scholarly journals Mechanics Based Statistical Prediction of Structure Size and Geometry Effects on Safety Factors for Composites and Other Quasibrittle Materials

2007 ◽  
Author(s):  
Zdenek Bazant
Keyword(s):  
Statistical Prediction ◽  
Safety Factors ◽  
Quasibrittle Materials ◽  
Geometry Effects ◽  
Size And Geometry Effects

scholarly journals Mechanics based statistical prediction of structure size and geometry effects on safety factors for composites and other quasibrittle materials

2008 ◽  
Vol 35 (1-3) ◽  
pp. 53-71 ◽  
Author(s):  
Zdeněk Bazant
Keyword(s):  
Mathematical Description ◽  
Structural Strength ◽  
Journal Article ◽  
Statistical Prediction ◽  
Probability Density Distribution ◽  
Safety Factors ◽  
Statistical Parameters ◽  
Size And Shape ◽  
Quasibrittle Materials ◽  
Nominal Strength

The objective of this paper1 is a rational determination of safety factors of quasibrittle structures, taking into account their size and shape. To this end, it is necessary to establish the probability density distribution function (pdf) of the structural strength. For perfectly ductile and perfectly brittle materials, the proper pdf's of the nominal strength of structure are known to be Gaussian and Weibullian, respectively, and are invariable with structure size and geometry. However, for quasibrittle materials, many of which came recently to the forefront of attention, the pdf has recently been shown to depend on structure size and geometry, varying gradually from Gaussian pdf with a remote Weibull tail at small sizes to a fully Weibull pdf at large sizes. This recent result is reviewed, and then mathematically extended in two ways: 1) to a mathematical description of structural lifetime as a function of applied (time-invariable) nominal stress, and 2) to a mathematical description of the statistical parameters of the pdf of structural strength as a function of structure size and shape. Experimental verification and calibration is relegated to a subsequent journal article.

Compatible Approach to Concrete Strength Characterization in the Design and Construction of Concrete Pavements

1997 ◽  
Vol 1568 (1) ◽  
pp. 89-95 ◽  
Author(s):  
Jorge B. Soares ◽  
Dan G. Zollinger
Keyword(s):  
Concrete Strength ◽  
Test Method ◽  
Concrete Pavements ◽  
Small Test ◽  
Geometry Effects ◽  
Construction Specification ◽  
Strength Characterization ◽  
Pavement Construction ◽  
Size And Geometry Effects ◽  
Actual Configuration

The effectiveness of a concrete pavement construction specification depends on the degree of correlation the criteria in the specification have to the material properties and behavior characteristics that govern the performance of pavements. Since concrete strength is determined on the basis of small test specimens, it is important that the strength measured in these specimens be representative of the strength within the actual configuration of a pavement system. A primary deficiency in this regard is that strengths obtained from different test specimens can be quite different from each other and from the strength of the concrete in the pavement. This fact raises the question of which specimen should serve as a representative concrete strength standard that would allow a reliable measure of concrete quality and yet provide a parameter that is compatible with design stress calculations. This deficiency is encompassed within size and geometry effects that are present when estimating strength from small test specimens. Since most distresses in concrete pavements are due to tension-induced cracking, it is only logical that tension-type tests be used to represent concrete resistance to failure. A simplified tension test method, based on the fracture mechanics theory, provides a solution to the deficiency by taking into account size and geometry effects. The method considers the geometry of the specimen from which the strength is being measured (e.g., cylinder) and the geometry of the structure to which the measured strength is being applied (e.g., pavement slab). This method makes it possible to circumvent the problem of obtaining a representative strength value from a small laboratory specimen.

Doped-channel micro-Hall devices: Size and geometry effects

2005 ◽  
Vol 98 (9) ◽  
pp. 094503 ◽  
Author(s):  
Vas. P. Kunets ◽  
Yu. I. Mazur ◽  
G. J. Salamo ◽  
O. Bierwagen ◽  
W. T. Masselink
Keyword(s):  
Geometry Effects ◽  
Size And Geometry Effects
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