• International conference on construction engineering and project management
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• 2024.07a
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• pp.160-166
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• 2024

In recent years, as buildings have become taller and taller, the continued usability of elevators after earthquakes has become an important issue. Conventional seismic design of elevators has focused mainly on inertial forces caused by earthquakes, but the influence of the story drift angle of buildings on elevator behavior has been unclear. Therefore, the objective of this study was to clarify the influence of the story drift angle of a building caused by an earthquake on the behavior of elevators through an experiment. The experiment specimens were the counterweight, guide rails, and surrounding components selected from the actual elevator components and mounted on a one-story steel pin frame. A static experiment was conducted using a hydraulic jack to apply force to the specimen by imposing the story drift angle on the steel frame. During the experiment, the reaction force at the end of the jack was monitored, and the displacement and strain of the counterweight, guide rails, and surrounding components were measured. The results of the experiments in one direction showed that even when the elevator components were subjected to a larger story drift angle than assumed in the seismic design of the building, no damage occurred that could lead to fallout.

• Journal of the Korean Arthroscopy Society
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• v.13 no.1
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• pp.82-85
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• 2009

Purpose: In anterior cruciate ligament (ACL) reconstruction, preservation of the remnant original tissue might promote graft healing and be helpful in proprioception. But this procedure is difficult and causes the notch impingement. So we introduce a surgical technique that makes a transtibial femoral tunnel at 10 or 2 o'clock position with preservation of remnant tissue. Surgical approach: We tried to preserve the remnant tissue and synovium as much as possible, especially those of tibial attachment and extending to the posterior cruciate ligament (PCL), so as to have some tension and to prevent notch impingement. We set the tibial drill guide at 40~45 degrees and the intra-articular guide tip was 1 mm anterior and medial to the conventional site. The starting point of tibial guide pin was proximal to the pes anserinus and anterior to the medial collateral ligament. When the reamer approached the cortical bone of the tibial articular surface, the reamer must be advanced very carefully to minimize injury to the remnant tissue. The tibial and femoral tunnel at 10 or 2 o'clock position were made with the reamer, the diameter of which was same with that of the graft. Conclusion: We report a remnant preserving technique in ACL reconstruction that makes a transtibial femoral tunnel at 10 or 2 o'clock position

• Journal of the Korean Arthroscopy Society
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• v.10 no.2
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• pp.209-213
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• 2006

Purpose: Conventional transtibial approach for the anterior cruciate ligament (ACL) reconstruction tended to place the femoral tunnel in too vertical position (11 or 1 o'clock), which could provide the postoperative anteroposterior (AP) stability but not provided the rotational stability. Therefore we present a surgical technique to make the transtibial femoral tunnel at 10 or 2 o'clock position. Surgical approach: To make a transtibial femoral tunnel at the 10 or 2 o'clock position, the direction and position of the tibial drill guide was important. We set the tibial drill guide at $40{\sim}45$ degrees and the intraarticular guide tip was 1 mm anterior and medial to the conventional site. The starting point for the guide pin on the proximal tibia was proximal to the pes anserinus and anterior to the medial collateral ligament. The tibial tunnel was initially drilled 1mm less than the diameter of the graft. Then femoral offset guide could be easily placed at 10 or 2 o'clock position through the tibial tunnel. The tibial tunnel and the femoral tunnel of 30 mm in length were made with the reamer that was same size with the graft. Conclusion: We report a surgical technique to create a transtibial femoral tunnel at 10 or 2 o'clock position in ACL reconstruction to provide the rotational stability as well as the AP stability.

• Journal of the Korean Arthroscopy Society
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• v.13 no.2
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• pp.174-178
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• 2009

Purpose: We introduce arthroscopic assisted core decompression for humeral head osteonecrosis. Operative technique: After diagnostic shoulder arthroscopy is performed using posterior and anterior portal, we make a 2 cm lateral skin incision approximately 3 cm distal to 1/3 of lateral margin of the acromion and place short gray cannula to prevent adjacent soft tissue injury when insert guide pin. Under C-arm fluoroscopic and arthroscopic guidance, 3 to 4 guide pins are inserted toward the necrotic area. Then we perform drilling using 7.0 mm reamer. Conclusion: We believe this technique is a less invasive approach and avoids the complications comparing to deltopectoral approach. Arthroscopic assisted core decompression is an effective procedure in management of early stage of the humeral head osteonecoris.

• Structural Engineering and Mechanics
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• v.25 no.1
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• pp.1-20
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• 2007

Dynamic behaviors of the contact surface between ball and raceway in a guideway mechanism vary with the applied loads and hence affect the mechanical responses of machine tools. The study aims to investigate the nonlinear characteristics of dynamic behaviors at the rolling contact interface in linear guideway mechanisms. Firstly, analytical method was introduced to understand the contact behaviors based on Hertz contact theory in a point-to-point way. Then, the finite element approach with a three-dimensional surface-to-surface contact model and appropriate contact stiffness was developed to study the dynamic characteristics of such linear guideways. Finally, experiments with modal test were conducted to verify the significance of both the analytical and the numerical results. Results told that the finite element approach may provide significant predictions. The study results also concluded that the current nonlinear models based on Hertz's contact theory may accurately describe the contact characteristic of a linear guideway mechanism. In the modal analysis, it was told that the natural frequencies vary a little with different loading conditions; however, the mode shapes are changed obviously with the magnitude of applied loads. Therefore, the stiffness of contact interface needs to be properly adjusted during simulation which may affect the dynamic characteristics of the machine tools.

• Transactions of Materials Processing
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• v.15 no.8 s.89
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• pp.609-614
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• 2006

Micro-alloyed steels(MA steels) for cold forging was developed to replace the usual quenched and tempered steel. MA steels have several advantages over the conventional quenched and tempered carbon steels. First of all, energy consumption could be lowered due to the elimination of spherodizing annealing and quenching/tempering heat treatment. Also, bending during quenching could be avoided when MA steels are applied for manufacturing of long fastener parts. However, larger amount of load is exerted on the dies compared than in the case of conventional mild steels, which might lead to the earlier fracture of dies, when MA forging steels are applied in forging practice. Therefore, die lift could be a critical factor to determine whether HA forging steels could be widely applied in cold forging practice. In the present study, authors have investigated the forging characteristics of non-heat treated micro-alloyed steel by using a series of experimental and numerical analyses. Firstly, microstructural features and its effect on the deformation behavior have been studied. Numerical analysis has been done on the forging of guide rod pin to investigate for the optimization of forging process and die stress prediction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.546-552
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• 2012

This paper is a study on squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material. For this, data of pressure and temperature dependent material properties of lining is achieved by using lining data base and exponential curve fit. Complex eigenvalue analysis is performed for predicting squeal noise frequency and instability and chassis dynamo test is performed for achieving squeal noise frequency, sound pressure level, occurrence temperature & pressure. Initial multi models are composed for considering complex interface conditions such as pad ear-clip, piston-housing and guide pin-torque member. The simulation result of base models is compared with the test result. Squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material is performed and analyzed using multi models. And additional condition is disc material property variation. Entire simulation conditions are combined and analyzed. Finally, this paper proposes direction of the warm squeal noise model.

• Clinics in Shoulder and Elbow
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• v.14 no.1
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• pp.94-98
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• 2011

Purpose: We present a case of anterior glenoid rim comminuted fracture that was treated with arthroscopic reduction and an AO headless compression screw (HCS) fixation. Materials and Methods: A 31-year old man complained of left shoulder pain after falling down on stairs. The anterior glenoid comminuted fragments were arthroscopically reduced. Fixation with an AO HCS was done after placement of 1.1 mm Kirschner wire as a guide pin through a standard cannulated anterosuperior portal. Results: Twelve months after the operation, union of the fracture was achieved and the range of motion was fully recovered. He did not complain of any discomfort during his activities of daily living. Conclusion: An AO HCS had various screw sizes and this was good for fixation of a small glenoid fracture and a long drill bit and screw driver were useful for fixation of deep seated glenoid fracture. A short guide wire could be replaced by a 1.1 mm K-wire. An AO HCS was useful for fixation of an anterior glenoid rim comminuted fracture.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.2
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• pp.114-125
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• 1993

In the present study the newly developed CAD/CAM system is applied to the process of the molding design, machining for mini-sized and precise processive die, and the production of press-stamped parts. When the design of a die was completed by means of CAD, wire cut NC data were generated with the aid of a design drawing in the CAD system and then inputed into the wire cut machine, and with the aid of a hole chart which had been made for this purpose, all the data were classified into the categories of CNC milling, jig boring, jig grinding, and machine center, and then developing a program of generating NC data, errors in process were reduced and programming time was shortened. The program was developed by using Autolisp language which was built-in the CAD, and realizing the intergation of designing a die, generating and processing NC data directly by a designer, designing time and machinery processing time were shorted. And the traditionally required working time for design. NC program required 6 days of work becomes 4 days of work by using the developed CAD/CAM system so that the efficiency shows 150% of the reduction working time. The prpgram of the design of the automation a progressive die mold was developed in the PC-Class Autocad system, therefore development expense could be reduced, and the integration of the CAD/CAM of the progressive die mold with the standard DB being built could be realized.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.2
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• pp.37-46
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• 2009

In this study, the seismic performance of the Buckling Restrained Knee Bracing (BRKB) system was evaluated through a pin-connected 1-bay 1-story frame. The BRKB system using a bolted channel section developed was composed of a steel plate as a load-resisting core member and two channel sections as a restrainment of the local and global buckling of the core plate. The main purpose of the BRKB system is to be used as an effective tool to re-strengthen/rehabilitate old low- and mid-rise RC frame buildings, which do not have enough seismic resistance to earthquake loadings. The main variables for the test specimens were the size of the core plates, stiffeners and the use of guide plates. The test results showed that the size of the core plate, which was the main element for the load-resisting member, was the most important parameter to achieve ductile behavior under tension as well as compression, until the maximum displacement exceed twice the design drift limit given by the AISC Seismic Provisions.