Experimental Investigation of Precast Prestressed Concrete Inverted Tee Girders with Multiple Web Openings for Service Systems PDF Download
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Author: James M. Thompson
Publisher:
ISBN:
Category : Precast concrete
Languages : en
Pages : 300
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Author: James M. Thompson
Publisher:
ISBN:
Category : Precast concrete
Languages : en
Pages : 300
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Book Description
Author: James M. Thompson
Publisher:
ISBN:
Category : Buildings
Languages : en
Pages : 156
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Author:
Publisher:
ISBN:
Category : Precast concrete
Languages : en
Pages : 922
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Author: Richard A. Miller (Professional engineer)
Publisher: Transportation Research Board
ISBN: 0309087937
Category : Concrete beams
Languages : en
Pages : 202
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Book Description
Introduction and Research Approach -- Findings -- Interpretation, Appraisal, and Application -- Interpretation, Appraisal, and Application -- References -- Appendixes.
Author: Jessica Lauren Salazar
Publisher:
ISBN:
Category :
Languages : en
Pages : 352
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Book Description
Pretensioned concrete girders are currently fabricated using 0.5- or 0.6-in. diameter prestressing strands. In recent years, however, it has become of interest to employ larger-diameter 0.7-in. diameter strands to reduce the number of strands and improve the efficiency of pretensioned concrete members. Such a transition requires a considerable initial investment that needs to be justified based on the benefits obtained. Furthermore, the use of 0.7-in. strands would increase the stresses within the end-region of pretensioned elements, which could lead to undesirable cracking and impact the serviceability of the girders. The work presented in this thesis consists of 1) a comprehensive parametric investigation to evaluate the benefits and limitations of using 0.7-in. strands in pretensioned bridge girders, and 2) a full-scale experimental study to investigate the behavior of pretensioned concrete girders with 0.7-in. strands at the time of prestress transfer. The parametric investigation was accomplished by designing thousands of bridge girders with different span lengths, concrete release strengths, and transverse spacings. The results showed that the most noticeable benefit of 0.7-in. strands over 0.6-in. strands was a reduction of up to 35 percent in the number of strands. However, the difference in the total weight of prestressing steel was insignificant. Increasing the release strength of concrete, at least to 7.5 ksi, was found essential to observe benefits in design aspects other than the number of strands. The experimental investigation involved the fabrication of two Tx46 and two Tx70 specimens at the Ferguson Structural Engineering Laboratory. All specimens employed 0.7-in. strands on a 2- by 2-in. grid and the standard detailing currently used for girders with smaller-diameter strands. The observed crack widths in the specimens upon prestress transfer did not exceed those typically observed in Tx-girders with smaller-diameter strands. Therefore, the use of 0.7-in. strands does not seem to trigger a need to modify the end-region detailing in Tx-girders. However, noticeably greater bursting and spalling forces were observed in the end regions of the specimens compared to the demands predicted by AASHTO LRFD provisions. The measured 24-hour transfer length from the specimens also exceeded estimates by AASHTO LRFD and ACI 318-14 provisions.
Author: Obi R. Igwe
Publisher:
ISBN:
Category : Concrete railroad ties
Languages : en
Pages : 230
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Author:
Publisher:
ISBN:
Category : Electronic book
Languages : en
Pages :
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Author: Jude O. Igwemezie
Publisher:
ISBN:
Category : Concrete railroad ties
Languages : en
Pages : 252
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Author: Amy J. Dimmerling
Publisher:
ISBN:
Category :
Languages : en
Pages : 210
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Book Description
Precast prestressed concrete girders have been used in bridge construction for several years in the United States. In general, these types of bridges have performed well in service conditions. Although the connections over the supports provide sufficient continuity for dead loads, which cause negative moments, there has been some concern about the ability of the connections to provide continuity for the positive moments caused by live loads. Cracking has been observed at the bottom of the diaphragm at the connection and this raises concern about the connection's performance. The National Cooperative Highway Research Program developed Project 12-53 to study the effectiveness of these connections. The focus of this research deals with the experimental testing part of project 12-53. Six specimens that represent portions of full-size bridges were tested under monotonic and cyclic loads to evaluate their performance after cracking occurs at the bottom of the diaphragm. Each connection was fatigued until the connection was considered to have failed. The bent strand and bent bar embedded connections performed well under service moments. Under negative moment all of the specimens performed well. Even after failure of the specimens they each were able to resist the negative moment. This was due to the bearing of the diaphragm against the beams. The crack closes and at this point there is no difference between the specimens. Under positive moment the embedded specimens were stiffer and the failure was more gradual than that of the not embedded specimens. The embedment adds to the stiffness of the specimens. The engagement of the diaphragm in the embedded specimens helps to prolong the failure. The warning signs of failure are more prominent in the embedded specimens. The bent bar specimens are stiffer than the bent strand but the failure occurs more rapidly. After all six of the short-length specimens are tested, full-size specimens will be tested. At that point, results from all testing will be compared and discussed providing conclusions about the behavior of positive moment connections. Also, recommendations are expected as to the design and construction of positive moment connections in precast/prestressed bridge girders made continuous.
Author:
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ISBN:
Category :
Languages : en
Pages :
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