• Journal of Welding and Joining
• /
• v.29 no.1
• /
• pp.85-89
• /
• 2011

Waste water is disposed to sewage disposal plant by underground PE double wall pipes. Various processes have been introduced to join PE pipes, but most of these methods have many disadvantages such as costs, lack of reliability and difficulties in joining, etc. Recently butt welding has been paid much attention to joint PE pipes as this process has many advantages such as cost, safety and reliability. In this study, newly developed heat plate, a patent-pending heat plate with a groove, was used to butt-weld PE double wall pipes with different misalignment gaps to simulate real underground conditions, and the butt welding temperature of PE pipe was determined by thermal analysis (Thermal Gravimetric Analysis, Differential Scanning Calorimetry and Dynamic Mechanical Analysis). The resulting joining characteristics of double wall pipes were compared with those from a conventional heat plate, in terms of stiffness, flattening and leakage tests. The results from the stiffness and flattening test showed that there were no big differences between the butt-welded joints made from these two plates. From the leakage test, although PE pipes welded with a conventional heat plate did leak below the required test conditions (10 min. at 0.75kgf/cm2), the pipes welded with a patent-pending grooved heat plate did not show any leakage even at a pressure 1.5 times higher than the required conditions. It was noted that by utilizing a grooved heat plate more complete fusion at the pipe joints could be obtained, which in turn induced a high quality joints.

• Computers and Concrete
• /
• v.18 no.6
• /
• pp.1083-1096
• /
• 2016

Beam-column joints are recognized as the weak points of reinforcement concrete frames. The ductility of reinforced concrete (RC) frames during severe earthquakes can be measured through the dissipation of large energy in beam-column joint. Retrofitting and rehabilitating structures through proper methods, such as carbon fiber reinforced polymer (CFRP), are required to prevent casualties that result from the collapse of earthquake-damaged structures. The main challenge of this issue is identifying the effect of CFRP on the occurrence of failure in the joint of a cross section with normal ductility. The present study evaluates the retrofitting method for a normal ductile beam-column joint using CFRP under monotonic and cyclic loads. Thus, the finite element model of a cross section with normal ductility and made of RC is developed, and CFRP is used to retrofit the joints. This study considers three beam-column joints: one with partial CFRP wrapping, one with full CFRP wrapping, and one with normal ductility. The two cases with partial and full CFRP wrapping in the beam-column joints are used to determine the effect of retrofitting with CFRP wrapping sheets on the behavior of the beam-column joint confined by such sheets. All the models are subjected to monotonic and cyclic loading. The final capacity and hysteretic results of the dynamic analysis are investigated. A comparison of the dissipation energy graphs of the three connections shows significant enhancement in the models with partial and full CFRP wrapping. An analysis of the load-displacement curves indicates that the stiffness of the specimens is enhanced by CFRP sheets. However, the models with both partial and full CFRP wrapping exhibited no considerable improvement in terms of energy dissipation and stiffness.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.4
• /
• pp.2385-2390
• /
• 2015

In the beginning run, urban railway had been required as transportation. But now days urban railway have stayed in the platform for long time, the platform is faced the problem that is improvement of environment as one of the living space. Thus, sliding automatic door on the basis of screen door have used in huge distribution market, hospital, restaurant and public office because it is comfortable that customer's convenience and entrance are controled. So screen door not only requires customer's convenience and safe, clean area and energy conservation but demands optimal design technology development of screen door system that is confirmed by element parts of design and confidence. In this paper, For secure confidence of screen door, after as modeling roller and frame's system, confirming the result for qualification of driving stiffness. And then it suggests that it is possible to increase performance and declines fraction defective of element's part.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.20 no.4
• /
• pp.443-451
• /
• 2007

The improvement of stiffness by the increase of thickness of deck plate or the reinforcement of longitudinal rib is one method among the effective methods to control fatigue damages occurring in orthotropic steel deck. It is likely that the increase of stiffness is effective to restrain local deformation caused by axial load in the steel deck. Therefore, in this study, the parameter studies for the reinforced structural details such as the bulk-head plate and vertical rib which is established to reduce the resultant stresses in the connection parts of the longitudinal rib and floor beam were performed with FE analysis. From the results, it was known that the reinforced structural detail with the bulk-head plate in the longitudinal ribs reduced overall the principal stresses at the connection parts, but the stress concentration increased in the weld toe parts which are occurring fatigue cracks. Also, it was estimated that the reinforced structural detail with the vortical rib in the longitudinal ribs because of the reduction of stress concentration in the weld toe parts is more effective details than the bulk-head plate.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.24 no.4
• /
• pp.157-167
• /
• 2020

In this study, a field bridge test was conducted to find the dynamic properties of cable supported bridges with resilient-friction base isolation systems (R-FBI). Various ambient vibration tests were performed to estimate dynamic properties of a test bridge using trucks in a non-transportation state before opening of the bridge and by ordinary traffic loadings about one year later after opening of the bridge. The dynamic properties found from the results of the tests were compared with an analysis model. From the result of the ambient vibration tests of the cable supported bridge with R-FBI, it was confirmed that the dynamic properties were sensitive to the stiffness of the R-FBI in the bridge, and the seismic analysis model of the test bridge using the effective stiffness of the R-FBI was insufficient for reflecting the dynamic behavior of the bridge. In the case of cable supported bridges, the seismic design must follow the "Korean Highway Bridge Design Code (Limit State Design) for Cable supported bridges." Therefore, in order to reflect the actual behavior characteristics of the R-FBI installed on cable-supported bridges, an improved seismic design procedure should be proposed.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2009.09a
• /
• pp.1118-1125
• /
• 2009

This study, as basic research which was intended to develope the surface reinforcement method using reinforcement material which is applicable to very soft ground in Korea, was aimed at proposing Bearing Capacity Evaluation method for the surface ground improvement method. To that end, a wide width tensile test using geotextile, geogrid and steel bar (substitute for bamboo) and 21 kinds of the laboratory model tests with the end restraint conditions of the reinforcement that comprises the constrained and partially constrained (3 types) conditions were conducted. According to result of tests, Terzaghi's bearing capacity method is adequate to calculate bearing capacity in non-stiff material(geotextile, geogrid). But, It can't adequate to stiff material(bamboo net). So, New bearing capacity method suggest surface reinforcement method of very soft ground which Terzaghi's bearing capacity method modify for effect of stiffness.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.23 no.2
• /
• pp.307-313
• /
• 1999

This study investigated material the type(sewn-in stamped-on etc) of the label and its placement(location on the product) on children's clothing in order to survey consumer complaints to suggest the improvement. The data were collected from label-producing companies by surveying children's clothing displayed at department store as well as by questionnaire to 205 consumers who were mothers of preschool children. The results were as follows : 1. 100% polyester was the most used raw material for brand labels and nylon was for care labels. 2. Most brand labels were one piece labels and located inside the back of neck line by sewn-in either on the top on each sides or on all four sides, Care labels were usually sewn-in on the inside of left-side seam line. The texture of care label was softer than that of brand label and two pieces of care labels were widely used, 3. 67.3% of consumers complained of its stiffness while 36.1% of consumers complained of rough surface and edge 85.4% of consumers complained of an itch caused by brand labels and claimed to detach labels. For care labels 36.6% expressed displeasure of stiffness of labels while 39% complained of annoyance due to too many pieces of labels. 4. Major suggestions from the consumers were change of raw materials and relocation of brand labels. For the care labels changes of material form and type of labels were suggested and one piece of label and smaller size were preferable.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 2006.06b
• /
• pp.271-278
• /
• 2006

We used polymers of alternating cationic and anionic nature to build up shells on fiber surfaces, strengthen the worn-out fibers and improve paper properties made from such fibers. OCC and ONP pulps were either dipped or salted out in the cationic polyallylamine, polyacrylamide and starch solutions. After centrifugal drying, these were followed by treatments in anionic polyacrylic acid, poly-acrylamide, and starch solutions, respectively. The shell-enhanced fibers were formed into handsheets and their physical properties evaluated. The results show that building multiple shells on worn-out fiber surfaces can strengthen the fibers and paper. The simpler and more practical impregnation-centrifuging treatment provided the desired effects, whereas salting out the polymers produced somewhat superior fibers. The latter process, were impractical, however. The first pair of polymeric shells imparted marked strength improvement, whereas later layers had diminishing efficacies. Overall, the methods can improve fiber quality, attaining paper strength requirements without resorting to expensive measures. Alternate cationic polymer and filler powders were also deposited on fiber surface based on the micriparticle system in an anticipation of stiffness gains. Platy minerals, such as montmorillonite, bentonite, sericite, clay and talc were added following cationic PAM. After dewatering of polymer-pigment shelled fiber of one to 3 pairs of layers, handsheets either calendered or uncalendered were evaluated. The results indicate that regardless of calendaring, stiffness of the handsheets did not improve appreciably while certain other strength properties showed gains. We also attempted the novel starch gel filler addition method wherein tapioca starch and filers (PCC, sericite or clay) were mixed at high solids content of 50% and cooked until gelatinized. The filled handsheets were dried under various conditions and then tested for their properties. Improvements in strengths of modified filled paper were observed.

• Physical Therapy Korea
• /
• v.28 no.1
• /
• pp.65-71
• /
• 2021

Background: The hamstring is a muscle that crosses two joints, that is the hip and knee, and its flexibility is an important indicator of physical health in its role in many activities of daily living such as sitting, walking, and running. Limited range of motion (ROM) due to hamstring tightness is strongly related to back pain and malfunction of the hip joint. High-frequency diathermy (HFD) therapy is known to be effective in relaxing the muscle and increasing ROM. Objects: To investigate the effects of HFD on active knee extension ROM and hamstring tone and stiffness in participants with hamstring tightness. Methods: Twenty-four participants with hamstring tightness were recruited, and the operational definition of hamstring tightness in this study was active knee extension ROM of below 160° at 90° hip flexion in the supine position. HFD was applied to the hamstring for 15 minutes using the WINBACK device. All participants were examined before and after the intervention, and the results were analyzed using a paired t-test. The outcome measures included knee extension ROM, the viscoelastic property of the hamstring, and peak torque for passive knee extension. Results: The active knee extension ROM significantly increased from 138.8° ± 9.9° (mean ± standard deviation) to 143.9° ± 10.4° after the intervention (p < 0.05), while viscoelastic property of the hamstring significantly decreased (p < 0.05). Also, the peak torque for knee extension significantly decreased (p < 0.05). Conclusion: Application of HFD for 15 minutes to tight hamstrings immediately improves the active ROM and reduces the tone, stiffness, and elasticity of the muscle. However, further experiments are required to examine the long-term effects of HFD on hamstring tightness including pain reduction, postural improvement around the pelvis and lower extremities, and enhanced functional movement.

• Structural Engineering and Mechanics
• /
• v.87 no.6
• /
• pp.585-599
• /
• 2023

Geopolymer concrete (GC) can be competently utilized as a practical replacement for cement to prevent a high carbon footprint and to give a direction toward sustainable concrete construction. Moreover, previous studies mostly focused on the axial response of glass fiber reinforced polymer (glass-FRP) concrete compressive elements without determining the effectiveness of repairing them after their partial damage. The goal of this study is to assess the structural effectiveness of partially damaged GC columns that have been restored using carbon fiber reinforced polymer (carbon-FRP). Bars made of glass-FRP and helix made of glass-FRP are used to reinforce these columns. For comparative study, six of the twelve circular specimens-each measuring 300 mm×1200 mm-are reinforced with steel bars, while the other four are axially strengthened using glass-FRP bars (referred to as GSG columns). The broken columns are repaired and strengthened using carbon-FRP sheets after the specimens have been subjected to concentric and eccentric compression until a 30% loss in axial strength is attained in the post-peak phase. The study investigates the effects of various variables on important response metrics like axial strength, axial deflection, load-deflection response, stiffness index, strength index, ductility index, and damage response. These variables include concentric and eccentric compression, helix pitch, steel bars, carbon-FRP wrapping, and glass-FRP bars. Both before and after the quick repair process, these metrics are evaluated. The results of the investigation show that the axial strengths of the reconstructed SSG and GSG columns are, respectively, 15.3% and 20.9% higher than those of their original counterparts. In addition, compared to their SSG counterparts, the repaired GSG samples exhibit an improvement in average ductility indices of 2.92% and a drop in average stiffness indices of 3.2%.