• International Journal of Highway Engineering
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• v.13 no.3
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• pp.65-73
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• 2011

Recently, researches to introduce the performance warranty contract are in progress for quality improvement of road pavements. The performance warranty contract is a type of contract in which contractors guarantee to maintain certain level of performance during a period from completion of construction. The contract use in Europe and the U.S is being increased because it has been known to contribute to improvement of structure quality, reduction of life cycle cost, development of construction techniques, and etc. The research on performance indicators, threshold values, and warranty durations is essential to effectively introduce the contract in Korea. In this study, literatures on the performance warranty contract for concrete pavements of the Minnesota, Indiana, and Florida of the U.S. were reviewed. Major distresses influencing the pavement performance were investigated and analyzed in the jointed concrete pavement sections of 21 Korean expressway routes to be compared to the performance indicators, threshold values, and warranty durations of the states. More accurate comparison is expected by investigation in planned sections for a long time.

• Journal of the Korean Wood Science and Technology
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• v.34 no.5
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• pp.11-18
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• 2006

This study was carried out to evaluate the mechano-sorptive deflection of shear creep of drift pin jointed solid wood. Specimens were the solid wood of Pinus densiflora. The joint was composed with steel plate and drift pin, 85mm in length and 10mm in diameter. The creep tests were conducted under the constant loads in an variable environment. Five different shearing loads were applied parallel to the grain of specimens. The shearing loads applied were 170, 340, 510, 680 and 850 kgf. The stress levels were 10, 20, and 30, 40 and 50% of the bearing strength obtained from the tension-type lateral strength test. The creep tests for specimens were carried out for 10300 hours. A few general conclusions could be drawn from this study: The mechano-sorptive deflection (${\delta}$ ms) is defined as ${\delta}\;ms={\delta}\;t-({\delta}\;c+{\delta}\;sh)-{\delta}\;o$, where ${\delta}$ t is the total deflection, ${\delta}$ c is the pure creep, ${\delta}$ sh is shrinkage-swelling behavior, and ${\delta}$ o is the initial deflection. Changes of relative humidity may cause more severe creep deflection than those of constant humidity, especially during the drying process. The mechano-sorptive behaviors of specimens, except the effects of shrinkage and swelling, gradually increased with increasing time. The deflection is increased in desorption process and recovered in adsorption process. The deflections of drift pin jointed solid wood under different loads showed almost same tendency in all specimens. Although the creep deflection tendencies of each series are very similar, the specimens subjected to a large shearing load exhibit large creep deflections in the desorption process than do those to the small shearing load specimens.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.8
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• pp.1250-1258
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• 1997

This paper reports on the development of a new foot for a quadrupedal jointed-leg type walking robot. The foot has 2 toes, one at the front and the other at the rear side, for stable landing on uneven ground by point contact. The toes can move up and down independantly, guided by double-wishbone shaped parallel links which enable the lower leg to rotate with respect to a remote center on the ground surface. The motion of each toe is damped by a hydropneumatic shock absorber integrated in the foot in order to absorb the dynamic landing shock. Furthermore, the new foot can reduce the maximum hip joint drive torque by shortening the moment arm length between the hip joint and the landing force vector on the ground. Intensive experiments were carried out in this study by using a one-leg walking model to investigate the soft landing performance of the foot which could be hardly offered by conventional robot feet such as a flat plate with a gimbal type ankle joint. And it was confirmed that the hip joint torque of the leg walking on the flat surface could be reduced remarkably by using the new foot.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.2
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• pp.87-96
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• 2012

With a view to determine a safe speed the limit of a manipulator arm, several experiments was performed with a multi-jointed manipulator in maintenance and decommissioning tasks of nuclear facilities. Under the simulated emergency conditions, which were generated with random combinations of manipulator arm speed, failure probability and failure type, response characteristics of human operators to various malfunctions of a manipulator arm were measured in terms of reaction time, number of false alarm, and number of misses. This paper demonstrated that failure type, manipulator axes and manipulator arm speed has significant effects on human reaction time. As a whole the reaction time was slightly increased with manipulator arm speed, which is showed somewhat different pattern due to failure type. The reaction time to an axis acting on a workpiece directly, which could flex and extend, was fastest and much more its standard deviation was small. Various factors which may affect safe speed were also described.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.679-680
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• 2006

Various different types of joining between High Tc superconducting(HTS) tapes were prepared and current-voltage(I-V) characteristic curves were investigated at 77 K, liquid nitrogen temperature. Two typos of HTS tapes wore used, one is no laminated tape(Sumitomo high strength type tape) and the other stainless steel laminated tape(AMSC(American Superconductors Inc.) 3ply tapes) Sample joints were lap-jointed with indium or solder. Joint resistances between Sumitomo tapes with 4-10 mm in length were estimated from I-V curves and in the range of $4-8n{\Omega}$ at 77 K. Joint resistances of AMSC tapes were in the range of $140-170n{\Omega}$, much higher than them of Sumitomo samples. The n-values of jointed HTS tapes were 50% of them with no joint. In AMSC tapes, indium is better than solder as the jointing material.

• Journal of the Korean Wood Science and Technology
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• v.24 no.1
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• pp.95-99
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• 1996

The bending and compression strength properties of two types Rhus verniciflua specimens, which made of no heat-treated wood and heat-treated wood for urushiol extraction, were measured. The heat-treated specimens were finger-jointed with either resorcinol-phenol or polyurethane resin adhesives, and the vertical type bending strength property was also measured in these specimens. The results obtained are as follows ; 1. The correlation coefficient between the compression strength and specific gravity in the specimens of no heat-treated and heat-treated wood was high. However there was no difference in compression strength property as affected by heat treatment. 2 The correlation coefficient between the bending strength and specific gravity in the specimens of no heat-treated and heat-treated wood was also high. However, there was no difference in bending strength property as affected by heat treatment. 3 The bending test showed high correlation between modulus of elasticity and modulus of rupture for the specimens made of no heat-treated and heat-treated wood. However, there was no difference in bending strength property between the specimens made of heat-treated and no heat-treated wood. 4. The efficiencies of bending strength test on the finger-jointed specimens of heat-treated wood with resorcinol-phenol and polyurethane resin adhesives were 0.85, 0.81. respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.769-776
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• 1997

An integral abutment bridge refers to a jointless bridge with capped-pile stub type abutment. It has been used for more than 50 years in the United States and Canada. This paper briefly describes design and utilization of the PC beam integral abutment bridge which is adapted for Korea and shows its excellent performance compared with that of a jointed bridge. This study introduces the characteristics of structural behaviors of the integral bridge and also mentions about its attributes and limitations.

• International Journal of Highway Engineering
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• v.11 no.2
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• pp.121-132
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• 2009

Thin bonded continuously reinforced concrete overlay(CRCO) was constructed on He existing jointed plain concrete pavement(HCP) surface at Seo-Hae-Ahn express highway in South Korea in order to evaluate its applicability and performance. Two sections of road were considered for this evaluation. In the first section, the concrete overlayer was placed and cut down to the existing layer to form transverse joints while CRCO was constructed on top of the existing layer in the second section. Early strength concrete(Type III) was utilized for both overlay sections. The depth of milling and the thickness of overlaid layer were 5 cm and 10 cm, respectively. Several vibrating wire gauges(VWG) were installed to evaluate the performance of CRCO with respect to curling, delamination, and crack propagation. As a result of the strength test, it was found that strength of the material reaches the design criteria within 1-3 days. Analysis with vibrating wire gauge(VWG) showed CRCO effectively restricts joint movement. High adhesive strength also was observed from the material regardless of length of aging. Meanwhile, transverse cracks were observed on the middle of the section where JPCP overlay was applied whereas arbitrarily cracks in transverse direction were observed on the section where CRCP was applied.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.31-38
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• 2009

The primary objective of this study was to estimate the deterioration degree of jointed concrete pavement which was major concrete pavement type in Korea. First of all, visual survey of concrete pavement was performed to observe deterioration types. In the result of visual survey, the majority of concrete pavement deterioration was investigated in joint area. It is appeared that most of the distresses are durability cracking and joint distress. Second, concrete core specimens were taken from eight locations including good section (4 locations) and bad section (4 locations) based on visual survey. The deterioration reasons of concrete pavement were analyzed with ultrasonic pulse velocity test, splitting tensile strength test, and image analysis for concrete core specimens. Among the image analysis test result for 21 concrete core specimens, only two specimens satisfied the Kansas DOT criteria of spacing factor, $250\;{\mu}m$, and the remains of 19 specimens were estimated to be above $250\;{\mu}m$. The durability factor of concrete was estimated very low. As a result, it was analyzed that the main deterioration reason of the deteriorated jointed concrete pavement was to be freezing and thawing damages.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.4
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• pp.23-32
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• 2023

The seismic performance of buried PE pipes is reported to be favorable due to their exceptional elongation capacity at break. Although a seismic performance evaluation procedure based on the response displacement method has been summarized in Korea for fusion-bonded PE pipes, there is currently no procedure available for mechanically jointed PE pipes. This article aims to present a seismic performance evaluation procedure based on the response displacement method specifically designed for mechanically jointed PE pipes in Korea. When employing the mechanical joining method for PE pipes, it is recommended to adhere to the evaluation procedure established for segment-type pipes. This involves assessing the stress induced by the pipe, the expansion and contraction strain of the joint, and the bending angle of the pipe joint. Furthermore, the coefficient of inhomogeneity of the soil, which is necessary for estimating the axial strain of the ground, is introduced. Additionally, a computation method for determining lateral displacement and reconsolidation settlement in soil susceptible to liquefaction is proposed. As a result of the sensitivity analysis considering the typical soil condition in Korea, the mechanically jointed PE pipe with a certain quality was shown to have good structural seismic safety when soil liquefaction was not considered. This procedure serves as a valuable tool for seismic design and evaluating the seismic performance of mechanically joined buried PE pipes, which are primarily utilized for connecting small-diameter pipes.