotega terranes that display an oceanic character, and the Mesquito Terrane, which is more compatible with continental crust.In the Pampean region of Argentina, we apply a regional-scale double-difference tomography algorithm to earthquake data recorded by the SIEMBRA (2007-2009) and ESP (2008-2010) broadband seismic networks to obtain high-resolution images of the South America lithosphere. We find that most of the upper mantle has seismic properties consistent with a depleted lherzolite or harzburgite, with two anomalous regions above the flat slab: a higher Vp/Vs ratio anomaly consistent with up to 10% hydration of mantle peridotite and a localized lower Vp/Vs ratio anomaly consistent with orthopyroxene enrichment. In addition, we study the geometry and brittle deformation of the subducting Nazca Plate by determining high-quality earthquake locations, slab contours, and focal mechanisms. Our results suggest that the subduction of the incoming Juan Fernandez Ridge controls the slab geometry and that ridge buoyancy and slab pull are key factors in the deformation of the slab. The spatial distribution of the slab seismicity suggests variability in the hydration state of the subducting Nazca Plate and/or in strain due to slab bending. These observations support the hypothesis that the along-trench variability in bathymetric features and hydration state of the incoming plate has profound effects in the subducting slab geometry and the upper plate structure in both flat and steeply dipping subduction zones.
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Hedeen, Tyler. "Provenance response to flat-slab subduction as recorded in detrital zircon signatures from the southern Alaskan forearc basin system." Thesis, University of Iowa, 2016. https://ir.uiowa.edu/etd/3094.
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Strata in the Cook Inlet forearc basin in south-central Alaska record the effects of tectonic events related to normal subduction and two flat-slab subduction events. Through detrital zircon geochronology we track provenance changes of strata deposited in a forearc basin in conjunction with these different subduction processes. Our data from strata deposited concurrent with normal subduction help to confirm previous provenance models of forearc basins that suggest provenance is sourced primarily from a proximal, coeval arc. However, compared to these models, our data from strata deposited coincident to flat-slab events show markedly different provenance signatures dependent upon: (1) geographic position relative to the flat-slab event; (2) pre-established, or lack thereof, topography; and (3) type of flat-slab event. Detrital zircon signatures of strata deposited in the Cook Inlet after flat-slab subduction of a mid-ocean ridge diversify to include older detritus found in the distal inboard region. This distal signature is then incrementally cut-off in younger strata due to deformation of the upper-plate from progressive insertion of a shallowly subducted oceanic plateau. Detrital zircon signatures for strata associated with each flat-slab event are largely older than depositional age due to the lack of coeval arc activity. Our data may help to improve the ability to recognize other flat-slab events through detrital zircon geochronology. In particular, changes in detrital zircon signatures found in strata deposited during flat-slab subduction of an oceanic plateau correlate well with the exhumation of rocks associated with the propagation of deformation in the over-riding plate due to plate coupling.
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Stevens, Andrea Lynn, and Andrea Lynn Stevens. "Cenozoic Evolution of the Sierras Pampeanas Tectonomorphic Zone Between 27.5°S and 30.5°S, Argentina." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/626329.
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The Andean Cordilleran orogenic system stretches over 7,000 km along the western margin of South America and serves as a useful laboratory to evaluate the causes of spatial and temporal variations in orogenic processes. Although the geology of the Andean margin is fundamentally controlled by the subduction of the Nazca plate beneath the South American plate, the style of deformation, basin morphology, exhumation history, and volcanic activity along this margin are remarkably heterogeneous in both time and space.
My Ph.D. work presents new data from the Miocene – Pliocene along-strike depocenters bounding the basement block uplifts of the Sierras Pampeanas and the fold and thrust belt of the Andean Precordilleran in the south Central Andes between ca. 27.5°S and 30.5°S. I use new observations from sedimentology, detrital zircon U-Pb data, and low-temperature thermochronology to evaluate the mechanisms driving basin organization, sedimentation, and exhumation. Geohistory analysis supports flexurally controlled basins between ca. 18 and 6 Ma with detritus derived exclusively from the active Precodillera to the west. Accelerated deformation in the Precordillera produced accelerated sedimentation from ca. 10 – 8.5 Ma. A deceleration of sedimentation from ca. 6 – 5 Ma was most likely controlled by heightened aridity. Around the same time, low-temperature thermochronometers record the widespread exhumation of the foreland basin system for over 300 km along strike, this may be driven by dynamically controlled uplift related to Miocene flat-slab subduction. Low-temperature thermochronometers suggest that the geothermal gradient throughout the late Miocene was ca. 35°C/km – 25°C/km and had not been significantly depressed as previously proposed.
Granite-cored ranges in the Sierras Pampeanas were sampled for low-temperature thermochronology to constrain the exhumation history of the region. Modeling of both apatite fission track and apatite (U-Th-Sm)/He thermochronometers demonstrates that these rocks have been close to the surface since the late Paleozoic. Reheating during the Cretaceous is attributed to elevated geothermal gradients due to back-arc rifting. Final exhumation (1- 2 km) occurred in the mid to late Miocene and may have been controlled by the onset of flat-slab subduction. These results suggest that the Sierras Pampeanas may have had inherited positive topography that has controlled basin organization and sediment distribution patterns since the Paleozoic.
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Gans, Christine. "Investigations of the Crust and Upper Mantle of Modern and Ancient Subduction Zones, using Pn Tomography and Seismic Receiver Functions." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/145719.
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Advances in seismology allow us to obtain "high-resolution" images of the Earth's subsurface. This dissertation summarizes the results of three seismic studies on three different continents, with the aim of better understanding the crust and upper mantle structure of seemingly disparate yet ultimately related regions. The seismic techniques of Pn tomography and P-wave receiver function (RF) analysis are applied to central Turkey (Pn tomography), western Argentina and southwestern Wyoming, USA (RF analysis). These studies look at both a present-day convergent margin (Andean subduction zone, Argentina) and two ancient ones (Bitlis-Zagros collision zone of Arabia-Africa with Eurasia, Turkey; Farallon subduction zone, Wyoming).Using Pn tomography, we were able to detect the limit of the slab rupture edge along the Central Anatolian Fault Zone, Turkey. Slab break-off is an important process that modifies the mantle in tectonically active regions, and the limit of the oceanic Arabian slab break-off along the Bitlis-Zagros Suture Zone, thought to have begun at 11 Ma, was previously undetermined.Using RF analysis, we obtained high-resolution images of the subducting slab beneath the Sierras Pampeanas, Argentina. Continental Moho contours roughly follow terrane boundaries, suggesting that ancient terranes continue to exert control over present-day continental deformation. Overthickened oceanic crust is often cited as a cause of flat slab subduction; our RF results indicate that the crust is moderately overthickened, around 11-16 km. Further, we image offsets in the RF arrivals that indicate the subducted slab is broken or offset in along trench-subparallel fractures.The crustal structure beneath southwestern Wyoming, the location of ancient Farallon flat slab subduction, was studied using RF analysis. Looking at regional crustal structure, results include a new depth to Moho map. Coherency of the seismic signal across the dense LaBarge array (55 stations, ~250 m spacing) was investigated, with results showing that complicated shallow structure can greatly impact the resulting RF signal. Modeling of RFs using synthetics helped to separate the complex signal containing multiple primary conversions and their reverberations, which interact constructively and destructively. The dense spacing of the LaBarge array allowed unique opportunities to investigate coherency of waveforms across very short distances.
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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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Fasola, Shannon Lee. "New perspective on the transition from flat to steeper subduction in Oaxaca, Mexico, based on seismicity, nonvolcanic tremor, and slow slip." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1461778598.
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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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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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Sanchez, Lohff Sonia K. "Upper plate response to varying subduction styles in the forearc Cook Inlet basin, south-central Alaska." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1530270586819066.
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Muňko, Matej. "Administrativní budova v Brně." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-391967.
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The subject of this work is a new administrative building in Brno, district Brno – Stred. The aim of this work is to create documentation for realization. Building has twelve floors, while every floor is rotated by 5° relative to the previous floor counterclokwise. Final rotation between the first and the last floor is 60°. On the first floor there is a restaurant, on the next eleven floors there are administrative spaces. Building is without basement and has a single-layer flat roof. The foundations are made from a system of piles, which co-work with the waterproof foundation slab. Whole construction system is made from cast-in-place reinforced conrete.
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Fletcher, Michael. "Plumes, Plates and Porphyries." Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/28474.
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This study developed an automated approach to understand plume and plate boundary interactions over time, investigating how flat slab and porphyry development are linked to formation mechanisms of major eastern Pacific Large Igneous Provinces (LIPs). Our method allows us to detail how the Shatsky-Hess conjugate collided with North America from 85 Ma, with the subducting front corresponding to porphyry development and matching divisions between shallow and flat slab areas. Our new formation model for the Enigma Ridge, conjugate to the Tuamotu Plateau, resolves problems for development of the Peruvian Flat Slab and the Nazca ridge, with porphyry deposits formed at the eastern tip or sides of the Enigma Ridge. We infer development of the metallogenically significant Juan Felix LIP by identifying the importance of overprinting relationships between plume trails and the potential effect of slow spreading on LIP size and note that it corresponds to the Altiplano Flat Slab, with related deposits forming between 44 Ma and 31 Ma. While deposits mainly form at the front of the flat slab or along its margins, deposits form to the north and south of the San Felix and Juan Fernandez plume trails between 36 Ma to 29 Ma. We provide an explanation for a previously unexplained set of deposits in SAM (64 to 51 Ma age), relating them to the collision of a San Felix-MOR interaction. We investigated the controversy over whether plumes may affect tectonic and metallogenic development at subduction zones or are instead suppressed or destroyed by descending flow and find that while plumes do survive relatively close interaction with a subduction zone, if they cross that zone then it takes tens of millions of years to re-establish themselves or they do not survive the interaction. Plumes identified in the geological record by non-tomographic methods, such as the Manus plume, may have either died or become temporarily suppressed by crossing a subduction zone.
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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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Hagen, Garrett Richard. "Performance-Based Analysis of a Reinforced Concrete Shear Wall Building." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/803.
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PERFORMANCE-BASED ANALYSIS OF A REINFORCED CONCRETE SHEAR WALL BUILDING
Garrett Richard Hagen
In this thesis, a special reinforced concrete shear wall building was designed per ASCE 7-05, and then the performance was investigated using the four analysis procedures outlined in ASCE 41-06. The proposed building was planned as a 6-story office building in San Francisco, CA. The structural system consisted of a two-way flat plate and reinforced concrete columns for gravity loads and slender structural walls for seismic loads. The mathematical building models utilized recommendations from ASCE 41-06 and first-principle mechanics. Moment-curvature analysis and fiber cross-section elements were used in developing the computer models for the nonlinear procedures. The results for the analysis procedures showed that the building met the Basic Safety Objective as defined in ASCE 41-06. The performance levels for the nonlinear procedures showed better building performance than for the linear procedures.
This paper addresses previously found data for similar studies which used steel special moment frames, special concentric braced frames, and buckling restrained braced frames for their primary lateral systems. The results showcase expected seismic performance levels for a commercial office building designed in a high seismicity region with varying structural systems and when using different analysis procedures.
Keywords: reinforced concrete structural walls, shear walls, performance-based analysis, ETABS, Perform-3D, flat plate, two-way slab.
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Macháček, Pavel. "Mateřská škola." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-225775.
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The subject of this project is a nursery school in Sokolnice. The building consists of four departments, facilities for personnel and kitchen. The building is designed as a two-storey cellarless building. It has concrete foundations. The external walls are designed from POROTHERM 425 T Profi bricks with internal insulation. The internal vertical construction is designed from POROTHERM bricks for thin-layer masonry. The supporting structure of roof is provided by slab method Spiroll. The entrance doors are made from aluminum sections, plastic windows. The building has single-layer flat roof with waterproofing coating.
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Tichý, Pavel. "Mateřská škola." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240350.
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The thesis deals with drafting project documentation for the new building of the kindergarten. The building is designed in two separate classes, each with a capacity of 24 children, facilities for teachers and classroom for smaller rings. Parts of the building is designed for the needs of kindergarten kitchen. The building has two floors, brick bearing system. Warmth contact insulation system with an insulating layer of polystyrene. Roofing flat roof of the building.
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Lyčka, Lukáš. "Punching Shear of Flat Slabs." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-408019.
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The use of flat slabs in constructions due to its many functional and economic advantages is wide-spread. Behavior of flat slabs in shear and flexure is a fairly complex problem. Therefore, the punching shear failure belongs to one of the most critical aspects in the design of concrete buildings. Over the last decades several buildings have collapsed due to the failure of the punching shear strength, resulting in loss of lives and financial damages. These disasters revealed gaps in the current (or former) design codes and recommendations. As a part of theoretical framework of the dissertation a method for predicting the punching shear strength of flat slabs was developed. Several experiments on scaled down slabs were conducted in order to verify the proposed method and for optimization of its parameters. Proposed method in development predicts the punching shear for slabs without shear reinforcement according to the EC2 and replaces the area of the shear crack with a system of struts and ties.
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Han, Ugur Burak. "Zdravotnické centrum." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265591.
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The aim of this diploma thesis is to design a health care center in Brno. The building is located in Ivanovice/Brno. The building is ambulatory health care center with two doctor's offices for adult patients, one doctor's office for child patients and one dentist's clinic. Also, there is a pharmacy in the building. Reinforced concrete strip foundation and reinforced concrete basement peripheral walls are designed for the building. For above ground floors, ceramic masonry blocks are designed for structural load bearing frame. Green roof solution is chosen for the roof of the building.
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Vymazal, Jakub. "Monolitický vícepodlažní stěnový objekt." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227273.
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Final thesis with tittle: "Monolithic multi-storey wall building" is processeed as a project documentation according to valid assesment. The object is located in the city of Boskovice, 35 Hybešova street. Its ground plan dimensions are 52,8m x 12,5m. Total height of object is 22,3m including roof-wall, measured from the level of base chink. There are enclosed balconies on the south direction. Movement between floors is ensured by 2-flighted stairs. Object is It is made of reinforced concrete. It is designed as 6-floor bulding with a flat roof. The main supporting construction is created by system of walls and reciprocally asigned ceilings, which are sticked together. Walls are designed as pillars. The building is assigned to a belt bases. Module dimensions are 8,7m in longitudinal direction and 5,2m in transversal direction. Height dimension is 3,0m. The thesis is dealing with the 1st upper floor.
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Azevedo, Aline Passos de. "Resistência e ductilidade das ligações laje-pilar em lajes-cogumelo de concreto de alta resistência armado com fibras de aço e armadura transversal de pinos." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-06122017-142903/.
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Neste trabalho analisa-se a resistência à punção e a ductilidade das ligações laje-pilar em doze modelos de lajes-cogumelo de concreto armado, nas quais se efetuam combinações de emprego de concreto de alta resistência, diferentes volumes de fibras de aço e uso de armadura transversal na forma de conectores de aço tipo pino. Todas as lajes são quadradas com 1160 mm de lado e 100 mm de espessura. A armadura de flexão foi composta de barras de aço de 10 mm espaçadas de tal forma a resistir a um momento fletor único em ambas direções. Os conectores, quando utilizados, foram dispostos radialmente e compostos de barras de aço de 6.6 mm soldadas a segmentos de ferro chato nas duas extremidades. Para avaliar a capacidade resistente dos modelos de ligação laje-pilar e observar o ganho de ductilidade que as fibras proporcionam, foram ensaiados segmentos-de-laje, os quais representam uma faixa destes modelos de ligação laje-pilar. Foi utilizado um sistema de ensaio dotado de atuador hidráulico servo-controlado, programado para ensaio com deformação controlada e aquisição contínua dos dados, o que permitiu a avaliação do comportamento pós-pico de resistência e a realização de medições de resistência residual. Várias hipóteses de cálculo foram utilizadas para avaliar a resistência última das ligações laje-pilar. Empregou-se um critério de classificação para caracterizar o tipo de ruptura em: punção ou flexão predominante ou uma combinação de punção-flexão. Constatou-se que o emprego de concreto de alta resistência, juntamente com armadura transversal, aumenta substancialmente a resistência da ligação laje-pilar, e quando combinado com fibras de aço, consegue-se um considerável aumento da ductilidade.This work analyses the punching shear resistance and ductility of slab-column connections on twelve concrete flat slab models. The model characteristics resulted from combinations of the application of high or ordinary strength concrete, different steel fiber volume fractions and use or not of shear reinforcement. All the slabs are square with 1,160 mm of side and 100 mm of thickness. The main flexural reinforcement was composed of 10 mm steel bars spaced in such a way to resist to the same bending moment in both directions. When used, the shear reinforcement of steel studs were disposed in radial directions and consisted of 6.6 mm steel bars welded to flat steel segments in their ends. To evaluate the resistant capacity of slab-column connection models and to observe the ductility that the fibers provide, they were rehearsed segments-of-slab, which represents a strip of these slab-column connection models. A testing system with a servo-controlled hydraulic jack was used and it was programmed for a controlled deformation test and continuous data acquisition. This method allowed the evaluation of the post-peak strength behavior and the measurement of residual resistance forces. Several calculations hypotheses were used to evaluate the ultimate strength of the slab-column connections. A classification criterium was applied to characterize the failure type as: predominant punching or flexure or a combination of punching-flexure. It was verified that the application of high strength concrete, together with shear reinforcement, increases substantially the slab-column connection strength, and, when combined with steel fibers, a considerable ductility increase is achieved.
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Musilová, Hana. "Mateřská škola." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-371974.
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Diploma thesis is processed in the form design documentation for constrution. New bulding of the kindergarten is situated in a cadastre unit of Blansko town. Building is located on a flat terrain.„T“ shaped building is designes as a double-storey in one part, second part of the building is single-story. A construction systém is bricked from ceramic block and it has no basement. The building is roofed by non-walkable flat roof. Part of the building is roofed by a ealkable flat terrace. A ceiling construction is made by hollow core slab. The kindergarten is consisted of three departmen, each for 20 children. There is a kizchen, offices, technical area and office for a logopedie in the building