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Evaluation Of Long Term Prestress Losses In Post Tensioned Box Girder Bridges
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Book Synopsis Evaluation of Long-term Prestress Losses in Post-tensioned Box-girder Bridges by : Pui-shum B. Shing
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.
Book Synopsis Prediction of Long-term Prestress Loss in Concrete Box Girder Bridges by : Seung Dae Kim
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.
Book Synopsis Prestress Losses in Pretensioned High-strength Concrete Bridge Girders by : Maher K. Tadros
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.
Book Synopsis An Introduction to Prestressing Losses with Post-Tensioning of Highway Box Girders by : J. Paul Guyer, P.E., R.A.
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.
Book Synopsis Continued Monitoring of the Varina-Enon Bridge: Estimation of Effective Prestress by : Seth Lindley
Download or read book Continued Monitoring of the Varina-Enon Bridge: Estimation of Effective Prestress written by Seth Lindley and published by . This book was released on 2022 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt: Prestress loss due to creep, shrinkage, and relaxation can cause serviceability issues, and in the case of structures post-tensioned with unbonded tendons, can reduce the flexural capacity. The accurate estimation of prestress losses is vital for making good decisions about the remaining life of a structure. The Varina-Enon Bridge is a post-tensioned concrete box-girder bridge near Richmond, Virginia. Flexural cracks in the bridge prompted an investigation into the magnitude of prestress loss experienced by the structure. Long-term prestress losses were estimated using two methods. First, a finite element model was created, and multiple code expressions for creep and shrinkage were applied to a time-step analysis of the structure. The code expressions investigated in this research were from the CEB-FIP 1978, CEB-FIP 1990, CEB-FIP 2010, and AASHTO (2017) codes. The second method utilized data from sensors installed on the bridge to back-calculate the effective prestressing force based on recorded openings of the flexural cracks. For the four spans monitored in this research, the field-determined effective prestress varied between 161 ksi and 166 ksi. Using the commercially available bridge design software, LARSA 4D, along with the creep and shrinkage model used in the original design, CEB-FIP 1978, the calculated effective prestress varied between 169 ksi and 171 ksi. This indicates that prestress losses were higher than anticipated in the original design, but the measured effective prestress was still, on average, about 96% of the design effective prestress. The more modern creep and shrinkage models of CEB-FIP 1990 and CEB-FIP 2010 also predicted higher than measured effective prestress, with both being very similar to CEB-FIP 1978. The effective prestress predicted by the AASHTO (2017) model was slightly higher. Calculation of flexural capacity using the effective prestress estimated by the field measurement system resulted in estimates of strength 1 to 4% smaller than using the effective prestress estimated by the original creep and shrinkage model used for design. Measured thermal gradients over the period studied in this project were smaller than the AASHTO LRFD design gradients; however, the restraint moment calculated for the worst case measured gradient was very similar to the restraint moment calculated using the design gradient.
Book Synopsis Time-dependent Behavior of Noncomposite and Composite Post-tensioned Concrete Girder Bridges by : A. I. Fadl
Download or read book Time-dependent Behavior of Noncomposite and Composite Post-tensioned Concrete Girder Bridges written by A. I. Fadl and published by . This book was released on 1976 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Prestress Loss in Four Box Girder Bridges in Northern Nevada by : N. Mangoba
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.
Book Synopsis Direct Field Measurement of Prestress Losses in Box Girder Bridges by : Joseph Frank Shields
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:
Book Synopsis Prestress Losses in a Post-tensioned R/c Box Girder Bridge in Southern Nevada by : M. Saiidi
Download or read book Prestress Losses in a Post-tensioned R/c Box Girder Bridge in Southern Nevada written by M. Saiidi and published by . This book was released on 1994 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis An Introduction to Prestressing Losses with Post-Tensioning of Highway Box Girders by : J. Paul Guyer
Download or read book An Introduction to Prestressing Losses with Post-Tensioning of Highway Box Girders written by J. Paul Guyer and published by Independently Published. 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.
Book Synopsis Life-Cycle Civil Engineering: Innovation, Theory and Practice by : Airong Chen
Download or read book Life-Cycle Civil Engineering: Innovation, Theory and Practice written by Airong Chen and published by CRC Press. This book was released on 2021-02-26 with total page 1758 pages. Available in PDF, EPUB and Kindle. Book excerpt: Life-Cycle Civil Engineering: Innovation, Theory and Practice contains the lectures and papers presented at IALCCE2020, the Seventh International Symposium on Life-Cycle Civil Engineering, held in Shanghai, China, October 27-30, 2020. It consists of a book of extended abstracts and a multimedia device containing the full papers of 230 contributions, including the Fazlur R. Khan lecture, eight keynote lectures, and 221 technical papers from all over the world. All major aspects of life-cycle engineering are addressed, with special emphasis on life-cycle design, assessment, maintenance and management of structures and infrastructure systems under various deterioration mechanisms due to various environmental hazards. It is expected that the proceedings of IALCCE2020 will serve as a valuable reference to anyone interested in life-cycle of civil infrastructure systems, including students, researchers, engineers and practitioners from all areas of engineering and industry.
Book Synopsis Fibre Optic Methods for Structural Health Monitoring by : Branko Glisic
Download or read book Fibre Optic Methods for Structural Health Monitoring written by Branko Glisic and published by John Wiley & Sons. This book was released on 2008-03-11 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of fibre optic sensors in structural health monitoring has rapidly accelerated in recent years. By embedding fibre optic sensors in structures (e.g. buildings, bridges and pipelines) it is possible to obtain real time data on structural changes such as stress or strain. Engineers use monitoring data to detect deviations from a structure’s original design performance in order to optimise the operation, repair and maintenance of a structure over time. Fibre Optic Methods for Structural Health Monitoring is organised as a step-by-step guide to implementing a monitoring system and includes examples of common structures and their most-frequently monitored parameters. This book: presents a universal method for static structural health monitoring, using a technique with proven effectiveness in hundreds of applications worldwide; discusses a variety of different structures including buildings, bridges, dams, tunnels and pipelines; features case studies which describe common problems and offer solutions to those problems; provides advice on establishing mechanical parameters to monitor (including deformations, rotations and displacements) and on placing sensors to achieve monitoring objectives; identifies methods for interpreting data according to construction material and shows how to apply numerical concepts and formulae to data in order to inform decision making. Fibre Optic Methods for Structural Health Monitoring is an invaluable reference for practising engineers in the fields of civil, structural and geotechnical engineering. It will also be of interest to academics and undergraduate/graduate students studying civil and structural engineering.
Book Synopsis Field-measured Post-tension Prestress Loss in Stress-relieved Strands by : James E. Richardson
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:
Book Synopsis Bridge Evaluation, Repair and Rehabilitation by : A.S. Nowak
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.
Book Synopsis Investigation of Long-term Prestress Losses in Pretensioned High Performance Concrete Girders by : Thomas E. Cousins
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.
Book Synopsis Long-term Continuity Moment Assessment in Prestressed Concrete Girder Bridges by : Veeravenkata S. Murthy Chebole
Download or read book Long-term Continuity Moment Assessment in Prestressed Concrete Girder Bridges written by Veeravenkata S. Murthy Chebole and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Simplified Method for Prediction of Long-term Prestress Loss in Post-tensioned Concrete Bridges by : Samer Amir Youakim
Download or read book A Simplified Method for Prediction of Long-term Prestress Loss in Post-tensioned Concrete Bridges written by Samer Amir Youakim and published by . This book was released on 2006 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt:
