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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 19 Abstracts search results
September 1, 2007
D.J. Carreira and T.D. Poulos
Differential shortening caused by creep and shrinkage of reinforced concrete columns and shear walls affects the serviceability of high-rise buildings. For structures up to 30 stories or 400 ft (120 m) high, the effects of creep and shrinkage are usually ignored without serious consequences. For reinforced concrete buildings beyond 30 stories, and for shorter buildings of hybrid or mixed construction, ignoring the effects of creep and shrinkage may create several undesirable conditions in the serviceability of the structure.
Owners of high-rise concrete buildings are aware of the potential for undesirable behaviors in service in both structural and in nonstructural elements from the effects of differential shortening of columns and shear walls. Examples include sloping floors; cracking of structural members and interior partitions; buckled elevator guide rails, misaligned elevator stops relative to floors, and damage to façade elements and plumbing risers. To minimize these behaviors, the structural engineer is challenged to predict, design for, and adjust for differential shortening in each of the structural components during construction, as well as forecast future behaviors.
The structural design process and related construction requirements are discussed and illustrated within.
This document presents research carried out in Chile for the study of the shrinkage behavior of Chilean concretes. The effect of the volume surface ratio, concrete slump, aggregate and cement type, nominal aggregate maximum size and admixture type were analyzed. A total of 82 different concrete mixtures with a mean cylinder compressive strength between 25 and 40 MPa at 28 days were studied, involving 492 test specimens. The evolution of the drying shrinkage strains was measured up to 1350 days of drying.
The applicability of six different prediction models is discussed in the light of the measured shrinkage strains. The prediction of drying shrinkage with ACI-209, B3, CEB-MC90, GL2000 and Sakata 1993 and 2001 models were compared with measured results of Chilean concretes. The results showed that current shrinkage models were not adequate to predict the drying shrinkage of the tested Chilean concretes. However, it was found that for Chilean conditions the best result was obtained with the Sakata models having a coefficient of variation less than 30% when the testing data of all concretes was considered in the analysis.
An appropriate methodology to carry out the updating of models was developed, based on the comparison of measured and predicted shrinkage values and the calibration of current proposed models. As a result an updated model to local conditions for use in design phase is proposed.
J.I. Lee, A. Scanlon, and M.A. Scanlon
This paper describes laboratory tests on nine simply supported one-way reinforced concrete members subjected to immediate live load and sustained load. The specimens are 12 ft (3.66 m) long supported on an 11 ft. (3.35 m) span, 12 in. (304.8 mm) wide, and 5 in. (127 mm) deep with two #3 bars at an effective depth of 4 in. (101.6 mm) providing a reinforcement ratio of 0.0046. The specimens were moist cured for up to seven days. Three specimens each were removed from the forms and subjected to immediate live load at three days, seven days, and twenty eight days followed by sustained load due to self weight. Each specimen was subjected to immediate full live load again after six months. Applied load and mid-span deflections were recorded under immediate live load and sustained load. The test results demonstrate the effect of shrinkage restraint provided by embedded bars on the flexural cracking of the specimens under applied load, as well as effects of early age loading on time-dependent response. Calculated deflections based on effective moment of inertia for immediate deflection and long time multipliers for time-dependent deflection are compared with measured deflections.
P.H. Bischoff and R.D. Johnson
This paper investigates the influence of shrinkage on tension stiffening in flexure and subsequent effect on short-term deflection in beams and slabs. While shrinkage is typically thought of as being a long-term effect, it can also have a significant effect on the initial short-term response (particularly for beams tested in the laboratory that are used to develop and validate theoretical models for predicting deflection). Shrinkage that takes place before the beam is loaded is locked into the member response, having the effect of reducing the cracking moment (caused by tensile stresses that develop in the concrete from restraint to shrinkage by the reinforcement) and causing a shift in the bare bar response of the cracked transformed section. The lower cracking moment and shift in the cracked member response both work together to increase the immediate (short-term) deflection of a member loaded in flexure. Neglecting this influence leads to a perception of reduced levels of tension stiffening and also affects comparison of theoretical deflection models with experimental results.
Editors: John Gardner and Mario A. Chiorino
This CD-ROM is a collection of papers prepared for a session held at the ACI 2007 Fall Convention in Puerto Rico on the effects of shrinkage and creep of concrete. The papers are organized into four groups: 1) design, construction, and behavior of bridge structures; 2) effect of concrete shrinkage and creep on the design and construction of tall buildings; 3) deflection and cracking serviceability of slabs, beams, and walls; and 4) other problems and basic questions.
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