• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.1
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• pp.104-111
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• 1997

Accounting for the additional damages come out from non-proportional loading path effect, material damage according to crystal structure dependence was studied. Microscopic observations of damaged material by SEM(Scanning Electron Microscope) showed crystal structure dependence. Biaxial in-phase loaded specimens showed the slips of same direction, which pararell each other, but biaxial 90.deg. out-of-phase loaded specimens showed multiply crossed slips. S. H. Doong and D. F. Socie reported that wavy/planar or planar slip material showed the increase in the cyclic hardening level during non-proportional cycling. From these results, the additional hardening and non-proportional loading effects were related with slip mechanism, and the slip mechanism was related with crystal structure. In the present study, a damage mechanism which accounts for the non-proportional loading effect from crystal structure dependence was considered and applied to A17075-T651.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.26 no.1
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• pp.11-17
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• 2020

This study conducted a case study and a questionnaire analysis in parallel. In the case study, a study was conducted on domestic manufacturer A by analyzing pallet loading efficiency of RRP(Retail Ready Packaging) products and pallet loading efficiency of MWC(Membership Wholesale Club) delivered products. As a result of the pallet loading efficiency simulation of 50 RRP products of Manufacturer A, it was 80.0% based on the T-11 type pallet and 84.3% based on the T-12 type pallet. It was found It refers that the route of producing the product from the manufacturer A and delivering it to the MWC A in the form of RRP resulted in the decrease of the pallet loading efficiency through the change of the loading pattern and the adjustment of the number of loads. As a result of analyzing the questionnaire about whether the overall efficiency of the supply chain will be improved if the operation of the packaging system considering the SCM(Supply Chain Management) aspect is χ² = 178.500, there was a statistically significant difference at the significance level of 0.000. Manufacturers and logistics companies answered "yes" the most, but distributors answered "is average" the most, confirming that the packaging can be constructed with the highest operational efficiency. Therefore, as a result of confirming the impact of packaging design considering the SCM aspect on logistics efficiency, it indicates the importance of closer collaboration between manufacturers and distributors.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.574-584
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• 2006

Bi-directional loading test data are available to evaluate the design parameters which reflect the characteristics of a construction method and the variations of ground at the site where drilled shafts are installed. The method to obtain the design parameters of a real bridge by hi-directional loading test was introduced. The plans of multi-level testing and installation of measuring instruments should be made according to the rough estimation of axial bearing capacity, the length of pile, and the construction method. While the relationship between end bearing resistance and displacement was obtained directly from the hi-directional loading test, the relationship between unit side resistance and displacement was calculated through the measuring values. 1% displacement of pile diameter was adopted as the criteria of failure for ultimate resistance. As the settlement of pile head at the total ultimate bearing capacity obtained from these method was less than 1.5 % of pile diameter, this method was conservative to use in the field.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.109-112
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• 2008

A performance of micro thruster was measured with catalyst bed that was prepared by different catalyst loading condition for the optimization of catalyst bed size. Among the catalyst loading conditions, pH level of precursor solution was changed by several solutions like Nitric acid or Sodium hydroxide. For the each case, it was heated at different drying temperatures that can affect the phase of catalyst loaded on support. From these results, it was studied that the effect of catalyst loading condition on the performance. 90wt% hydrogen peroxide was used as a monopropellant, and platinum was chosen as a catalyst. Characteristic velocity efficiency and temperature efficiency were used for the performance evaluation.

• Steel and Composite Structures
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• v.43 no.5
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• pp.673-688
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• 2022

Post-earthquake fire is a major threat since most structures are designed allowing some damage during strong earthquakes, which will expose a more vulnerable structure to post-earthquake fire compared to an intact structure. A series of experimental research on steel-concrete composite beam-to-column joints subjected to fire after cyclic loading has been carried out and a clear reduction of fire resistance due to the partial damage caused by cyclic loading was observed. In this paper, by using ABAQUS a robust finite element model is developed for exploring the performance of steel-concrete composite joints in post-earthquake fire scenarios. After validation of these models with the previously conducted experimental results, a comprehensive numerical analysis is performed, allowing influential parameters affecting the post-earthquake fire behavior of the steel-concrete composite joints to be identified. Specifically, the level of pre-damage induced by cyclic loading is regraded to deteriorate mechanical and thermal properties of concrete, material properties of steel, and thickness of the fire protection layer. It is found that the ultimate temperature of the joint is affected by the load ratio while fire-resistant duration is relevant to the heating rate, both of which change due to the damage induced by the cyclic loading.

• Journal of the Korean Wood Science and Technology
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• v.31 no.3
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• pp.61-69
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• 2003

This study investigated the effect of moisture content and loading direction on dowel bearing strength of two types of SCL. Dowel bearing tests of LVL and PSL were conducted with two different MC level, 7.5% and 19%, and two different oriention, L-direction(loading parallel to grain) and X-direction(loading perpendicular to grain). Most of specimens showed typical load-deformation curves and intersected 5% offset line. Failure modes were classified into two categories; spliting(for L-direction specimens) and peeling(for X-direction specimens). Dowel bearing strength generally decreased with increasing MC. The decreasing rate was more significant in X-directon. ESG also decreased with increasing MC, and the ratio of ESG of 7.5% versus 19% was about 1.47. Dowel bearing strength of LVL and PSL in L-direction was higher than that of X-direction. This results indicated that MC and loading orientation had a significant effect on dowel bearing strength of SCL. The average dowel bearing strength of LVL were higher than that of PSL in each loading direction. Two types of probability distribution model were chosen to quantify strength distribution, normal and 2-parameter weibull distribution. The two models showed good agreement with the data, especially in lower tail of the cumulative distribution. Normal and 2-parameter weibull distribution seemed to proper model of the dowel bearing strength for each MC levels.

• Structural Engineering and Mechanics
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• v.84 no.3
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• pp.361-373
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• 2022

This paper examines the flexural performance of concrete beams reinforced with glass fibre-reinforced polymer (GFRP) bars under fatigue loading. Experiments were carried out on concrete beams of size 1500×200×100 mm reinforced with 10 mm and 13 mm diameter GFRP bars under fatigue loading. Experimental investigations revealed that fatigue loading affects both strength and serviceability properties of GFRP reinforced concrete. Experimental results indicated that (i) the concrete beams experienced increase in deflection with increase in number of cycles and failed suddenly due to snapping of rebars and (ii) the fatigue life of concrete beams drastically decreased with increase in stress level. Analytical model presented a procedure for predicting the deflection of concrete beams reinforced with GFRP bars under cyclic loading. Deflection of concrete beams was computed by considering the aspects such as stiffness degradation, force equilibrium equations and effective moment of inertia. Nonlinear finite element (FE) analysis was performed on concrete beams reinforced with GFRP bars. Appropriate constitutive relationships for concrete and GFRP bars were considered in the numerical modelling. Concrete non linearity has been accounted through concrete damage plasticity model available in ABAQUS. Deflection versus number of cycles obtained experimentally for various beams was compared with the analytical and numerical predictions. It was observed that the predicted values are comparable (less than 20% difference) with the corresponding experimental observations.

• Steel and Composite Structures
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• v.50 no.6
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• pp.689-703
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• 2024

Construction of high-rise structures, formwork systems that can be installed quickly, resistant to external loads, can be used more than once, have become a necessity. Timber and composite timber materials are preferred in the formation of such formwork systems due to their durability, ease of assembly, light weight and easy to use more than one time. Formwork beams are the most commonly used structural component in the formation of such formwork systems, and these beams can be damaged for different reasons during their lifetime. In this study, H20 top P type timber formwork beams with 1800 and 2450 mm length which is among the products of DOKA(c) company is damaged under the effect of static loading up to a high load level of 85% of the maximum ultimate capacity and after being retrofitted using anchored CFRP strips, performance and behavior of the beams under the influence of various loading types such as static, fatigue and impact are investigated experimentally. Two different lengths of retrofitted timber formwork beams were tested by applying monotonic static, fatigue and impact loading and comments were made about the effects of the retrofit method on performance under different loading types.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.1
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• pp.74-78
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• 2014

Objectives: Purpose of this study was to evaluate the noise level exposures at the different cannonball type and locations in the tank gun drill ranges. Methods: We visited the tank gun drill ranges and measured with a sound level meter(3M Quest SoundPro$^{TM}$) with the value of Peak(dB(A)). Results: The highest peak value of impulse noise level averaged 166.3 dB(A) at the site of loading solider. The highest peak value of impulse noise level by size of cannonball averaged 165.9 dB(A) at the 120 mm size cannonball of the tank. This result was significantly different from the other size of cannonballs such as 7.62 mm, 90 mm, and 105 mm(p < 0.001). Among the four types of soldier site on the tank, average noise levels of loading soldier, 156.6 dB(A), were higher than the other three types of soldier site (p > 0.05). Conclusions: This study confirmed that there were needed for a proper control to reduce the amount of impulse noise exposure at the tank gun drill ranges.

• Geomechanics and Engineering
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• v.31 no.1
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• pp.87-97
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• 2022

The excessive settlement and deformation of disintegrated carbonaceous mudstone (DCM) embankments under dynamic loading have long been problems for engineers and technicians. In this work, the characteristics and mechanism of the plastic deformation of DCM under different degrees of compaction, water contents and confining pressures were studied by static triaxial, dynamic triaxial and scanning electron microscopy testing. The research results show that the axial stress increases with increasing confining pressure and degree of compaction and decreases with increasing water content when DCM failure. The axial strain at failure of the DCM decreases with increasing confining pressure and degree of compaction and increases with increasing water content. Under cyclic dynamic stress, the change in the axial stress level of the DCM can be divided into four stages: the stable stage, transition stage, safety reserve stage and unstable stage, respectively. The effects of compaction, water content and confining pressure on the critical axial stress level which means shakedown of the DCM are similar. However, an increase in confining pressure reduces the effects of compaction and water content on the critical axial stress level. The main deformation of DCM is fatigue cracking. Based on the allowable critical axial stress, a method for embankment deformation control was proposed. This method can determine the degree of compaction and fill range of the embankment fill material according to the equilibrium moisture content of the DCM embankment.