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1
Davis, Brent M. "Evaluation of prestress losses in an innovative prestressed precast pavement system". Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4516.
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Thesis (M.S.) University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 22, 2007) Includes bibliographical references.
2
Xiang, Ziru. "Synergic identification of prestress and moving forces for prestressed concrete bridges". Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/116900/1/Ziru_Xiang_Thesis.pdf.
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This thesis is a comprehensive study of a synergic identification of prestress and moving forces for prestressed concrete bridges. An innovative synergic identification method is proposed, and validated by the numerical and experimental tests. Results illustrate that both moving/stationary excitation and the prestress force can be estimated accurately and stably for different kinds of bridges.
3
Hodges, Hunter Thomas. "Top Strand Effect and Evaluation of Effective Prestress in Prestressed Concrete Beams". Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/36300.
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The first objective of this thesis was to assess the effect of casting orientation on bond strength in pretensioned prestressed concrete members. The "top strand effect" was evaluated through transfer and development length tests of prestressed concrete beams. Eight beams were cast with normal orientation, while four beams were cast with inverted orientation so that a significant depth of fresh concrete was placed below prestressing strands. Discrete transfer lengths were determined at the ends of each beam by measuring concrete surface strains. Inverted casting orientation caused an average 70 percent increase in transfer length. Some transfer lengths in beams with inverted casting orientation exceed current ACI and AASHTO code provisions. All measured transfer lengths were less than 90 strand diameters (45 in. for 0.5 in. diameter strands). Ranges of development length were determined through iterative load testing. The top strand effect on development length was more qualitative than quantitative. Ranges of development length in normal beams were conservatively less than code provisions. Ranges of development length in beams with inverted casting orientation were much closer to and sometimes exceeded code provisions. It is recommended that ACI and AASHTO code provisions for the development length of prestressing strand be modified to include the same magnification factors that are specified for the development length of deformed bars with twelve or more inches of fresh concrete placed below.
The second objective of this thesis was to compare experimentally measured prestress losses to theoretical calculations. Theoretical prestress losses were calculated according to PCI and AASHTO Refined methods. These methods produced similar results. Prestress losses were experimentally measured by vibrating wire gages and flexural load testing. Vibrating wire gages were used to monitor internal concrete strains. Two methods were used to reduce vibrating wire gage data: an upper/lower bound method and a basic method. The upper/lower bound method produced distorted data that was unreasonable in some cases. The basic method was more reasonable, but resulted in some prestress loss measurements that were greater than theoretical predictions. Flexural load testing was used to back calculate prestress losses from crack initiation and crack reopening loads. Prestress losses measured by crack initiation loads were generally greater than theoretical values. Losses measured by crack reopening loads were distorted. The distortion was attributed to difficulty in isolation of the correct crack reopening load. Large measurements of prestress losses by the basic vibrating wire gage and crack initiation methods suggested that losses occurred between the time when concrete was poured and prestress transfer occurred. Such losses are not accounted for in current code provisions. More research is recommended to determine the magnitude of these additional losses and their effect on design.
Master of Science
4
Hussin, Manal Kamil. "Identification of prestress force in prestressed concrete box girder bridges using ultrasonic technology". Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/117669/8/Manal_Hussin_Thesis.pdf.
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This research was aimed to develop an ultrasonic technology to identify the prestressing force in new and exciting prestressed concrete box girder bridges. The research study included finite element analysis and laboratory testing of a scaled down prestressed concrete box-girder bridge model. New approaches for ultrasonic testing and prestressed force identification were developed and tested successfully.
5
Ali, Hussam A. "Corrosion in prestressed concrete". Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79993.
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There is a need to enhance our understanding of the corrosion mechanisms and their effect on the level and loss of prestressing forces. This research program consisted of accelerated corrosion tests on eight prestressed concrete prisms, measuring 127 x 127 x 2,060 mm, with three different levels of prestress (0, 30, and 60% of the ultimate strength of prestressing strand). The aim of the investigation was to simulate and monitor the corrosion of prestressing strands in prestressed systems. The specimens were submerged in a saline solution and subjected to an impressed constant voltage, aimed at accelerating the corrosion of the strands.During the corrosion period, various electrochemical tests were performed to monitor the corrosion activity as a function of elapsed time. Strains at selected locations were measured regularly to check the instantaneous level of prestress. At the end of the experiment, the prestressing strands were removed from the concrete, visually inspected, and weighed. They were also tested in tension to determine their residual tensile strength and their mode of failure.
An assessment of the electrochemical results did not point to any relationship between the initial levels of prestress and the corrosion activity. A similar observation was made in verifying the effect of the initial level of prestress on the corrosion activity as manifested in the residual tensile strength of the strands or their final measured weights.
This research program was therefore valuable to the practicing engineer in the design and maintenance of durable prestressed concrete structures. The findings confirmed that the risk and extent of corrosion in all prestressing strands in corrosive environments are roughly similar, regardless of the initial prestressing level.
6
Nicklisch, Arndt W. 1975. "Adaptively prestressed concrete structures". Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9144.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2000.Includes bibliographical references (leaves 93-96).
Passive structures react effectively to only one dominant loading condition. Adaptive structures in contrast can deal with multiple loading conditions and unanticipated events at the same time. Truly adaptive civil structures do not exist. Concrete structures can be made adaptive through variable prestressing. Design concepts for an adaptive prestressed concrete girder are formulated in this research. Loading conditions and desired capabilities of the proposed system are defined. The system architecture is composed of sensors, a monitoring and control scheme, and actuators. These system components perform state identification, decision-making, and implementation of actions. Each system component is assigned requirements that are necessary to deal with all loading conditions in an appropriate way. Existing sensor technologies are explained and evaluated with respect to their capabilities to fulfill their functional requirements. A monitoring scheme is designed to interpret data assessed by the sensors for state identification. Adaptive control systems cannot be designed with conventional control algorithms. New control decision systems such as neural nets, expert systems, and fuzzy logic systems are needed for this task. Here, these systems are presented in general as forms of adaptive control. For each loading condition of the proposed system, a control strategy is developed. For the control of fluctuating live loads, a fuzzy logic based control scheme is proposed. Criteria for the selection of actuator technologies are given, and candidate actuator technologies are described and evaluated. Lastly, the problems associated with integrating the system components into a single system are discussed.
by Arndt W. Nicklisch.
S.M.
7
Pathirage, Thisara Shamane. "Identification of prestress force in prestressed concrete box girder bridges using vibration based techniques". Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/112767/1/Thisara%20Shamane_Pathirage_Thesis.pdf.
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This research was aimed to develop a new vibration based non-destructive method to identify the effective prestress force in prestressed concrete box girder bridges. The research study included theoretical development, finite element analysis and laboratory testing of a scaled down box girder bridge model. A new approaches for vibration analysis of box girder bridge decks and prestress force identification were developed and tested successfully.
8
Huthman, Ibrahim O. "3D Printing for Prestressed Concrete". Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1483544593929285.
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9
Umakanthan, Saravanan. "Mechanics of prestressed and inhomogeneous bodies". Texas A&M University, 2005. http://hdl.handle.net/1969.1/4241.
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In finite elasticity, while developing representation for stress, it is customary to require
the reference configuration to be stress free. This study relaxes this requirement
and develops representations for stress from a stressed reference configuration. Using
the fact that the value of Cauchy stress in the current configuration is independent of
the choice of the reference configuration, even though the formula used to compute
it depends on the choice of the reference configuration, the sought representation is
obtained. It is then assumed that there exists a piecewise smooth mapping between
a configuration with prestresses and a configuration that is stress free, and the representation
obtained above is used to study the mechanical response of prestressed
bodies. The prestress fields are obtained by directly integrating the balance of linear
momentum along with the traction free boundary condition. Then, different classes
of boundary value problems for the type of inhomogeneous and prestressed bodies of
interest are formulated and studied. For the cases studied, it is found that even the
global measures like axial-load required to engender a given stretch ratio for a prestressed
body vary from the homogeneous stress free bodies, though not significantly.
The local measures - stress and deformation - in a prestressed body differ considerably
from their homogeneous stress free counterparts. The above gained knowledge is applied
to understand the mechanics of circumflex arteries obtained from normotensive and hypertensive micro-mini pigs. It is found that the deformation of these arteries
when subjected to inflation and axial extension is not of the form r = r(R), õ =
ã, z = Z. Comparison is also made between the response of an artery at various
levels of smooth muscle activation and stretch ratio as well as normotensive and
hypertensive specimens, using statistical methods.
10
Matthews, Debra Sue. "Blast effects on prestressed concrete bridges". Online access for everyone, 2008. http://www.dissertations.wsu.edu/Thesis/Summer2008/D_Matthews_072908.pdf.
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11
Wang, Zhongsheng. "VIbration behaviour of prestressed concrete beams". Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420369.
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12
Carroll, B. C. "Behaviour of prestressed grout bond joints". Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/38255.
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13
Sivanendran, Shobana. "CFRP prestressed concrete exposed to moisture". Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/270196.
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In environments of high moisture exposure, carbon fibre-reinforced polymer (CFRP) reinforcement is believed to be a good alternative to steel due to its non-corrosive properties. However the CFRP matrix experiences other types of changes, mechanical deterioration and transverse swelling, with exposure to moisture and sustained stresses. Specifically for structural applications, few studies have investigated the effects of moisture and stress-induced matrix-dominated changes to the CFRP-concrete bond when the CFRP rods are cast into concrete as prestressed reinforcement. Experiments were conducted to measure the transverse swelling and moisture uptake rates of stressed and unstressed CFRP rods immersed in water and concrete pore solution (CPS). CFRP rods were also embedded in concrete and immersed in water to observe whether the transverse swelling of the rods would cause the concrete to crack. Pull-out tests were conducted on stressed and unstressed CFRP rods cast in concrete cubes and immersed in water for up to 125 days. Six CFRP prestressed concrete prisms were fabricated, three were immersed in water for over 125 days and three were left in lab conditions before being tested in three-point bending. Moisture-induced transverse swelling did not appear to cause cracking of the concrete covering CFRP rods in water, contrary to the prediction of the thick-walled cylinder model, but possibly caused an increase in the CFRP-concrete radial contact pressure. The imposition of sustained bending stresses on wet CFRP rods was found to cause premature failure, believed to be a result of matrix softening and microcracking. These observations of swelling and matrix degradation were believed to affect the CFRP-concrete bond. The pull-out tests of unstressed CFRP rods indicated an increased likelihood for bond failure in the CFRP matrix with moisture exposure. This resulted in greater variations in the ultimate and residual bond stresses of the wet samples compared to the dry controls. For the prestressed pull-out samples, higher magnitudes of prestressing resulted in lower bond failure loads. Both outcomes are indicative of matrix weakening with moisture and stress exposure. However despite this, the three-point bending tests revealed no significant differences in behaviour between the wet and dry prestressed prisms. Although the wet prisms exhibited slightly greater variation in their post peak load behaviour compared to the dry prisms, in line with the observations from the pull-out tests. The work from this thesis reveals that despite observations of matrix deterioration and transverse swelling in CFRP rods exposed to moisture and stress, the effect of these changes to the overall behaviour of a CFRP prestressed concrete member are minimal. Any long-term effects are unlikely to cause significant changes to the behaviour of the member. However, the CFRP-concrete bond may be more variable in members exposed to moisture, which should be allowed for in the design process. Therefore CFRP is a promising alternative to steel reinforcement in high moisture environments, with good long-term durability.
14
Ruiz, Meléndez Sergio 1974. "Dynamics of prestressed concrete railway bridges". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/84298.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2001.Includes bibliographical references (leaves 80-81).
by Sergio Ruiz Meléndez.
M.Eng.
15
Zafer, Algahtani Nabeel Al. "Pocket-type prestressed brickwork retaining walls". Thesis, University of Edinburgh, 1992. http://hdl.handle.net/1842/11666.
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This thesis presents the results of a study into the behaviour of post-tensioned pocket type brickwork retaining walls. An analytical and experimental study was carried out to examine the behaviour of the wall up to failure. The programme of work considered the effect of the following parameters on the perfromance of the wall: (i) vertical concentrated eccentric load; (ii) percentage area of steel; (iii) pocket spacing and wall slenderness; (iv) type of wall bond. The results of the analyses were compared with those based on the Code of Practice, B.S 5628, Part 2, 1985. A computer program was written in Fortran to predict the ultimate moment of the wall panels, using predicted equilibrium equations. Good agreement was found between the theoretical and experimental results. The results show that post-tensioned pocket type brickwork retaining walls have a large nominal strength, largely due to the presence of prestressing forces and the behaviour of the walls as homogenous cantilevers. The most effective pocket spacing was found to be h/3, and the maximum spacing should be limited to give an aspect ratio which is greater than 1.15. The study confirms the applicability of prestressed brick masonry for structures such as slabs and retaining walls irrespective of the type of brickwork bond.
16
Lai, Hoke Sai. "Partially prestressed concrete internal square panel". Thesis, University of Leeds, 1986. http://etheses.whiterose.ac.uk/301/.
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This work is concerned with the general behaviour of an internal panel in a column supported multi-bay floor structure, under the influence of various prestressing tendon arrangements. The prestressing effects are studied with the help of a finite element package (PAFEC), representing the prestressing forces by equivalent vertical loads. From a variety of possible spacing arrangements, the distribution of prestressing moments is shown to be most effective in counteracting the moments due to externally imposed load when the tendons are narrowly banded in the column vicinity. The effects of tendon arrangement on slab behaviour are further investigated by means of an experimental programme comprising three series of ten tests of 1.5m span partially prestressed panel with typical span to depth ratio, levels of loading, levels of prestress and geometry of tendon profiles. The models were fixed along the edges to simulate the continuity of an internal panel in a multi-panel slab system. Post-tensioned tendons were arranged in various patterns, as currently employed in construction practice, to induce either a medium or a low level of prestress in the test panel, conforming to the design recommendations of a number of codes of practice. Test results indicated that the serviceability behaviour of the slabs with a low level of prestress was strongly influenced by the tendon distribution and the amount of non-prestressed reinforcement. Slabs with tendons banded closely in the column area exhibited a higher cracking load and were stiffer after cracking. The flexural strength of the test slabs was found to be greater than that predicted by yield line theory and the increase was attributed to membrane action. The experimental values of tendon stress at ultimate load and of punching shear were compared with those obtained by various design methods.
17
Angomas, Franklin B. "Behavior of Prestressed Concrete Bridge Girders". DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/405.
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For this research, prestress losses were monitored in six HPC bridge girders. These measured losses were compared to predicted losses according to four sources. Prestress loss predictive methods considered for this research were: 1- AASHTO LRFD 2004, 2- AASHTO LRFD 2004 Refined, 3- AASHTO LRFD 2007, and 4- AASHTO LRFD Lump Sum method. On the other hand, the camber prediction methods used in the present research were: 1- Time dependent method described in NCHRP Report 496, 2- PCI multiplier method, and 3- Improved PCI Multiplier method. For the purpose of this research, long-term prestress losses were monitored in select girders from Bridge 669 located near Farmington, Utah. Bridge 669 is a three-span prestress concrete girder bridge. The three spans have lengths of 132.2, 108.5, and 82.2 feet long, respectively. Eleven AASHTO Type VI precast prestressed girders were used to support the deck in each span. The deflection of several girders from a three-span, prestressed, precast concrete girder bridge was monitored for 3 years. Fifteen bridge girders were fabricated for the three span-bridge. Ten girders from the exterior spans had span length of 80 feet, and five girders from the middle span had span length of 137 feet. From the results of this research, in both the 82- and 132-foot-long, the AASHTO LRFD 2004 Refined Method does a better job predicting the prestress loss and it can be concluded that all the prediction methods do a better job predicting the loss for the larger girders. The Lump Sum method predicted very accurately the long term prestress loss for the 132-foot-long girders.
18
Muller, John Francis. "Serviceability of prestressed concrete railway sleepers". Thesis, Queensland University of Technology, 1985. https://eprints.qut.edu.au/36475/1/36475_Muller_1985.pdf.
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In 1984, prestressed concrete members of a left hand, trial 1 in
16 concrete sleepered turnout were subjected to strain gauge
measurements under coal traffic in Central Queensland. However,
the results were inadequate to permit finalisation of standards
for sleepers generally. Consequently, strain gauges were
installed across the entire rail seat cross-sections of eight
standard sleepers in 1985 to ascertain the effects of artificially
produced rail defects on prestressed concrete sleeper performance
under coal traffic conditions. This operation was carried out
in 1985 and the results analysed by the author in conjunction
with finite element analyses of a sleeper model using the SAP IV
programme available at the Queensland Institute of Technology
Computer Centre, Brisbane. Both field strain results and finite
element analyses indicated clearly that distributions of strains
and stresses are nonlinear across the rail seat cross-section.
Whilst simple bending theory has normally been used for sleeper
analysis, caution is required due to the increasing stress
gradients towards the outer fibres both top and bottom. Criteria
for design of prestressed concrete sleepers for traffic speeds
below 100 km/h have now been able to be finalised. Other
aspects such as bond development of prestressing tendons, dynamic
test performance under accelerated load testing and track buckling
considerations are encompassed. Special sleeper types are
also discussed.
19
Lindley, Seth Michael. "Investigation of the Time-Dependent Longitudinal Flexural Behavior of the Varina-Enon Bridge". Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/92799.
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Post-tensioned concrete is a building technology which provides a compressive force to concrete via steel tendons. This combination of steel and concrete allows for the construction of lighter and stiffer structures. Post-tensioned concrete is widely utilized throughout the United States highway system and bridge construction. Over time, the force in the prestressing strands is reduced by delayed strains in the concrete. The accurate estimation of this prestress loss is vital for making good decisions about the remaining capacity of a structure and the infrastructure system at large.
The Varina-Enon Bridge is a post-tensioned concrete box-girder bridge in Richmond Virginia. Cracks in the bridge prompted an investigation into the magnitude of prestress loss experienced by the structure. To estimate prestress loss, a computer model of the structure was created. In addition, data from sensors previously installed on the bridge were used to back calculate prestress loss.
It was found that the estimation of losses from the field closely matched those estimated at the construction of the bridge. Additionally, more updated loss models estimated similar, or slightly smaller values for prestress loss.Master of Science
Post-tensioned concrete is a building technology which provides a compressive force to concrete via steel tendons. This combination of steel and concrete allows for the construction of lighter and stiffer structures. Post-tensioned concrete is widely utilized throughout the United States highway system and bridge construction. Over time, the force in the prestressing strands is reduced by delayed strains in the concrete. The accurate estimation of this prestress loss is vital for making good decisions about the remaining capacity of a structure and the infrastructure system at large. The Varina-Enon Bridge is a post-tensioned concrete box-girder bridge in Richmond Virginia. Cracks in the bridge prompted an investigation into the magnitude of prestress loss experienced by the structure. To estimate prestress loss, a computer model of the structure was created. In addition, data from sensors previously installed on the bridge were used to back calculate prestress loss. It was found that the estimation of losses from the field closely matched those estimated at the construction of the bridge. Additionally, more updated loss models estimated similar, or slightly smaller values for prestress loss.
20
Nassar, Adil J. "Investigation of Transfer Length, Development Length, Flexural Strength and Prestress Loss Trend in Fully Bonded High Strength Lightweight Prestressed Girders". Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/32941.
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Encouraged by the performance of high performance normal weight composite girders, Virginia Department of Transportation has sought to exploit the use of high strength lightweight composite concrete (HSLWC) girders to achieve economies brought about by the reduction of dead loads in bridges. Transfer Length measurements conducted on two AASHTO Type IV HSLWC prestressed girders, resulted in an average transfer length of 17 inches, well below the AASHTO and ACI guidance.
Two girders composed of HSLWC AASHTO Type II girders and a 48" x 8" normal weight 4000-psi concrete deck were produced. The HSLWC Type II girders were cast of concretes with a compressive strength of 6380 psi and unit weight of 114 pcf. Full scale testing of the girders was conducted to evaluate development length and flexural strength in HSLWC composite girders. Embedment lengths of five, six and eight feet were evaluated. Tests indicated a development length of about 72 inches, marginally below the ACI and AASHTO stipulation. Four of eight strands in the girders showed general bond failure nevertheless, the tested girders exceeded their theoretical flexural capacity by 24 to 30 percent.
A third composite girder was cast of a high strength normal weight concrete (HSNWC) Type II girder, and topped with a 48" x 8" normal weight 4000-psi concrete deck. This girder was intended as a control specimen to contrast its test results with the HSLWC composite girders. The targeted compressive strength of both the HSLWC and HSNWC AASHTO beams was 8000 psi. The compressive strength of the HSNWC mixture, however, was about 8990 psi compared to 6380 psi for the HSLWC mixture.
Prestress losses in HSLWC AASHTO Type IV girders monitored over a nine-month period were found to be less than those calculated using the ACI and PCI models. Furthermore, the ACI model indicated that the effective prestressess retained in the HSLWC girders in 30 year's time are greater than 50% of the specified tensile strength of the strands.Master of Science
21
Osborn, Parry. "Ultimate Shear Capacity and Residual Prestress Force of Full-Scale, Forty-One-Year-Old Prestressed-Concrete Girders". DigitalCommons@USU, 2010. https://digitalcommons.usu.edu/etd/591.
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The ultimate shear capacity of prestressed concrete beams is difficult to predict accurately, especially after being in service for an extended period of time. The Utah Department of Transportation asked researchers at Utah State University to experimentally determine the existing shear capacity of 41-year-old prestressed, decommissioned concrete bridge girders and then provide recommendations on how to increase that ultimate shear capacity. This thesis presents the research findings that relate to the existing shear capacity of the prestressed concrete girders. Eight AASHTO Type II bridge girders were tested up to failure by applying external loads near the supports to determine their ultimate shear capacities. The measured results were then compared to calculated values obtained using the AASHTO LRFD bridge design code, and the ACI 318-08 design code. Prestress losses were also measured by means of a cracking test and then compared to values calculated according to the AASHTO prestress loss equations. Both the ultimate shear capacities and the residual prestress forces were used to evaluate the girders after being in service for more than 40 years.
22
Xu, Jiangong Barnes Robert W. "Nondestructive evaluation of prestressed concrete structures by means of acoustic emissions monitoring". Auburn, Ala, 2008. http://hdl.handle.net/10415/1429.
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23
Tso, Karmen. "Full-range behaviour of concrete beams partially prestressed with unbonded tendons". Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B38225578.
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Gosaye, Fida Kaba Jonathan. "Behaviour and design of prestressed steel structures". Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/34395.
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The behaviour and design of prestressed steel structures, with an emphasis on trussed arches, are examined in this thesis. For long-span structural systems, where self-weight becomes an increasingly dominant component of the design loading, significant material savings can be achieved through the use of high tensile strength steel cables in conjunction with conventional steelwork. Further benefits can be achieved by prestressing the cables. In the system currently being investigated, the prestressed cables, which are housed within the bottom chord of tubular arched trusses, apply a compressive force to the chord members, which is opposite in nature to the resultant forces arising from the externally applied gravity loads. The stability of the trussed elements under prestress and the load--deformation response of the prestressed elements to the subsequent application of tensile loading are examined analytically, numerically and experimentally, with good correlation achieved between the three approaches. The benefits of prestressing, in terms of increased member strength and stiffness, are demonstrated, and optimal prestress levels are investigated. In instances of load reversal (e.g. due to wind uplift) in trusses without horizontal end anchorage that would allow catenary forces to develop, the presence of prestress can become detrimental. To examine this, a total of eight pin-ended cable-in-tube systems, featuring both non-grouted and grouted members, were tested in compression. Increasing initial prestress levels was found to reduce the capacity of the system in compression, but initial prestress was shown to be less detrimental than externally applied compressive loading of the same magnitude, due to the absence of second order bending moments. Finite element models were developed and, following accurate replication of test results, were used to generate parametric results for a range of member slendernesses and prestress levels. The test and FE results were compared against capacity predictions based on a proposed modified Perry-Robertson design method. Consistent, accurate and generally safe-side predictions were achieved. Following the examination of behaviour of individual prestressed elements within the truss, a series of analytical and numerical models of the full arched truss system were developed to investigate its global structural behaviour. Parametric studies revealed that the horizontal end boundary conditions, prestress level, truss depth and diagonal member arrangements were the key parameters influencing the stiffness, load bearing capacity and failure mode of the structure.
25
El, Metwally Ahmed Salah. "Prestressed composite girders with corrugated steel webs". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0006/MQ38626.pdf.
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26
Elfergani, Hisham. "Acoustic emission analysis of prestressed concrete structures". Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/49383/.
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This thesis examines the role of Acoustic Emission (AE) as a non-destructive testing (NDT) technique for prestressed and reinforced concrete structures. The work focuses on the development of experimental techniques and data analysis methods for the detection, location and assessment of AE from prestressed and reinforced concrete specimens. This thesis reveals that AE can be used to detect the onset of corrosion activity in wire in the interface between prestressed concrete and mortar as found in prestressed concrete pipes. Furthermore, this technique can be used to locate the corrosion activity on different size prestressed concrete samples. By correlation between three parameters of classical AE analysis techniques (traditional parameters), damage can be detected and located whilst the corrosion area, macro crack and crack propagation can be identified. However, it cannot classify the crack type. Different damage modes, including corrosion activity, micro/macro cracking formation, crack propagation and wire failure generate different types of AE signals with varying amplitudes and absolute energy emitted. A novel analysis approach has been used on composite materials (concrete, mortar and steel) to evaluate differing crack types by a combination of the classical acoustic emission analysis technique and advanced analysis Rise time / Amplitude (RA) and Average Frequency (AF), results proved the effectiveness of the developed techniques for damage detection and classification crack types. The relationship between RA value and AF value can be used to determine the crack area and classify it as either tensile crack type, other type (shear movement) or no crack. The results of the research have demonstrated that the AE technique is valid in larger scale monitoring and hence the potential for monitoring real structures such as prestressed concrete pipes. Use of Kernel Density Estimation Function (KDEF) provides improved visualisation of the data to represent clearly the RA/AF values. Key Words: Acoustic Emission, Corrosion, Reinforced Concrete, Prestressed Concrete, Micro and Macro Concrete Cracks, Crack classification, Source Location, Damage Assessment, Monitoring.
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Chan, Andrew Kay Ching. "Impact behaviour of model prestressed concrete beams". Thesis, University of Sheffield, 1986. http://etheses.whiterose.ac.uk/3484/.
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This research work investigates the impact behaviour of prestressed concrete beams. A total number of forty 1000 mm long model beams with a rectangular section of 44 x 65 mm were cast. The beams were divided into four with ten beams in each series. Each beam was prestressed by four 1.6 mm diameter piano vire3 and the shear reinforcement va3 varied from series to series. The test rig available was modified so that the beam could have pin-end supports with a span of 600 mm and a static or impact load could be applied at the midspan. A total number of 40 static tests (8 static and 32 post-impact-static) and 32 impact tests were performed. The static load was applied by a screw jack via a one meter long steel pressure bar. The impact load was produced by the impact of a 350 mm steel cylinder projected at velocities of 4 to 17 m/s by compressed air onto the same pressure bar. In each impact test, the impact force-time history was recorded by the electrical resistance foil strain gauges attached on the pressure bar. The transient deflections at various positions along the span were measured by linear variable differential transducers and the reaction was measured by aluminium load cells on which electrical resistance strain gauges were fixed. A dynamic plastic model proposed by Ezra(90) was developed and applied in conjunction 'with the one-degree of freedom system to evaluate the maximum dynamic midspan deflection, reactions, energy absorption capacity and the initial impact beam velocity. A comparison was made between the predicted and the experimental results.
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Roumani, N. A. "The shear strength of prestressed brickwork sections". Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374836.
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Buchner, Susanne. "Full scale testing of prestressed concrete structures". Thesis, University of Surrey, 1989. http://epubs.surrey.ac.uk/804425/.
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Montague, T. I. "Concrete blockwork diaphragm walls - prestressed and unprestressed". Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293672.
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ARAUJO, RICARDO RODRIGUES DE. "STRUCTURAL BEHAVIOUR OF PRESTRESSED STAYED STEEL COLUMNS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=31841@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE EXCELENCIA ACADEMICA
Colunas de aço estaiadas e protendidas são conhecidas como excelente solução em escoramento de grandes estruturas, como colunas de coberturas de lonas tensionadas, etc. Este trabalho apresenta uma série de ensaios experimentais tridimensionais em escala real desenvolvidos para determinação do comportamento estrutural de colunas de aço estaiadas e protendidas. Foram estudadas as variações no nível de protensão e na rigidez dos estais, além de descrever como os ensaios experimentais das três colunas de aço estaiadas são realizados: compreendendo os materiais utilizados; um novo sistema de medição de força nos estais; os passos e dificuldades na montagem das três colunas e o sistema de protensão aplicado. Existem alguns parâmetros que influenciam diretamente na resistência dessas colunas estaiadas, como por exemplo, a altura da coluna, o diâmetro externo, entre outros. Devido ao comportamento complexo deste tipo de colunas e ao grande esforço computacional para simulação do comportamento estrutural, através de uma análise paramétrica, optou-se por utilizar um projeto de experimentos junto com redes neurais a fim de extrapolar e obter novos resultados para carga crítica do sistema estrutural sem a necessidade de análise por programas de elementos finitos. De forma a complementar a tese, realizou-se um estudo do comportamento do sistema estrutural sujeito a ações dinâmicas através do programa de elementos finitos ANSYS com o objetivo de determinar as frequências naturais associadas aos seus modos de vibração. Também foi estudada a aplicação de um carregamento súbito para determinação do fator de amplificação dinâmico da coluna de aço estaiada e protendida.
Prestressed steel columns are known as an efficient structural solution for great variety of temporary or permanent supporting systems for large span spatial frames and tensile surface structures. This work presents of full-scale three-dimensional tests carriedout for the assessment of structural behaviour of prestressed stayed steel columns. It was studied the effect prestress force level, stiffness of column braces and stays. Test setup and a new force measuring system for the column stays is fully described. Prestressed stayed steel columns have their strength dependant of parameters like: length, hollow section diameter, brace length and stiffness and axial stiffness of stays. Due to the complex behaviour of such columns that demands great computational effort for numerical simulations required for a parametric analysis it was used an experiment design tool coupled with neural network techniques employed to generate new data for the prestressed column buckling load. A study of the dynamic behaviour of prestressed columns using the finite element package ANSYS was carried-out in order to determine the column natural frequencies and their associated vibration modes. It was also studied the application of sudden loads to determine the dynamic amplification factor of this type of prestressed stayed steel column.
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IUNES, YVELYNE BIANCA FERREIRA. "OPTIMUM TENDON PROFILES IN PRESTRESSED CONCRETE BEAMS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1998. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1402@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORUNIVERSIDADE FEDERAL DO PARÁ
O presente trabalho contém a formulação, implementação e teste de um modelo para determinação do traçado ótimo de cabos de protensão, bem como do valor da força de protensão mínima correspondente, em vigas isotáticas e hiperestáticas. Na formulação, será considerado que o cabo de protensão possui um desenvolvimento segmentado em parábolas do segundo grau, onde o comprimento dessas parábolas serão pré- estabelecidos. Serão feitas ainda simplificações em relação à força de protensão e às perdas de protensão. Com a introdução de tais simplificações e com um artifício de mudança de variáveis, estaremos diante de um problema de programação linear, onde as incógnitas do problema serão a força de protensão e os coeficientes dos trechos de parábolas que representam a geometria do cabo. O objetivo desse problema de programação linear, será minimizar o custo da protensão, de forma que algumas restrições, previamente estabelecidas, sejam atendidas. Tais restrições, limitarão a geometria do cabo, uma vez que o mesmo deve ser contínuo, representado por curvas suaves, e estar contido dentro da viga, e limitarão as tensões nos bordos extremos da viga de forma que as Normas Brasileiras NBR 8681, NBR 7197 e NBR 7187 sejam atendidas. Serão considerados diversos casos de carga e as seções de estudo serão pré-definidas. Como resultado do projeto teremos o traçado ótimo de um cabo médio, e a força de protensão mínima P0, onde já estarão incluídas as perdas imediatas. A implementação da formulação foi desenvolvida em linguagem C, padrão ANSI, o que garante que o mesmo código possa ser compilado em computadores diferentes e por compiladores diferentes, facilitando a portabilidade do programa. Para a otimização, foi utilizado o programa comercial LINDO- Linear Interactive and Discrete Optimizer, que permite uma interação com o usuário, é prático e de grande eficiência. Serão testados e analisados quatro exemplos, variando em sua complexidade. Das quatro vigas testadas, uma foi apresentada por Calçada (1993) em seu artigo "Traçado Óptimo de Cabos de Pré-esforço em Pórticos", e as outras três foram projetadas por engenheiros em escritórios de cálculo estrutural. As duas soluções de projeto, a dada pelo programa e a obtida pelos escritórios, são comparadas de modo a validar tanto a formulação como o programa implementado.
This work is concerned with the formulation, implementation and test of a model for determination of the minimum prestressing force and the optimum tendon profile, to prestressed isostatics and hiperestatics beams. It will be considered in formulation, that the prestressing cable has a development segmented in second grade parabolas, in which the length of each one will be predetermined. In addition, simplifications will be considered with regard to the prestressing force and the prestressing losses. With these assumptions and an artifice of variables change, linear programming problem will be obtained, where the variables will be the prestressing force and the parabolas coefficients that represent the cable geometry. The objective of this linear programming problem will be to minimize the prestressing cost, based on some constraints. These constraints will limit the cable geometry, since this one has to be continue, represented for smooth curves and to be inside of the beam, and will limit the stresses at the top and at the bottom fibers of each studied sections according to Brazilian Codes NBR 8681, NBR 7197 e NBR 7187. Different loads cases will be considered and the studied sections will be predetermined. As project result, we will have an optimum tendon medium profile and the minimum prestressing force P0, where the immediate losses will be included. The formulation implementation was developed in "C" language, ANSI standard, which guarantees that the same code can be compiled in different computers and for different compilers, making the program portability easy. For optimization, the commercial program LINDO- Linear Interactive and Discrete Optimizer was used, which allows interaction with the user, is practical and very efficient. Four examples with different complexity will be tested and studied. From four beams tested, one was presented by Calçada (1993) in his paper "Traçado Óptimo de Cabos de Pré-esforço em Pórticos", and the other ones were designed by engineers in structural design offices. The two design solutions, the one given by the program and the other obtained by the offices, are compared in order to validate both the formulation and the program implemented.
El presente trabajo contiene la formulación, implementación y pruebas de un modelo para determinación del trazado ótimo de cables de protensión, bien como del valor de la fuerza de protensión mínima correspondiente, en vigas isotáticas y hiperestáticas. En la formulación, será considerado que el cable de protensión posee un desarrollo segmentado en parábolas de segundo grado, de dimensiones prestablecidas. Se considerarán simplificaciones en relación a la fuerza de protensión y a las pérdidas de protensión. Con la introducción de tales simplificaciones y con un artificio de cambio de variables, estaremos frente a un problema de programación lineal, donde las incógnitas del problema serán la fuerza de protensión y los coeficientes de los intervalos de parábolas que representan la geometría del cable. El objetivo de este problema de programación lineal será minimizar el costo de la protensión, de forma que sean atendidas algunas restricciones, previamente establecidas. Tales restricciones, limitarán la geometría del cable, que debe ser contínuo, representado por curvas suaves, y estar contenido dentro de la viga; y limitarán las tensiones en los bordes extremos de la viga para atender las Normas Brasileiras MBR 8681, MBR 7197 y MBR 7187. Se considerarán diversos casos de carga y las secciones de estudio serán predefinidas. Como resultado del proyecto tendremos el trazado óptimo de un cable medio y la fuerza de protensión mínima P0, donde estarán incluidas las pérdidas inmediatas. La implementación fue desarrollada en lenguaje C, padrón ANSI, que garantiza que el mismo código pueda ser compilado en computadores diferentes y por compiladores diferentes, facilitando la portabilidad del programa. Para la optimización, fue utilizado el programa comercial LINDO - Lineal Interactive and Discrete Optimizer, que permite una interacción con el usuario, es práctico y de gran eficiencia. Se analizaron cuatro ejemplos, variando su complejidad. De las cuatro vigas, una fue presentada por Calzada (1993) en su artículo "Trazado Ótimo de Cabos de Pré-esforzo en Pórticos", y las otras tres fueron projectadas por ingenieros de cálculo extructural. Las dos soluciones del proyecto, la dada por el programa y la obtenida por los ingenieros, son comparadas para evaluar la formulación del modelo y la implemantación del programa.
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Gomez, Nicolas M. Eng Massachusetts Institute of Technology. "Design of prestressed, fabric-formed concrete beams". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111507.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 60-62).
Fabric forms and prestressing are both technologies for concrete structures that allow for less material to do more work. This thesis seeks to assess the feasibility and performance of fabric formed, prestressed beams with a keyhole cross-section, while varying parameters such as concrete strength, loading, beam depth, and prestressing force. They are designed for flexure via a sectional method, starting with the critical midspan section, and each section is iterated in an effort to minimize the beam weight. Beam strength and deflections are determined and once met, they are compared to more traditional prestress designs. Such beams are found to be governed primarily by strength criteria, as deflections are found to be minimal. These fabric formed beams can use nearly an identical amount of material as conventional I-beams with a constant cross-section, while requiring a higher prestressing force. Prestressed fabric formed beams are less efficient than an I-beam section, but should not be discounted as a viable element, because of their aesthetic appeal and further potential for optimization.
by Nicolas Gomez.
M. Eng.
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Lobato, de Sousa Monteiro de Morais Miguel Nuno. "Ductility of beams prestressed with FRP tendons". Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614171.
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Brand, W. W. (Willem Wouter). "Reliability assessment of a prestressed concrete member". Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52430.
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Thesis (MScEng)--University of Stellenbosch, 2001.ENGLISH ABSTRACT: First-order second-moment structural reliability methods are used to assess the reliability of a prestressed concrete beam. This beam was designed for imposed office floor loads and partitions following the limit states design method as provided for by the applicable South African structural codes, viz SABS 0100-1:1992 and SABS 0160:1989. The reliability is examined at two limit states. At the ultimate limit state of flexure the ultimate moment of resistance must exceed the applied external moment at the critical section, while at the serviceability limit state of deflection the deflection must satisfy the codespecified deflection criteria. Realistic theoretical models are selected to express the flexural strength and deflection of the prestressed concrete member, while appropriate probabilistic models are gathered from the literature for loading, resistance and modelling uncertainties. The calculated reliability index at the ultimate limit state of flexure (3.10) is lower than expected in view of the fact that this represents a non-critical limit state in the case of a Class 2 prestressed concrete member. This condition can be explained with reference to the relatively high uncertainty associated with the modelling error for flexural strength. The calculated reliability index at the serviceability limit state of deflection (l.67) compares well with acceptable practice. The study further focuses on the sensitivity of the reliability at the two limit states of interest to uncertainty in the various design parameters. The ultimate limit state of flexure is dominated by the uncertainty associated with the modelling error for flexural strength, while the contribution to the overall uncertainty of the ultimate strength and area of the prestressing steel and the effective depth is less significant. In comparison the reliability at the serviceability limit state of deflection is not dominated by the uncertainty associated with a single basic variable. Instead, the uncertainty associated with the modelling error, creep factor and prestress loss factor are all significant. It was also demonstrated that the variability in beam stiffness is not a major source of uncertainty in the case of a Class 2 prestressed concrete member. It is recommended that the present code provisions for ultimate strength and deflection should be reviewed to formulate theoretical models with reduced systematic and random errors. The effect of the uncertainty associated with the creep and prestressed loss factors should also be adressed by adjustment of the partial material factor for concrete at the serviceability limit state of deflection. Furthermore, research must be directed towards formulating an objective failure criterion for deflection. The uncertainty in the deflection limit must therefore be quantified with a probability distribution.
AFRIKAANSE OPSOMMING: Eerste-orde tweede-moment struktuur betroubaarheid metodes word ingespan om die betroubaarheid van 'n voorspanbeton balk te bereken. Hierdie balk is ontwerp vir opgelegte kantoor vloerbelasting en partisies volgens die grenstoestand ontwerp metode soos beskryf in die toepaslike Suid-Afrikaanse boukodes, naamlik SABS 0100-1: 1992 en SABS 0160: 1989. Die betroubaarheid word ondersoek by twee grenstoestande. By die swiglimiet van buiging moet die weerstandsmoment die eksterne aangewende moment oorskrei by die kritieke balksnit, terwyl die defleksie die kriteria soos voorgeskryf deur die kode moet bevredig by die dienslimiet van defleksie. Realistiese teoretiese modelle word gebruik om die buigsterkte en defleksie van die voorspanbeton balk te bereken. Verder is geskikte waarskynlikheid modelle uit die literatuur versamelom die belasting, weerstand en modelonsekerhede te karakteriseer. Die betroubaarheid indeks soos bereken vir die swiglimiet van buiging (3.10) is laer as wat verwag sou word in die lig van die feit dat hierdie nie 'n kritieke grenstoestand verteenwoordig in die geval van 'n Klas 2 voorspan element nie. Dit kan verklaar word met verwysing na die relatiewe groot onsekerheid wat geassosieer word met die modellering fout vir buigsterkte. Die berekende betroubaarheid indeks vir die dienslimiet van defleksie (1.67) vergelyk goed met aanvaarde praktyk. Die studie fokus verder op die sensitiwiteit van die betroubaarheid by die twee grenstoestande onder beskouing ten opsigte van die onsekerheid in die verskillende ontwerp parameters. By die swiglimiet van buiging word die onsekerheid oorheers deur die bydrae van die modelering fout vir buigsterkte. Die bydraes tot die totale onsekerheid deur die swigsterkte en area van die voorspanstaal sowel as die effektiewe diepte is minder belangrik. By die dienslimiet van defleksie word die betroubaarheid nie oorheers deur die onsekerheid van 'n enkele basiese veranderlike nie. In stede hiervan is die onsekerheid van die modellerings fout, kruipfaktor en voorspan verliesfaktor almal noemenswaardig. Daar word verder aangetoon dat die veranderlikheid in balkstyfheid nie 'n belangrike bron van onsekerheid in die geval van 'n Klas 2 voorspan element is nie. Daar word aanbeveel dat die bestaande voorskrifte in die kode vir buigsterkte en defleksie aangespreek moet word deur teoretiese modelle met klein modelonsekerhede te formuleer. Die uitwerking van die onsekerheid van die kruip- en voorspan verliesfaktore kan aangespreek word deur 'n aanpassing te maak in die parsiële materiaalfaktor vir beton in die geval van die dienslimiet van defleksie. Navorsing moet verder daarop gemik wees om 'n objektiewe falingskriterium vir defleksie te formuleer. Die onsekerheid van die toelaatbare defleksie moet dus gekwatifiseer word deur 'n waarskynlikheidsverdeling.
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Ibell, Timothy. "Behaviour of anchorage zones for prestressed concrete". Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259477.
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Ozel, Alperen. "Seismic Design of a Prestressed Concrete Bridge". ScholarWorks@UNO, 2016. http://scholarworks.uno.edu/td/2181.
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Latest advancements in software have become an indispensable tool in structural analysis. The main goal of this thesis is to examine dynamic responses of bridges in seismic activity with the help of such tool as CSi Bridge. Therefore, throughout this study, a prestressed concrete bridge model will be thoroughly designed. In the first section, the required materials and structural components will be introduced. The following section will cover calculations required for modeling. The actual modeling of the structure will be carried out in Section 3. In Section 4, the set of required analysis for seismic design such as modal, pushover and response spectrum will be conducted. Lastly, in Section 5, analysis results will be evaluated. Thus, by examining the entire model, its construction, materials used, provided properties and conditions such as location on earth, seismic magnitude, it will be determined whether the design is sufficient and acceptable or not.
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Cojocaru, Razvan. "Lifting Analysis of Precast Prestressed Concrete Beams". Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/32464.
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Motivated by Robert Mastâ s original papers on lifting stability, this research study provides a method for predicting beam behavior during lifting, with application in the construction of bridges. A beam lifting cracking limit state is developed based on analytical equations for calculating the roll angle of the beam, the internal forces and moments, the weak-axis and strong-axis deflections, and the cross-sectional angle of twist. Finite element simulations are performed to investigate the behavior of concrete beams during lifting and to validate the proposed method. Additionally, a statistical characterization of beam imperfections is presented, based on recently conducted field measurements of beam lateral sweep and eccentricity of lift supports. Finally, numerical examples for two typical precast prestressed concrete beam cross-sections are included to demonstrate the proposed method.Master of Science
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Campbell, Tara. "Prestressed Steel Girders for Two Span Bridges". University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1447690927.
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Osofero, Adelaja Israel. "Behaviour and design of prestressed stayed columns". Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9589.
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The load-carrying capacity of slender columns is limited by global instability. However, through the addition of strategically placed cross-arms and external prestressed cables, buckling displacements can be inhibited and the load-carrying capacity considerably enhanced. Such systems, known as prestressed stayed columns offer efficient and lightweight structural solutions. Previous research on prestressed stayed columns has been largely analytical and numerical studies. To the knowledge of the author, experimental investigations into the antisymmetric and interactive modes of buckling in stayed columns have not been attempted hitherto. In addition, although some previous studies have attempted to investigate the optimum prestressing configuration of stayed columns for design purposes, generic design guidance for this type of structural component has been lacking. Therefore, the primary aim of the current study is to conduct experimental and numerical investigations into the possible buckling and post-buckling behaviour and to develop an efficient design method for these structural components. A full scale experimental investigation has been conducted with a total of 18 test specimens to demonstrate the critical modes of buckling (symmetric and antisymmetric) with interactive post-buckling. This has also investigated the imperfection sensitivity of the stayed columns. Nonlinear finite element (FE) modelling was conducted in parallel with the experiments. These models were utilized, after successful validation against the experimental results, to investigate the sensitivity of the stayed system to the variation of key parameters. Subsequently, an efficient design method for prestressed stayed columns has been developed, including design charts and equations relating the resistance of the stayed column system to the level of the initial prestress in the cables for varying cross-arm lengths and global imperfection levels. Structural reliability analysis, using the procedures in Annex D of EN 1990, was conducted to evaluate the design safety factor. Worked examples of the proposed design method are also presented to demonstrate the developed procedure for diiferent key cases. It is shown that a straightforward yet rational design method has been formulated.
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Moore, Wendy LeAnn. "Performance of fire-damaged prestressed concrete bridges". Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Moore_MS_09007dcc806789ec.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2008.Appendix included as 690 pages at end of thesis. Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed June 8, 2009) Includes bibliographical references (p. 133-138).
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Barr, Paul J. "Consistent crudeness in prestressed concrete girder design /". Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/10128.
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Dymond, Benjamin Zachary. "Shear Strength of a PCBT-53 Girder Fabricated with Lightweight, Self-Consolidating Concrete". Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/35949.
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The research conducted was part of a project sponsored by the Virginia Department of Transportation and the Virginia Transportation Research Council. One PCBT-53 girder was fabricated with lightweight, self-consolidating concrete. An additional composite cast-in-place lightweight concrete deck was added at the Virginia Tech Structures and Material Laboratory.
The project had two specific goals. The first was to experimentally determine the shear strength of the bridge girder. The initial tests focused on the web-shear strength of the girder, and the second tests focused on the flexure-shear strength. The theoretical predictions for the web shear strength were all conservative when compared to the experimentally measured failure strength. The theoretical predictions of the flexure-shear strength were typically unconservative because during the flexure-shear test the girder reached the nominal flexural strength, and a failure occurred in the previously damaged region of the beam. Shear strength was also predicted using the design material properties. Results from these calculations suggested that the equation for the steel contribution to shear strength proposed in the NCHRP Simplified Method were unconservative.
Further investigation into the results from the web-shear test showed that the maximum nominal shear strength calculated using the AASHTO LRFD Specifications was typically unconservative. Test results from this project suggested that the constant multiplier of 0.25 used in the LRFD equation for Vnmax may be too high. Further research may be needed to accurately quantify an upper limit on the shear strength. Additionally, predictions of the initial web-shear cracking load were conservative when using the AASHTO Standard Specifications and the NCHRP Simplified Method. The initial web-shear crack angle was under-predicted using the AASHTO LRFD Specifications.
The second goal was to monitor the change in prestress over time (and hence the prestress loss) occurring in the PCBT-53 girder. Prestress losses were experimentally measured by vibrating wire gages (measured changes in concrete strain) and flexural load testing. Measured prestress losses were compared to a theoretical prediction calculated using the AASHTO Refined Method. The amount of prestress recorded at any given time using vibrating wire gages was greater than predictions from the AASHTO Refined method. The effective prestress measured just prior to deck placement was higher than the theoretical prediction, and the measured effective prestress at the time of testing was also higher than the theoretical effective prestressing force. The effective prestress value calculated using the flexural crack initiation method was significantly lower than the effective prestress values predicted by both the code provisions and the vibrating wire gages; however, the effective prestress value calculated using the flexural crack re-opening method corresponded very well with the effective prestress values predicted by the code provisions and measured by the vibrating wire gages. The discrepancy in the crack initiation effective prestress values may be due to prestress losses occurring between placement of the concrete and transfer of the prestress force. These losses are not taken into account when using current code provisions to estimate prestress losses. Additional research is recommended to determine if these losses occur in bulb-tee girders, and if so, to quantify them.
Finally, from test results within the scope of this research project, design of prestressed bulb-tee girders with lightweight, self-consolidating concrete is practical. The current AASHTO LRFD Specifications provided conservative results when predicting the shear strength of the PCBT-53. Additionally, prestress losses in PCBT girders fabricated with lightweight, self-consolidating concrete were less than those predicted using the AASHTO Refined method.Master of Science
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Chan, Ka-ho Enoch. "Experimental and numerical studies of concrete beams prestressed with unbonded tendons". Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B40988004.
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Hui, Macarious Kin Fung. "Anchorage of stirrups in prestressed concrete I-girders". Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57783.
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The current research investigates the performance of commonly-used non-code-compliant stirrup detailing in concrete I-girder bridges, specifically when the lower hooks on the stirrups are oriented parallel to the longitudinal prestressing strands and are not bent around any longitudinal bars. Such detailing does not meet the specifications in the Canadian Highway Bridge Design Code CSA S6-06. An experimental investigation was conducted on full-scale partial sections of a concrete I-girder to evaluate the performance of such non-code-compliant stirrup anchorages by comparing their performance to the performance of code-compliant stirrup anchorages. An analysis of an example concrete I-girder bridge was conducted to determine the demands on the stirrup anchorage during the tests. In the tests, the flexural tension force was applied to the prestressing strand while a diagonal force was applied to the web of the test specimens at approximately 30° to the longitudinal axis of the specimen. Two pairs of stirrups were fixed to a support as the diagonal force was applied. The ratio of the slip of the stirrup to the strain along the exposed length of the stirrup, which equals to the debonded length, was monitored in order to observe the performance of the stirrup anchorage. After applying many cycles of the diagonal force, including about 100 cycles after yielding of the stirrups, the non-code-compliant hooks were found to perform adequately.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Taki, Ismail M. "Load distribution in test loaded prestressed concrete piles". Thesis, University of Ottawa (Canada), 1987. http://hdl.handle.net/10393/11090.
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Daher, Yehia Mohamad. "Behavior of lightly prestressed members with unbonded tendons". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq22589.pdf.
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Rashed, Abdelaziz A. "Rational design of prestressed and reinforced concrete tanks". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq29097.pdf.
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Miltenburg, Roger J. "Membrane behaviour in one-way prestressed concrete slabs". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0007/MQ30752.pdf.
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Suh, Kwangsuk. "Underwater FRP repair of corrosion damaged prestressed piles". [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001601.
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