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Showing papers on "Compressive strength published in 1980"


Journal ArticleDOI
TL;DR: In this paper, an empirical strength criterion for rocks and rock masses is proposed, which includes the uniaxial compressive strength of the intact rock material and introduces two dimensionless parameters, m and s.
Abstract: An empirical strength criterion for rocks and rock masses is proposed. The nonlinear criterion includes the uniaxial compressive strength of the intact rock material and introduces two dimensionless parameters, m and s. The parameter m varies with rock type, the angle of interblock or interparticle friction and the degree of block or particle interlock. The parameter s varies from 1.0 for intact rock material to zero for granular aggregates and depends on the interparticle tensile strength and the degree of interlock within the rock mass. For anisotropic rock, both m and s vary with the orientations of the planes of weakness to the principal stress directions. Approximate relationships between rock type, rock mass quality indices, and the rock mass strength parameters m and s, are presented. These relationships have been found useful in preliminary design calculations for slopes and underground excavations in jointed rock.

1,386 citations


Journal ArticleDOI
01 Mar 1980

177 citations


Journal ArticleDOI
TL;DR: In this article, the same range of resins were used as a matrix material for a series of composites reinforced with carbon, glass and aromatic polyamide fibres, and the composites were unidirectionally reinforced, having been manufactured by pultrusion, and were compression tested in the fibre direction.
Abstract: The compression behaviour of a series of polyester resins of various compositions and in different states of cure has been investigated. Their mechanical characteristics having been established, the same range of resins was then used as a matrix material for a series of composites reinforced with carbon, glass and aromatic polyamide fibres. The composites were unidirectionally reinforced, having been manufactured by pultrusion, and were compression tested in the fibre direction after a series of experiments to assess the validity of a simple testing procedure. “Rule of Mixtures” behaviour occurred in glass-polyester composites up to limiting volume fractions (V f) of 0.31 for strength and 0.46 for elastic modulus, the compression modulus being equal to the tensile modulus, and the apparent fibre strength being in the range 1.3 to 1.6 GPa at this limiting V f. At a V f of 0.31 the strengths of reinforced polyesters were proportional to the matrix yield strength, σ my, and their moduli were an inverse exponential function of σ my. For the same matrix yield strength a composite with an epoxy resin matrix was stronger than polyester based composites. At V f=0.30, Kevlar fibre composites behaved as though their compression modulus and strength were much smaller than their tensile modulus and strength, while carbon fibre composites were only slightly less stiff and weaker in compression than in tension. The compression strengths of the polyester resins were found to be proportional to their elastic moduli.

134 citations


Journal ArticleDOI
TL;DR: In this article, the nominal values for compressive strength, limits of elasticity (yield point), strain, elastic modulus and apparent density are reported for the cancellous bone of the femoral head and condyle.
Abstract: The time independent material behavior of cylindrical specimens obtained from the cancelous bone of 20 cadaveric human femora were determined. In this part of the publication, the nominal values for compressive strength, limits of elasticity (yield point), strain, elastic modulus and apparent density are being reported for the cancellous bone of the femoral head and condyle. The correlations between the various parameters are analysed. A positive linear correlation between the four parameters compressive stength, limit of elasticity, modulus of elasticity and apparent density could not be excluded. The material properties vary considerably both within one single bone and between individuals. Compressive strength, modulus of elasticity and apparent density found for cancellous bone of the femoral head are greater than those found in the condyles. Within the condyles, compressive strength, elastic modulus and apparent density increase from the proximal parts to the parts closer to the joint. The medial femoral condyle showed higher compressive strength than the lateral one. Relating each of the three other parameters to the apparent density of the individual specimen did not result in equalizing the data for the material properties. This indicates that the mechanical properties of cancellous bone are strongly related to the direction of loading.

117 citations



Journal ArticleDOI
TL;DR: In this article, the nominal values for compressive strength, limits of elasticity (yield point), strain, elastic modulus and apparent density are reported for the cancellous bone of the femoral head and condyle.
Abstract: The time independent material behavior of cylindrical specimens obtained from the cancellous bone of 20 cadaveric human femora were determined. In this part of the publication, the nominal values for compressive strength, limits of elasticity (yield point), strain, elastic modulus and apparent density are being reported for the cancellous bone of the femoral head and condyle. The correlations between the various parameters are analysed. A positive linear correlation between the four parameters compressive stength, limit of elasticity, modulus of elasticity and apparent density could not be excluded. The material properties vary considerably both within one single bone and between individuals. Compressive strength, modulus of elasticity and apparent density found for cancellous bone of the femoral head are greater than those found in the condyles. Within the condyles, compressive strength, elastic modulus and apparent density increase from the proximal parts to the parts closer to the joint. The medial femoral condyle showed higher compressive strength than the lateral one. Relating each of the three other parameters to the apparent density of the individual specimen did not result in equalizing the data for the material properties. This indicates that the mechanical properties of cancellous bone are strongly related to the direction of loading.

93 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the properties of lightweight aggregates with low particle density in combination with artificially introduced air voids in the mortar matrix and found that the use of preformed aqueous foams proved to be especially suitable.

92 citations


01 Jan 1980
TL;DR: Examples are given to show that provided these limitations are recognised the test can be successfully used to measure the strength of rock samples and classify rock.
Abstract: Conversion factors correlating point load strength with uniaxial compressive strength are subject to errors. In addition, test results may be affected by sample anisotropy. Examples are given to show that provided these limitations are recognised the test can be successfully used to measure the strength of rock samples and classify rock.

82 citations


Journal ArticleDOI
TL;DR: In this article, a method was devised to accurately determine this shear strength, taking the strength distribution of glass fiber into consideration Calculated strength values based on the shear strenght obtained by the method were in better agreement with the experimental observations.
Abstract: In discontinuous fiber-reinforced composites, the shear strength at the fiber–matrix interface plays an important role in determining the reinforcing effect In this paper, a method was devised to accurately determine this shear strength, taking the strength distribution of glass fiber into consideration Calculated strength values based on the shear strenght obtained by the method were in better agreement with the experimental observations than those calculated by employing the shear strength obtained on the assumption that the fiber strength was uniform The tensile strength of composites increases with increasing aspect ratio of the reinforcing fibers This trend is almost the same regardless of the kind of matrix, the nature of interfacial treatment, and the environmental temperature When composites are reinforced with random-planar orientation of short glass fibers of 15 times the mean critical fiber length, the tensile strength of composite reaches about 90% of the theoretical strength of composites reinforced with continuous glass fiber Reinforcing with glass fibers 5 times the critical length, the tensile strength reaches about 97% of theoretical However, from a practical point of view, it is adequate to reinforce with short fibers of 15–20 times the mean critical fiber lenght

75 citations


Journal ArticleDOI
TL;DR: In this article, the authors explored a statistical strength theory based on a Weibull distribution and found that the presence of a stress gradient in the flexure-test results in an apparent increase in tensile strength as compared to the tensile test under uniform stress.
Abstract: Tensile data on unidirectional composites generated from a flexure test usually yield a higher strength than observed from a standard tensile coupon. According to a statistical-strength theory based on a Weibull distribution, the presence of a stress gradient in the flexure-test results in an apparent increase in tensile strength as compared to the tensile test under uniform stress. In the present paper, this concept is explored by utilizing data from unidirectional graphite-epoxy composites to compare with theoretical results generated from a two-parameter Weibull distribution. A larger variation in tensile strength is observed from tensile-coupon data than from flexure data. Such differences are not in accordance with strength theories based on a uniform flaw distribution and raise questions concerning variability of the test methods, as well as sources of material variability.

74 citations


Journal ArticleDOI
01 Mar 1980
TL;DR: In this article, a theoretical model about cutting slots in rock is discussed, which aims mainly at a qualitative description and as a consequence of that at finding the relevant rock parameters, such as compressive strength, fracture toughness etc.
Abstract: A Theory About Cutting Rock With a Water Jet It is commonly accepted that parameters like compressive strength, fracture toughness etc. are relevant parameters controlling the resistance to mechanical destruction of rock. Parameters like these have no explicit relevance, however, in destruction of rock with a continuous high pressure water jet. A theoretical model about cutting slots in rock is discussed. The model aims mainly at a qualitative description and as a consequence of that at finding the relevant rock parameters. A rock is shown to be characterized by its threshold pressure which can be interpreted as a measure of its “microscale” tensile strength and by its erosion resistance which can be interpreted as the square of the slenderness ratio of the pores of the rock divided by the diameter of the grains.

Patent
18 Nov 1980
TL;DR: In this paper, a multicellular monolithic ceramic body having many gas passages partitioned by thin walls is made of aluminum titanate as a major cnstituent and has less than 0.15% of a thermal expansion coefficient at 1000° C.
Abstract: A multicellular monolithic ceramic body having many gas passages partitioned by thin walls is made of aluminum titanate as a major cnstituent and has less than 0.15% of a thermal expansion coefficient at 1000° C. and higher than 350 kg./cm2 of a compressive strength as zero of an open frontal area as the properties in the direction along the gas passages and more than 35% of a porosity.

Journal ArticleDOI
TL;DR: In this paper, the effect of free water, age and curing conditions on the strength-loading-rate relationship of concrete, mortar and neat cement paste was studied, and the analytical form of the relationship between the stress-strain curve and strain rate of concrete and equations were proposed which closely agree with the existing data.
Abstract: Synopsis The effect of the free water, age and curing conditions upon the strengthlloading-rate relationship of concrete, mortar and neat cement paste was studied. It was found that the moisture content at the time of testing was one of the most important factors influencing this relationship, but any variables such as age or curing regime which affect the internal structure of the solid phase also have an influence. The data obtained under the different loading methods indicated that, when a specimen made from cement paste is loaded at slower rates up to approximately one-third of its ultimate strength value, the resulting ultimate strength is increased. However, ifa slower rate of loading is continued throughout the test, the ultimate strength is decreased significantly. This result is used to find the analytical form of the relationship between the stress-strain curve and strain rate of concrete and equations are proposed which closely agree with the existing data.


Journal ArticleDOI
TL;DR: In this paper, an attempt has been made to correlate the uniaxial compressive strength and Young's modulus of gabbros and basalts with Schmidt hammer rebound number, the point load strength index, Is(50) and the degree of weathering.
Abstract: An attempt has been made to correlate the uniaxial compressive strength and Young's modulus of gabbros and basalts with Schmidt hammer rebound number, the point load strength index, Is(50) and the degree of weathering. Sixty three samples of gabbro and thirty of basalt from the ophiolitic complex of Pindos zone (Northern Greece) have been collected by core drilling and tested accordingly. The results have been processed using techniques from the statistical software SPSS. Some of the equations produced show relatively high correlation coefficients, all significant at a significance level higher than 95%. The equations establish reliable prediction models for the uniaxial compressive strength and modulus of elasticity of the above rock types by means of simple tests which can be carried out in the field.



01 Jan 1980
TL;DR: In this article, the AXIPLANE program is used for finite element analysis of concrete structures loaded in the short-term up until failure and its predictions are compared with experimental data.
Abstract: This report deals with nonlinear finite element analysis of concrete structures loaded in the short-term up until failure. A profound discussion of constitutive modelling on concrete is performedj a model, applicable for general stress states, is described and its predictions are compared with experimental data. This model is implemented in the AXIPLANEprogram applicable for axisymmetric and plane structures. The theoretical basis for this program is given. Using the AXIPLANEprogram various concrete structures are analysed up until failure and compared with experimental evidence. These analyses include panels pressure vessel, beams failing in shear and finally a specific pull-out test, the Lok-Test, is considered. In these analyses, the influence of different failure criteria, aggregate interlock, dowel action, secondary cracking, magnitude of compressive strength, magnitude of tensile strength and of different post-failure behaviours of the concrete are evaluated. (Continued on next page) May 1980 Riso National Laboratory, DK 4000 Roskilde, Denmark Moreover, it is shown that a suitable analysis of the theoretical data results in a clear insight into the physical behaviour of the considered structures. Finally, it is demonstrated that the AXIPLANE-program for widely different structures exhibiting very delicate structural aspects gives predictions that are in close agreement with experimental evidence. INIS descriptors; A CODES, CLOSURES, COMPRESSION STRENGTH, CRACKS, DEFORMATION, FAILURES, FINITE ELEMENT METHOD, PRESTRESSED CONCRETE, PRESSURE VESSELS, REINFORCED CONCRETE, SHEAR PROPERTIES, STRAIN HARDENING, STRAIN SOFTENING, STRAINS, STRESS ANALYSIS, STRESSES, STRUCTURAL MODELS, TENSILE PROPERTIES, ULTIMATE STRENGTH. UDC 539.4 : 624.012.4 : 624.04 ISBN 87-550-0649-3 ISSN 0106-2840

10 Sep 1980
TL;DR: In this paper, the results of compression tests of Al2O3 performed over a wide range in temperature and strain rate are interpreted in terms of dominant damage mechanisms, such as tensile (Mode I) growth of predominantly axial microcracks, and each characteristic of a specific temperature-strain rate regime.
Abstract: : The results of compression tests of Al2O3 performed over a wide range in temperature and strain rate are interpreted in terms of dominant damage mechanisms. It is shown that compressive failure in Al2O3 is caused by one of three different mechanisms, each based on tensile (Mode I) growth of predominantly axial microcracks, and each characteristic of a specific temperature-strain rate regime. The concepts developed should be applicable to other strong ceramics. In addition, indentation experiments were carried out for a variety of ceramics. It is found that the threshold for microfracture during elastic-plastic indentation corresponds to radial, rather than subsurface median, crack formation. This is contrary to the fundamental assumption of existing models for threshold crack nucleation by sharp indenters or particles; the results indicate the need to modify the stress field calculations used in these models. (Author)

Journal ArticleDOI
TL;DR: In this paper, an experimental investigation to determine the effectiveness of intermediate longitudinal reinforcement in limiting shear strength decay of reinforced concrete members is presented, and the results indicated that intermediate longitudinal re-laminations provided significant and useable improvement for members with maximum shear stresses between three and six times the square root of the specified compression strength of concrete.
Abstract: An experimental investigation to determine the effectiveness of intermediate longitudinal reinforcement in limiting shear strength decay of reinforced concrete members is presented. Test specimens consisted of fourteen exterior beam-column subassemblies. Variables included shear stress, percentage of beam transverse reinforcement, percentage of longitudinal reinforcement and shear span to depth ratio in addition to the presence of two layers of intermediate longitudinal reinforcement in half the specimens. Test results indicated that intermediate longitudinal reinforcement provided significant and useable improvement in shear strength retention for members with maximum shear stresses between three and six times the square root of the specified compression strength of concrete.

Journal ArticleDOI
TL;DR: In this paper, a study was made of the comparative lifetimes of plasma-sprayed ZrO 2 Y 2 O 3 thermal barrier coatings on Rene 41 in short and long thermal cycles to 1040°C in a 0.3 Mach flame.

Journal ArticleDOI
TL;DR: In this paper, the authors pointed out that it is well known that rocks are usually weaker in tension and that the Young's modulus and Poisson's ratio may also be different.


Journal ArticleDOI
TL;DR: In this paper, a relation between the compressive strength, the strain at maximum stress and the thermal strain was found in the tests as a function of temperature, and it was shown that the strength of concrete increases with the decrease of temperature.

Journal ArticleDOI
TL;DR: In this article, a study has been made of the Los Angeles abrasion test in relation to the compressive strength of a wide variety of rocks being quarried to meet the growing demand for aggregates around Jeddah.
Abstract: Summary A study has been made of the Los Angeles abrasion test in relation to the compressive strength of a wide variety of rocks being quarried to meet the growing demand for aggregates around Jeddah. It was found that the results of compressive strength as determined by the Schmidt rebound hammer could be used to predict the Los Angeles abrasion test results. The aggregates tested are of volcanic and plutonic origins and are basic to acidic in composition. A rock material strength map of the Jeddah area illustrates that most of the coarse-grained plutonic rocks are of low strength and the corresponding Los Angeles abrasion values for these rocks are high, rendering them unsuitable, — especially when the aggregate is to be used in road or building construction or is to be subjected to high wear.

Journal ArticleDOI
TL;DR: In this paper, the compressive strength of mortars made from blends of slag, fly ash and portland cement was examined, and no apparent interactions were found between granulated slag and fly ash used together.


Journal ArticleDOI
TL;DR: In this paper, a series of slate-based autoclaved aerated concretes with a wide range of densities and fracture properties were investigated, showing that fracture surface energy, determined by the work of fracture method, at present offers the most satisfactory approach to the evaluation of toughness of these materials.

Patent
Shizuka Shimanuki1, Hiroshi Sato1, Toshimi Matsumoto1, Tsutomu Onuma1, Seishin Kirihara1 
06 May 1980
TL;DR: In this paper, the authors proposed a method for making same wherein a plurality of weld metals, such as martensitic steel and austenitic steel, differing in coefficient of thermal expansion from each other are deposited in a plurality thicknesswise of the welded structure in a gap defined by structural members.
Abstract: A welded structure and a method for making same wherein a plurality of weld metals, such as martensitic steel and austenitic steel, differing in coefficient of thermal expansion from each other are deposited in a plurality of layers thicknesswise of the welded structure in a gap defined by structural members to be welded in such a manner that a layer of the weld metal of higher coefficient of thermal expansion is covered by a layer of the weld metal of lower coefficient of thermal expansion in a weld formed, to improve brittle fracture strength, fatigue strength and stress corrosion cracking resistance of the weld. By subjecting the welded structure to stress relief annealing treatment, it is possible to produce compressive stress on the surface of the layer of the weld metal of lower coefficient of thermal expansion.

Journal ArticleDOI
TL;DR: In this article, the effect of fiber strength on the compressive strength of aligned fiber reinforced composites was investigated, and failure appeared to have been initiated by plastic collapse of the fibres while being fully supported by the matrix.
Abstract: Experiments were carried out to determine the effect of fibre strength on the compressive strength of aligned fibre reinforced composites. The steel reinforcing rods used in this work were hardened to different degrees to control their strength. The compressive strength of composites made with these rods was governed by the Rule of Mixtures, and was a linear function of both volume fraction and fibre strength. The failure strain of the composites was less than one sixth of the matrix yield strain, and failure appears to have been initiated by plastic collapse of the fibres while being fully supported by the matrix.