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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 91 Abstracts search results
Document:
SP128-57
Date:
November 1, 1991
Author(s):
F. Watanabe and K. Ohsumi
Publication:
Symposium Papers
Volume:
128
Abstract:
A new method to enhance the moment-curvature relations of reinforced concrete sections in post-yield range of deformation was developed. The point of the idea is to introduce the sequential yielding of different grade longitudinal bars in a section with the progress of section curvature. The section then does not have any negative stiffness up to the yielding of highest grade bars and results in very ductile behavior. To confirm the advantages of the new method, flexural analyses and loading tests were carried out on reinforced concrete columns with different grade longitudinal bars. The results of theoretical calculations and loading tests indicated that the combined use of different grade longitudinal bars can considerably improve the flexural behavior of reinforced concrete sections.
DOI:
10.14359/3269
SP128-79
Steven G. Provenghi and Gregg E. Brandow
This is an actual case-study of a four-story reinforced concrete parking structure with ultra-thin, two-way flat slabs with drop panels. The slabs were 4.50 in. thick on bays as large as 27 x 27 ft with midspan deflections as much as 5.50 in. The evaluation included physical inspections to evaluate crack patterns as well as nondestructive tests to locate reinforcing steel and full-scale load tests per ACI recommendations to evaluate the strength of the structural slab. Recommendations for repair and strengthening were accomplished by a combination of external post-tensioning with king-post type trussing below the floor slabs and with a gravity-fed polymer repair of the structural cracks found within the slab.
10.14359/3272
SP128-21
Jens Holm and Per Goltermann
The manifestation of cracking in concrete has been considered. Using thin-section techniques, it is possible to analyze crack patterns in concrete. Based on classical mechanics theories, the crack patterns can be categorized according to the stress situation at the point of incipient cracking. Various deteriorating mechanisms in concrete cause different stress conditions in the hardened cement paste, in the aggregate, and at their interface. Combining the features of crack patterns in a given concrete with other data secured from petrographic analysis of thin sections and knowledge of the mechanisms of various deteriorating (or harmless) processes, it is possible to diagnose with increased accuracy the field performance of the concrete.
10.14359/1958
SP128-03
K. W. Nasser and P. S. H. Lai
This paper describes an investigation that was carried out to determine the within-test variability of various nondestructive test methods and their correlation with the corresponding compressive strength. The nondestructive test methods that were studied were the pin penetration, the ultrasonic pulse velocity, and the nuclear density gage. The tests were performed on solid concrete blocks, cylinders, and reinforced concrete slabs at different ages. The within-test variability of the direct readings of the ultrasonic pulse velocity was small compared to the pin penetration and nuclear density gage. However, when the readings were translated into strength, the within-test variabilities of the standard compression test were about the same as the other methods. The relationship between strength and the pin penetration and pulse velocity readings were good, while the relationship between the density of fresh and hardened concrete and the nuclear gage readings were satisfactory.
10.14359/3627
SP128-07
Hemant S. Limaye and Donald F. Meinheit
Over the last 3 years, an impact-echo technique has proven to be an effective evaluation tool in identifying defects and locating embedded items in concrete structures. The advantages of the method are that it is nondestructive, relatively easy to calibrate, and testing can be conducted from one surface of the element under test. Operating experience with the impact-echo technique has shown that, within known limitations, the technique can provide a rapid nondestructive means for performing certain concrete condition surveys.
10.14359/3636
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