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Author: Richard A. Miller (Professional engineer)
Publisher: Transportation Research Board
Published: 2004
Total Pages: 202
ISBN-13: 0309087937
DOWNLOAD EBOOK →Introduction and Research Approach -- Findings -- Interpretation, Appraisal, and Application -- Interpretation, Appraisal, and Application -- References -- Appendixes.
Author: Angela Marie Mueller
Publisher:
Published: 2002
Total Pages: 244
ISBN-13:
DOWNLOAD EBOOK →Continuous precast/prestressed bridges are formed by placing the girders end to end and then pouring a slab and intermediate diaphragms. The girders carry the dead load of the structure as simple spans but are continuous for live loads. These connections provide sufficient negative moment continuity, however their effectiveness in providing positive moment continuity is questionable. Cracking has been observed in bridges of this type due largely to time dependent effects and this has raised questions regarding the bridges performance. The National Cooperative Highway Research Program (NCHRP) Project 12-53 was developed to study the effectiveness of the connections between precast/prestressed bridge girders made continuous. This thesis presents a portion of the experimental work for project 12-53. Six specimens, representing portions of full-scale bridges, were tested and fatigued to evaluate their performance after cracking has occurred. The loading procedure represents extreme loading events occurring after cracking at the diaphragm has occurred and the structure is subjected to normal traffic loads. Data from each specimen was analyzed and the results were compared for each connection type. The specimens were designed to evaluate the effect of the use of bent bars versus bent strands, embedment, and the addition of web bars and/or stirrups to a bent bar connection with regard to performance. It was found that all connection types would provide adequate negative moment continuity. Each detail provided differing levels of crack control; however cracking did not significantly affect the stiffness of the specimen. The best method for providing better crack control and a more efficient section is to embed the girder into the diaphragm. There is little difference between bent bar and bent strand connections and both seem to offer sufficient crack control. Additional stirrups in the diaphragm slightly increase the stiffness of the connection. The main advantage to adding stirrups would be the ductility that is added to the connection. The addition of web bars was very effective, but is not recommended. Although the addition increases the strength of the connection, it causes cracking of the ends of the girders and is difficult to construct.
Author: Amy J. Dimmerling
Publisher:
Published: 2002
Total Pages: 210
ISBN-13:
DOWNLOAD EBOOK →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: R. G. Oesterle
Publisher: Transportation Research Board National Research
Published: 1989
Total Pages: 108
ISBN-13:
DOWNLOAD EBOOK →This report documents and presents results of a study to determine time-dependent behavior and relevant design criteria for simple-span precast, prestressed bridge girders made continuous. A questionnaire was used to determine current practice. Creep and shrinkage tests of steam-cured concrete loaded at an early age were made. Computer simulations were used to investigate the effects of time-dependent material behavior and variation in design parameters on the effective continuity for live load plus impact. The findings suggest that positive moment connections in the diaphragms at the piers are not required and provide no structural advantages. The findings also suggest that effective continuity for live load plus impact can vary from 0 to 100% dependent on the design parameters and timing of construction. Computer analyses were also used to determine an upper limit for the amount of negative moment reinforcement over the supports to insure full moment redistribution and attainment of maximum bridge strength. New computer programs were developed for simplified analysis to determine time-dependent effects and service moments. Recommendations for design procedures were presented and design examples given.
Author: Mary Beth Deisz Hueste
Publisher:
Published: 2016
Total Pages: 211
ISBN-13:
DOWNLOAD EBOOK →The Texas Department of Transportation designs typical highway bridge structures as simple span systems using standard precast, pretensioned girders. Spans are limited to about 150 ft due to weight and length restrictions on transporting the precast girder units from the prestressing plant to the bridge site. Such bridge construction, while economical from an initial cost point of view, may become somewhat limiting when longer spans are needed. This project focused on developing additional economical design alternatives for longer span bridges with main spans ranging from 150-300 ft, using continuous precast, prestressed concrete bridge structures with in-span splices. Phase 1 of this study focused on evaluating the current state-of-the-art and practice relevant to continuous precast concrete girder bridges and recommending suitable continuity connections for typical Texas bridge girders; the findings are documented in the Volume 1 project report. This report summarizes Phase 2 of the research including detailed design examples for shored and partially shored construction, results of a parametric design study, and results of an experimental program that tested a full-scale girder containing three splice connections. The parametric design study indicated that for bridges spanning from 150-300 ft, continuous precast, prestressed concrete girder bridges with in-span splices can provide an economical alternative to steel girder bridges and segmental concrete box girder construction. The tested splice connections performed well under service level loads. However, the lack of continuity of the pretensioning through the splice connection region had a significant impact on the behavior at higher loads approaching ultimate conditions. Improved connection behavior at ultimate conditions is expected through enhanced connection details. Recommendations for design of continuous spliced precast girders, along with several detailing suggestions are discussed in the report.
Author: Pedro Pacheco
Publisher: CRC Press
Published: 2015-06-09
Total Pages: 460
ISBN-13: 1315687194
DOWNLOAD EBOOK →Throughout the last decades, the increasing development of the urban metropolis and the need to establish fundamental infrastructure networks, promoted the development of important projects worldwide and several Multi-Span Large Bridges have been erected. Certainly, many more will be erected in the next decades. This international context undoubted
Author: Reid Wilson Castrodale
Publisher: Transportation Research Board
Published: 2004
Total Pages: 603
ISBN-13: 0309087872
DOWNLOAD EBOOK →At head of title: National Cooperative Highway Research Program.
Author: Ronak Yogeshchandra Shah
Publisher:
Published: 2001
Total Pages: 618
ISBN-13:
DOWNLOAD EBOOK →Constructability implementation right from project conception to completion results in gains to owners, designers, fabricators, and contractors in terms of time and cost without compromising on quality. Constructability implementation optimizes all the phases of a construction project including planning, design, and construction stages. Success of constructability implementation can be easily measured by taking into consideration cost and schedule performance. Higher the degree of constructability implementation, the more efficiently a constructor can build, eventually leading to an economical project for the owner. The use of constructability to reduce costs and simplify construction implies neither lower quality nor compromise in design. Constructability requires that companies, particularly owners, go beyond conventional approaches to project execution by expanding front-end planning and investing additional effort in order to anticipate potential problems. The degree to which a constructability program is needed varies greatly with the size and complexity of a project. The work undertaken herein concentrates on studying constructability application in detail, when to use and how to use constructability, and effectively and efficiently implementing it for providing positive moment connections in bridges.
