Author: Mauricio Lopez Publisher: ISBN: Category : Concrete Languages : en Pages :
Book Description
This multi-scale investigation aimed to provide new knowledge and understanding of creep and shrinkage of high performance lightweight concrete (HPLC) by assessing prestress losses in HPLC prestressed members in a large-scale study; by quantifying the effect of the constituent materials and external conditions on creep and shrinkage in a medium-scale study; and by improving the fundamental understanding of creep and shrinkage in a small-scale study. Creep plus shrinkage prestress losses were between two and eight times lower than those estimated for the design standards and approximately 50% of those measured in similar strength normal weight high performance concrete girders. The lower creep and shrinkage exhibited by HPLC was found to be caused by a synergy between the pre-soaked lightweight aggregate and the low water-to-cementitious material ratio matrix. That is, the water contained in the lightweight aggregate contributes to enhance hydration by providing an internal moist curing. The water in the aggregate also contributes to maintain a high internal relative humidity which reduces or eliminates autogenous shrinkage. This higher internal relative humidity also reduces creep by preventing load-induced water migration. Finally, lightweight aggregate exhibits a better elastic compatibility with the paste than normal weight aggregate. This improved elastic matching and the enhanced hydration are believed to reduce peak deformations at the ITZ which further decreases creep and shrinkage.
Author: Edward Creed Vincent Publisher: ISBN: Category : Concrete Languages : en Pages : 70
Book Description
In addition to immediate elastic deformations, concrete undergoes time-dependent deformations that must be considered in design. Creep is defined as the time-dependent deformation resulting from a sustained stress. Shrinkage deformation is the time-dependent strain that occurs in the absence of an applied load. The total strain of a concrete member is the sum of elastic, creep, and shrinkage strains. Test beams for the Pinner's Point Bridge were produced by Bayshore Concrete Products Corp. using a high-strength normal weight concrete (HSC) mixture and the Chickahominy River Bridge beams using a high-strength lightweight concrete (LTHSC) mixture. The test beams and the Chickahominy River Bridge beams were fabricated with thermocouples to track interior concrete temperatures, and vibrating wire gages (VWGs) were placed at the center of prestressing to record changes in strain. Laboratory creep and shrinkage testing was conducted on specimens prepared with identical materials and similar mixture proportions in the casting of the bridge beams. The temperature profile from the beams during steam curing was used to produce match-cured specimens for laboratory testing. Two match-cured batches were produced, along with two standard cured batches. The creep room had a temperature of 23.0 ł 1.7ʻC (73.4 ł 3ðF) and a relative humidity of 50 ł 4%. Companion shrinkage specimens were also placed in the creep room. Measurements were taken on the creep and shrinkage specimens using a Whittemore gage. Four HSC cylinders were also equipped with embedded VWGs so that the interior and exterior strains could be compared. The Whittemore and VWG elastic and creep strains were similar, while the VWGs recorded significantly less shrinkage. The measured creep and shrinkage strains were compared to different prediction models to determine which model was the most accurate. The models considered were ACI 209, ACI 209 modified by Huo, CEB Model Code 90, AASHTO-LRFD, Gardner GL2000, Tadros, and Bazant B3. The ACI 209 modified by Huo was the most accurate in predicting time-dependent strains for the HSC mixture. The best overall predictor for the LTHSC time-dependent deformations was the Gardner GL 2000 model for the standard cure LTHSC specimens, whereas the ACI 209 model was the best predictor of the total stains and individual time-dependent deformations for the match-cured LTHSC mixture.
Author: Publisher: ISBN: Category : Concrete Languages : en Pages : 314
Book Description
This report is concerned with the prediction of the long-time creep and shrinkage behavior of concrete. It is divided into three main areas. l. The development of general prediction methods that can be used by a design engineer when specific experimental data are not available. 2. The development of prediction methods based on experimental data. These methods take advantage of equations developed in item l, and can be used to accurately predict creep and shrinkage after only 28 days of data collection. 3. Experimental verification of items l and 2, and the development of specific prediction equations for four sand-lightweight aggregate concretes tested in the experimental program. The general prediction equations and methods are developed in Chapter II. Standard Equations to estimate the creep of normal weight concrete (Eq. 9), sand-lightweight concrete (Eq. 12), and lightweight concrete (Eq. 15) are recommended. These equations are developed for standard conditions (see Sec. 2. 1) and correction factors required to convert creep coefficients obtained from equations 9, 12, and 15 to valid predictions for other conditions are given in Equations 17 through 23. The correction factors are shown graphically in Figs. 6 through 13. Similar equations and methods are developed for the prediction of the shrinkage of moist cured normal weight concrete (Eq. 30}, moist cured sand-lightweight concrete (Eq. 33}, and moist cured lightweight concrete (Eq. 36). For steam cured concrete the equations are Eq. 42 for normal weight concrete, and Eq. 45 for lightweight concrete. Correction factors are given in Equations 47 through 52 and Figs., 18 through 24. Chapter III summarizes and illustrates, by examples, the prediction methods developed in Chapter II. Chapters IV and V describe an experimental program in which specific prediction equations are developed for concretes made with Haydite manufactured by Hydraulic Press Brick Co. (Eqs. 53 and 54}, Haydite manufactured by Buildex Inc. (Eqs. 55 and 56), Haydite manufactured by The Cater-Waters Corp. (Eqs. 57 and 58}, and Idealite manufactured by Idealite Co. (Eqs. 59 and 60). General prediction equations are also developed from the data obtained in the experimental program (Eqs. 61 and 62) and are compared to similar equations developed in Chapter II. Creep and Shrinkage prediction methods based on 28 day experimental data are developed in Chapter VI. The methods are verified by comparing predicted and measured values of the long-time creep and shrinkage of specimens tested at the University of Iowa (see Chapters IV and V) and elsewhere. The accuracy obtained is shown to be superior to other similar methods available to the design engineer.
Author: Thomas E. Cousins Publisher: Transportation Research Board ISBN: 030925888X Category : Architecture Languages : en Pages : 91
Book Description
"TRB's National Cooperative Highway Research Program (NCHRP) Report 733: High-Performance/High-Strength Lightweight Concrete for Bridge Girders and Decks presents proposed changes to the American Association of State Highway and Transportation Officials' Load and Resistance Factor Design (LRFD) bridge design and construction specifications to address the use of lightweight concrete in bridge girders and decks. The proposed specifications are designed to help highway agencies evaluate between comparable designs of lightweight and normal weight concrete bridge elements so that an agency's ultimate selection will yield the greatest economic benefit. The attachments contained in the research agency's final report provide elaborations and detail on several aspects of the research. Attachments A and B provide proposed changes to AASHTO LRFD bridge design and bridge construction specifications, respectively; these are included in the print and PDF version of the report. Attachments C through R are available for download below. Attachments C, D, and E contain a detailed literature review, survey results, and a literature summary and the approved work plan, respectively. Attachment C; Attachment D ; Attachment E; Attachments F through M provide details of the experimental program that were not able to be included in the body of this report. Attachment F; Attachment G; Attachment H; Attachment I; Attachment J; Attachment K; Attachment L; Attachment M. Attachments N through Q present design examples of bridges containing lightweight concrete and details of the parametric study. Attachment N; Attachment O; Attachment P; Attachment Q. Attachment R is a detailed reference list."--Publication information.
Author: Tada-aki Tanabe Publisher: CRC Press ISBN: 0203882954 Category : Technology & Engineering Languages : en Pages : 1552
Book Description
CREEP, SHRINKAGE AND DURABILITY MECHANICS OF CONCRETE AND CONCRETE STRUCTURES contains the keynote lectures, technical reports and contributed papers presented at the Eighth International Conference on Creep, Shrinkage and Durability of Concrete and Concrete Structures (CONCREEP8, Ise-shima, Japan, 30 September - 2 October 2008). The topics covered
Author: Hubert Rüsch Publisher: Springer Science & Business Media ISBN: 1461254248 Category : Technology & Engineering Languages : en Pages : 296
Book Description
This book is based on Reinforced Concrete-Prestressed Concrete, Volume 2, Accounting for the Effects of Creep and Shrinkage on the Behavior of Structural Systems by Hubert Rusch and Dieter Jungwirth, which appeared in German in 1976. Even then, it was Hubert Rusch's fervent wish to have his thoughts on the deformations of concrete translated into English in order to reach a wider audience. His earlier efforts to contribute a study to the Series of Monographs of the Ameri can Institute had unfortunately not succeeded. Despite a serious illness, Hubert Rusch undertook, with his characteristic prudence and thoroughness, the preparatory work for the translation and related revision of his book. Unfortunately fate did not grant him the satisfaction of seeing his work completed. Hubert Rusch died on October 17, 1979. In writing this book, Hubert Rusch drew on his many years of devoted study of the creep problem. These investigations go back to 1934. His awareness of the plastic deformation of concrete under sustained load, which had been reported to him on the occasion of an American sojourn, led him to discover the causes of a major building collapse. At his urging, Professor A. Hummel published, in 1935, a critical survey of the test results then available on concrete creep.
Author: Mauricio Lopez
Author: Edward Creed Vincent
Author: 
Author: Thomas E. Cousins
Author: Tada-aki Tanabe
Author: Truman R. Jones
Author: Hubert Rüsch
Author: ACI Committee 209--Creep and Volume Changes in Concrete
Author: Truman Jones (R.)
Author: Walter Damian Mesia