• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.3
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• pp.201-209
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• 2002

Crib wall system is one of segmental crib type wall. Crib walls are constructed from separate members with no bonds between them other than frictional. The wall units are divide into two main types termed headers and stretchers. The headers run from the front to the back of the wall, perpendicular to the wall face. The cells are created by forming a grid by stacking individual wall components known as headers and stretchers. The body of wall consists of a system of open cell which are filled with a granular material. The design of crib retaining wall is usually based on conventional design methods derived from Rankine and Coulomb theory so that is able to resist the thrust of soil behind it, because it may be assumed that the wall acts as a rigid body. However, deformation characteristics of crib walls cannot be assumed as monolithic. They consist of individual members which have been stacked to creat a three dimensional grid. Therefore, the segmental grid allows relative movement between the individual member within the wall. The three dimensional flexible grid leads to stress distribution by interaction behavior between soil and crib wall. Therefore, in this study, in order to analysis the trends of deflection of crib wall system, new numerical models based on the results of Brandl's full scale test are introduced for design concept.

• Journal of the Korean Ceramic Society
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• v.40 no.9
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• pp.874-880
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• 2003

The effect of h-BN content on microstructure, mechanical properties, and machinability of AlN-BN based machinable ceramics were investigated. The relative density of sintered compact decreased with increasing h-BN content. The four-point flexural strength also decreased from 238 MPa of monolith up to 182 MPa by the addition of 30 vol％ h-BN. Both low Young's modulus and residual tensile stress, formed by the thermal expansion coefficient difference between AIN and h-BN, might cause the strength drop in AlN-BN composite. The crack deflection, and pull-out phenomena increased by the plate-like h-BN. However, the fracture toughness decreased with h-BN content. The second phases, consisted of YAG and ${\gamma}$-Al$_2$O$_3$, were formed by the reaction between Al$_2$O$_3$ and Y$_2$O$_3$. During end-milling process, feed and thrust forces measured for AlN-(10～30) vol％ BN composites decreased with increasing h-BN particles, showing excellent machinability. Also, irrespective of h-BN content, relatively good surfaces with roughness less than 0.5 m (Ra) could be achieved within short lapping time.

• Journal of the Society of Disaster Information
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• v.16 no.4
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• pp.796-805
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• 2020

Purpose: A static loading test was performed to evaluate the ultimate flexural strength of a girder in which 80MPa high-strength concrete was synthesized on the compressive flange of the I-shape steel girder. Method: This test is designed and fabricated two types of specimens with different shear-connection specifications, and evaluated their ultimate flexural behavior until reaching the extreme event limit states. In addition, the ultimate strength was evaluated by comparing the test results and the results of the strain compatibility method. Result: By confirming the displacement within 0.02mm as a result of the relative slip measurement, it was verified that the two specimens secured perfect bonding. Therefore, the difference in the shear specification does not have a great effect on the stiffness, and if the specimens are completely synthesized, there is no difference in the behavior until it reaches the extreme-event limit states. Conclusion: The girder to be tested has a working load within the elastic range and meets the usability requirements for allowable deflection. Therefore, even if a part of the casing is subjected to the tensile force at the level of cracking, the deck will first reach the compression failure due to the role of the reinforcing bar.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.475-485
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• 2008

This paper intends to enhance the reliability and performance of domestic elastomeric bearings through the proposal of directions for the improvement of their stiffness regard to the Korean industrial standard KS F 4420 relative to the evaluation of design/fabrication/quality. Therefore, comparative analysis of the compressive elastic modulus, stiffness measurement method and performance evaluation method of KS F 4420 with those of Eurocode, Japanese bearing manual, and ISO code was performed, and measurement tests on the compressive stiffness and shear stiffness of common elastomeric bearings produced in Korea were conducted. The experimental results reveal that differences of about 20% and 13% occurred respectively for the compressive stiffness and shear stiffness according to the definition adopted for the stiffness. The measured values for the stiffness of the domestic elastomeric bearings were also verified to exhibit large deviation from the formula proposed by KS F 4420. Elastomeric bearings that does not have appropriate compressive stiffness required at the design can result in uneven deflection at supports of bridges and excessive stress in girders. Accordingly, the establishment of compressive elastic modulus formula and performance evaluation criteria fitted to the domestic circumstances through the execution of performance evaluation of bearings presenting diversified shapes and shape factors appears to be necessary for the domestic bearings to meet the performance required in design.