6— properties of high strength concrete

... testing effort 1.3—Definition of high- strength concrete Since the definition of high- strength concrete has changed over the years, the Committee defined a range of concrete strengths for its activities, ... coefficient of variation than normalstrength concrete, not because of the strength level, but because a higher degree of control is maintained in the production and testing of high- strength concrete ... CONTROL AND TESTING OF HIGH- STRENGTH CONCRETE Fig 4.5.4—Effect of spherically-seated platen on measured compressive strength of 150 mm (6 in.) cylinders as a function of concrete strength (adapted...

Ngày tải lên: 24/10/2014, 21:59

... the expense of a lower flexural strength The achievement of both high flexural strength and high flexural ductility is not easy If a beam section can attain high flexural strength and high flexural ... Although a high- strength concrete is more brittle than a normalstrength concrete, its higher compressive strength, which leads to a larger balanced steel area, does allow a higher flexural strength ductility ... performance of the beam section to be achieved In other words, the use of high- strength concrete could allow a higher flexural strength to be achieved at the same flexural ductility, or a higher flexural...

Ngày tải lên: 17/06/2016, 14:09

... Advantages of High- Strength Concrete in Columns,” Concrete International, April 1989 11 Colaco, J P., “75-Story Texas Commerce Plaza, Houston—The Use of High- Strength Concrete, ” High- Strength Concrete, ... Bending Properties of High- Strength Concrete, ” SP-87, American Concrete Institute, Detroit, 1985, pp 147-178 49 Ibrahim, Hisham, and MacGregor, James G., “Flexural Behavior of High- Strength Concrete ... of ACI 318-63 Based on similar tests of concrete columns with concrete strengths ranging from 79 to 98 MPa, Nedderman46 proposed a lower limit on β1 of 0.65 for concrete strengths in excess of...

Ngày tải lên: 24/10/2014, 17:26

... 10 2.2 Mechanical Properties of Concrete at Elevated Temperatures 10 2.3 Spalling of High Strength Concrete at Elevated Temperature 13 2.4 Mechanical properties of Concrete after Heating ... Behavior of High Strength Steel at Elevated Temperatures 30 3.1 Overview 30 3.2 Chemical Compositions of High Strength Steel 30 3.3 Microstructure of High Strength Steel at High ... the mechanical properties of concrete at/after elevated temperatures, mechanical properties of steel at elevated temperatures, spalling behavior of high strength concrete (HSC) at high temperature...

Ngày tải lên: 08/09/2015, 18:17

... and trapping properties of the stacks, which could reduce the reliability of the MOS devices due to the weaker dielectric strength of the grain boundaries Finally, the influence of the environment ... thickness of the high- k layer is observed [23], leading to a smaller equivalent oxide thickness (EOT) [17] The impact of the polycrystallization of the Al O layer on the electrical conduction of the ... the results of the statistical analysis of the image, indicating the number, density, and size of the regions with a smaller conductivity (black regions) Note that the average size of these areas...

Ngày tải lên: 21/06/2014, 06:20

... form of machinability comparison  ‘Homogeneity of material’ , refers to a uniformity of its microstructure and having isotropic properties used This latter problem of lack of homogeneity of the ... general-purpose definition, as follows: The totality of all the properties of a work material which affect the cutting process and, the relative ease of producing satisfactory products by chip-forming ... way of a ‘Design of Experiments’ (DoE), in combination with ‘Value Analysis’ (VA) approach to the production problem This strategic technique to the problems of ‘machinability comparisons’ of...

Ngày tải lên: 21/06/2014, 22:20

... ANOVA: Total Sum of Squares about the mean: n ¯ � (y  − y ) i= ↓ Sum of squares – due to Source1 ↓ Sum of squares – due to Source2 ↓ Sum of squares – due to Source3 ↓ Sum of squares – due ... or residual Sum of Squares The technique of analysis of variance decomposes this total ‘sum of squares’ into the parts shown above, for a case in which four identifiable sources of variation are ... ‘Deployment of quality through deployment of quality functions’ (Akao, 1988) It is often known as the ‘House of Quality’ , because the tabulated graphical representation looks similar to that of a house...

Ngày tải lên: 21/06/2014, 22:20

... way: ‘The ratio of the magnitude of the output of a system with respect to that of the input – the conditions of operation and measurements must be specified’ (Smith, 1993, et al.) of increasing ... result from a range of multifarious and often linked-factors, they include: • Depth of cut (DOC) – can be considered as the principal cause and, for the prospective control of chatter The DOC ... until the commencement of chatter, then‘backing-off ’ at this level The prediction of chatter’s onset can be found analytically, this value being based upon thorough knowledge of material stiffness...

Ngày tải lên: 21/06/2014, 22:20

... of the true nature of the actual surface condition If this machined workpiece was to be used in a critical and highly-stressed in-service environment, then the user would have a false sense of ... measurement 50 ‘Sampling length’ , is often termed ‘Meter cut-off ’ , or simply the ‘cut-off ’ length and its units are millimetres The most common cut-offs are: 0.25, 0.8, 2.5, 8.0, 25.0 mm ... arithmetic mean of the absolute departures of the roughness profile from the mean line’ (i.e see Fig 163b and c) It can be expressed as follows: lr Ra = �lr � � z(x) � dx  (units of m) NB  The...

Ngày tải lên: 21/06/2014, 22:20

... the profile from the highest peak down Hence, peaks and valleys have accordingly different weights One of the problems that has arisen from utilising this technique for a topographical profile, ... quantities and it is a measure of the extent of this affiliation, thus producing its ‘correlation coefficient’ which can then be utilised *For example, having a sample of pairs of observations ‘x’ and ... region of the tool (i.e insert) only the conduction term remains ∴ Rate of heat generation (˙ ) = σ ε q ˙ Where: ‘σ’ was obtained from an emprical function of: ‘ε’ , ‘˙’; plus ‘T’ ε NB  This rate of...

Ngày tải lên: 21/06/2014, 22:20

... tensile strength of 1400 N mm–2) For Cast steel/iron: Endurance limit = 0.45 tensile strength (i.e up to tensile strength of 600 N mm–2), Endurance limit = 275 N mm–2 (i.e above a tensile strength of ... limit’ being about half its tensile strength, with an approximation often utilised: For steels: Endurance limit = 0.5 tensile strength (i.e up to a tensile strength of 1400 N mm–2), Endurance limit = 700 ... rather than being the result of wear It can be considered as a form of fatigue failure, because of the cycles of loading and unloading during cutting, leading to particles of tool material being removed...

Ngày tải lên: 21/06/2014, 22:20

... 177e, this now being a ‘composite’ of the sum of the: machine/labour/overhead costs (Cm); with tooling cost (CT) The zenith of this curve (Fig 177e), represents the highest production rate (Prmax) ... sensitivity of 1% of its mean designed force, Such a dynamometer requires a natural frequency of at least times the ‘forcing frequency’ , The strain-gauged circuit elements should produce the minimum of ... realistic time period75 The design of most of today’s multi-component dynamometers use piezoelectric elements which are quintessentially comprised of a stack of quartz discs, or plates with accompanying...

Ngày tải lên: 21/06/2014, 22:20

... minute portion of the apparent real of contact (‘Aa’) – even after the contacting asperities of the softer material has plastically deformed (i.e yielded) Thus: Ar = Fn /σy (i) 78 ‘Law(s) of friction’ , ... loading, the top of these asperities will yeild, creating a real area of contact until such a time, that they are capable of supporting an applied load In the main, for the vast majority of engineering ... ‘frictional laws’ with the observation that: ‘The coefficient of friction* is substantially independent of the speed of sliding.’ *Coefficient of friction (µ) = F/N Thus, the friction force is proportional...

Ngày tải lên: 21/06/2014, 22:20

... Static strength – is affected by the yeild point of the workpiece material, which in turn, is influenced by the presence of residual stresses, • Dynamic strength – of the part in-service can often ... some form of harmonic effects present: departures-from-roundness characteristics (i.e a combination of harmonic influences present) The exposed sterile surface (Fig 185), is the result of highly ... that an improvement of metallographical inspection of a sectioned machined surface can be made without unduly affecting any form of surface distortion, ‘tapersectioning’ has often been utilised...

Ngày tải lên: 21/06/2014, 22:20

... 1998 Fick, A.E [Laws of Diffusion], Annals of Physics (Leipzig, Germany), Vol 170, 59, 1855 Field, M and Kahles, J.F Review of Surface Integrity of Machined Components Annals of the CIRP, Vol 20(2), ... constructed, to high- light their particular influence on functional performance In the majority of cases given in Table 13, the influence of these sub-surface defects tends to be of significance, ... dislocations reduce the strength of the material, as less force is necessary to alter the atomic lattice Dislocation motion of atoms is a complex subject, which goes beyond the scope of the present text,...

Ngày tải lên: 21/06/2014, 22:20

... Tools J of Manuf Science, Vol 119, 681–688, 1997 Tay, A.A.O A Review of Methods of Calculating Machining Temperature J of Matls Processing Tech., Vol 36, 225–257, 1993 Taylor, F.W On the Art of Cutting ... Higgins, R.A Properties of Engineering Materials Hodder and Stoughton Educ., 1979 Influence of Metallurgy on Hole Making Operations American Soc of Metals (Ohio), 1978 Influence of Metallurgy ... F.W On the Art of Cutting Metals Trans of ASME, Vol 28, 31, 1907 Thomsen, E.G., Application of the Mechanics of Plastic Deformation to Metal Cutting Annals of the CIRP, Vol 14, 113–123, 1966 Tlusty,...

Ngày tải lên: 21/06/2014, 22:20

... scatter of modulus of elasticity data (Fig 6.3) HIGH- STRENGTH CONCRETE 363R-25 Fig 6.3—Modulus of elasticity versus square root of concrete strength, incorporating lower- and higher -strength concrete ... average compressive strength of concrete used as the basis for selection of concrete proportions, psi (MPa) modulus of rupture of concrete, psi (MPa) splitting cylinder strength of concrete, psi (MPa) ... 1.2—Definition of high- strength concrete In 2001, Committee 363 adopted the following definition of HSC: concrete, high- strength concrete that has a specified compressive strength for design of 8000...

Ngày tải lên: 28/06/2014, 00:20

... modeling of the ring test should be based on the material properties and experimental values of concrete at five days (after casting) The mechanical properties of the concrete at five days of age ... particular layer exceeds the tensile strength of concrete (f’ t) The ring specimens The FEM of the ring test was performed using the software of ANSYS The dimensions of the ring setup and the boundary ... presented in Table Table Properties of material of the concrete and steel Material Elastic modulus, Ec, GPa Compressive strength, f’c, MPa Tensile strength, f’ t, MPa Poison’s ratio Concrete W/B=0.40...

Ngày tải lên: 21/07/2014, 17:21

... time of ACI 318 allows concrete mixtures to be proportioned HIGH- STRENGTH CONCRETE WITH PORTLAND CEMENT AND FLY ASH setting, h) method of placement, and i) workability 211.4R-3 high- strength concretes ... made of cardboard strength, which has been identified in normal strength material are not recommended for casting high- strength concretes, has been found to be valid for higher strength concrete ... relatively high strength in a short period of time Cap thickness should be as thin as practical, in the range of l/l6 to l/s in for high- strength concrete specimens A commercially available high- strength...

Ngày tải lên: 24/10/2014, 17:40

... flexural strength is of interest, ASTM C 78 or C 293 can be used Maximum flexural strength is calculated at the section of maximum moment corre- 544.2R-4 MANUAL OF CONCRETE PRACTICE Fig 3-Flexural strength- Calculated ... resistance of concrete at an early age has prompted the proposal of several methods These involve measurement of the length and width of concrete cracks Ring, rectangular, square, and combinations of ... of Concrete Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading) Standard Test Method for Unit Weight, Yield, and Air Content (Gravimetric) of Concrete...

Ngày tải lên: 24/10/2014, 22:11