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International Concrete Abstracts Portal

Showing 1-5 of 14 Abstracts search results

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: 

SP117-10

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: 

SP117-09

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: 

SP117-06

Date: 

October 1, 1989

Author(s):

R. M. Samra and W. L. Gamble

Publication:

Symposium Papers

Volume:

117

Abstract:

A rational method of analysis is developed that can be used on a computer to determine the behavior of reinforced concrete columns under sustained service loads. At specific time intervals, trial-and-error procedures are used to establish strain compatibility and equilibrium conditions at each of several cross sections of a member. Curvatures are integrated to find the deflected shape, and an iterative approach is used to find the stable deflected shape if there are secondary moments. The analysis calculates the effect of creep on the stress redistribution between concrete and steel and on the deflections of members subjected to variable axial loads and variable moments. The effects of shrinkage and cracking are also included. The applicability of the analysis is partially verified by comparison with laboratory and field investigations reported by various researchers. In most cases, a good correlation is obtained between the analytical results and the measured results.

DOI:

10.14359/2817

Document: 

SP117-02

Date: 

October 1, 1989

Author(s):

K. Van Breugel an C. Van Der Veen

Publication:

Symposium Papers

Volume:

117

Abstract:

An analytical procedure is described for predicting the development of vertical cracks in thin-walled and thick-walled cylindrical structures subjected to membrane forces and thermal loads. Sustained, axisymmetrical (thermal) loads and thermal cyclic loading may jeopardize, due to cracking, the serviceability (in this case the tightness) of thin-walled cylinders. Mathematically obtained crack patterns have been compared with field observations: a good agreement between theory and practice could be established from this comparison. On the basis of a reliable prediction of crack patterns, cost-benefit analyses are feasible to weigh crack control measures against possible repair costs in case these measures were neglected. An example of such an analysis shows an initial increase of reinforcement in view of crack control to be preferable to repair (grouting) of cracks.

DOI:

10.14359/2809

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