Posted by: Shahin - 11-11-2012, 05:16 AM - Forum: Archive
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Dear members
Full title: Wave Propagation in Structures: Spectral Analysis Using Fast Discrete Fourier Transform
Author(s): James F. Doyle
Publisher: Springer, 2nd ed., 1997
Language: English
ISBN 978-0-387-94940-6
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Here you can find the German National Annexes to the Eurocodes.
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Some are missing:
DIN EN 1992-2/NA
DIN EN 1992-3NA
DIN EN 1993-3-1-NA
DIN EN 1996-1-2/NA
DIN EN 1999-1-3/NA
Some are in draft while the finals have been publihed already.
Durability Evaluation of Post-Tensioned Concrete Beam Specimens after Long-Term Aggressive Exposure Testing
Author: Turco, G P | Size: 4.24 MB | Format:PDF | Quality:Original preprint | Publisher: University of Texas, Austin | Year: 2007 | pages: 174
This report focuses on the forensic analysis and evaluation of large-scale post-tensioned beam specimens after nearly 8 years of extremely aggressive exposure testing. The research was funded jointly by both the Federal Highway Administration and the Texas Department of Transportation. The relationship between durability performance and the following variables was evaluated in this study: level of applied load and initial cracking, level of prestress, duct type, strand type, grout type, grouting method, use of encapsulated system for anchorage protection, and galvanized duct splice type. In addition, the applicability of half-cell potentials and chloride penetration tests for evaluating the likelihood of corrosion was examined. Major findings were: 1) Mixed reinforcement (also known as partial prestressing) performed poorly from a durability standpoint. Only fully prestressed beams offered better durability performance than those which were not prestressed at all. 2) Corrugated steel galvanized ducts performed very poorly. Large holes were found in the ducts, and in some cases several inches of the ducts completely corroded away. 3) Corrugated plastic ducts offer better performance as long as they are "robust." 4) Non-flowfilled epoxy coated strand and galvanized strand offered no significant improvement in long-term durability over conventional strand. 5) Installing plastic caps over anchorheads rather than just filling the anchorage pocket with nonshrink grout increases the long-term durability of the anchorage.
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Prestress Losses in Prestressed Bridge Girders Cast with Self-Consolidating Concrete
Author: Ruiz, Edmundo D Floyd, Royce W Staton, Blake W University of Arkansas, Fayetteville Do, Nam H University of Arkansas, Fayetteville Hale, W Micah University of Arkansas, Fayetteville | Size: 893 KB | Format:PDF | Quality:Original preprint | Publisher: Mack-Blackwell Transportation Center | Year: 2008 | pages: 94
The use of prestressed concrete bridges in Arkansas is becoming more common. The increase in steel costs has contributed to the popularity of prestressed bridge girders. Prestressed girders are particularly common in areas that border neighboring states (and these areas are also typically rural). Self Consolidating Concrete (SCC) is a recent advancement in the concrete industry. SCC is a type of concrete that can be placed without consolidation and is beginning to be widely accepted. Some states are allowing the use of SCC bridge girders. SCC is not much different from conventional concrete. The constituent materials are the same, but SCC typically contains more fine aggregate and cement, but less coarse aggregate. This research program examined the prestress losses of beams cast with SCC and compares those to losses of control beams cast with conventional concrete of the same compressive strength. Additionally, the research program examined the transfer and development length of SCC beams.
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Effects of Increasing the Allowable Compressive Stress at Release on the Shear Strength of Prestressed Concrete Girders
Author: Heckmann, Christopher University of Texas, Austin Bayrak, Oguzhan University of Texas, Austin | Size: 9.46 MB | Format:PDF | Quality:Original preprint | Publisher: University of Texas, Austin | Year: 2008 | pages: 173
In recent years, several research projects have been conducted to study the feasibility of increasing the allowable compressive stress in concrete at prestress transfer, currently defined as 0.60f'ci in the AASHTO LRFD Bridge Design Specifications. Increasing the limit would result in many economical and design benefits for the precast concrete industry, such as increased span lengths and faster turnover of beams in stressing beds. This research study focuses on the effects of increasing the allowable compressive stress at release on the shear strength of prestressed concrete members, a topic which has not yet been explored by past research projects. The current experimental work is funded under Texas Department of Transportation (TxDOT) Project 5197, which initiated in 2004 at the University of Texas at Austin. In the shear performance evaluation, 18 shear tests were performed. In the shear tests, the beams were loaded to fail in web-shear, with a shear span to depth ratio of 2.22. The diagonal cracking shears and shear capacities were experimentally measured for all specimens tested. All test specimens were TxDOT Type-C highway bridge girders (40-inch deep pretensioned I-beams) and were fabricated by three different precast plants in Texas. The compressive stress at release for the test specimens ranged from 0.56f'ci to 0.76f'ci. The measured cracking shears and shear capacities were compared to the estimated cracking shears and shear capacities, as calculated using ACI 318-08 and AASHTO LRFD (2007), and the effects of higher release stresses on shear strength and serviceability were evaluated by examining the conservativeness and accuracy of the predictions. Based on the experimental results summarized in this report, an increase in the allowable maximum compressive stress in concrete in the end regions of prestressed concrete beams at prestress transfer to 0.65f'ci or 0.70f'ci can be justified.
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Researchers conducted an experimental program to investigate the viability of producing self-consolidating concrete (SCC) using locally available aggregate, and the viability of its use in the production of precast prestressed concrete bridge girders for the State of Minnesota. Six precast prestressed bridge girders were cast using four SCC and two conventional concrete mixes. Variations in the mixes included cementitious materials (ASTM Type I and III cement and Class C fly ash), natural gravel and crushed stone as coarse aggregate, and several admixtures. The girders were instrumented to monitor transfer length, camber, and prestress losses. In addition, companion cylinders were cast to measure the compressive strength and modulus of elasticity, and to monitor the creep and shrinkage over time. The viability of using several test methods to evaluate SCC fresh properties was also investigated. The test results indicated that the overall performance of the SCC girders was comparable to that of the conventional concrete girders. The measured, predicted, and calculated prestress losses were generally in good agreement. The study indicated that creep and shrinkage material models developed based on companion cylinder creep and shrinkage data can be used to reasonably predict measured prestress losses of both conventional and SCC prestressed bridge girders.
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i need a paper which has examined behavior of sample 2d reinforced concrete moment frame under reverse load and .
i want to use this experimental model for modeling that in seismostruct software and check the experimental and analytical result of that under reverse load .
could you have this kind of paper?please if you have upload here ,
This report documents the findings of a Texas Department of Transportation sponsored research project to study self-consolidating concrete (SCC) for precast concrete structural applications. Self-consolidating concrete is a new, innovative construction material that can be placed into forms without the need for mechanical vibration. The mixture proportions are critical for producing quality SCC and require an optimized combination of coarse and fine aggregates, cement, water, and chemical and mineral admixtures. The required mixture constituents and proportions may affect the mechanical properties, bond characteristics, and long-term behavior, and SCC may not provide the same in-service performance as conventional concrete (CC). Different SCC mixture constituents and proportions were evaluated for mechanical properties, shear characteristics, bond characteristics, creep, and durability. Variables evaluated included mixture type (CC or SCC), coarse aggregate type (river gravel or limestone), and coarse aggregate volume. To correlate these results with full-scale samples and investigate structural behavior related to strand bond properties, four girder-deck systems, 40 ft (12 m) long, with CC and SCC pretensioned girders were fabricated and tested. Results from the research indicate that the American Association of State Highway Transportation Officials Load and Resistance Factor Design (AASHTO LRFD) Specifications can be used to estimate the mechanical properties of SCC for a concrete compressive strength range of 5 to 10 ksi (34 to 70 MPa). In addition, the research team developed prediction equations for concrete compressive strength ranges from 5 to 16 ksi (34 to 110 MPa). With respect to shear characteristics, a more appropriate expression is proposed to estimate the concrete shear strength for CC and SCC girders with a compressive strength greater than 10 ksi (70 MPa). The researchers found that girder-deck systems with Type A SCC girders exhibit similar flexural performance as deck systems with CC girders. The AASHTO LRFD (2006) equations for computing the cracking moment, nominal moment, transfer length, development length, and prestress losses may be used for SCC girder-deck systems similar to those tested in this study. For environments exhibiting freeze-thaw cycles, a minimum 16-hour release strength of 7 ksi (48 MPa) is recommended for SCC mixtures.
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Allowable Compressive Stress at Prestress Transfer
Author: Schnittker, Brian University of Texas, Austin Bayrak, Oguzhan University of Texas, Austin | Size: 7.94 MB | Format:PDF | Quality:Original preprint | Publisher: University of Texas, Austin | Year: 2008 | pages: 206
In 2004, the Texas Department of Transportation (TxDOT) initiated Project 5197 to investigate the feasibility of increasing the allowable compressive stress limit at prestress transfer. Initially, the live load performance of 36 specimens was evaluated by Birrcher and Bayrak (TxDOT Report 5197-1, 2007). Report 5197-4 presents the subsequent research conducted based on recommendations of Birrcher and Bayrak (2007). In this portion of TxDOT Project 5197, 45 Type-C beams and 10 4B28 box beams were tested to experimentally determine their cracking load. The Type-C beams were produced in four different fabrication plants using conventionally consolidated concrete. The 10 4B28 box beams were produced in two fabrication plants using concrete mixture designs of both self consolidating concrete as well as conventional concrete. For all specimens, measured cracking loads were compared to predicted cracking loads. The data from the 45 Type-C beams and 10 box beams were added to the 36 beams investigated by Birrcher and Bayrak (2007) to compile a comprehensive set of data from 91 specimens. An appropriate maximum compressive stress limit was determined from the ability to accurately predict the load at which cracking occurred. As the maximum compressive stress at prestress transfer was increased, a decline in cracking load prediction accuracy was observed. For the specimens subjected to high compressive stresses at release (greater than 0.65f’ci), the concrete in the pre-compressed tensile zone was subjected to the non-linear inelastic range causing microcracking to occur. This non-linear behavior (due to microcracking) was unaccounted for in prestress losses or standard design equations (P/A±Mc/I). Based on the analysis of the results, an increase of the allowable compressive stress limit at prestress transfer to 0.65f’ci is justified. Additionally, the use of self consolidating concrete with a maximum compressive stress of 0.65f’ci is not recommended.
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High-Strength Self-Consolidating Concrete Girders Subjected To Elevated Compressive Fiber Stresses
Author: Myers, John J | Size: 773 KB | Format:PDF | Quality:Original preprint | Publisher: Missouri University of Science and Technology, Rolla | Year: 2008 | pages: 70
There are limited measurements documented in the literature related to long-term prestress losses in self consolidated concrete (SCC) members. Recorded test data have shown variations in mechanical property behavior of SCC compared to conventional high strength concrete (HSC) mixtures in the 8-12 ksi range. Over the past year, precast manufacturers such as Coreslab Structures, Inc., in Marshall, MO have experienced inconsistencies in camber behavior with SCC which may be attributed to mechanical property variations, but variation in stress may also be a contributing factor. Additionally, increasing the allowable fiber stress limit is desired for full utilization of materials and members, as long as structural performance is maintained. Furthermore, accurate prediction of time-dependant prestress losses is essential for determination of the effective prestress force, which affects serviceability prediction and structural performance. Further investigation is required.
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