• Polymer(Korea)
• /
• v.37 no.5
• /
• pp.642-648
• /
• 2013

There is a kind of abnormal noise known to come from the stick-slip mechanism induced by frictional impulses during the sliding of two polymeric plates. In this work, quantitative analysis of abnormal noise is carried out based on experimental results. Some combinations of polymer plates, such as an ABS base-plate contacted to ABS, PP, MIPS, and POM plates, which are well-known materials used in home-appliances, are studied to obtain the best combination of polymer plates in order to reduce the abnormal noise. For the experiments, a rig for the test was set up and a methodology was proposed. In addition, the effects of the surface roughness of the plate, the normal loading force, and the relative sliding speed between the two contact plates were evaluated in order to understand the reason for the abnormal noise. Through this experimental work, the optimal combination of materials was ABS/POM system to reduce the noise in real industrial applications.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.11 no.6
• /
• pp.201-212
• /
• 2007

This study presents experimental results of Steel-PSC mixed structural system having front-rear plate connection between Steel and Prestressed Concrete. Two kinds of Steel-PSC mixed structural system of 5.4m length were tested to evaluate flexural behaviors under four point loading, and 4 kinds of specimens with and without prestressing force at R & L type connection were tested to observe the shear behavior. Based on the test results of load-deflection curves and failure modes of specimens, it is found that the proposed L shape connection with front-rear plate connection between Steel and Prestressed Concrete has higher strength and stiffness. From the study, Steel-PSC mixed structural system with L shaped connection has a better structural performance in connection part.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.12 no.4
• /
• pp.79-86
• /
• 2008

Four RC shear wall specimens with a/d of 2.2 are designed. And a flexural retrofitting is performed for one specimen by both enlarging wall section and adding additional vertical reinforcements. Also the effectivity of jaketting wall sides is evaluated for the two methods using only steel plate or welded wire mesh with enlargement of section. Cyclic loads are applied to the retrofitted specimens according to the loading history proposed by ACI under constant axial force. Test result showed that the strength and ductility of specimen were improved where the section was enlarged after the installation of additional vertical reinforcements. Confining the ends of wall by U shape W.W.F. with enlargement of section showed most excellent structural capacity regarding to the strength and ductility. Retrofitting by using steel plate was much effective not only to protect the abrupt decrease of strength after yield but also to improve the deformation capacity.

• Smart Structures and Systems
• /
• v.25 no.2
• /
• pp.241-254
• /
• 2020

Using confined shape memory alloy (SMA) bar or plate, this study proposes an innovative self-centering damper. The damper is essentially properly machined SMA core, i.e., bar or plate, that encased in buckling-restrained device. To prove the design concept, cyclic loading tests were carried out. According to the test results, the damper exhibited desired flag-shape hysteretic behaviors upon both tension and compression actions, although asymmetric behavior is noted. Based on the experimental data, the hysteretic parameters that interested by seismic applications, such as the strength, stiffness, equivalent damping ratio and recentering capacity, are quantified. Processed in the Matlab/Simulink environment, a preliminary evaluation of the seismic control effect for this damper was conducted. The proposed damper was placed at the first story of a multi-story frame and then the original and controlled structures were subjected to earthquake excitations. The numerical outcome indicated the damper is effective in controlling seismic deformation demands. Besides, a companion SMA damper which represents a popular type in previous studies is also introduced in the analysis to further reveal the seismic control characteristics of the newly proposed damper. In current case, it was found that although the current SMA damper shows asymmetric tension-compression behavior, it successfully contributes comparable seismic control effect as those having symmetrical cyclic behavior. Additionally, the proposed damper even shows better global performance in controlling acceleration demands. Thus, this paper reduces the concern of using SMA dampers with asymmetric cyclic behavior to a certain degree.

• The Journal of Korean Academy of Prosthodontics
• /
• v.28 no.1
• /
• pp.43-61
• /
• 1990

The laser reflexion method is a new technique which permits precise contactless measurement and observation of tooth mobility as well as tooth movement. The purposes of this study were to clarify the reliability of the laser reflexion method in clinical application and to measure the abutment tooth movement according to clasp design. This study was designed to determine 1) How much a bending movement of the impression plate stand affects the position of the reflexion pattern and how precise the patient bites into plate 2) Which clasp design causes greater movement of the abutment tooth. Under medium and maximum bite forces, tests were performed on central loading position which was 13mm distal to terminal abutment tooth of distal extension removable partial denture. The movement in the mesiodistal and buccolingual directions was measured. The Duncan's New Multiple-Range test was used to compare the means for the four castings under each direction-load combination; and the paired sample t-test was for medium and maximum bite forces. From this experiment, the following results were obtained. 1. The Roach clasp, the combination clasp, the RPI clasp, and the Akers clasp did not significantly differ in their effects on buccolingual movement of the abutment tooth. 2. The direction of abutment tooth movement was not significantly altered by clasp design and all abutment tooth movements were oriented distobuccally. 3. Under medium bite force, the Akers clasp caused greater distal movement of the abutment tooth than did the combination clasp and the RPI clasp. Under maximum bite force, the Akers clasp caused greater distal movement of the abutment tooth than did the RPI clasp. 4. The testing apparatus and procedures used in this study(laser reflexion method) proved to be reliable in clinical application.

• Journal of the Korean Geosynthetics Society
• /
• v.18 no.1
• /
• pp.55-65
• /
• 2019

This paper describes results of experimental and numerical analyses, in order to analyze a reinforcement effect of concrete mat on open cut restoration of underground cavity. The plate loading tests were conducted to evaluate a reinforcement effect of concrete mat, at reinforcement depths from the ground surface of 10 cm, 20 cm, and 30 cm. The result showed that the reduction ratio of stress (earth pressure) was about 60% at all reinforcement depth. The reinforcement effect considering ground surface settlement and reduction ratio of stress based on laboratory tests and numerical analysis was significant, at reinforcement depths from the ground surface of 10 cm~20 cm. LFWD test results showed that subgrade modulus was the largest when concrete mat was installed 20 cm below ground surface. Therefore, it is effective to reinforce concrete mat within 20 cm from the surface, when the underground cavity due to damage of underground utilities was formed in the height direction to the bottom of the pavement layer.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.1
• /
• pp.19-29
• /
• 2023

An ultra-high strength prestressed prismatic beam of 100 MPa in compressive strength was developed by increasing the watertightness of concrete by utilizing centrifugal molding processes without adding expensive admixtures such as silica fume. The ultra-high strength centrifugal shaped square beam installed on the wall is composited with the upper slab concrete and then subjected to a service load. Horizontal shear stress is generated by bending between the centrifugal molding beam and the floor plate, which causes the beam and floor plate to perform composite behavior through shear connections such as studs and rebars. In this study, a flexural load test was performed on a mock-up specimen that was synthesized by fabricating an RC slab on top of a 100 MPa-class centrifugal shaped beam produced at the factory. proven reliability.

• Journal of the Korea Concrete Institute
• /
• v.17 no.2 s.86
• /
• pp.281-290
• /
• 2005

This paper presents experimental and analytical studies on long-term behavior of square CFT columns under central axial loading. Two loading cases are considered; (1) the load applied only at the inner concrete of the column and (2) the load applied simultaneously on both the concrete and the steel tube. Four specimens of square CFT columns were tested under the two loading cases, and basic creep test for two concrete specimens was performed to find out the creep properties of the inner concrete. Three-dimensional finite element analysis models were established and verified with the experimental results. The verification shows that the prediction for the long-term behavior of actual square CFT columns is possible from the three dimensional finite element modeling considering the bond behavior between steel tube and inner concrete. Also, experimental results and numerical calculations revealed that the bond stress Induced by the confinement pressure as well as the slip between inner concrete and steel tube were increased with time In the first loading case. However, the confinement by the loading Plate was decreased with time while increasing confinement effect by the steel tube was observed over time. In contrast no confinement effects occur in the second loading case.

• Journal of the Korea Concrete Institute
• /
• v.21 no.2
• /
• pp.139-146
• /
• 2009

Experimental study was performed to evaluate the long-term behavior of CFRP (carbon fiber reinforced polymer) strips under sustained loads including prestressing force in strengthening RC members with post-tensioned CFRP strips. Two types of CFRP strip such as unidirectional CFRP strip and hybrid CFRP strip which is composed of carbon fiber and steel plate were considered. Also two types of loading scheme were included in this study. Direct sustained loading test had been carried out to estimate the creep deformation and relaxation of CFRP strips including slip deformation at both mechanical anchorages for over 700 days. Also, flexural sustained loading test had been conducted to estimate the initial prestress losses on clamping the CFRP strips at jacking anchorages for over 90 days. From the sustained loading tests, it was observed that stress losses of unidirectional CFRP strips due to the creep deformation and relaxation of material itself and slip deformation at mechanical anchorage were ignorable. On the other hand, significant stress losses caused by the yielding of steel embedded in CFRP strips were found in case of hybrid CFRP strips due to the initial jacking force over steel yielding stress. Also, initial prestress losses during setting of CFRP strips on mechanical anchorage were about 10% of intial jacking force, which must be considered in the design.

• Journal of Korean Society of Steel Construction
• /
• v.15 no.2
• /
• pp.167-174
• /
• 2003

This paper presented the results of cyclic loading tests of 7 full-scale beams to column subassemblages with improved connection detail i.e., fillets of the stiffening plates at the column corners and ends of the stiffener-to-beam flange weld. Major findings from the test results were: (1) Fillets reduced the stress concentrations that may cause early brittle fractures and considerably improved the cyclic performance compared to the detail without fillets. (2) As the width of the stiffening plate increased, the stiffness and peak strength increased and energy dissipation capacity decreased. (3) While all specimens failed by a fracture, they could develop a total rotation of 0.04 radian required for special moment resisting frames.