Download or read book Prestress Losses in Pretensioned High strength Concrete Bridge Girders written by Maher K. Tadros and published by Transportation Research Board. This book was released on 2003 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The HCM includes three printed volumes (Volumes 1-3) that can be purchased from the Transportation Research Board in print and electronic formats. Volume 4 is a free online resource that supports the rest of the manual. It includes: Supplemental chapters 25-38, providing additional details of the methodologies described in the Volume 1-3 chapters, example problems, and other resources; A technical reference library providing access to a significant portion of the research supporting HCM methods; Two applications guides demonstrating how the HCM can be applied to planning-level analysis and a variety of traffic operations applications; Interpretations, updates, and errata for the HCM (as they are developed);A discussion forum allowing HCM users to ask questions and collaborate on HCM-related matters; and Notifications of chapter updates, active discussions, and more via an optional e-mail notification feature."--Publisher.
Download or read book Prestress Losses in Pretensioned High strength Concrete Bridge Girders microform written by Al-Omaishi, Nabil and published by Ann Arbor, Mich. : University Microfilms International. This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book High Strength Prestressed Concrete Bridge Girders written by Theresa Marie Ahlborn and published by . This book was released on 1998 with total page 936 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigation of Long term Prestress Losses in Pretensioned High Performance Concrete Girders written by Thomas E. Cousins and published by . This book was released on 2005 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt: Effective determination of long-term prestress losses is important in the design of prestressed concrete bridges. Over-predicting prestress losses results in an overly conservative design for service load stresses, and under-predicting prestress losses, can result in cracking at service loads. Creep and shrinkage produce the most significant time-dependent effect on prestress losses, and research has shown that high performance and high strength concretes (HPC and HSC) exhibit less creep and shrinkage than conventional concrete. For this reason, the majority of traditional creep and shrinkage models and methods for estimating prestress losses, over-predict the prestress losses of HPC and HSC girders. Nine HPC girders, with design compressive strengths ranging from 8,000 psi to 10,000 psi, and three 8,000 psi lightweight HPC (HPLWC) girders were instrumented to determine the changes in strain and prestress losses. Several creep and shrinkage models were used to model the instrumented girders. For the HPLWC, each model over-predicted the long-term strains, and the Shams and Kahn model was the best predictor of the measured strains. For the normal weight HPC, the models under-estimated the measured strains at early ages and over-estimated the measured strains at later ages, and the B3 model was the best-predictor of the measured strains. The PCI-BDM model was the most consistent model across all of the instrumented girders. Several methods for estimating prestress losses were also investigated. The methods correlated to high strength concrete, the PCI-BDM and NCHRP 496 methods, predicted the total losses more accurately than the methods provided in the AASHTO Specifications. The newer methods over-predicted the total losses of the HPLWC girders by no more than 8 ksi, and although they under-predicted the total losses of the normal weight HPC girders, they did so by less than 5 ksi.
Download or read book High strength Concrete Prestressed Bridge Girders written by Theresa M. Ahlborn and published by . This book was released on 2000 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Extending Span Ranges of Precast Prestressed Concrete Girders written by Reid Wilson Castrodale and published by Transportation Research Board. This book was released on 2004 with total page 603 pages. Available in PDF, EPUB and Kindle. Book excerpt: At head of title: National Cooperative Highway Research Program.
Download or read book Prestress Losses and Cambers of High Performance Concrete Bridge Girders written by Zhiyong Liang and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Time dependent Analysis of Pretensioned Concrete Bridge Girders written by Brian D. Swartz and published by . This book was released on 2010 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Model of Strain related Prestress Losses in Pretensioned Simply Supported Bridge Girders written by José Manuel Gallardo Méndez and published by . This book was released on 2014 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: Prestressed concrete construction relies on the application of compressive stresses to concrete elements. The prestressing force is typically applied through the tensioning of strands that react against the concrete and induce compression in the concrete. Loss of prestress is the decrease of this pre-applied stress. The conservative estimation of the prestress losses is imperative to prevent undesired cracking of the prestressed element under service loads. A large fraction of the prestress losses is a consequence of concrete deformations. This fraction of the losses can be identified as strain-related losses, and these occur due to instantaneous elastic shortening, and time-dependent creep and shrinkage. Creep and shrinkage of concrete depend on many factors that are extremely variable within concrete structures. The time-dependent behavior of concrete is not well-understood, but recent findings in the topics of concrete creep and shrinkage provide a better understanding of the underlying mechanisms affecting the nature of these two phenomena. However, current design practices and prestress loss estimation methods do not reflect the state-of-the-art knowledge regarding creep and shrinkage. The main objective of this dissertation was the study and estimation of strain-related prestress losses in simply supported pretensioned bridge girders. Simply supported pretensioned girders are widely designed, produced and frequently used in bridge construction. Due to this common use, pretensioned concrete bridge girders has become fairly standardized elements, which results in a reduced variability in the behavior of pretensioned bridge girders, as compare to that of less standardized concrete structures. Hence, a simplified method was calibrated to estimate prestress losses within pretensioned girders to an adequate level of accuracy. To achieve an acceptable accuracy experimental data from the monitoring of pretensioned simply supported girders was used for the calibration of the method. The accuracy of this simplified method is comparable to that achievable using more elaborate methods developed for generic concrete structures.
Download or read book Camber and Prestress Losses in High Performance Concrete Bridge Girders written by James Michael Stallings and published by . This book was released on 2001 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Pre stress Loss Due to Creep in Precast Concrete Decked Bulb tee Girders Under Cold Climate Conditions written by Drew E. Vandermeer and published by . This book was released on 2019 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents guidelines for estimating pre-stress loss in high-strength precast pretensioned concrete Decked Bulb-Tee (DBT) bridge girders in cold climate regions. The guidelines incorporate procedures yielding more accurate predictions of shrinkage and concrete creep than current 2017 American Association of State Highway and Transportation Officials (AASHTO) specifications. The results of this report will be of particular interest to researchers and cold climate bridge design engineers in improved predictions of design life and durability. The use of high-strength concrete in pre-tensioned bridge girders has increased in popularity among many state highway agencies. This fact is due to its many beneficial economic and constructability aspects. The overall cost of longer girders with increased girder spacing in a bridge that is precast with high strength concrete can be significantly reduced through the proper estimating factors. Recent research indicates that the current provisions used for calculating prestress losses in cold regions for high-strength concrete bridge girders may not provide reliable estimates. Therefore, additional research is needed to evaluate the applicability of the current provisions for estimating pre-stress losses in high-strength concrete DBT girders. Accurate estimations of pre-stress losses in design of pre-tensioned concrete girders are affected by factors such as mix design, curing, concrete strength, and service exposure conditions. The development of improved guidelines for better estimating these losses assists bridge design engineers for such girders and provide a sense of security in terms of safety and longevity. The research includes field measurements of an environmentally exposed apparatus set up to measure shrinkage, creep and strain in cylinders loaded under constant pressure for a full calendar year.
Download or read book Optimized Sections for High strength Concrete Bridge Girders written by and published by . This book was released on 2006 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Flexural Behavior of Prestressed Girder with High Strength Concrete written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The advantages of using high strength concrete (HSC) have led to an increase in the typical span and a reduction of the weight of prestressed girders used for bridges. However, growing demands to utilize HSC require a reassessment of current provisions of the design codes. The objective of one of the research projects, recently initiated and sponsored by the National Cooperative Highway Research Program (NCHRP), NCHRP Project 12-64, conducted at North Carolina State University is to extend the use of the current AASHTO LRFD design specifications to include compressive strength up to 18,000 psi (124 MPa) for reinforced and prestressed concrete members in flexure and compression. This thesis deals with one part of this project. Nine full-size AASHTO girders are examined to investigate the behavior of using different concrete compressive strength and subjected to the flexural loadings. The experimental program includes three different configurations of prestressed girders with and without a deck slab to investigate the behavior for the following cases: 1) the compression zone consists of normal strength concrete (NSC) only; 2) the compression zone consists of HSC only; and 3) the compression zone consists of a combination of two different strengths of concrete. An analytical model is developed to determine the ultimate flexural resistance for prestressed girders with and without normal compressive strength concrete. The research also includes investigation of the transfer length and the prestress losses of HSC prestressed girders. Based on materials testing and extensive data collected from the literature, a new equation is proposed to calculate the elastic modulus for normal and high strength concrete.
Download or read book Behavior of Prestressed Concrete Bridge Girders written by Franklin B. Angomas and published by . This book was released on 2009 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Effect of New Prestress Loss Estimation Procedure on Precast Pretensioned Bridge Girders written by David Benjamin Garber and published by . This book was released on 2014 with total page 684 pages. Available in PDF, EPUB and Kindle. Book excerpt: The prestress loss estimation provision in the AASHTO LRFD Bridge Design Specifications was recalibrated in 2005 to be more accurate for "high-strength [conventional] concrete." Greater accuracy may imply less conservatism, the result of which may be flexural cracking of beams under service loads. Concern with a potential lack of conservatism and the degree of complexity of these recalibrated prestress loss estimation provisions prompted the investigation to be discussed in this dissertation. The primary objectives of this investigation were: (1) to assess the conservatism and accuracy of the current prestress loss provisions, (2) to identify the benefits and weaknesses of using the AASHTO LRFD 2004 and 2005 prestress loss provisions, and (3) to make recommendations to simplify the current provisions. These objectives were accomplished through (1) the fabrication, conditioning, and testing of 30 field-representative girders, (2) the assembly and analysis of a prestress loss database unmatched in size and diversity when compared with previously assembled databases, and (3) a parametric study investigating the design implications and sensitivity of the current loss provisions. Based on the database evaluation coupled with the experimental results, it was revealed that the use of the AASHTO LRFD 2005 prestress loss provisions resulted in underestimation of the prestress loss in nearly half of all cases. A loss estimation procedure was developed based on the AASHTO LRFD 2005 provisions to greatly simplify the procedure and provide a reasonable level of conservatism.
Download or read book Shear Capacity of in Service Prestressed Concrete Bridge Girders written by Paul Barr and published by . This book was released on 2010 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: The design procedure to calculate the shear capacity of bridge girders that was used forty years ago is very different than those procedures that are recommended in the current AASHTO LRFD Specifications. As a result, many bridge girders that were built forty years ago do not meet current design standards, and in some cases warrant replacement due to insufficient calculated shear capacity. However despite this insufficient calculated capacity, these bridge girders have been found to function adequately in service with minimal signs of distress. The objective of this research was to investigate the actual in service capacity of prestressed concrete girders that have been in service over an extended period of time.
Download or read book Instrumentation and Monitoring of High Performance Concrete Prestressed Bridge Girders written by Vellore S. Gopalaratnam and published by . This book was released on 2001 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt:
