• Structural Engineering and Mechanics
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• 제55권3호
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• pp.675-686
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• 2015

The use of ground granulated blast furnace slag (GGBFS) from steel industries waste is showing perspective application in civil engineering as partial substitute to cement. Use of such waste conserves natural resources and minimizes the space required for landfill. The GGBFS used in the present work is of ultra fine size and hence serves as micro filler. In this paper strength and durability characteristics of ultra fine slag based high strength concrete (HSC) (with a characteristic compressive strength of 50 MPa) were studied. Cement was replaced with ultra fine slag in different percentages of 5, 10, and 15% to study the compressive strength, porosity, resistances against sulfate attack, sorptivity and chloride ion penetration. The experiments to study compressive strength were conducted for different ages of concrete such as 7, 28, 56, and 90 days. From the detailed investigations with 16 mix combinations, 10% ultra fine slag give better results in terms of strength and durability characteristics.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.719-724
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• 2001

In this study, wedge splitting tensile test(WST) using dye penetration method was carried out to investigate cracking criterion and fracture characteristics of concrete. For the this purpose, three levels of compressive strength of 180, 300 and 600 kgf/$\textrm{cm}^2$ and five testing age of 1, 3, 7, 14 and 28 days were selected as test variables. The specimen was loaded in a controlled manner and then dye was inserted at the load of 40%, 70% of the presumed peak load and at the load of 90% just after peak load. The fracture process zone was measured at each load step of a specimen. Test results were compared with analytic results by linear elastic fracture mechanics(LEFM) and numerical results through fictitious crack model(FCM) and finite element method(FEM).

• Structural Engineering and Mechanics
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• 제51권3호
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• pp.403-412
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• 2014

In this paper, enhancement of corrosion and chloride resistance of high performance self compacting concrete (SCC) through incorporating nanosilica into the binder has been investigated. For this purpose, different mixtures were designed with different amounts of silica fume and nano silica admixtures. Different binder contents were also investigated to observe the binder content effect on the concrete properties. Corrosion behavior was evaluated by chloride penetration and resitivity tests. Water absorption and capillary absorption were also measured as other durability-related properties. The results showed that water absorption, capillary absorption and Cl ion percentage decreased rather significantly in the mixtures containing admixtures especially blend of silica fume and nano silica. By addition of the admixtures, resistivity of the SCC mixtures increased which can lead to reduction of corrosion probability.

• 대한기계학회논문집
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• 제18권10호
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• pp.2495-2500
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• 1994

A method of prediction for the fatigue life of surface crack, that is, initial cracks grow and penetrate through the thickness, was presented in the previous study of the author. Effects of parameters such as the initial crack length, material factors, etc., for the life were discussed. In this paper, the probabilistic distribution of the life is calculated. Effects of the distribution of parameters for the distribution of life were also discussed.

• Journal of Welding and Joining
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• 제26권6호
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• pp.97-102
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• 2008

It is well known that there exist two typical fatigue crack initiation locations in ship structures: one is the weld toe and the other is the weld root where partial penetration weld is performed. In particular, it is important for fillet weldments to avoid weld root cracking in order to prevent catastrophic failure particularly in ship structures. Therefore detail considerations are required for cruciform joints with partial penetration when there is a possibility of weld root crack initiation. For these reasons, fatigue tests on welded joints were performed in this study. Concept of stress intensity factor(SIF) by means of fracture mechanics is applied for predicting fatigue life of fillet welded joints.

• Structural Engineering and Mechanics
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• 제82권5호
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• pp.587-594
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• 2022

Behavior of concrete elements under the effect of high-speed projectiles has gain increasing interest recently. It's necessary to understand how far the concrete can absorb the effect of bullets in order to save the occupants when design security and military infrastructures. This study presents a total of 18 concrete slabs casted and tested under reinforcement ratios, 0%, 0.35% and 0.7%. Parameters interested were slab thickness, (50 mm, 100 mm, and 150 mm) and type of weapon. All specimens tested to investigate their response under the effect of attacking by two common types of weapon. In general, it was found that projectile penetration was controlled by their thickness regardless the steel reinforcement ratio. However, the steel reinforcement controls the damage.

• Coupled systems mechanics
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• 제12권2호
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• pp.103-125
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• 2023

The present research is focused on the study of plane harmonic waves in a two-dimensional orthotropic magneto-thermoelastic media with fractional order theory of generalized thermoelasticity in the light of two-temperature and rotation due to time harmonic sources. Here, we studied three types of waves namely quasi-longitudinal (QL), quasi-transverse (QTS) and quasi thermal (QT) waves. The variations in the wave properties such as phase velocity, attenuation coefficient and specific loss have been noticed with respect to frequency for the reflected waves. Further the value of amplitude ratios, energy ratios and penetration depth are computed numerically with respect to angle of incidence. The numerical simulated results are presented graphically to show the effect of fractional parameter based on its conductivity (0<α<1 for weak, α=1 for normal, 1<α≤2 for strong conductivity) on all the components.

• Structural Engineering and Mechanics
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• 제89권3호
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• pp.301-308
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• 2024

Concrete carbonation is a continuous and slow process from the outside to the inside, in which its penetration slows down with the increased depth of carbonation. In this paper, the results of the evaluation of the measurement of concrete carbonation depth using a non-destructive ultrasonic testing method are presented. According to the results, the relative nonlinear parameter caused more sensitivity in carbonation changes compared to Rayleigh's fuzzy velocity. Thus, the acoustic nonlinear parameter is expected to be applied as a quantitative index to recognize carbonation effects. In this research, combo diagrams were developed based on the results of ultrasonic testing and the experiment to determine carbonation depth using a phenolphthalein solution, which could be considered as instructions in the projects involving non-destructive ultrasonic test methods. The minimum and maximum accuracy of this method were 89% and 97%, respectively, which is a reasonable range for operational projects. From the analysis performed, some useful expressions are found by applying the regression analysis for the nonlinearity index and the carbonation penetration depth values as a guideline.

• Coupled systems mechanics
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• 제3권1호
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• pp.53-71
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• 2014

Accurate prognoses of the durability of concrete structures require a detailed description of the continuously running aging processes and a consideration of the complete load history. Therefore, in the framework of continuous porous media mechanics a model is developed, which allows a detailed analysis of the most important aging processes of concrete as well as a flexible coupling of different processes. An overview of the prediction model and the balance equations is given. The material dependent model equations, the consequences of coupling different processes and the solution scheme are discussed. In two case studies the aging of concrete due to hydration and chloride penetration are presented, which illustrate the capabilities and the characteristics of the developed model.

• 터널과지하공간
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• 제19권6호
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• pp.479-489
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• 2009

터널 굴착시 굴진면 전방의 지반상태를 사전에 파악하는 것은 터널의 안정성을 증가시킴과 동시에 시공성을 향상시켜 경제적인 터널 시공을 할 수 있도록 한다. 이에 본 연구에서는 터널 천공시 획득되는 천공데이터를 이용하여 굴진면 전방의 암반강도를 예측하고자 하였다. 이는 암반강도가 현장에서 암반분류 및 지보패턴 설계 등의 핵심인자로 가장 보편적으로 활용될 뿐만 아니라, 암반강도의 변화를 통해 굴진면 전방의 지반상태 변화를 예측하는데도 활용할 수 있기 때문이다. 이를 위해 본 연구에서는 다양한 강도 특성을 보이는 균질한 암석시험편을 대상으로 착암기 종류를 변화시켜가며 천공실험을 수행하였다. 실험결과 천공속도는 다른 천공데이터들과 착암기의 종류 및 암석의 강도에 따라 고유한 값을 보이는 것으로 나타났다. 또한, 동일한 암석에 대해 천공시 타격압이 증가하면 천공속도는 선형적으로 비례하여 증가하는 것으로 나타났다. 이러한 결과를 바탕으로 본 연구에서는 터널 시공 현장에서 착암기의 제원, 현장 계측 데이터 및 천공속도와 암반강도의 상관관계를 이용하여 터널 굴진면 전방의 암반강도를 예측할 수 있는 방안을 제안하였다.