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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 20 Abstracts search results
Document:
SP76-07
Date:
October 1, 1982
Author(s):
M. S. Khalil, W. H. Dilger, and A. Ghali
Publication:
Symposium Papers
Volume:
76
Abstract:
A computer-aided, step-by-step method is presented for the study of time-dependent stresses and deformations of pre-stressed concrete frames. The method is used to investigate the effectiveness of deferring the final connections between column or walls and slabs in building frames and allowing the slabs to slide on the columns during post-tensioning. The joints are then constructed at a later date. A second investigation concentrates on the stresses developed in a cast-in-place, normally-reinforced closure strip cast sometime after post-tensioning of the floors in a long continuous frame. Results obtained for the two examples are evaluated and the possibility of excessive stresses and cracking is discussed.
DOI:
10.14359/6788
SP76-18
Karim W. Nasser and H. M. Marzouk
The present tests were made to measure creep of mass concrete containing fly ash at six different temperatures of 70 to 450 F (21.4 to 232 C). At each temperature three stress levels were applied for over 20 months and they were 750, 1200, and 1500 psi (5.17, 8.27, and 10.34 MPa). The results showed that, in general, creep strains increased with a rise in temperature, and the maximum increase occurred at 450 F (232 C). It was also found that beyond 180 days, creep strains vary linearly with stress-strength ratios at temperatures of 70, 160, 350, and 450 F (21.4, 71, 177, and 232 C). However, at temperatures of 250 and 300 F (121 and 149 C), the strains were non-linear with stress-strength ratios at all ages. Based on the experimental results, a basic expression for creep of mass concrete containing fly ash at high temperature was suggested. Results of previous investigation on the effect of high temperature on the strength and elasticity of concrete con-taining fly ash were used to explain the creep behavior at various temperatures.
10.14359/6799
SP76-11
Heinrich Trost
An appropriate time-dependent constitutive relation of concrete based on the physical principle of superposition is derived. This simple stress-strain relation is discussed in solving relaxation problems in which the change of stresses is asked for under given strain conditions. In the discussion of special problems in prestressed concrete, first demonstrated are the differential settlements of supports of continuous beams. The time-dependent deformations and changes of stresses in steel and concrete are illustrated. An especially useful equation is given for calculating the so-called loss of prestress force under the real conditions of the bonded steel in the concrete section.
10.14359/6792
SP76-12
P. Balaguru and Edward G. Nawy
An analytical method to calculate the time dependent stresses and strains in RC columns is presented. Linear viscoelastic models are used to simulate the time dependent behavior of both plain and reinforced concrete. Both concentrically and eccentrically loaded columns are considered. The experimental results are used to obtain the parameters of the model, namely the spring constants and viscosity coefficients. For the concentrically loaded column, the proposed method is compared with the available experimental results. The model predictions are reasonably accurate. A flow chart presents the sequence of operations for the time dependent analysis of concentrical-ly loaded columns. Numerical examples are also presented to further clarify the calculation procedures.
10.14359/6793
SP76-19
Dobrosav Jevtic
Creep tests were conducted on a number of concrete specimens. Numerous prestressed concrete beams were tested for determining deflection, relaxation, and failure under long-term loading. Some of the tests are still in progress.
10.14359/6800
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