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Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 13 Abstracts search results
Document:
SP141-09
Date:
December 1, 1993
Author(s):
Sami W. Tabsh and Alex Aswad
Publication:
Symposium Papers
Volume:
141
Abstract:
A reliability-based approach is used to recommend allowable edge loads for precast hollow core slabs. Full-scale test results are used to predict the statistical parameters of the resistance at the edge. The study indicated that the allowable load is a function of dead-to-live load ratio and concrete strength. The analysis is extended to include system reliability of the whole slab due to different failure modes. The failure modes include flexure at midspan and total shear at the ends, in addition to local failure at the edge. The system modeling is composed of a series system made up of three partially correlated elements. A numerical example is also included for illustration. The approach will help engineers make a rational selection of allowable edge loads that occur around large floor openings.
DOI:
10.14359/3965
SP141-11
Dimitrios G. Goulias, W. R. Hudson , and German Claros
In recent years, highway agencies and constructors have used improved construction techniques and materials for better pavement quality. However, newly constructed portland cement concrete pavement surfaces are not always being built to the desired level of ride quality; thus, there is a need for an improved smoothness specification to insure the best riding quality. This paper documents the development and evaluation of end-result smoothness specifications for portland cement concrete pavements in Texas. Based on available equipment and prior studies, the California Profilograph was selected as the instrument for use in developing the specification. Because there are several types of California profilographs, the study team compared two instruments by two different manufacturers. This paper presents the results of this comparison, along with a methodology for defining a recommended specification.
10.14359/3981
SP141-01
Bryant Mather
The customary criterion for establishing grades of structural concrete is the crushing strength measured in an arbitrary manner on a standardized specimen stored in a stipulated fashion for approximately a month after making. In some parts of the world, the specimen is a cube, and in other parts of the world, the specimen is a cylinder. There have been debates as to how the strength at 28 days can be predicted from procedures performed at early ages, especially 24 hr, on the grounds that a month is not soon enough. The intent of this paper is to suggest that the only time that really is "soon enough" to know that the grade of the concrete in any batch is correct is before the concrete is discharged from the concrete mixer into the forms. It is suggested, therefore, that effort would preferably be expended upon insuring that the materials used are those intended and the proportions in which they are used are those that were intended. If this is the case, the grade of concrete will be proper at all ages, and testing at any age is merely confirmation.
10.14359/3987
SP141-02
G. M. Idorn
The three power centers in the world today must support the tremendous concrete construction and building investments that are needed in the developing regions where 90 percent of the world's population lives. Concurrently, renovations and renewals are required in industrial countries. Profound updating of conventional concrete technology is necessary, recognizing the differences between the behavior of test samples of concrete under laboratory conditions and of field concrete. For example, the historic development of curing concrete is reviewed with emphasis on the methods for monitoring heat development during curing of modern concrete. Proposals for wider transfer of this technology are also presented.
10.14359/3988
SP141-03
Nicholas J. Carino
In-place testing is used to estimate the compressive strength of concrete in a structure by measuring another related property. A strength relationship is used to convert the in-place test results to an estimate of the compressive strength. Statistical methods are needed for reliable estimates of in-place strength. Such methods should account for the uncertainties in the measured property, the uncertainty of the strength relationship, and the variability of the in-place concrete. Standard statistical procedures for dealing with these uncertainties have not yet been adopted in North American practice. Recommendations are provided for developing the strength relationship, and a reliable, easy-to-use approach is presented to estimate in-place characteristic strength.
10.14359/3989
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