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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 14 Abstracts search results

Document: 

SP117-09

Date: 

October 1, 1989

Author(s):

M. K. Tadros,A. Yousef, and Y. S Joo

Publication:

Symposium Papers

Volume:

117

Abstract:

Deals primarily with statically indeterminate beams where settlement of the supports can produce stresses. A method of estimating the effects of support settlement is presented. The method accounts for the fact that soil consolidation and the corresponding support settlement often develop over an extended period of time. The method also demonstrates that creep of concrete can reduce the ultimate settlement-induced stresses in uncracked members by as much as 60 percent of the elastic values. Furthermore, flexural cracking of concrete results in reduction of the member stiffness. This corresponds to further relief of the settlement-induced stresses. Field studies on the effects of settlement in several bridges are presented. The relationship between the amount of settlement and its structural effects is illustrated.

DOI:

10.14359/2824

Document: 

SP117-10

Date: 

October 1, 1989

Author(s):

U. Ersoy and T. Tankut

Publication:

Symposium Papers

Volume:

117

Abstract:

Two case studies are presented as examples illustrating the problem of shrinkage in reinforced concrete buildings in Central Turkey, where humidity is quite low and extreme temperature changes take place. The first case discussed is a structure consisting of one-bay frames with curved beams spanning 36 m. Axial tension created by shrinkage had reduced the axial thrust in the beams causing a considerable drop in the flexural capacity and leading to severe cracking. The second case presented is a grain bin where vertical cracks in the silo walls were explained mainly by the restraining effect of the rigid foundation against shrinkage deformations. Types and causes of shrinkage cracks are discussed, and the methods of analysis used are briefly explained for each case. The estimated values of shrinkage deformations in dry climates with extreme temperature changes are compared with experimental values, and some serious possible consequences are explained.

DOI:

10.14359/2830

Document: 

SP117-12

Date: 

October 1, 1989

Author(s):

M. R. Resheidat

Publication:

Symposium Papers

Volume:

117

Abstract:

Internal algorithms for creep and shrinkage when substituted by approximate algebraic equations lead to the adoption of a computational procedure substantially independent of linear equations adopted in the time-dependent prediction model. Presented herein are the numerical results of stresses and strains of reinforced and post-tensioned concrete bridge box-sections where creep and shrinkage are considered. Field measurements of deformations have been recorded and compared with the corresponding numerical results obtained by utilizing a computer program. Results are presented in a graphical form. It may be concluded that the computer method is a convenient tool for describing the behavior of structural concrete sections considering creep and shrinkage in connection with performance and service ability.

DOI:

10.14359/2837

Document: 

SP117-13

Date: 

October 1, 1989

Author(s):

C. J. Hookham and T. L. Bailey

Publication:

Symposium Papers

Volume:

117

Abstract:

Long-term durability of reinforced and prestressed concrete structures in U.S. nuclear power plants was identified as a critical issue in the feasibility studies of plant life extension. Evaluation of concrete structures at several operating plants included studies of known concrete degradation modes, performance of condition surveys/testing, and service life prediction. Results indicate that service lives of 60 or more years are achievable, provided that preservation activities are conducted for these concrete structures.

DOI:

10.14359/2843

Document: 

SP117-05

Date: 

October 1, 1989

Author(s):

P. Arumugasaamy and R. N Swamy

Publication:

Symposium Papers

Volume:

117

Abstract:

Long-term behavior of in situ reinforced concrete columns in two structures during construction, occupancy, and service is reported. Extensive strain and moisture movements were made up to about 10 years of service, and long-term movements at 25 to 30 years were then estimated. The stress history experienced by the columns in the second structure was monitored through a stress meter embedded in one of the columns, and the influence of reinforcement and the time-dependent movements on the stress history is described. The gradual but significant stress redistribution with time and the resulting concrete-steel load transfer is also discussed. Results show that the time-dependent deformation in in situ columns occurred over a very long period of time and continue to occur at a very small rate. However, the majority of movements in the columns occurred during the first 5-year period after construction of the columns. It is shown that dead load appears to be the predominant load carried by the columns. The design steel stress has been exceeded in several columns within 10 years of service life; however, none of the steel is expected to yield in 50 years of service life. Based on the in situ performance of columns along with other available data, a design recommendation is made to incorporate the effects of load transfer from concrete to steel at the design stage.

DOI:

10.14359/3324

123

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