• Explosives and Blasting
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• v.26 no.2
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• pp.52-63
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• 2008

Recently the demand of demolition for the unnecessary cylindrical silo structure is increasing due to deterioration and unsatisfactory functional conditions and the issue of demolition is becoming a major highlight. This case study introduced the explosive demolition of the cylindrical silo structure by felling method. The results of explosive demolition conducted on cylindrical silo structure using the felling method show, A silo had collapsed precisely according to estimated direction but in case of B silo there was a minor difference. The lower colunms and ring girder support was designed to the hinge line but in reality the lower colunms of the silo did not do its structural support role and only the ring girder support did its role successfully. As for the impact vibration, most of the measurements were within the estimated range.

• International Journal of Concrete Structures and Materials
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• v.8 no.3
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• pp.185-199
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• 2014

As the national transportation infrastructure ages and deteriorates, many existing bridges require frequent and costly maintenance and repairs. The objective of this work was to synthesize new and existing types of beam end coatings and treatments that have been proven to extend the life of new and existing concrete and steel bridge beams. A comprehensive literature review, along with online surveys and phone interviews of State department of transportations (DOTs) and coating manufacturers was conducted to gather information about existing and recently developed technologies. The study revealed that while many promising coatings and treatments are offered on the market, there is a lack of readily available laboratory results that would enable direct comparison of the available methods. This finding applies in terms of the coatings' durability and the potential for extending the service life of existing bridges. Most of the interviewed State DOTs' personnel assessed the products listed in respective DOT's Qualified Products Lists as performing 'well'. However, there was significant variability between states in the type of the products used. Among the agencies contacted, none was able to suggest the most promising or advanced products, either for concrete or steel bridge beam end treatments. This suggests that comprehensive laboratory evaluation would be necessary for selecting the best available beam end treatments and coatings.

• Journal of Chest Surgery
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• v.33 no.8
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• pp.643-647
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• 2000

From March 1988 to June 1994, 275 CarboMedics cardiac valve prostheses(199 mitral, 70 aortic and 3 tricuspid) were implanted in 226 consecutive patients(mean age 39 years, male/female 90/136) by one surgical team operating on adult cardiac patients at Kyungpook University Hospital. Total follow up represented 16,848 patient-months(mean 76 months) and follow up rate was 96%. One hundred and forty-nine patients(66%) wer in NYHA functional class III or IV preoperatively, and 204 patients(99.5%) were in class I or II postoperatively. Early mortality was 4.9% and late death was 9.3%. The actuarial survival at 81 months was 86.l2$\pm$3.1%. The linearized incidence of valve-related death, prosthetic valve thrombosis, anticoagulation-related hemorrhage, non-structural dysfunction and reoperation were 0.71%, 0.43%, 0.07%, 0.21%, and 0.14% respectively. The 81-month rate of freedom from all valve related complications and deaths including hospital mortality was 88.1$\pm$2.5%. Thee facts suggest that the CarboMedics cardiac valve has excellent result, low incidence of valve-related complications and no structureal deterioration.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.850-853
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• 2006

This paper presents a primary study for a new method of enhancing measurement using impedance analysis method, which is widely used for structure health monitoring. Many of skyscrapers, bridges, tunnels, which have been built up several years, and nearly reached their operating life due to aging crack, material deterioration, and so on. therefore, the health monitoring technique has obtained considerable attention. The usage of the PZT sensor is proposed, and the coupling torque of bolt-connection overlapping beam is assumed. By using the torque wrench, it is easy to apply torque of different values to each bolt. The coupling torque is adjusted gradually from $3N{\cdot}m\;to\;0N{\cdot}m$ with the decrement of $1N{\cdot}m$. Simultaneously, the impedance peak variation is measured. The peak frequency variation can be determined through the change of bolt coupling torque.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.8
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• pp.24-32
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• 2006

Using a deterministic design optimization, the effect of uncertainty can result in violation of constraints and deterioration of performances. For this reason, design optimization is required to guarantee reliability for constraints and ensure robustness for an objective function under uncertainty. Therefore, this study drew Monte Carlo Simulation(MCS) for the evaluation of reliability and robustness, and selected an artificial neural network as an approximate model that is suitable for MCS. Applying to the aero-structural optimization problem of aircraft wing, we can explore robuster optima satisfying the sigma level of reliability than the baseline.

• Food Science of Animal Resources
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• v.36 no.5
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• pp.650-655
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• 2016

This study investigated the effects of artificial supercooling followed by still air freezing (SSF) on the qualities of pork loin. The qualities of pork frozen by SSF were compared with the fresh control (CT, stored at 4℃ for 24 h), slow freezing (SAF, still air freezing) and rapid freezing (EIF, ethanol immersion freezing) treatments. Compared with no supercooling phenomena of SAF and EIF, the extent of supercooling obtained by SSF treatment was 1.4℃. Despite that SSF was conducted with the same method with SAF, application of artificial supercooling accelerated the phase transition (traverse from -0.6℃ to -5℃) from 3.07 h (SAF) to 2.23 h (SSF). The observation of a microstructure indicated that the SSF prevented tissue damage caused by ice crystallization and maintained the structural integrity. The estimated quality parameters reflected that SSF exhibited superior meat quality compared with slow freezing (SAF). SSF showed better water-holding capacity (lower thawing loss, cooking loss and expressible moisture) and tenderness than SAF, and these quality parameters of SSF were not significantly different with ultra-fast freezing treatment (EIF). Consequently, the results demonstrated that the generation of supercooling followed by conventional freezing potentially had the advantage of minimizing the quality deterioration caused by the slow freezing of meat.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1031-1036
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• 2000

In this study, a numerical simulation that can effectively predict the strengthening effect of repaired aged RC structures is developed using the axial deformation link elements. In repaired structures, concrete and interface are modeled as quasi-brittle materials. An elastic-perfectly plastic constitutive relationship is introduced for reinforcing bars. Also, a linear-elastic relationship for repair materials such as FRP or CFS. Structural deterioration in terms of corrosion of steel rebar is considered. The interfacial property between steel and concrete which is reduced by corrosion of steel rebar is obtained by comparing numerical results with experimental results of pull out tests. Obtained values are used in repaired reinforced concrete structures under flexural loading conditions. To investigate strengthening effect of the structures repaired with carbon fiber sheet(CFS), repaired and unrepaired RC structures are analyzed numerically. From analysis, rip-off, debonding and rupture failure mechanisms of interface between substrate and CFS can be determined. Finally, strengthening effect according to the variation of interfacial material properties is investigated, and it is shown that interfacial material properties have influence on the mechanical behavior of repaired structure systems Therefore, the developed numerical method using axial deformation link elements can use for determining the strengthening effects and failure mechanism of repaired aged RC structure.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.111-114
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• 2005

While the existing reinforced concrete flat plate(RC flat plate) has a lot of advantages including reduced building height, it has some weak points such as many steel bars and the brittle rupture by punching shear. Compared with the RC flat plate, the post-tensioned flat plate (PT flat plate) has not only the same merits, but it also makes longer span possible and induces slab-column connections to be failed with the ductile behavior rather than with the brittle behavior by means of post-tensioning. However, it is difficult to define the joint behavior of PT flat plate under vertical and lateral loads since there are limit experimental results. For this reason, the experimental study is undertaken to investigate the comparison of behavior of PT flat plate and RC flat plate, and how flat plate(Gravity Load Resisting System) is displaced as lateral loads, like the wind and the earthquake, are occur. The result of this experiment shows that PT flat plate is generally superior to RC flat plate in terms of controlling crack, postponing stiffness deterioration, energy dissipation, etc.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.469-472
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• 2005

With all ensuring the fire resistance structure as a method of setting the required cover thickness to fire, the RC is significantly affected from the standpoint of its structural stability that the compressive strength and elastic modulus is reduced by fire. Normally, the degradation of concrete member exposed to fire is largely dependent on the fire scale and fire condition. There is therefore a need to precisely predict the deterioration and fire damage of the exposed member. Thus, this work estimated the temperature distribution inside a member taking into consideration of the thermal properties by means of finite element method(FEM). The estimation results in a little higher prediction value than the experimental value in surface layer and is almost coincident with the experiment as the heating depth increase. From this work it can be known that the simulation application of FEM using the thermal properties of concrete member in high temperature gives rise to the confident prediction in the prediction of temperature distribution.

• International Journal of Concrete Structures and Materials
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• v.11 no.2
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• pp.391-401
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• 2017

In this study, the effects of water-to-binder (W/B) ratio and replacement ratio of blast furnace slag (BFS) on the compressive strength of concrete were first investigated to determine an optimized mixture. Then, using the optimized high-strength concrete (HSC) mixture, hooked steel fibers with various aspect ratios and volume fractions were used as additives and the resulting mechanical properties under compression and flexure were evaluated. Test results indicated that replacement ratios of BFS from 50 to 60% were optimal in maximizing the compressive strength of steam-cured HSCs with various W/B ratios. The use of hooked steel fibers with the aspect ratio of 80 led to better mechanical performance under both compression and flexure than those with the aspect ratio of 65. By increasing the fiber aspect ratio from 65 to 80, the hooked steel fiber volume content could be reduced by 0.25% without any significant deterioration of energy absorption capacity. Lastly, complete material models of steel-fiber-reinforced HSCs were proposed for structural design from Lee's model and the RILEM TC 162-TDF recommendations.