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Book Behavior at the Corners of Skewed Single span Cast in place Post tensioned Box Girder Bridges

Download or read book Behavior at the Corners of Skewed Single span Cast in place Post tensioned Box Girder Bridges written by Phillip M. Holthaus and published by . This book was released on 2009 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: In today's textbooks, analyzing prestressed members and bridges takes a two-dimensional approach. Two-dimensional analysis is the only way to analyze prestressed bridges and members because otherwise the hand calculations are extremely difficult. Skewed bridges, however, need to be analyzed and designed three-dimensionally. Based on engineering inspection, it is possible to tell how a non-skewed symmetric bridge will behave. However, the knowledge of how a skewed bridge will behave cannot be obtained by inspection only. Finite element analysis can be used to model a bridge and discover how the bridge will react to dead loads and post-tensioning forces. When a bridge is built on a skew, the acute corners of the bridge support much less concrete weight than the obtuse corners of the bridge. If the post-tensioning force causes a decrease in load at the acute corners of the skewed bridge and if the skew of the bridge is great enough, there is a concern that there could be uplift at these acute corners of the bridge. Uplift at any corner of the bridge should not be allowed. The objective of this study is to investigate a simple span skewed box girder bridge to see if any uplift occurs at the acute corners of the bridge due to post-tensioning forces. After careful study of a skewed simple span cast-in-place post-tensioned box girder bridge, it was found that the post-tensioning force actually transfers more downward force into the acute corners of the bridge. Based on this study, the post-tensioning force will not cause uplift in the acute corners of the skewed bridge.

Book Behaviour at the Mid span of Post Tensioned Simple Span Skewed Box Girder Bridges

Download or read book Behaviour at the Mid span of Post Tensioned Simple Span Skewed Box Girder Bridges written by Shree Krishna Tripathi and published by . This book was released on 2020 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many highway bridges are skewed to maintain the profile of natural obstacles to road like rivers, and depressions. Generally, we analyze straight bridge girders making it a line element which makes our hand calculations simpler. However, if we follow the same procedure for skewed bridges like straight ones, we cannot fully visualize and determine their behavior properly which may lead to over estimation or underestimation on different structural forces like bending moment, shear force and most importantly deflection. It is because when we look on skewed bridges in three dimension, the ends of the bridges are skewed to the centerline of the bridges and we can clearly realize that the concrete materials in the acute side is less than that in the obtuse side. If the skew angle is relatively large, it might be the case that there is unbalancing forces along the cross section of the skewed bridge which might lead to the camber at the center of the bridge to be inclined to the vertical which might tend to rotate the entire bridge about the vertical plane. This implies that highly skewed bridges tend to attract more torsion making the design more complicated. If these aspects are not taken into consideration, the skewed bridges might not be good fit while taking the limit state of serviceability. This thesis paper investigates into the three-dimensional analysis of a skewed bridge. Finite element modeling is utilized to analyze the skewed bridges and we can know how it behaves. After the modeling and analysis of a simple span cast in place post tensioned skewed bridge, it is seen that the deflection and bending moment at the mid-span of a skewed bridge is less compared to the non-skewed bridge. Moreover, a skew effect factor is also found which is very useful while designing skewed bridges.

Book Structural Behavior of a Skew Two Span Reinforced Concrete Box Girder Bridge Model Detailed tables of experimental and analytical results

Download or read book Structural Behavior of a Skew Two Span Reinforced Concrete Box Girder Bridge Model Detailed tables of experimental and analytical results written by and published by . This book was released on 1980 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Structural Behavior of a Skew Two Span Reinforced Concrete Box Girder Bridge Model Response during ultimate loading to failure

Download or read book Structural Behavior of a Skew Two Span Reinforced Concrete Box Girder Bridge Model Response during ultimate loading to failure written by and published by . This book was released on 1980 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Prediction of Long term Prestress Loss in Concrete Box Girder Bridges

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 Evaluation of Long term Prestress Losses in Post tensioned Box girder Bridges

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 74 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 An Introduction to Prestressing Losses with Post Tensioning of Highway Box Girders

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.