Pervasiveness of Excessive Segmental Bridge Deflections: Wake-Up Call for Creep
TL;DR: In this paper, the authors investigated the long-time deflection evolution of Koror-Babeldaob (KB) bridge in the island nation of Palau and showed that the terminal logarithmic deflection trend can be predicted well by a simple extrapolation of the measured 1000-day deflection under the hypothesis of proportionality to the compliance function increment since the time of span closing.
Abstract: An obsolete standard recommendation for creep design led to significant underestimation of the observed 18-year deflections of the Koror-Babeldaob (KB) Bridge in the island nation of Palau. A search for data on similar bridges revealed that 56 other large-span, prestressed concrete, segmentally erected box girders (66 by the time of proof) have been found to exhibit excessive long-time deflections. There are probably many more in existence. The observed deflections give no sign of approaching a finite bound, as implied in the empirical ACI Committee 209, CEB-fib, and GL models for creep. They were found to evolve approximately logarithmically beginning at about 1000 days after span closing. While sufficient data for the finite element creep analysis of these deflections were not obtainable, comparisons with accurate deflection solutions for the KB Bridge showed that the terminal logarithmic deflection trend can be predicted well by a simple extrapolation of the measured 1000-day deflection under the hypothesis of proportionality to the compliance function increment since the time of span closing. Comparisons of the extrapolations according to various creep models show that the underestimation of long-time deflections is much less severe for the theoretically based Model B3 than it is for the three other models, and that the terminal trend is logarithmic. A simple update of this model that gives the same mean terminal trend as the 56 bridges is devised that should allow for improving the durability of segmental bridges.
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TL;DR: In this paper, the creep properties of calcium silicate hydrates (C-S-H) are assessed by means of nanoindentation creep experiments on a wide range of substoichiometric cement pastes.
231 citations
TL;DR: The segmental prestressed concrete box girder of Koror-Babeldaob (KB) bridge in Palau, which had a record span of 241 m (791 ft) and collapsed in 1996 as a consequence of remedial prestressing, after a 3-month delay as mentioned in this paper.
Abstract: The segmental prestressed concrete box girder of Koror-Babeldaob (KB) Bridge in Palau, which had a record span of 241 m (791 ft), presents a striking paradigm of serviceability loss because of excessive multidecade deflections. The data required for analysis have recently been released and are here exploited to show how the analysis and design could be improved. Erected segmentally in 1977, this girder developed a midspan deflection of 1.61 m (5.3 ft) compared with the design camber after 18 years, and it collapsed in 1996 as a consequence of remedial prestressing, after a 3-month delay. Compared with three-dimensional analysis, the traditional beam-type analysis of box girder deflections is found to have errors up to 20%, although greater errors are likely for bridges with higher box-width-to-span ratios than the KB Bridge. However, even three-dimensional finite-element analysis with step-by-step time integration cannot explain the observed deflections when the current American Concrete Institute, Japan Society of Civil Engineers, Comite Euro-International du Beton (or Comite Euro- International du Beton—Federation internationale de la precontrainte), and Gardner and Lockman prediction models for creep and shrinkage are used. These models give 18-year deflection estimates that are 50-77% lower than measured and yield unrealistic shapes of the deflection history. They also predict the 18-year prestress loss to be 46-56% lower than the measured mean prestress loss, which was 50%. Model B3, which is the only theoretically based model, underestimates the 18-year deflection by 42% and gives a prestress loss of 40% when the default parameter values are used. However, in Model B3, several input parameters are adjustable and if they are adjusted according to the long-time laboratory tests of Brooks, a close fit of all the measurements is obtained. For early deflections and their extrapolation, it is important that Model B3 can capture realistically the differences in the rates of shrinkage and drying creep caused by the differences in the thickness of the walls of the cross section. The differences in temperature and possible cracking of the top slab also need to be taken into account. Other paradigms on which data have recently been released are four bridges in Japan and one in the Czech Republic. Their excessive deflections can also be explained. The detailed method of analysis and the lessons learned are presented in Part II. DOI: 10.1061/(ASCE)ST.1943-541X .0000487. © 2012 American Society of Civil Engineers. CE Database subject headings: Creep; Shrinkage; Box girders; Serviceability; Deflection; Span bridges. Author keywords: Prestressed box girder; Bridges; Segmental erection; Shear lag; Design standards; Concrete; Relaxation.
189 citations
TL;DR: In this article, the authors present a novel approach to solve the problem of plagiarism in the context of biomedical data analysis, which is accepted for publication, but it is copyrighted by RILEM, and readers must contact Riellem for permission to reprint or use the material in any form.
Abstract: The original publication is available at the publisher’s web site: http://link.springer.com/article/10.1617/s11527-014-0485-2/fulltext.html#copyrightInformation.
This article is accepted for publication, it is copyrighted by RILEM, and readers must contact RILEM for permission to reprint or use the material in any form.
162 citations
Cites background from "Pervasiveness of Excessive Segmenta..."
...Department of Transportation (DoT), led to a collection of multi-decade deflection data of 69 large-span prestressed bridges from around the world, most of which suffered excessive deflections resulting in bridge closing or costly retrofit [3]....
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01 Jan 2015
TL;DR: In this paper, a new prediction model for creep and shrinkage is presented, named B4, which builds on the theoretically justified model B3, which is a RILEM recommendation from 1996.
Abstract: In response to the continuously advancing concrete technology, a new prediction model for creep and shrinkage is presented. This model, named B4, builds on the theoretically justified model B3, which is a RILEM recommendation from 1996. Improvements to the model allow for enhanced multi-decade predic- tion, distinguish between the drying and autogenous shrinkage, and introduce new equations and parame- ters to capture the effects of various admixtures and aggregate types. The development and justification of the model is described in three companion articles which follow.
131 citations
TL;DR: The first large worldwide database of creep and shrinkage tests was assembled at Northwestern University (NU) in 1978 as discussed by the authors and was expanded as the RILEM database in 1992 and further in 2008.
Abstract: The first large worldwide database of creep and shrinkage tests was assembled at Northwestern University (NU) in 1978. It was expanded as the RILEM database in 1992 and further in 2008. A major expansion, completely restructured and verified, named the NU Database, is now presented. The number of the test curves of creep and drying shrinkage is more than doubled and over 400 test curves of autogenous shrinkage are added. The database covers longer measurement periods and encompasses the effects of admixtures in modern concrete mixtures. The database contains roughly 1400 creep and 1800 shrinkage curves, of which approximately 800 creep and 1050 shrinkage curves contain admixtures. Their analysis shows significant influence of admixtures on the creep and shrinkage behavior. The mixture proportions, testing conditions, and specimen geometries are documented in greater detail, and information on the admixture contents and aggregate types is included. The new database makes it possible to calibrate and verify improved creep and shrinkage prediction models. Additionally, the statistics of the mixture parameters, strength distributions, and scatter of the compliance curves have been extracted for applications in reliability engineering and probabilistic performance assessment. Data analysis brings to light various recommendations for testing and recording, and suggests corrections of various oversights distorting the reported data. These recommendations would make future test data more useful, consistent, complete, and reliable. The NU database is now available for free download at www. civil.northwestern.edu/people/bazant/ as well as at www.baunat.boku.ac.at/creep.html.
97 citations
References
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01 Jan 2000
TL;DR: The 2003 AASHTO Subcommittee on Design, Task Force on Geometric Design was held in Charleston, South Carolina during the period July 13 through July 16, 2003 as mentioned in this paper and the purpose of the meeting was to review several documents undergoing revision, review the proposed revisions to the superelevation discussion in the Green Book, consider future research, and other administrative matters of concern to the Task Force Membership.
Abstract: The annual meeting of the AASHTO Subcommittee on Design, Task Force on Geometric Design was held in Charleston, South Carolina during the period July 13 through July 16, 2003. The purpose of the meeting was to review several documents undergoing revision, review the proposed revisions to the superelevation discussion in the Green Book, consider future research, and other administrative matters of concern to the Task Force Membership.
1,786 citations
01 Jul 1995
TL;DR: In this paper, a model for the characterization of concrete creep and shrinkage in the design of concrete structures is recommended, which is simpler, agrees better with the experimental data and is justified better theoretically than the previous models.
Abstract: A model for the characterization of concrete creep and shrinkage in the design of concrete structures is recommended. It is simplier, agrees better with the experimental data and is justified better theoretically than the previous models. The model complies with the general guidelines recently formulated by RILEM TC 107. Justification of the model and various refinements are to be published shortly in two parts.
623 citations
Book•
12 Nov 2001
TL;DR: Reference EPFL-BOOK-102881 URL: http://www.wiley.co.uk/inelastic/ Record created on 2007-04-23, modified on 2016-08-08.
Abstract: Reference EPFL-BOOK-102881 URL: http://www.wiley.co.uk/inelastic/ Record created on 2007-04-23, modified on 2016-08-08
526 citations
01 Apr 1972
TL;DR: In this paper, the authors present a rigorous formulation of the effective modulus method and extend it to the case of a variable elastic modulus and an unbounded final value of creep.
Abstract: • IN THE CREEP ANALYSIS OF concrete structures two kinds of errors are involved. One stems from the inaccurate knowledge of the creep law, and its minimization is a problem of materials re search. The second error is caused by the simpli fication of analysis, which designers introduce to avoid the complexities of an exact analysis. In the sequel, only accuracy or exactitude in the latter sense will be of concern. The simplest and the most widespread among the simplified methods of analysis is the well known effective modulus method, whose error with regard to the theoretically exact solution for the given creep law is known to be quite large when aging of concrete, i.e., the change of its properties with the progress of hydration, is of significance (see Table 2 discussed below). How ever, a surprisingly simple way of refinement of this method has been recently discovered by Trost, 1 on the basis of approximate and mostly intuitive considerations. The intent of this paper is to present a rigorous formulation of this method and to extend it to the case of a variable elastic modulus and an unbounded final value of creep.
445 citations
385 citations