Download or read book Direct Field Measurement of Prestress Losses in Box Girder Bridges written by Joseph Frank Shields and published by . This book was released on 1989 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Field Measurement and Evaluation of Time dependent Losses in Prestressed Concrete Bridges written by Okey U. Onyemelukwe and published by . This book was released on 1997 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Field Study of Prestress Losses in a Box Girder Bridge in a Low Humidity Environment written by Eric James Hutchens and published by . This book was released on 1994 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bridge Evaluation Repair and Rehabilitation written by A.S. Nowak and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 618 pages. Available in PDF, EPUB and Kindle. Book excerpt: Evaluation, repair and rehabilitation of bridges are increasingly important topics in the effort to deal with the deteriorating infrastructure. For example, in the United States about 40 percent of the nation's 570,000 bridges are classified, according to the Federal Highway Administra tion's (FHW A) criteria, as deficient and in need of rehabilitation and replacement. In other countries the situation is similar. FHW A estimates the cost of a bridge replacement and reha bilitation program at 50 billion dollars. The major factors that have contributed to the present situation are: the age, inadequate maintenance, increasing load spectra and environmental contamination. The deficient bridges are posted, repaired or replaced. The disposition of bridges involves clear economical and safety implications. To avoid high costs of replacement or repair, the evaluation must accurately reveal the present load carrying capacity of the struc ture and predict loads and any further changes in the capacity (deterioration) in the applicable time span. Accuracy of bridge evaluation can be improved by using the recent developments in bridge diagnostics, structural tests, material tests, structural analysis and probabilistic methods. There is a need for an international exchange of advanced experience to increase the research effi ciency. The Workshop is organized on the premise that the exchange of existing American and European experience in the area of bridge evaluation, repair and rehabilitation is beneficial for both parties involved.
Download or read book Field measured Post tension Prestress Loss in Stress relieved Strands written by James E. Richardson and published by . This book was released on 1984 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Scientific and Technical Aerospace Reports written by and published by . This book was released on 1976 with total page 1072 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Prestress Loss in Four Box Girder Bridges in Northern Nevada written by N. Mangoba and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Four new post-tensioned, box girder bridges in Northern Nevada were instrumented during construction to collect data on the possible adverse effects of high variation in relative humidity (RH) and temperature on prestress losses. The bridges were monitored at short intervals during the first month after stressing and in two-month intervals afterwards. For each bridge, the measured data consisted of concrete surface strains on two girders, creep strains on concrete cylinders at the bridge sites, shrinkage strains on cylinders at the site and at the laboratory, and deflection of the midspan relative to the ends of the structures. The actual time-dependent prestress losses were compared to two current loss prediction methods: the AASHTO lump-sum estimate of prestress losses and the time-step methos of determining losses by Naaman. To determine the effects of changes in RH on the losses, the climatic data of the area were incorporated into the calculated losses.
Download or read book An Introduction to Prestressing Losses with Post Tensioning of Highway Box Girders written by J. Paul Guyer, P.E., R.A. and published by Guyer Partners. This book was released on 2018-09-23 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: Introductory technical guidance for civil and structural engineers and construction managers interested in prestressing losses with post-tensioning of highway box girders. Here is what is discussed: 1. PRESTRESSING LOSSES 2. TIME-DEPENDENT LOSSES.
Download or read book Creep and Shrinkage Losses in Highly Variable Climates written by Mehdi Saiidi and published by . This book was released on 2003 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Techniques for Measuring Existing Long term Stresses in Prestressed Concrete Bridges written by and published by . This book was released on 1990 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Various stress measurement techniques were evaluated in this study. The evaluation included a state-of-the-art review of existing techniques and analytical studies of these techniques. Based on analytical results, the flat-jack direct stress measurement technique was evaluated in laboratory and field tests. Based on these tests, a manual of instruction was written to describe the equipment and procedures required to obtain reliable direct stress measurement. This is the Executive Summary which summarizes the findings of this research project.
Download or read book Proceedings of the 9th International Conference on Civil Engineering written by Guangliang Feng and published by Springer Nature. This book was released on 2023-06-17 with total page 627 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book is a compilation of selected papers from the 9th International Conference on Civil Engineering (ICCE2022). The work focuses on novel research findings on seismic technology of civil engineering structures, High-tech construction materials, digitalization of civil engineering, urban underground space development. The contents make valuable contributions to academic researchers and engineers.
Download or read book Evaluation of Long term Prestress Losses in Post tensioned Box girder Bridges written by Pui-shum B. Shing and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most of the recent highway bridges built in California have post-tensioned, cast-in-place, concrete box-girder superstructures rigidly connected to bridge columns. However, methods provided in the current (2007 and 2010) AASHTO LRFD Bridge Design Specifications for estimating long-term prestress losses are essentially based on research focused on pretensioned members and are not adequate for post-tensioned bridge girders. Long-term prestress losses in post-tensioned members are expected to be smaller than those in pretensioned members due to two main factors. One is the higher amount of mild reinforcement present in posttensioned bridge girders, which provides a higher restraint to the creep and shrinkage of concrete, and the other is that post-tensioning could take place a long while after the girders have been cast and the concrete has reached a more mature age, which results in a lower creep. The main objectives of the study reported here were to assess the accuracy of the long-term prestress-loss estimation methods given in the current AASHTO LRFD Specifications for post-tensioned bridge girders, and to develop more suitable analysis methods for these members.
Download or read book Next Generation of Bridge Columns for Accelerated Bridge Construction in High Seismic Zones written by Mostafa Tazarv and published by . This book was released on 2014 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt: Longitudinal bar debonding allowed spread of yielding and prevented premature failure of reinforcements in UHPC-filled duct connections and grouted coupler column pedestal. The SMA-reinforced ECC column showed superior seismic performance compared to a conventional column in which the plastic hinge damage was limited to only ECC cover spalling even under 12% drift ratio cycles. The column residual displacements were 79% lower than CIP residual displacements on average due to the superelastic NiTi SMA longitudinal reinforcement, and higher base shear capacity and higher displacement capacity were observed. The analytical modeling methods were simple and sufficiently accurate for general design and analyses of precast components proposed in the present study. The proposed symmetrical material model for reinforcing NiTi superelastic SMA was found to be a viable alternative to the more complex asymmetrical model.
Download or read book Seismic Performance of RC Bridge Columns Reinforced with Two Interlocking Spirals written by Juan F. Correal and published by . This book was released on 2004 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Prediction of Long term Prestress Loss in Concrete Box Girder Bridges written by Seung Dae Kim and published by . This book was released on 2009 with total page 345 pages. Available in PDF, EPUB and Kindle. Book excerpt: Post-tensioned cast-in-place concrete box girder bridges are the most popular type for new bridge construction in California since this class of bridges shows an increased ability to resist and dissipate seismic loads for long-span structures. However, due to the long-term behavior of the construction materials .i.e. concrete and steel, tension forces induced by prestressing decrease over time as a result of creep and shrinkage of concrete and steel relaxation, which is called long-term prestress loss. This loss is one of the most important factors to consider in designing and analyzing this type of bridges. Although the inaccurate prediction of the loss is not considered to impose severe effects on the ultimate capacity of the structures, it is known to lead to critical problems at the design and service stages. Underestimating the prestress loss can cause cracking and excessive deflection during service stage and overestimating it could lead to uneconomic design. A number of bridge specifications use varied approximations currently to predict the long-term prestress losses. However, they show significant scatter in values of their estimates even under the same environmental conditions. This diversity of prediction mainly results from two sources of error. The first source of the error is related to inaccurate material characteristics: the coefficients for creep and shrinkage of concrete. The other comes from excessive simplification in the method of analysis in the specifications. Consequently, the goals of this research are to verify which specifications can provide more accurate creep and shrinkage strains and to propose a simple yet more comprehensive analysis procedure to predict the long-term prestress losses including effects from important structural- and material-level parameters. To meet these objectives, monitoring responses from bridges in service and investigating material characteristics from cylinder specimens are in progress on four bridge spans of I5-I805 and I215-CA91 in San Diego and Riverside, California, respectively. Also, a simple analysis method which could be easily applied in the design is improved by incorporating the effects from the five parameters: transverse shear deformation, loading events, and horizontal reinforcements as structural-level parameters, compressive strength of concrete and thermal creep from accumulation of temperature variation as material-level parameters. The results from this research are validated by comparing with the predictions in current specifications and data from the monitored spans on I5- I805 and I215-CA91.
