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1
Maruri, Rodolfo Felipe. "Iterative computer analysis of post-tensioned concrete beams and frames." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/19510.
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West, Jeffrey Steven. "Durability design of post-tensioned bridge substructures /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Schokker, A. J. "Improving corrosion resistance of post-tensioned substructures emphasizing high performance grouts /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Herman, Reagan Sentelle. "Behavior of stiffened compression flanges of trapezoidal box girder bridges." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3035950.
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Kajewski, Stephen L. "Post-tensioning and its effect on multi-level formwork load distribution." Thesis, Queensland University of Technology, 1998. https://eprints.qut.edu.au/36033/8/36033_Digitised_Thesis.pdf.
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Multi-level concrete buildings requrre substantial temporary formwork
structures to support the slabs during construction. The primary function of
this formwork is to safely disperse the applied loads so that the slab being
constructed, or the portion of the permanent structure already constructed, is
not overloaded. Multi-level formwork is a procedure in which a limited
number of formwork and shoring sets are cycled up the building as
construction progresses. In this process, each new slab is supported by a
number of lower level slabs. The new slab load is, essentially, distributed to
these supporting slabs in direct proportion to their relative stiffness.
When a slab is post-tensioned using draped tendons, slab lift occurs as a
portion of the slab self-weight is balanced. The formwork and shores
supporting that slab are unloaded by an amount equivalent to the load
balanced by the post-tensioning. This produces a load distribution inherently
different from that of a conventionally reinforced slab.
Through , theoretical modelling and extensive on-site shore load
measurement, this research examines the effects of post-tensioning on multilevel
formwork load distribution. The research demonstrates that the load
distribution process for post-tensioned slabs allows for improvements to
current construction practice. These enhancements include a shortening of
the construction period; an improvement in the safety of multi-level
form work operations; and a reduction in the quantity of form work materials
required for a project.
These enhancements are achieved through the general improvement in
safety offered by post-tensioning during the various formwork operations.
The research demonstrates that there is generally a significant improvement
in the factors of safety over those for conventionally reinforced slabs. This
improvement in the factor of safety occurs at all stages of the multi-level
formwork operation. The general improvement in the factors of safety with
post-tensioned slabs allows for a shortening of the slab construction cycle
time. Further, the low level of load redistribution that occurs during the
stripping operations makes post-tensioned slabs ideally suited to reshoring
procedures. Provided the overall number of interconnected levels remains
unaltered, it is possible to increase the number of reshored levels while
reducing the number of undisturbed shoring levels without altering the
factors of safety, thereby, reducing the overall quantity of formwork and
shoring materials.
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Sicha, Jakub. "Statické řešení zastřešení nádrže." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409778.
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Al-khaja, Waheeb Ahmed Amin. "Time-dependent losses in post-tensioned prestressed concrete." Thesis, University of Leeds, 1986. http://etheses.whiterose.ac.uk/179/.
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An investigation has been undertaken into the factors affecting the time-dependent deformations, prestress losses and deflections of Class 1 uncracked prestressed concrete beams. The main influencing factors considered were environmental conditions, loading conditions,size and shape of members and concrete mix composition. Twenty seven beams consisting of both I- and rectangular sections with different concrete mixes, and tested under different environmental and loading conditions, were monitored for a period of one year. Tests were also conducted on short I- and rectangular beams and cylindrical control specimens to determine the shrinkage and creep properties of various concrete mixes including some with PFA and admixtures. A comprehensive assessment has been undertaken to determine the reliability of various methods of predicting deformations, prestress losses and deflections by comparing current prediction methods with experimental results obtained during this research programme. The use of experimentally determined material parameters for creep and shrinkageq is also considered in the prediction methods. Proposals are made for improving prediction by the current British Code: BS8110: 1985.
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Wu, Zhongxin. "Effective Post-Tensioned Splicing System for Prestressed Concrete Piles." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6605.
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Precast prestressed concrete piles are widely used in deep foundation construction. Due to unexpected site soil conditions and difficulties associated with transportation and handling long precast piles, splicing is sometimes necessary at the construction site.
Available splicing methods utilize steel type connections that are more suitable for reinforced concrete construction and result in limited tensile capacity at the splice. This dissertation describes studies associated with the development of a new post-tensioned splicing system using staggered, embedded anchorages. The new system has the potential to provide the same tensile capacity as a one piece prestressed pile.
To develop the post-tensioned splicing system it was necessary to conduct varied numerical analyses to solve immediate technical problems associated with the design, fabrication and testing of a prototype. This included the design of a self-stressing prestressing bed, optimization of the shape of the embedded anchorages and their layout within the piles being spliced. The focus of the dissertation is on non-linear finite element studies conducted to model the flexure behavior of prototype laboratory and full-sized spliced piles in comparison to their identical non-spliced counterpart.
Though finite element analysis of prestressed elements is not new, issues relating to modeling post-tensioned, spliced elements with embedded, staggered anchorages have not been the subject of any previous investigation and constitute the principal contribution of this study.
Nonlinear finite element analysis was conducted using ANSYS. The William-Warnke failure criterion used to establish concrete failure. A three-dimensional analysis was conducted in which SOLID65 element was used for modeling concrete and LINK8 for the prestressing strands. The post-tensioning ducts were modeled using PIPE20 elements. Perfect bond was assumed between the concrete and the ducts. Embedded anchorages were modeled as fixed locations within the concrete. Epoxy used to join the two splicing surfaces was modeled using contact elements. Since the layout of the post-tensioning ducts was staggered, a full model was required. In contrast, advantage was taken of symmetry for the analysis of the one piece controls.
The finite element model was able to accurately capture the flexural behavior of both the control and the spliced piles. The results suggested that tensile separation at the splice interface acted as a pivot about which the section rotated. As a result, the compression failure zone in the spliced pile was confined to a smaller region compared to the control.
The stress distribution in the spliced pile indicated that the concrete in the cover above the splice was crushed at the ultimate stage before the steel had yielded. As a result, the ultimate capacity of the spliced pile was controlled by concrete failure.
The results also indicated that, among the multiple layers of post-tensioning strands, only one approached yield while others remained in the elastic range. As a result, when the applied load was released, the spliced pile rebounded back to a large degree, which resulted in a much smaller residual permanent deformation. This behavior of a spliced pile can be beneficial for structures in a seismic zone because it will induce smaller secondary moments.
This study helped to refine and improve the new post-tensioned splicing system. Its availability makes it possible to extend and further improve the concept without the need for costly prototype fabrication and testing.
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Karimnassaee, Ali 1959. "FLEXURAL BEHAVIOR OF LIGHTLY REINFORCED UNBONDED POST-TENSIONED CONCRETE BEAMS." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/275510.
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Hengprathanee, Songwut. "Linear and Nonlinear Finite Element Analyses of Anchorage Zones in Post-Tensioned Concrete Structures." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11253.
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Linear and nonlinear finite element analyses are used for the investigation of rectangular anchorage zones with the presence of a support reaction. The investigation is conducted based on four load configurations consisting of concentric, inclined concentric, eccentric, and inclined eccentric loads. The method of model construction is illustrated thoroughly. The influence of several parameters, including anchorage ratio, inclination of prestressing load, eccentricity, magnitude of the reaction force, bearing plate ratio, and the location of the reaction force, is studied. Both graphical and numerical presentations of the results from each load configuration are given. Improved equations, which are modified from the equations presented in the AASHTO Standard Specifications (2002), are proposed. The results from the equations are compared to those from the finite element method. Nonlinear finite element analysis is used to verify the applicability of the equations and to study a new bursting steel arrangement.
Linear and nonlinear finite element analyses are also used for the study of non-rectangular anchorage zones. Four basic load configurations, including concentric, eccentric, inclined concentric, and inclined eccentric loads, are investigated. The shell element is selected for the construction of the finite element models. Several parameters, consisting of anchorage ratio, inclination of prestressing load, eccentricity, web thickness, ratio of web thickness to flange thickness, and flange width, are chosen for parametric studies. The results from the studies are presented graphically and numerically. Equations to calculate the bursting force and location of the force are developed from the Strut-and-Tie Model approach. The verification of the formulations and the investigation of bursting steel arrangement are conducted using nonlinear finite element analysis.Ph. D.
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Krauser, Gaelyn B. "Optimization of Two-Way Post-Tensioned Concrete Floor Systems." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/181.
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This thesis investigates a parametric study of a flat plate floor system designed using post-tensioning. The load balanced by the post-tensioning, the slab depth, and the strength of concrete were varied to create the parametric study of a hotel/condominium grid layout. In order to perform the parametric study, research was conducted on the development of post-tensioning, methods of analysis for two-way slab design, and post-tensioning methods of analysis. Design was conducted by hand through a series of Excel spreadsheets and compared to results found using the computer analysis program, ADAPT-PT. The designs found in the parametric study were then used to perform a cost analysis across ten cities in the United States: Atlanta, Boston, Chicago, Denver, Houston, Los Angeles, Miami, Phoenix, San Francisco, and Seattle.
The designs from the hand analysis and the ADAPT-PT model provided similar results for the post-tensioning, and both methods provide an adequate design. The use of ADAPT-PT is recommended because of its ease of use and quick calculation capabilities. The designs of the hand analysis were quantified and along with unit prices gathered from contractors and suppliers the cost analysis found that the design with 100% of the dead load balanced provided the least expensive solution for all the cities, and the design using a 6000 psi strength concrete provide the most expensive solution for all cities. The least expensive slab design was $9.02 per square foot in Atlanta, Georgia, and the most expensive slab design was $24.96 per square foot in Miami, Florida. A more rigorous parametric study in the future may provide a better optimization for the hotel/condominium slab investigated as the parametric study of this thesis found costs which varied by less than 10% between the most expensive and least expensive slabs in the ten cities.
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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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NACHT, PEDRO KAJ KJELLERUP. "INTERACTIVE GRAPHICS TOOL FOR SERVICEABILITY LIMIT STATE STRESS CHECK OF PRESTRESSED CONCRETE BEAMS WITH POST-TENSIONED BONDED TENDONS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=27386@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROEste trabalho apresenta o desenvolvimento de uma ferramenta computacional gráfico-interativa para a verificação de vigas de concreto protendido com pós-tração aderente ao estado limite de serviço, de acordo com a norma brasileira NBR 6118:2014. A ferramenta é uma extensão (addin) para o Autodesk Robot Structural Analysis Professional , que serve como plataforma de modelagem estrutural. A partir de dados fornecidos pelo usuário através de uma interface gráfica, o programa desenvolvido calcula todas as perdas de protensão que ocorrem ao longo da vida-útil da estrutura, assim como os carregamentos equivalentes à protensão durante este período. O trabalho apresenta os métodos de cálculo tradicionais das perdas imediatas e diferidas, obtidos da NBR 6118, e as modificações que tiveram que ser feitas para permitir um cálculo incremental. Exemplos de utilização do programa e dos cálculos necessários também são apresentados e comprovam, pelos bons resultados obtidos, o acerto na escolha da metodologia escolhida. Como resultado, a ferramenta apresenta duas saídas: uma planilha contendo os esforços e as tensões atuantes na viga ao longo de sua vida-útil e verificações destes valores em relação aos limites estabelecidos para o estado limite de serviço; e o modelo estrutural no Robot apresenta os carregamentos equivalentes da protensão. O usuário pode então adotar estes carregamentos em demais cálculos da estrutura, enquanto a planilha pode ser utilizada para verificar com facilidade se a protensão atende às condições de serviço.
This work presents the development of an interactive graphics computational tool for the verification of prestressed concrete beams with posttensioned bonded tendons to the serviceability limit state stress check according to the Brazilian code NBR 6118:2014. The tool is an add-in for Autodesk Robot Structural Analysis Professionalr, which serves as a structural modeling platform. With data supplied by the user through a graphics user interface, the program here developed calculates all relevant prestress losses that occur throughout the structure s life-cycle, along with the prestressing s equivalent loads during this period. The traditional calculation methods, obtained in the NBR 6118, are presented along with the modifications which had to be implemented in order to allow for incremental loss calculations. Usage examples and the necessary calculations are presented and, through the results obtained, validate the adopted methodology. As results, the program presents two outputs: a spreadsheet containing the resultant forces and stresses and a check of these values with respect to the permissible stresses in the serviceability limit state; and the Robot model presents the prestress equivalent loads. The user may then use these loads in additional calculations. The spreadsheet may be used to easily check if the prestress is sufficient with respect to serviceability conditions.
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Shmerling, Robert Zachary. "STRUCTURAL CONDITION ASSESSMENT OF PRESTRESSED CONCRETE TRANSIT GUIDEWAYS." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3529.
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Objective condition assessment is essential to make better decisions for safety and serviceability of existing civil infrastructure systems. This study explores the condition of an existing transit guideway system that has been in service for thirty-five years. The structural system is composed of six-span continuous prestressed concrete bridge segments. The overall transit system incorporates a number of continuous bridges which share common design details, geometries, and loading conditions. The original analysis is based on certain simplifying assumptions such as rigid behavior over supports and simplified tendon/concrete/steel plate interaction. The current objective is to conduct a representative study for a more accurate understanding of the structural system and its behavior. The scope of the study is to generate finite element models (FEMs) to be used in static and dynamic parameter sensitivity studies, as well load rating and reliability analysis of the structure. The FEMs are used for eigenvalue analysis and simulations. Parameter sensitivity studies consider the effect of changing critical parameters, including material properties, prestress loss, and boundary and continuity conditions, on the static and dynamic structural response. Load ratings are developed using an American Association for State Highway Transportation Officials Load and Resistance Factor Rating (AASHTO LRFR) approach. The reliability of the structural system is evaluated based on the data obtained from various finite element models. Recommendations for experimental validation of the FEM are presented. This study is expected to provide information to make better decisions for operations, maintenance and safety requirements; to be a benchmark for future studies, to establish a procedure and methodology for structural condition assessment, and to contribute to the general research body of knowledge in condition assessment and structural health monitoring.M.S.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil Engineering
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Luis, Alberto Bedriñana Mera. "SEISMIC PERFORMANCE AND SEISMIC DESIGN OF DAMAGE-CONTROLLED PRESTRESSED CONCRETE BUILDING STRUCTURES." Kyoto University, 2018. http://hdl.handle.net/2433/235084.
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White, Samuel Lewis. "Controlled Damage Rocking Systems for Accelerated Bridge Construction." Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2014. http://hdl.handle.net/10092/9186.
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Bridge substructures are generally constructed using cast-in-place concrete and designed to undergo inelastic deformation in earthquake events. Although this construction approach has proven to be economical and provides adequate seismic performance through the formation of ductile plastic hinges, there are downsides relating to construction speed and quality, and post-earthquake repairability.
This thesis explores two categories of Accelerated Bridge Construction (ABC) connection types, which use precast concrete instead of cast-in-place concrete to offer advantages including increased construction speed and quality. High Damage (HD) ABC connection types emulate the seismic behaviour of cast-in-place construction through the formation of ductile plastic hinges.
Controlled Damage (CD) ABC connection types use unbonded post-tensioned precast connections to offer additional advantages including reduced residual drifts, limited and controlled damage and simple repair options. Novel buckling-restrained, fused mild steel energy dissipators suitable for use in CD connections are also developed and tested. These designs utilise 'dry' fabrication to simplify the fabrication process and minimise cost.
Half-scale experimental testing is carried out to demonstrate both the assembly processes and behaviour under reversed cyclic uniaxial and biaxial loading representing an earthquake event. Following benchmark testing, repair strategies are applied to the CD connection types and the columns are tested again, representing a subsequent earthquake event. Good results are obtained from all cases with relatively straightforward construction and repair processes. With further developments and testing, the connection types proposed can provide competitive alternatives to conventional bridge pier design with regard to seismic performance and life cycle costs, with the additional benefits associated with precast construction.
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Bosworth, Kyle Judson. "Health Monitoring of the Veterans' Glass City Skyway: Vibrating Wire Strain Gage Testing, Study of Temperature Gradients and a Baseline Truck Test." Connect to Online Resource-OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1197693985.
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Thesis (M.S.)--University of Toledo, 2007.Typescript. "Submitted as partial fulfillment of the requirements for the Master of Science in Civil Engineering." "A thesis entitled"--at head of title. Bibliography: leaves 86-87.
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Dočkal, Miloš. "Rekonstrukce mostu přes údolí u Dobrušky." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227736.
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The final thesis is focused on design a bridge construction. across the valley near Dobruška. The existing bridge is convenient and it will be replaced by a new bridge construction. The bridge is situated on motorway I/14 and it is used to transfer across the valley and Brtevsky brook.The bridge construction is designed in three alternatives. The chosen variant is a post-tensioned two-beam concrete construction with a lenght of 88,5 metres and a width of 14,0 metres. The calculation of load is solved in Scia Engineer 2014. The construction is designed in accordance with valid standards and it is made a drawing documentation.
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Kalců, Martin. "Stavebně technologický projekt realizace Místní komunikace ve Žďáru nad Sázavou." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227843.
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This diploma thesis deals with the development of constructive technology project od local road in Žďár nad Sázavou. Specifically, there is a solution prestressed reinforced concrete construction of the bridge over the Sázava river according to the extent of the diploma work.
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Němec, Petr. "Projekt zastřešení výstavní haly." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226442.
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The Diploma’s thesis is focused on the design of selected parts of reinforced concrete exhibition hall (prestressed concrete purlin, prestressed concrete girder, reinforced concrete column, reinforced concrete footing, post-tensioned concrete girders). The load calculation (the self weight, the permanent load, the wind load, the snow load and imposed load), the design and the review of selected reinforced concrete items and the drawing documentation are included in this thesis.
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Zavadil, Bronislav. "Rekonstrukce budovy pivovaru s předpjatými stropními deskami." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226419.
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Aim of this master's thesis is an optimized design of locally supported ceiling slab of building of social center with account of span of columns and height of slab. Structure must be assessed in terms of limit state and service limit state by ČSN EN 1992-1-1 General rules and rules for buildings after design.
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Pelikán, Adam. "Střecha plaveckého stadionu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226932.
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This diploma thesis is about designing the structure of roof of swimming stadium. Three solutions are created - concrete arc with tie, steel truss slab and concrete pretensioned membrane. One choosed solution - concrete pretensioned membrane - is afterwards developed. In the beginning there are several designs of geometry fulfilling the requirements for given type of structure being created. In part of static calculation, the parametrical mathematical model in form of macro in APDL language for Ansys software has been created. Afterwards all the parameters (initial state of cables, level of pretension, dimensions of membrane and peripheral frame, etc.) has been optimized in order to the membrane be fulfilling criterias for ultimate limit state and serviceability limit state. Afterwards other selected parts of structure has been checked. On basis of designed geometry and design checks in static calculation the drawings of conctruction and designed parts has been created. In the end, the 3D model of the structure has been created in graphical software Rhinoceros. Then visualizations of structure in concstruction stages and after completion has been rendered.
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Liška, Jaroslav. "Rekonstrukce visuté lávky v Kroměříži." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409798.
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The Diploma thesis deals with the reconstruction design of a footbridge in the city of Kroměříž, Czech Republic. The footbridge would serve as safe transport for pedestrians over the Morava river. The main objective of the thesis is to conceive two or three reconstruction designs. The most suitable one will be opted for and elaborated in more detail. Eventually, strengthening of the bridge by means of additional prestressing using mono-strand post-tensioning systems is picked as the best solution of the planned reconstruction. The monostrand post-tensioning system is led under the deck, the cross section being outside. External cables are anchored in concrete blocks built around existing supports. Load-generated internal forces are calculated on a spatial bar model with non-linear first-order analysis. The calculation is executed using the finite element method in the midas Civil programme. The chosen reconstruction design is then assessed against load capacity limit states, and functionality. Also, the designed reconstruction is assed for dynamic effects. Results are compared with existing structure, and verified against the real-time tensometric measurement-obtained data. Dimensions, assessment of load-bearing structure, and structural details are all made according to valid Eurocodes.
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Mertová, Eliška. "Dálniční most přes široké údolí." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265345.
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The aim of this diploma thesis was the design of three possible variants, how to span the wide and deep valley with a bridge. After an evaluation, situation of the highway on the only wide load-bearing structure which is constituted by a box girder with transverse cantilevers supported by prefabricated bar braces, was chosen as an optimal solving. The load- bearing structure made of post- tensioned concrete is going to be incrementally launched and be supported by one-column pillars along an axis of the motorway. The work is composed of a detailed design of this preferred variant, which is processed according to the ultimate and serviceability limit state including the construction stage analysis of the bridge by the construction technology by an incremental launching method.
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Nani, Pavel. "Most nad potokem Bystrice." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227167.
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The subject of my diploma thesis is a detailed static calculation of the post-tensioned concrete road bridge across Bystrica creek near Banska Bystrica in Slovakia. The bridge is element of turning ramp a motorway R1. The spatial curvature continuous bridge has 9 fields. It was made a spatial curvature computational model of the bridge for a structural analysis. The model was comparison with a straight computational model of the bridge. It is made comparison effect of the construction bridge in stages on the size of the internal forces too. The load-bearing structure was checked according to CSN EN 1992-1-1, CSN EN 1992-2 and CSN 73 6214.
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Kotík, Libor. "Konstrukce sila na cukr." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227611.
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The matter of this thesis is static design and examination of prestressed storage tank to 50000 tons of sugar. Computational model of the steel roof structure is processed and its effect on the silos. Loads is provided of sugar. Optimal design is performed and assessment ultimate and serviceability limit state reinforced concrete and prestressing horizontal silo wall including local load. Next, it is performed the design of a reinforced concrete of the plane bed and column and assessment at the ultimate limit state. The thesis is also drawing documentation, technical report and visualization of construction process. The aim of this work is to the design of the main components based on the required storage capacity tank, mechanical properties of the stored material and technical amenities.
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Engelmann, Michael. "Spannglasträger – Glasträger mit vorgespannter Bewehrung." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-229676.
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Glas und Beton sind sich in wesentlichen Materialeigenschaften ähnlich: Beide zeigen gegenüber einer hohen Druckfestigkeit eine vergleichsweise geringe Zugfestigkeit und versagen spröde. Diese Analogie führte zur Entwicklung bewehrter Glasträger, die sich durch eine aufgeklebte Stahllasche an ihrer Biegezugkante auszeichnen. Dadurch wurden die Übertragung von Zugkräften auch im Rissfall möglich, sodass ein duktiles Bauteilverhalten erreicht und der im Konstruktiven Glasbau notwendige Nachweis der Resttragfähigkeit erfüllt wird. Glasträger mit verbundlos vorgespannter Bewehrung – Spannglasträger – stellen die Fortführung dieses Analogiegedankens dar. Neben einer gezielten Steigerung der Erstrisslast, können die Träger planmäßig überhöht werden. Damit wird einer bisher üblichen Überdimensionierung mit der Anordnung nicht ausgenutzter „Opferscheiben“ entgegen gewirkt und sichere sowie materialeffiziente Konstruktionen mit maximaler Transparenz ermöglicht. Diese Konstruktionsweise wurde bislang ausschließlich für einzelne Sondierungsuntersuchungen in breiter Variantenvielfalt genutzt. Eine Systematik und einheitliche Bezeichnungsweise ist nicht vorhanden. Darüber hinaus beschränken sich verfügbare Ergebnisse auf die Beschreibung der Tragfähigkeit, ohne die Resttragfähigkeit explizit zu belegen oder die Dauerhaftigkeit nachzuweisen. Mit dieser Arbeit wurde anhand einer Analogiebetrachtung zum Eurocode 2 eine Bezeichnungsweise für bewehrte und vorgespannte Glasträger entwickelt und für vorhandene Konstruktionen erfolgreich angewendet. Darin zeigt sich, dass der Stand der Technik auf diese Weise charakterisierbar ist. Zusätzlich wird die These aufgestellt, dass sich das Tragverhalten von Spannglasträgern wie im Stahlbeton- und Spannbetonbau beschreiben und die auftretenden Spannkraftverluste analog berechnen lassen. Diese These wird mithilfe experimenteller Studien als Kern dieser Arbeit untersucht und durch eine ergänzende numerische Modellierung bestätigt. Zunächst wird das Tragverhalten im Kurzzeit-Biegeversuch an 15 Prüfkörpern unter variierten Bewehrungsgraden und Vorspannkräften untersucht. Dabei zeigen sich gesteigerte Erstrisslasten sowie ein sicheres Verhalten im Anschluss an die Belastung. Durch die Vorspannung wird das Tragverhalten gezielt beeinflusst. Zusätzlich erbringt eine zerstörungsfreie Untersuchungsreihe an 28 Prüfkörpern unter konstanter Gebrauchslast über 1000 Stunden erstmals eine Beschreibung der auftretenden Spannkraftverluste. Diese sind maßgeblich von der horizontalen Durchbiegung sowie der daraus resultierenden Belastung der Zwischenschicht im Verbund-Sicherheitsglas abhängig. Aus der Größenordnung der Verluste lässt sich schlussfolgern, dass eine Begrenzung dieses Verformungsanteils sowie eine konstruktive Entlastung der Zwischenschicht notwendig sind. Zudem wird die Änderung der Vorspannkraft unter einer Temperaturlast beschrieben. Im Ergebnis zeigt sich, dass dieser Lastfall mittels der linearen Balkentheorie beschreibbar und der damit assoziierte Spannkraftverlust berechenbar ist. Die Resttragfähigkeit von 24 Spannglasträgern wird mithilfe eines eigens entwickelten Prüfverfahrens bestätigt. Während die Bewehrung einerseits eine Überbrückung von Rissflanken ermöglicht, verursacht die Vorspannkraft andererseits im teilzerstörten Tragsystem bisweilen ein frühzeitiges Versagen. Daher wird empfohlen, die baukonstruktive Detailentwicklung zu intensivieren, um einen größeren Sicherheitsvorteil aus der Konstruktionsweise zu generieren. Die Arbeit beinhaltet erstmals eine systematische Datensammlung zum Tragverhalten von Spannglasträgern. Es zeigt sich, dass auf eine Anordnung von „Opferscheiben“ zugunsten einer steigenden Materialeffizienz nicht nur verzichtet werden kann, sondern im Sinne eines effektiven Tragverhaltens verzichtet werden muss. Mit der vorgeschlagenen Bezeichnungsweise, den abgeleiteten konstruktiven Maßnahmen sowie den gezeigten Untersuchungsmethoden besteht nunmehr die Möglichkeit, sichere und dauerhafte Spannglasträger zu entwerfen und deren Trageffizienz zu belegenGlass and concrete share essential material characteristics: Their compressive strength exceeds their tensile strength considerably and both of them fail in a brittle manner. This analogy led to the development of reinforced glass beams, which are improved by means of adhesively bonded steel sections in the tensile zone. This improvement allowed for a direct transfer of tensile loads in a post-breakage state and resulted in a ductile structural element, which met the special demand of structural glass for a sufficient residual loadbearing capacity. Glass beams with unbonded, post-tensioned reinforcement – Spannglass Beams – carry this analogy concept on. The members will comprise an increased initial fracture strength and may be uplifted intentionally. This development has rendered the need for over-dimensioning by removing unnecessary sacrificial layers, which will result in a material efficient structure and will maximise transparency. Solely single exploratory investigations have used this idea in a wide variety of options so far. There is neither a uniform classification nor a consistent nomenclature. Furthermore, available results are limited to the concise description of the short-term load-bearing properties without proving the residual load-bearing capacity explicitly and confirming longterm durability. This thesis describes the development and the application of a nomenclature for reinforced and pre-compressed glass beams in an analogy study according to Eurocode 2. The state of technology can be characterised in this manner. Additionally, the research describes the load-bearing behaviour as well as the calculation of the loss of pre-stress of Spannglass Beams by analogy with concrete structures. As the key section of this thesis, this statement is examined by means of comprehensive experimental studies and completed by a numerical calculation. Primarily, the load-bearing behaviour of 15 specimens in short-term bending tests and a variety of reinforcement ratios and pre-stress levels were determined. The results show an increase of initial fracture strength as well as safe behaviour after failure. The pre-stress changes the load-bearing performance significantly. Furthermore, a non-destructive study including a constant loading for 1000 h describes the loss of pre-stress in 28 specimens for the first time. The horizontal deflection and the thus resulting shear stresses of the interlayer material of a laminated glass section are the critical parameters. From the magnitude of losses it may be concluded that the deflections need to be limited and the interlayer foils need to be relieved from stress. Moreover, the structural response during a change in temperature is in good agreement with the results obtained from linear beam theory. This allows for an estimation of the associated losses. Finally, a specifically developed test approach confirms the residual load-bearing capacity of 24 specimens. The reinforcement shows the ability to bridge cracks in the glass. However, it should be noted that pre-stress occasionally causes an early failure of the partially broken Spannglass cross-section. Therefore, intensifying the development of structural details in order to generate an increased advantage concerning safety is recommended. This contribution contains a systematic acquisition of analytical, experimental and numerical data regarding the loadbearing characteristics of Spannglass Beams for the first time. The use of a sacrificial layers is not necessary. Even more, to reach the most effective load-bearing behaviour, it is necessary to abandon them completely. Implementing the developed nomenclature, realising the recommended structural provisions and using the proposed methods, it is now possible to compose safe and durable Spannglass Beams as well as prove their structural efficiency
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Salas, Pereira Rubén Mario. "Accelerated corrosion testing, evaluation and durability design of bonded post-tensioned concrete tendons." 2003. http://wwwlib.umi.com/cr/utexas/fullcit?p3118069.
Full text
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Salas, Pereira Rubén Mario 1968. "Accelerated corrosion testing, evaluation and durability design of bonded post-tensioned concrete tendons." 2003. http://hdl.handle.net/2152/12506.
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Medina, Chávez César Iván. "Development and implementation of a mechanistic-empirical design procedure for a post-tensioned prestressed concrete pavement (PCP)." 2003. http://wwwlib.umi.com/cr/utexas/fullcit?p3116120.
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Johnson, Stacy Tawfig Kamal Mtenga Primus V. "Analytical modeling of fiber reinforced post-tensioned concrete anchorage zones." 2006. http://etd.lib.fsu.edu/theses/available/etd-07052006-101416.
Full textAbstract:
Thesis (M.S.)--Florida State University, 2006.Advisor: Kamal Tawfig and Primus Mtenga, co-advisors, Florida State University, College of Engineering, Dept. of Civil & Environmental Engineering. Title and description from dissertation home page (viewed Sept. 15, 2006). Document formatted into pages; contains ix, 87 pages. Includes bibliographical references.
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Medina, Chávez César Iván. "Development and implementation of a mechanistic-empirical design procedure for a post-tensioned prestressed concrete pavement (PCP)." 2003. http://hdl.handle.net/2152/12357.
Full text
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Rebentrost, Mark. "Deformation Capacity and Moment Redistribution of Partially Prestressed Concrete Beams." 2004. http://hdl.handle.net/2440/37933.
Full textAbstract:
Ductility is a measure of the ability of a material, section, structural element or structural system to sustain deformations prior to collapse without substantial loss of resistance. The Australian design standard, AS 3600, imposes minimum ductility requirements on structural concrete members to try to prevent premature non-ductile failure and hence to ensure adequate strength and ductile-type collapse with large deflections. The requirements also enable members to resist imposed deformation due to differential settlement, time effects on the concrete and temperature effects, whilst ensuring sufficient carrying capacity and a safe design. Current AS 3600 requirements allow a limited increase or reduction in elastically determined bending moments in critical regions of indeterminate beams, accommodating their ability to redistribute moment from highly stressed regions to other parts of the beam. Design moment redistribution limits and ductility requirements in AS 3600 for bonded partially prestressed beams are a simple extension of the requirements for reinforced members. The possibility of premature non-ductile failure occurring by fracture of the reinforcement or prestressing steel in partially prestressed members has not adequately addressed. The aim of this research is to investigate the overload behaviour and deformation capacity of bonded post-tensioned beams. The current ductility requirements and design moment redistribution limits according to AS 3600 are tested to ensure designs are both safe and economical. A local flexural deformation model based on the discrete cracked block approach is developed to predict the deformation capacity of high moment regions. The model predicts behaviour from an initial uncracked state through progressive crack development into yielding and collapse. Local deformations are considered in the model using non-linear material laws and local slip behaviour between steel and concrete interfaces, with rigorous definition of compatibility in the compression and tension zones. The model overcomes limitations of past discrete cracked block models by ensuring compatibility of deformation, rather than strain compatibility. This improvement allows the modeling of members with multiple layers of tensile reinforcement and variable depth prestressing tendons having separate material and bond properties. An analysis method for simple and indeterminate reinforced and partially prestressed members was developed, based on the proposed deformation model. To account for the effect of shear in regions of high moment and shear present over the interior supports of a continuous beam, a modification to the treatment of local steel deformation in the flexural model, based on the truss analogy, was undertaken. Secondary reactions and moments due to prestress and continuity are also accounted for in the analysis. A comparison of past beam test data and predictions by the analysis shows the cracking pattern and deformation capacity at ultimate of flexural regions in reinforced and partially prestressed members to be predicted with high accuracy. The analysis method accurately predicts local steel behaviour over a cracked region and deformation capacity for a wide range of beams which fail either by fracture of steel or crushing of the concrete. A parametric study is used to investigate the influence of different parameters on the deformation capacity of a typical negative moment region in a continuous beam. The structural system consists of a bonded post-tensioned, partially prestressed band beam. The primary parameters investigated are the member height and span-to-depth ratio; relative quantity of reinforcing and prestressing steel; material properties and bond capacity of the steels; and lastly the compression zone properties. Results show that the effects of the various parameters on the overload behaviour of partially prestressed beams follow the same trends as reinforced beams. A new insight into the local steel behaviour between cracks is attained. The deformation behaviour displays different trends for parametric variations of the local bond capacity, bar diameter and crack spacing, when compared to past analytical predictions from comparable studies. The discrepancy in findings is traced back to the definition of the plastic rotation capacity and the sequencing of the yielding of the steels. Compared to the other local deformation models, the current model does not assume a linear distribution of strain at a crack. The current findings highlight an important difference between predicted behaviours from different deformation compatibility requirements in local deformation models which has not yet been discussed in the literature. The local deformation model evaluates the relationship between maximum steel strain at a crack and average steel deformation over a crack spacing for the entire loading history. The total steel percentage, hardening properties of the steel and concrete strength are shown by the model to have the greatest effect on these steel strain localisation factors. Section analysis, as currently used in design, can be improved with the proposed simplification of the relationships to identify and quantify the effects of steel fracture on deformation capacity and strength. The numerical effort required to simulate the overload behaviour of practical beam designs with multiple reinforcement elements and a prestressing tendon are currently too great to be used in an extensive numerical study. The numerically more efficient smeared block approach is shown to accurately predict the ultimate carrying capacity of prestressed beams failing by crushing of the concrete. Consequently, this method is adopted to study the allowable limits of moment redistribution in the present investigation, Simplified relationships of the steel strain localisation factors evaluated in the parametric study of deformation capacity is used to predict maximum steel strains and premature failure. The limits of moment redistribution in bonded, post-tensioned partially prestressed band beams are explored by comparing the design load and predicted carrying capacity, for different section ductilities and design moment redistribution. In addition, the effects of different concrete strengths, up to 85 MPa, along with as three reinforcing and prestressing steel ductilities are quantified and compared to current Australian and international design requirements. Limitations in the carrying capacity are investigated for different reinforcement and prestress uniform elongation capacities. More than one thousand beam simulations produce results showing that current design moment redistribution and ductility requirements in the Australian design code for concrete structures (AS 3600) are sufficient for normal strength concretes (less than 50 MPa). A suggestion for design moment redistribution limits, section ductility requirements and steel ductility limits is made for members constructed from higher strength concretes. A special high steel ductility class is proposed for both the reinforcement and prestressing steel to allow moment redistribution in higher strength concrete. No moment redistribution is proposed for members reinforced with low ductility (Class L) steel. An increase of the current elongation limit of Class L steel from 1.5 % to 2.5% is suggested to ensure strength and safety. An increase in the current ductility requirements from fsu/ fsy=1.03 and elongation equal to 1.5% to fsu/fsy=1.05 and 2.5% elongation for low ductility Class L steel is suggested to ensure strength and safety.Thesis (Ph.D.)--Civil and Environmental Engineering, 2004.
34
Rebentrost, Mark. "Deformation capacity and moment redistribution of partially prestressed concrete beams." Thesis, 2004. http://hdl.handle.net/2440/37933.
Full textAbstract:
Ductility is a measure of the ability of a material, section, structural element or structural system to sustain deformations prior to collapse without substantial loss of resistance. The Australian design standard, AS 3600, imposes minimum ductility requirements on structural concrete members to try to prevent premature non-ductile failure and hence to ensure adequate strength and ductile-type collapse with large deflections. The requirements also enable members to resist imposed deformation due to differential settlement, time effects on the concrete and temperature effects, whilst ensuring sufficient carrying capacity and a safe design. Current AS 3600 requirements allow a limited increase or reduction in elastically determined bending moments in critical regions of indeterminate beams, accommodating their ability to redistribute moment from highly stressed regions to other parts of the beam. Design moment redistribution limits and ductility requirements in AS 3600 for bonded partially prestressed beams are a simple extension of the requirements for reinforced members. The possibility of premature non-ductile failure occurring by fracture of the reinforcement or prestressing steel in partially prestressed members has not adequately addressed. The aim of this research is to investigate the overload behaviour and deformation capacity of bonded post-tensioned beams. The current ductility requirements and design moment redistribution limits according to AS 3600 are tested to ensure designs are both safe and economical. A local flexural deformation model based on the discrete cracked block approach is developed to predict the deformation capacity of high moment regions. The model predicts behaviour from an initial uncracked state through progressive crack development into yielding and collapse. Local deformations are considered in the model using non-linear material laws and local slip behaviour between steel and concrete interfaces, with rigorous definition of compatibility in the compression and tension zones. The model overcomes limitations of past discrete cracked block models by ensuring compatibility of deformation, rather than strain compatibility. This improvement allows the modeling of members with multiple layers of tensile reinforcement and variable depth prestressing tendons having separate material and bond properties. An analysis method for simple and indeterminate reinforced and partially prestressed members was developed, based on the proposed deformation model. To account for the effect of shear in regions of high moment and shear present over the interior supports of a continuous beam, a modification to the treatment of local steel deformation in the flexural model, based on the truss analogy, was undertaken. Secondary reactions and moments due to prestress and continuity are also accounted for in the analysis. A comparison of past beam test data and predictions by the analysis shows the cracking pattern and deformation capacity at ultimate of flexural regions in reinforced and partially prestressed members to be predicted with high accuracy. The analysis method accurately predicts local steel behaviour over a cracked region and deformation capacity for a wide range of beams which fail either by fracture of steel or crushing of the concrete. A parametric study is used to investigate the influence of different parameters on the deformation capacity of a typical negative moment region in a continuous beam. The structural system consists of a bonded post-tensioned, partially prestressed band beam. The primary parameters investigated are the member height and span-to-depth ratio; relative quantity of reinforcing and prestressing steel; material properties and bond capacity of the steels; and lastly the compression zone properties. Results show that the effects of the various parameters on the overload behaviour of partially prestressed beams follow the same trends as reinforced beams. A new insight into the local steel behaviour between cracks is attained. The deformation behaviour displays different trends for parametric variations of the local bond capacity, bar diameter and crack spacing, when compared to past analytical predictions from comparable studies. The discrepancy in findings is traced back to the definition of the plastic rotation capacity and the sequencing of the yielding of the steels. Compared to the other local deformation models, the current model does not assume a linear distribution of strain at a crack. The current findings highlight an important difference between predicted behaviours from different deformation compatibility requirements in local deformation models which has not yet been discussed in the literature. The local deformation model evaluates the relationship between maximum steel strain at a crack and average steel deformation over a crack spacing for the entire loading history. The total steel percentage, hardening properties of the steel and concrete strength are shown by the model to have the greatest effect on these steel strain localisation factors. Section analysis, as currently used in design, can be improved with the proposed simplification of the relationships to identify and quantify the effects of steel fracture on deformation capacity and strength. The numerical effort required to simulate the overload behaviour of practical beam designs with multiple reinforcement elements and a prestressing tendon are currently too great to be used in an extensive numerical study. The numerically more efficient smeared block approach is shown to accurately predict the ultimate carrying capacity of prestressed beams failing by crushing of the concrete. Consequently, this method is adopted to study the allowable limits of moment redistribution in the present investigation, Simplified relationships of the steel strain localisation factors evaluated in the parametric study of deformation capacity is used to predict maximum steel strains and premature failure. The limits of moment redistribution in bonded, post-tensioned partially prestressed band beams are explored by comparing the design load and predicted carrying capacity, for different section ductilities and design moment redistribution. In addition, the effects of different concrete strengths, up to 85 MPa, along with as three reinforcing and prestressing steel ductilities are quantified and compared to current Australian and international design requirements. Limitations in the carrying capacity are investigated for different reinforcement and prestress uniform elongation capacities. More than one thousand beam simulations produce results showing that current design moment redistribution and ductility requirements in the Australian design code for concrete structures (AS 3600) are sufficient for normal strength concretes (less than 50 MPa). A suggestion for design moment redistribution limits, section ductility requirements and steel ductility limits is made for members constructed from higher strength concretes. A special high steel ductility class is proposed for both the reinforcement and prestressing steel to allow moment redistribution in higher strength concrete. No moment redistribution is proposed for members reinforced with low ductility (Class L) steel. An increase of the current elongation limit of Class L steel from 1.5 % to 2.5% is suggested to ensure strength and safety. An increase in the current ductility requirements from fsu/ fsy=1.03 and elongation equal to 1.5% to fsu/fsy=1.05 and 2.5% elongation for low ductility Class L steel is suggested to ensure strength and safety.Thesis (Ph.D.) -- University of Adelaide, Dept. of Civil and Environmental Engineering, 2004
35
Lee, Jun Ki 1975. "Evaluation of external post-tensioned tendons using vibration signatures." Thesis, 2007. http://hdl.handle.net/2152/3490.
Full textAbstract:
Recent findings regarding corrosion of post-tensioned bridges have highlighted the urgent need to develop reliable methods to predict the behavior of the structural system after damage has occurred and inspection techniques to assess the condition of the structure. Corrosion in strands is undesirable in that it often progresses without visual signs of distress, but may cause a brittle failure. To complicate the inspection, access to the strands for visual inspection is usually blocked by the concrete cross section. To date, significant efforts have been taken to improve the durability of the post-tensioned bridges. However, the behavior of the post-tensioned bridges with corrosion damage is not clearly understood and the currently available inspection techniques tend to provide only limited information about the nature and extent of the damage. The research project discussed in this dissertation was developed is to evaluate the feasibility of using the vibration technique to detect and estimate the extent of damage in an external tendon due to corrosion. To accomplish this goal, damage was induced in five specimens, which were monitored periodically to correlate the measured changes in the frequency response to the level of damage. The induced damage simulated the degradation of a post-tensioned structure from corrosion. This dissertation describes the experimental program and the numerical scheme used to estimate the condition of the specimens. Three types of specimens were tested during the experimental phase of the research: individual strands, cables specimens, and external tendons. A series of tension tests of individual strands were conducted to investigate changes in the uniaxial behavior after damage was induced. Simulated damage included uniform corrosion of the strand, mechanical wire cuts, and an initial defect in one wire. Three cable specimens and one tendon specimen were subjected to fatigue loading. The loading was selected to simulate the loss of cross-sectional area in the strands, and also caused grout damage. The frequency response of the specimens was recorded periodically during the fatigue tests and acoustic sensors were used to detect the occurrence of wire breaks. A second tendon specimen was exposed to an acid solution to simulate the hydrogen induced cracking in the strand at three different locations along the length of the specimen. A number of wires fractured during the exposure test and damage was inspected visually. Natural frequencies were also measured periodically. The residual prestressing force in of the specimens was extracted from the measured natural frequencies. The stiff string model was used to determine optimum values of tension and flexural stiffness from the frequency response. The numerical results from this optimization demonstrated the feasibility of using the vibration technique as a nondestructive testing method for external tendons.
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Vincent, Thomas J. "Prediction of deformations in post-tensioned prestressed suspended slabs in tall buildings." 2009. http://hdl.handle.net/2440/61075.
Full textAbstract:
The research presented in this thesis focuses on the accuracy of predicting deflections and cambers in partially prestressed suspended slabs. Precision in predicting this behaviour accurately is complex due to the large number of variables which affect the behaviour of suspended prestressed slabs. This level of complexity is particularly relevant for post tensioned slabs due to the numerous on site construction steps. Many of the variables are hard to determine accurately due to their tendency to be unique for each construction site. Variables such as ambient temperatures, concrete material properties, stressing times, applied loads, loading times, prop movement and humidity are all examples of these properties. Hence, when predicting the behaviour of post tensioned suspended slabs of a multi storey building there always remains a degree of uncertainty. The research presented in this thesis addresses crucial areas of this topic and ultimately aims to supply reinforced concrete designers and constructors with additional confidence when predicting this behaviour. The requirement for this project surfaced during the design stages of 151 Pirie, a multistorey building constructed in Adelaide, Australia. The design project for 151 Pirie was particularly complex due to a very ambitious construction timeline. The strict construction timeline was imposed due to the contractual agreement of early occupancy of the top three floors (of a 9 storey building). The client purchasing the top floors required functioning office space within a matter of months. This contract created a construction priority of erecting the bare structural requirements up to and including the top three floors in the shortest possible time. Fittings and services to the top three floors was then the secondary priority. Fitting and services to the lower floors (which would usually be achieved before the upper floors) would be performed at a later date. Excessive deflection limits of the slabs due to the accelerated construction were a major concern for the client. The effect on the deformation performance due to the accelerated construction was difficult to predict for the designer. Therefore, this project was born to help supply confidence to the designer and concrete supplier for this construction scenario. This research project was designed to assist in the close monitoring and recording of the construction process of 151 Pirie. Due to the nature of data collection, data from this construction site would be limited in its benefits for the current construction. However, the data obtained would be vital for future projects by providing a log of onsite slab performance data as well as explanations of delays or other general outcomes with the construction process. Therefore, the aim of this research is to present the issues that were faced, the methods used to overcome these issues as well as displaying the vast amounts of site specific data documented within this project for future reference. In this research a wide range of concrete material properties were collected and monitored closely on site as well as in the laboratory. The experimental testing created large detailed database of concrete material properties as well as other relevant factors such as surveyed deflections and construction timing. Concrete material properties were the primary focus of this research due to their direct effect on member performance. The database was sufficiently large to allow a meaningful statistical data analysis to be performed on the compressive strength (f’[subscript]c), modulus of elasticity (E[subscript]c) and tensile strength (f’[subscript] t) of the concrete samples. This analysis supplied a detailed understanding of the statistical relationship between different concrete material properties. A Monte Carlo simulation was performed, with multiple deflection and camber models, to create a statistical distribution of predicted deflections and cambers from the statistical distribution of concrete material properties. This statistical output is then critically analysed and compared to the surveyed data. Proposed improvements to the process of predicting deflections and cambers have been outlined. These improvements have then been utilised in the construction of a finite element style program. Finally, the multiple predictions of column strip and mid panel deformation are compared to the short term surveyed deflections. It is summarised that the improvements suggested and implemented in the finite style analysis yield results with a higher degree of accuracy. The accuracy and benefits of the suggested improvements has been justified and proven by the application of multiple examples and a parametric study.http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1366459
Thesis (M.Eng.Sc.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2009
37
Vincent, Thomas J. "Prediction of deformations in post-tensioned prestressed suspended slabs in tall buildings." Thesis, 2009. http://hdl.handle.net/2440/61075.
Full textAbstract:
The research presented in this thesis focuses on the accuracy of predicting deflections and cambers
in partially prestressed suspended slabs. Precision in predicting this behaviour accurately is complex due to the large number of variables which affect the behaviour of suspended prestressed slabs. This level of complexity is particularly relevant for post tensioned slabs due to the numerous on site construction steps. Many of the variables are hard to determine accurately due to their tendency to be unique for each construction site. Variables such as ambient temperatures, concrete material properties, stressing times, applied loads, loading times, prop movement and humidity are all examples of these properties. Hence, when predicting the behaviour of post tensioned suspended slabs of a multi storey building there always remains a degree of uncertainty. The research presented in this thesis addresses crucial areas of this topic and ultimately aims to supply reinforced concrete designers and constructors with additional confidence when predicting this behaviour.
The requirement for this project surfaced during the design stages of 151 Pirie, a multistorey
building constructed in Adelaide, Australia. The design project for 151 Pirie was particularly
complex due to a very ambitious construction timeline. The strict construction timeline was
imposed due to the contractual agreement of early occupancy of the top three floors (of a 9 storey
building). The client purchasing the top floors required functioning office space within a matter of months. This contract created a construction priority of erecting the bare structural requirements up to and including the top three floors in the shortest possible time. Fittings and services to the top three floors was then the secondary priority. Fitting and services to the lower floors (which would usually be achieved before the upper floors) would be performed at a later date. Excessive deflection limits of the slabs due to the accelerated construction were a major concern for the client. The effect on the deformation performance due to the accelerated construction was difficult to predict for the designer. Therefore, this project was born to help supply confidence to the designer
and concrete supplier for this construction scenario. This research project was designed to assist in the close monitoring and recording of the construction process of 151 Pirie. Due to the nature of data collection, data from this construction site would be limited in its benefits for the current construction. However, the data obtained would be vital for future projects by providing a log of onsite slab performance data as well as explanations of delays or other general outcomes with the construction process. Therefore, the aim
of this research is to present the issues that were faced, the methods used to overcome these issues as well as displaying the vast amounts of site specific data documented within this project for future reference. In this research a wide range of concrete material properties were collected and monitored closely on site as well as in the laboratory. The experimental testing created large detailed database of concrete material properties as well as other relevant factors such as surveyed deflections and
construction timing. Concrete material properties were the primary focus of this research due to
their direct effect on member performance. The database was sufficiently large to allow a
meaningful statistical data analysis to be performed on the compressive strength (f’[subscript]c), modulus of elasticity (E[subscript]c) and tensile strength (f’[subscript] t) of the concrete samples. This analysis supplied a detailed understanding of the statistical relationship between different concrete material properties. A Monte Carlo simulation was performed, with multiple deflection and camber models, to create a
statistical distribution of predicted deflections and cambers from the statistical distribution of
concrete material properties. This statistical output is then critically analysed and compared to the surveyed data. Proposed improvements to the process of predicting deflections and cambers have been outlined. These improvements have then been utilised in the construction of a finite element style program. Finally, the multiple predictions of column strip and mid panel deformation are compared to the short term surveyed deflections. It is summarised that the improvements suggested and implemented in the finite style analysis yield results with a higher degree of accuracy. The accuracy and benefits of the suggested improvements has been justified and proven by the application of multiple examples and a parametric study.Thesis (M.Eng.Sc.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2009
38
Moore, Andrew Michael 1984. "Shear behavior of spliced post-tensioned girders." Thesis, 2014. http://hdl.handle.net/2152/26882.
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By its nature a spliced girder must contain a number of post tensioning tendons throughout its length. The focus of the experimental program described in this dissertation is the evaluation of the strength and serviceability of post-tensioned girders loaded in shear, and, more specifically, how a post-tensioning duct located in the web of a girder affects the shear transfer mechanism of a bulb-tee cross-section. Due to the limited number of tests in the literature conducted on full-scale post-tensioned girders, eleven shear tests were performed on seven prestressed concrete bulb-tee girder specimens. Of these tests, ten were conducted on specimens that contained a post-tensioning duct within their web and additional pretensioning reinforcement in their bottom and top flanges. The remaining shear test was conducted on a control specimen that did not have a post-tensioning tendon but contained the same pretensioning reinforcement as the post-tensioned girder specimens. The behavioral characteristics of these eleven test specimens at service level shear forces and at their ultimate shear strengths were evaluated in regards to five primary experimental variables: (i) the presence of a post-tensioning duct, (ii) post-tensioning duct material (plastic or steel), (iii) web-width, (iv) duct diameter, and (v) the transverse reinforcement ratio. The findings of this experimental study are described in detail within this dissertation, but can be summarized by the following two points. (i) No differences were observed in the ultimate or service level shear behavior in girders containing plastic grouted ducts when compared to those containing steel grouted ducts and (ii) The current procedure of reducing the effective web width to account for the presence of a post-tensioning duct is ineffective because it addresses the incorrect shear transfer mechanism. A method that correctly addresses the reduction in shear strength due to the presence of a post-tensioning duct was developed and verified using the tests performed during this experimental program and tests reported in the literature.text
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Amato, Lucio Roger. "CFRP Tendons For The Repair Of Post-Tensioned, Ubonded Concrete Buildings." Thesis, 2009. http://hdl.handle.net/1974/1775.
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The deterioration of prestressed concrete structures due to corrosion is a costly problem. This problem is accelerated in cold weather climates where de-icing salts are used. These salts accelerate the corrosion of the steel tendons greatly reducing the service life of the structures and leading to constant costly repairs. Recent research has shown composite materials such as Fibre Reinforced Polymers (FRP) to be suitable alternatives to steel, providing similar strength without being susceptible to electrochemical corrosion. Carbon FRP in particular has great promise for prestressed applications, showing resistance to corrosion in environments that might be encountered in concrete and experiencing less relaxation than steel.
This thesis outlines the testing and implementation of a post-tensioned system that uses CFRP tendons to replace corroded, unbonded post-tensioned steel tendons. This system was then implemented in a parking garage in downtown Toronto. To the author’s knowledge, this is the first example of an unbonded, post-tensioned tendon replacement using FRP tendons. The system used split wedge anchors designed specifically for CFRP tendons at the University of Waterloo. The dead end was anchored by directly bonding the tendon to the concrete slab. Overall, the system was shown to work and provide a durable solution for unbonded post-tensioning systems. The CFRP tendon was successfully inserted in the opening left by the removal of the corroded tendon and stressed. It was found that the current anchorage configuration experienced large load losses of up to 60 % during the transfer. Changing the orientation of the anchor was found to reduce the load lost to a range of 1 % to 9 %.Thesis (Master, Civil Engineering) -- Queen's University, 2009-04-09 15:30:59.865
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王大衡. "Study of the Variation of Natural Frequencies for Post-Tensioned Prestressed Concrete Beams." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/53681839997704299509.
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博士國立臺灣海洋大學
河海工程學系
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Abstract The purpose of this thesis is to understand the variation of natural frquencies for concrete beams subjected to prestressing forces. And this understanding might provide a useful method for applicating to the safety inspection of prestressed concrete structures.The natural frequency of axial-loaded concrete beam would decrease with increasing applied compressive force, and the natural frequency of tensioned cable would increase with increasing tensile force. However, the variation of natural frequency of prestressed concrete beam (PCB) consisting of concrete and cable has rarely been discussed based on both the rigorous mathematic model and experimental results. In this study, a testing program was conducted and Rayleigh’s method was used to derive an approximate equation for computing natural frequency. The results indicate that (1) the natural frequency would decrease with increasing prestressing force for PCB with eccentric parabolic tendon, but would be no change for PCB with eccentric straight tendon, (2) the model based on Rayleigh’s method is proved to be adequate for estimating the first mode natural frequency for PCB, and (3) a modified calculating method for effective moment of inertia is shown to be well to predict the immediate deflections for PCB under non-linear condition.
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WANG, NAN-LONG, and 汪南龍. "Flexural behavior of post-tensioned high strength fly-ash prestressed concrete beams with unbonded tendons." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/80176202839505386196.
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Kurama, Yahya Cüneyt. "Seismic analysis, behavior, and design of unbonded post-tensioned precast concrete walls /." Diss., 1997. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9730301.
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Perez, Felipe de Jesus. "Experimental and analytical lateral load response of unbonded post-tensioned precast concrete walls /." Diss., 2004. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3127533.
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El-Sheikh, Magdy Thabet Mahmound. "Seismic analysis, behavior, and design of unbonded post-tensioned precast concrete frames /." Diss., 1997. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9814956.
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Pape, Torill. "Investigating the correlation between pre- and post-demolition assessments for precast, post-tensioned beams in service for 45 years." Thesis, 2008. http://hdl.handle.net/1959.13/807506.
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Research Doctorate - Doctor of Philosophy (PhD)The Sorell Causeway Bridge, located in Tasmania, Australia, was completed in 1957 and was the first precast, post-tensioned bridge constructed in Australia. However after only 45 years of service, the bridge was replaced due to increasing concerns surrounding the level of corrosion of the prestressing strands in the beams. Prior to its decommission, an extensive and costly investigation program was carried out on the bridge in an attempt to determine the rate of deterioration and establish the remaining margin of safety. Despite the number of investigations and the resulting large quantities of information, the questions surrounding the safety of the bridge remained unanswered. The issue is thus raised: what do field investigations of reinforced or prestressed concrete structures with evidence of corrosion deterioration tell engineers about the actual condition of the structure? Three beams of varying condition (good, average, poor) were salvaged from the bridge demolition for further detailed examination to investigate the degree of correlation between pre-demolition field investigations and the physical condition of the steel post-demolition. The investigations included the use of conventional non-destructive techniques such as cover, half-cell potential and concrete resistivity surveys, and destructive techniques such as chloride profiling, carbonation depth measurement, and full-scale load testing, all of which were used to determine the likely risk of corrosion and likely corrosion rate for each beam. The results of these investigations were subsequently reviewed in relation to the physical condition of the steel. In general, all non-destructive tests were found to be inconclusive in relation to evidence of steel corrosion and the corrosion risk guidelines recommended in the literature. It was also apparent that these techniques were incapable of detecting steel pitting, a primary concern for the current investigation. Chloride profiles were variable and inconsistent in relation to steel corrosion and the chloride thresholds recommended in the literature. Carbonation was found to exist at prestressing levels in some locations and appeared to be influenced by the orientation and geometry of the beams. All beams did not achieve the estimated design capacity and corrosion had significantly impaired the ultimate capacity and ductility of beams in the worst condition. Aerobic and anaerobic corrosion products were identified via XRD analysis. These included Magnetite, Goethite, Akaganeite, Lepidocrocite, chloride based Green Rust (I), and Iron (III) Oxide Chloride. The phenomenon of “chloride weeping”, or droplets of highly acidic ferrous chloride, was observed forming on some steel/concrete interfaces on freshly cut concrete surfaces. Several other unexplainable observations were made during the course of the present investigations. These included bright, metallic pit surfaces; pits with concentric rings; black, wet rust covering bright, metallic surfaces; and unusual pitting profiles. A possible explanation for these observations may be the implication of microbiological activity in the corrosion process. Further research is required to confirm these observations.
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GALES, JOHN. "Transient High-Temperature Prestress Relaxation of Unbonded Prestressing Tendons for use in Concrete Slabs." Thesis, 2009. http://hdl.handle.net/1974/5218.
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Unbonded post-tensioned (UPT) flat plate concrete slabs have seen widespread use in multi-storey office and condominium buildings since the 1960s. The popularity of these systems can be attributed to various economic and structural benefits, including reductions in slab thickness, storey height, building mass, and excellent deflection control over large spans. The “inherent fire resistance” of these systems is often quoted as a key additional benefit as compared with competing structural systems. Such statements are apparently based largely on satisfactory results from large scale standard fire resistance tests performed on UPT slabs during the 1960s and on experience from real fires in UPT buildings. However, much remains unknown about the true structural behaviour of continuous multiple bay UPT slabs in real building fires. For instance, relatively little data exist on the effects of elevated temperature on cold drawn prestressing steel under realistic, sustained service stress levels. The primary objective of this thesis is to provide a greater understanding of the high-temperature performance (predominantly related to prestress relaxation) of prestressing steel used in UPT flat plate slabs. A computational model is developed, extending previous research by others, to predict transient high temperature stress relaxation (i.e., prestress loss) for a tendon in a typical UPT multiple span flat plate concrete slab under transient heating and cooling. The computational model is validated by comparison against a series of novel high temperature experiments on locally-heated, stressed, and restrained prestressing tendons with realistic as-built configurations. Reasonable agreement between measured and predicted prestress losses is observed, although some refinement of the model’s input parameters may be required. Test data also indicate that the most crucial fire scenario on a UPT concrete slab may be localized heating rather than a global, fully developed fire. The model is subsequently used to predict the capacity in flexure and punching shear of a UPT flat plate structure under various spatial and temporal heating regimes. The results highlight the need for particular care in the construction of UPT slabs to ensure adequate, robust concrete cover for structural fire safety.Thesis (Master, Civil Engineering) -- Queen's University, 2009-09-24 18:27:25.559