• Steel and Composite Structures
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• v.27 no.2
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• pp.229-242
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• 2018

High strength steel is widely used in industrial applications to improve the load-bearing capacity and reduce the overall weight and cost. To take advantage of the benefits of this type of steel in construction, an innovative hybrid fabricated member consisting of high strength steel tubes welded to mild steel plates has recently been developed. Component-scale uniaxial and multiaxial cyclic experiments have been conducted with simultaneous constant or varying axial compression loads using a multi-axial substructure testing facility. The structural interaction of high strength steel tubes with mild steel plates is investigated in terms of member capacity, strength and stiffness deterioration and the development of plastic hinges. The deterioration parameters of hybrid specimens are calibrated and compared against those of conventional steel specimens. Effect of varying axial force and loading direction on the hysteretic deterioration model, failure modes and axial shortening is also studied. Plate and tube elements in hybrid members interact such that the high strength steel is kept within its ultimate strain range to prevent sudden fracture due to its low ultimate to yield strain ratio while the ductile performance of plate governs the global failure mechanism. High strength material also significantly reduces the axial shortening in columns which prevents undesirable frame deformations.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.133-141
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• 2002

Isotropic rock and anisotropic rock have different tensile strength which has the greatest influence on rock failure. In this study, elastic modulus of anisotropic rock is obtained through uniaxial compression test, and tensile strength and tension failure behavior are analyzed through indirect tensile strength test. Stress concentration factor of a specimen at the center is obtained from anisotropic elastic modulus and strain by indirect tensile strength test. Theoretical solutions for tensile strength of isotropic and anisotropic rock are compared. Stress concentration factor of anisotropic rock is either higher or lower than isotropic rock depending on the inclination angle of bedding plane. The use of stress concentration factor of isotropic rock resulted in overestimation or underestimation of tensile strength.

• Journal of the Korean Geotechnical Society
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• v.30 no.1
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• pp.27-36
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• 2014

In this study, laboratory test was carried out on uniaxial compressive strength by making 320 specimens in total, which were divided into two groups considering the curing time of 7 and 28 days for 80 cases mixed with stabilizers of 8%, 10%, 12%, 14% of 20 cases of clayey, sandy, and gravel mixed ground conditions to understand laboratory strength characteristics of deep mixing specimen for field application in various ground conditions. As a laboratory result, all specimen showed a clear tendency to have uniaxial compressive strength increase as the curing time and the stabilizer mixing ratio increased, and the strength increments depending on the age by ground types were, around 40.0% for clayey and gravel mixed grounds, 48.4% for sandy grounds which was the highest, and for the increment of stabilizers, around 37.0% for grounds with mixing ratio less then 14%, and 49.6% when the ratio was 14% which was the highest. Also, with sandy grounds, it showed a tendency to have a constant amount of strength increment as the stabilizer mixing ratio increased, for clayey mixed grounds, the strength increment tendency seemed to be similar to gravel mixed grounds. Due to these tendencies, it is concluded that we are able to propose a stabilizer mixing ratio for various ground conditions.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.157-165
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• 1999

When the ultimate strength of a concrete flexural member is evaluated, the effect of member size is usually not considered. For various types of loading, however, the strength always decreases with the increment of member size. In this paper the size effect of a flexural compression member is investigated by experiments. For this purpose, a series of C-shaped specimens subjected to axial compressive load and bending moment was tested using three different sizes of specimens with a compressive strength of 528 kg/$cm^2$. According to test results the size effect on flexural compressive strength was apparent, and more distinct than that for uniaxial compressive strength of cylinders. Finally a model equation was derived using regression analyses with experimental data.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1412-1419
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• 2005

Preventing the infiltration of rainwater into the landfill site is the main purpose of the final cover in landfill sites. Compacted clay layer or geomembrain have been used as a conventional landfill final cover. But they have several disadvantages when damages might occur due to puncturing, differential settlement and desiccation or freeze and thaw. For this reason, as an alternative method SRSL(Self Recovering Sustainable Liner) has been developed. Adopting the precipitation reaction of two chemical material, by forming precipitates that fill the pores, and lower the overall permeability of the liner. The advantage of this method is that when fracture of the liner occurs the remaining reactants of the two layers form precipitates that fill the fracture and recover the low permeability of the liner. In this study, the recovering ability of the SRSL with a crack due to the seasonal variation or differential settlements was investigated by permeability tests. And in order to estimate the durability of the SRSL after freeze/thaw and desiccation, uniaxial compression strength tests were performed.

• Computers and Concrete
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• v.22 no.6
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• pp.539-550
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• 2018

Concrete is highly non-linear material which is originating from the transition zone in the form of micro-cracks, governs material response under various loadings. In this paper, the constitutive models published by many researchers have been used to generate novel stiffness parameters and constitutive curves for concrete. Following such linear material formulations, where the energy is conservative during the curvature, and a nonlinear contribution to the concrete has been made and investigated. In which, nonlinear concrete elastic modulus modeling has been developed that is capable-of representing concrete elasticity for grades ranging from 10 to 140 MPa. Thus, covering the grades range of concrete up to the ultra-high strength concrete, and replacing many concrete models that are valid for narrow ranges of concrete strength grades. This has been followed by the introduction of the nonlinear Hooke's law for the concrete material through the replacement of the Young constant modulus with the nonlinear modulus. In addition, the concept of concrete elasticity index (${\varphi}$) has been proposed and this factor has been introduced to account for the degradation of concrete stiffness in compression under increased loading as well as the multi-stages micro-cracking behavior of concrete under uniaxial compression. Finally, a sub-routine artificial neural network model has been developed to capture the concrete behavior that has been introduced to facilitate the prediction of concrete properties under increased loading.

• Computers and Concrete
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• v.30 no.4
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• pp.257-267
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• 2022

Two different types of rubber aggregates (40 mesh rubber powder and 1-4 mm rubber particles respectively) were devised to substitute fine aggregates at 10%, 15%, 20% and 30% by volume in self-compacting concrete to investigate their basic mechanical properties. The results show that with the increase of rubber content, the reduction of compressive strength, splitting tensile strength and static modulus of elasticity gradually increase, and energy dissipation performance gradually increase. The rubber addition significantly reduces brittleness and decelerates damaged process. Whilst, the effect of rubber particles is greater when they are finer. Considering the mechanical properties, the optimal rubber content is 10%. It is recommended that the rubber volume content in rubberized concrete (RC) should not be higher than 20%. In addition, a constitutive model under uniaxial compression was proposed basing on the strain equivalent principle of Lemaitre and the damage theory, which was in good agreement with the test curves.

• Geomechanics and Engineering
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• v.4 no.4
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• pp.281-294
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• 2012

Filtration using granular media such as quarried sand, anthracite and granular activated carbon is a well-known technique used in both water and wastewater treatment. A relatively new pre-filtration method called pebble matrix filtration (PMF) technology has been proved effective in treating high turbidity water during heavy rain periods that occur in many parts of the world. Sand and pebbles are the principal filter media used in PMF laboratory and pilot field trials conducted in the UK, Papua New Guinea and Serbia. However during first full-scale trials at a water treatment plant in Sri Lanka in 2008, problems were encountered in sourcing the required uniform size and shape of pebbles due to cost, scarcity and Government regulations on pebble dredging. As an alternative to pebbles, hand-made clay pebbles (balls) were fired in a kiln and their performance evaluated for the sustainability of the PMF system. These clay balls within a filter bed are subjected to stresses due to self-weight and overburden, therefore, it is important that clay balls should be able to withstand these stresses in water saturated conditions. In this paper, experimentally determined physical properties including compression failure load (Uniaxial Compressive Strength) and tensile strength at failure (theoretical) of hand-made clay balls are described. Hand-made clay balls fired between the kiln temperatures of $875^{\circ}C$ to $960^{\circ}C$ gave failure loads of between 3.0 kN and 7.1 kN. In another test when clay balls were fired to $1250^{\circ}C$ the failure load was 35.0 kN compared to natural Scottish cobbles with an average failure load of 29.5 kN. The uniaxial compressive strength of clay balls obtained by experiment has been presented in terms of the tensile yield stress of clay balls. Based on the effective stress principle in soil mechanics, a method for the estimation of maximum theoretical load on clay balls used as filter media is proposed and compared with experimental failure loads.

• Journal of the Korean Geosynthetics Society
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• v.15 no.2
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• pp.1-12
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• 2016

In this study, laboratory mixture design test and field test were performed to evaluate applicability of eco-friendly binder material (CMD-SOIL) using desulfurized dust in deep cement mixing method (DCM). As a result of laboratory mixture design test, the uniaxial compressive strength of CMD-SOIL was up to 1.136 times bigger than slag cement by changing the water content, mixing rate, and W/B. Also, it had shown the strength up to 1.222 times bigger in shell content and up to 1.363 times in mixing of floating soil. As a result of field test, field strength/laboratory design criterion strength ratio (${\lambda}$) is shown 0.77. And this result was similar to earlier studies. From this result, CMD-SOIL can show the same efficiency compared with existing binder.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.12
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• pp.1435-1440
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• 2014

The effects of the specimen size and temperature on the compressive strength of ATJ graphite were investigated. Compressive tests were conducted in accordance with ASTM C 965 at room temperature, $700^{\circ}C$ and $900^{\circ}C$. Three types of cylindrical specimen at room temperature were used in uniaxial tests, where the diameter-to - length ratios were one to two for the ASTM standard specimen, one to one for the Type I specimen, and one to 0.5 for the Type II specimen. Two kinds of cylindrical specimens, with and without antioxidant coating, were tested at elevated temperature. The Compressive strength of the expanded specimens(Type I, II) were slightly higher than that of standard specimen at room temperature. The compressive strength of a specimen with antioxidant coating increased as the temperature increased to $900^{\circ}C$. In contrast, that of the non-coated specimen decreases sharply due to the oxidation of the specimen.