• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.421-424
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• 2006

This study, in order for perceiving the mechanical attribute followed by the explosive spalling of high strength concrete material under high temperature and evaluating capacity of endurance of material, targets understanding capacity of endurance of material such as explosive spalling in high temperature, temperature by thickness of clothing, transformation extent, transformation speed and displacement, stocking the maximum load based on the Allowable Stress Design Method. As a result of experimenting the explosive spalling attribute of high strength concrete material, the one possibly causing serious damage is the 50 MPa concrete. In all aspects of 60 MPa concrete, explosive spalling happens. Especially, it is hazardous enough to reveal all the iron bar. All explosive spalling is intensively concentrated on the surface of concrete for the first $5{\sim}25$ minutes, which urges for the explosive spalling protection action. As a result of evaluating the structural safety by the transformation of high strength concrete, while beam assures the fire safety meeting regulation, 60 MPa shows the dramatic increase of transformation, which only counts 84% of safety. In a column, both the concrete exclusion and excessive explosive spalling are concentrated upper part of column, which brings about the dramatic transformation, so it only meets the 50% of safety regulation. Likewise, in 80, 100 MPa concrete which was never experimented considering the condition of domestic structural endurance stocking devices, the faster collapse is expected.

• Fire Science and Engineering
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• v.25 no.1
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• pp.42-49
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• 2011

In the high temperature situation like in a fire, the high strength of concrete (HSC) has extreme danger named explosive spalling. It is assumed that the major cause of explosive spalling is water vapour pressure inside concrete. This paper examines the effect of the compressive strength and the moisture content on the initial occurrence of explosive spalling. For the effective experiment of the initial explosive spalling, the curve of ISO834 temperature profile is applied on the basis of 15 minute and 30 minute. As a result, the more increase the compressive strength and the moisture content, the more increase the occurrence and phenomenon of explosive spalling. This paper analyzes the territory of explosive spalling depending the compressive strength and the moisture content. The explosive spalling is not examined in the case of the compressive strength 50~100 MPa and the moisture content below 3% and the compressive strength over 100 MPa and the moisture content below 1%. Also, due to the HSC, which makes it more difficult to transport vapour and moisture, very high vapour-pressure may occur close to the surface, there is a greater risk that HSC spalls compared with normal strength concrete (NSC).

• Explosives and Blasting
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• v.17 no.4
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• pp.32-50
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• 1999

This study deals with interface charactristics of tube and tubesheet of the nuclear steam generator by the explosive expansion in order to take advantage of optimum expansion ratio, pull-out strength and leakage tightness and improvement of the resisitance on the stress corrosion cracking for low residual stress. The paper also show the relationship between roll, hydraulic and explosive expansion. The results obtain are as follows (1) Because of the explosive bonding is to use the high speed pressure and energy by the explosive, workability is good, bonding region is homogenous (2) Expansion ratio is 2.7%, Pull-out strength 850kg, Leakage strength $500kg/cm^2$. Clearance gap is 10~30mm in case of explosive expansion and interface structure of the tube and tubesheet is optimum condition. (3) As the transition region of the explosive expansion is inactive, the resistance of the stress corrosion cracking is increases 30~40% compare to the roll and hydraulic expansion.

• Steel and Composite Structures
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• v.31 no.3
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• pp.233-242
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• 2019

Early detection of damage bonding state such as insufficient bonding strength and interface partial contact defect for the explosive clad pipe is crucial in order to avoid sudden failure and even catastrophic accidents. A generalized and efficient model of the explosive clad pipe can reveal the relationship between bonding state and vibration characteristics, and provide foundations and priory knowledge for bonding state detection by signal processing technique. In this paper, the slender explosive clad pipe is regarded as two parallel elastic beams continuously joined by an elastic layer, and the elastic layer is capable to describe the non-uniform bonding state. By taking the characteristic beam modal functions as the admissible functions, the Rayleigh-Ritz method is employed to derive the dynamic model which enables one to consider inhomogeneous system and any boundary conditions. Then, the proposed model is validated by both numerical results and experiment. Parametric studies are carried out to investigate the effects of bonding strength and the length of partial contact defect on the natural frequency and forced response of the explosive clad pipe. A potential method for identifying the bonding quality of the explosive clad pipe is also discussed in this paper.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.05a
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• pp.21-25
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• 2008

It is the aim of this study to investigate the fire resistance design Guidelines for high-strength concrete structure for example compressive strength more than 40Mpa. It is well know that explosive spalling due to fire attack of high strength concrete is related to concrete failure. so, the purpose of this study introduce the fire A Studty on the Fire Resistance Design Guidelines for High-Strength Concrete Structures of AIK for the response of explosive spalling of high strength concrete.

• The Journal of Korean Physical Therapy
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• v.36 no.5
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• pp.177-183
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• 2024

Purpose: Variables, such as torque and power, have been measured to evaluate the muscle function. This study examined the effects of a warm-up protocol, including dynamic stretching (DS), on the explosive strength of knee extensors, as well as torque and power. Methods: Twenty-nine healthy young adults participated in this study. Three warm-up protocols, including DS of knee extensors, were used as interventions: (1) DS, (2) DS combined with antagonist muscle static stretching (AMSS), and (3) DS combined with repetitive passive movements (RPM). The outcome measures were the following variables of the knee extensors evaluated using an isokinetic dynamometer: rate of torque and velocity development (RTD and RVD), isometric and isokinetic peak torque (PT), and average power (AP). Results: The results of the two-way (warm-up and time) repeated-measures ANOVA revealed a main effect of time for isometric PT (p=0.001). Post-hoc analysis revealed a significant increase in isometric PT in the post-test compared to the pre-test regarding the DSAMSS (p=0.001) and DS-RPM (p=0.047) warm-up protocols. Conclusion: The three warm-up protocols (DS, DS-AMSS, and DS-RPM) do not appear to influence explosive strength and isokinetic strength at a rapid angular velocity. Considering the relatively high volume of DS used in this study, this may be due to the influence of muscle fatigue. These findings suggest that tailored warm-up protocols for fast muscle contraction and joint acceleration, unlike isometric PT corresponding to static contraction, may require a different approach from existing methods.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.323-325
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• 2013

This study on the proposes a spalling mechanism based on the results of a fire resistance test of HSC(High Strength Concrete) considering important factors of spalling occurrence. The factors considered in this two-sided are fire resistance test to ISO 834 fire curve. In this study, explosive spalling phenomena in the specimens were investigation.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.477-480
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• 2006

Normally, 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. Especially, high strength concrete and lightweight aggregate concrete is occurred serious fire performance deterioration by explosive spalling. Thus, this study is concerned with explosive spalling of lightweight concrete using structural lightweight aggregate. From the experimental test result, lightweight aggregate concrete is happened explosive spalling. The decrease of cross section caused by explosive spalling made sharp increasing gradient of inner temperature.

• Physical Therapy Rehabilitation Science
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• v.13 no.3
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• pp.304-314
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• 2024

Objective: This study aimed to investigate the association of explosive strength with muscle mass and muscle function measured using traditional methods such as peak torque (PT) and joint angular velocity (PAV). Design: Cross-sectional study Methods: Twenty-nine healthy adults (14 males and 15 females) participated in this study. Body mass index and appendicular skeletal muscle index (ASMI) were measured using bioelectrical impedance analysis. The explosive strength of the knee extensors was evaluated by measuring the rate of torque development (RTD) and rate of velocity development (RVD). RTD was analyzed by dividing it into early (0-50 ms) and late (100-200 ms) muscle contraction phases. In addition, PT and PAV were measured as traditional methods for assessing muscle function. Results: According to regression analysis, PAV accounts for 24.7% and 66.9% of the variance of RTD 0-50 (p=0.006) and RVD (p<0.001), respectively. On the other hand, ASMI (p=0.035) and isometric PT (p=0.001) explained 49.2% of the RTD 100-200. Conclusions: Early RTD is mainly predicted by PAV, which is thought to be a result of muscle fiber type. Therefore, PAV presents the possibility of an alternative method to evaluate explosive performance. Late RTD seems to be related to ASMI or isometric PT. The findings of this study are expected to contribute to musculoskeletal rehabilitation and evaluation in that they revealed factors contributing to early and late muscle contraction.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.2
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• pp.133-140
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• 2011

High strength concrete used for large structures is vulnerable to fire due to explosive spalling when it is heated. Recently, various research is conducted to enhance the fire-resistance of the high strength concrete by reducing the explosive spalling at the elevated temperature. In this study, a heat transfer analysis model is proposed for a fiber-embedded fire-resistant high strength concrete. The material model of the fire-resistant high strength concrete is selected from the calibrated material model of a high strength concrete incorporating thermal properties of fibers and physical behavior of internal concrete at the elevated temperature. By comparing the simulated results using the calibrated model with the experimental results, the heat transfer model of the fiber-embedded fire-resistant high strength concrete is proposed.