• International Journal of High-Rise Buildings
• /
• v.11 no.3
• /
• pp.181-187
• /
• 2022

POSCO E&C has completed Parc.1 project successfully. The construction period was 42months, and 1.5 million workers were participated till completion. To meet schedule management and quality control, POSCO E&C has adopted a lot of technologies such as GPS measurement, 3D scanning, vibration control, stack effect control, column shortening control, etc

• Earthquakes and Structures
• /
• v.16 no.3
• /
• pp.295-310
• /
• 2019

This study attempts to develop new simplified approximate formulas to predict the fundamental natural periods of vibration (T) for bearing wall systems engaged with special reinforced concrete shear walls (RCSW) under seismic loads. Commonly, seismic codes suggested empirical formulas established by regression analysis of measured T for buildings during earthquake motions. These formulas depend on structure type, building height, number, height and length of SW, and ratio of SW area to base area of structure. In this study, a parametric investigation is performed for T of 110 selected models of bearing RCSW systems with varying structural height, configuration of horizontal plans including building width, number and width of bays, presence of middle corridors and core SWs. For this purpose, a 3D non-linear response time history (TH) analysis is implemented using ETABS v16.2.1. New formulas to estimate T are anticipated and compared with those obtained from formulas of IBC 2012 and ASCE/SEI 7-10. Moreover, the study examines responses of an arbitrarily two selected test model of 60 m and 80 m in height with presence of SWs having middle corridors. It is observed that the performance of the tested buildings is different through arising of considerable errors when using codes' formulas for estimating T. Accordingly, using the present proposed formulas exhibits more reasonable and safer design compared to codes' formulas. The results showed that equitable enhancement is promising to improve T formulas approaching enhanced and accurate estimation of T with reliable analysis, design, and evaluation of bearing RCSW systems.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.6
• /
• pp.2804-2811
• /
• 2012

In this study, It is developed a retrofitting procedure of RC column with rectangular section to archive the target displacement at failure. Nonlinear behavior of the column is considered as the equivalent linear system. First, target displacement is determined, and then elastic displacement spectrum is constructed to estimate the equivalent natural vibration period of the SDOF system. After natural vibration period is determined, required strength is calculated using secant stiffness based on the mass of system. In accordance with, obtained force-displacement relationship through non-linear fiber based section analysis, retrofit design was carried out to meet required strength. As a result, retrofitted RC column can confirm that the improved seismic performance. It is observed that the proposed design procedure can be applicable to seismic retrofitting design of columns.

• Explosives and Blasting
• /
• v.39 no.2
• /
• pp.15-26
• /
• 2021

Domestic electronic detonators are used widely in many quarry and construction sites since its launch at 2013. In the case of SOC projects conducted in the city, most of them are designed in high-depth to reduce complaints. The high-depth excavation needs a long construction period and huge cost for building shaft and ventilation hole. Mechanical excavation method is applied when safety things are located nearby the site. Solidity of rock and machine's performance affect on the method's efficiency. So as the efficiency is getting lower, the construction period is extended, and the cost is increases as well. This case study is about changing the machine excavation method to the blasting method which is electronic detonator applied at the shaft construction site in the city. This is an example of using electronic detonators on the construction site in reducing blast-noise and vibration while meeting environmental regulatory standards.

• Explosives and Blasting
• /
• v.39 no.3
• /
• pp.24-34
• /
• 2021

Electronic detonators are widely used in various construction sites due to accurate delay time. Including the cases with exceeded noise and vibration from site using electric/non-electric detonator, electronic detonators are used to improve blast fragmentation or to reduce the cost of secondary partial blasting. Furthermore, the number of cases using electronic detonators are increased for reduction of the cost and construction period by maximizing operations efficiency. This case study is about applying electronic detonators on large section station, tunnel construction site which is the part of urban area GTX A project. Although it was initially planned to utilize non-electric detonators, damage was inflicted on safety-thing. We have considered blasting method using electronic detonators as solution of this problem. By applying electronic detonators, we not only satisfied environmental regulations but also prevented nearby safety-thing from getting damaged. In addition, we were able to shorten the construction period than the initial plan by conducting single simultaneous blasting on large section station, in order to ensure safe and efficient construction.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2004.05b
• /
• pp.506-510
• /
• 2004

A torque transmission system composed of several gears and couplings is flexible. In order to get an exact response of motor, the torsional vibration due to an unexpected change of motor speed must be suppressed. Therefore, it is very important that motor control suppress vibration. Various methods to control it including dual inertia system are proposed. Specially, the method of vibration suppression is that vibration can be suppressed to fee㏈ack the estimated torsion torque via the disturbance observer filter being of normal filter. The suitable Proportional controller and coefficient parameter can be designed using CDM and the torsional vibration also be suppressed, but it has a low degree of adaptability to disturbance. The PID controller can be designed easily, but makes the excessive overshoot and oscillation for system response in the early period. To resolve these problems, simple and practical PID controller with two degree of freedom is proposed recently that it ran improve performance of obeying the reference unconcerned in any disturbance by changing the proportional gain by two degree of freedom parameter. But it has also the defect that parameter a must be changed to obtain the ideal Proportional parameter. On this paper, we design the controller which automatically adjusts parameter u using fuzzy Algorithm to overcome such defects. Also, we compare the proposed method with established one and evaluate them to confirm performance of the designed controller.

• The Journal of the Acoustical Society of Korea
• /
• v.35 no.3
• /
• pp.192-201
• /
• 2016

Condition Monitoring System (CMS) has been used to detect unexpected faults of wind turbine caused by the abrupt change of circumstances or the aging of its mechanical part. In fact, it is a very hard work to do regular inspection for its maintenance because wind turbine is located on the mountaintop or sea. The purpose of this study is to find out distribution patterns of vibration signals measured from the main mechanical parts of wind turbine according to its operation condition. To this end, acceleration signals of main bearing, gearbox, generator, wind speed, rotational speed, etc were measured through the long period more than 2 years and trend analyses on each signal were conducted as a function of the rotational speed. In addition, correlation analysis among the signals was done to grasp the relation between mechanical parts. As a result, the vibrations were dependent on the rotational speed of main shaft and whether power was generated or not, and their distributions at a specific rotational speed could be approximated to Weibull distribution. It was also investigated that the vibration at main bearing was correlated with vibration at gearbox each other, whereas vibration at generator should be dealt with individually because of generating mechanism. These results can be used for improving performance of CMS that early detects the mechanical abnormality of wind turbine.

• Journal of Society of Occupational Therapy for the Aged and Dementia
• /
• v.12 no.2
• /
• pp.87-95
• /
• 2018

Objective : Vibration stimulators are easier to obtain in clinical settings than other treatment tools, and it is advantageous that the arm activation training can be performed passively. Despite the following advantages, recent studies on vibration sense have not been activated yet. The purpose of this study was to investigate the effect of vibration sensation on the hands of the affected upper limb on unilateral reduction of stroke patients. Method : Patients with unilateral neglect due to stroke were enrolled in this study for about 3 weeks from October 19, 2018 to November 7, The research design used ABA design among the single-subject experimental research design, and a total of 18 circuits (4 baseline, 6 intervention, 3 baseline regression) were performed once a day on weekdays Respectively. MMES-K was used to select the subjects. Line bisection test (LBT), Albert's test and Star Cancellation Test (SCT) were used as unilateral neglect test. For the analysis, the baseline and intervention period measurements were visually analyzed using graphs and mean values were used. Result : All three evaluations showed that the number of errors missed during the training period was lower than the baseline period, and this decrease remained after training. The error was reduced by an average of $2{\pm}1.2$ omissions and an average omissions of $0.6{\pm}0.5$ omitting an average of $4.5{\pm}1$ omissions in the line break test. As a result of the Albert test, the average error decreased by $22.5{\pm}1.9$ omissions and $8{\pm}7.3$ omissions and $0.3{\pm}0.5$ omissions, respectively. In the star clearance test, the average error decreased from $26{\pm}4.6$ to $21.8{\pm}1.7$ and $20{\pm}0$, respectively. Conclusion : In this study, vibrotactile stimulation therapy showed a continuous effect on improving unilateral neglect. Based on these findings, further research should be conducted in order to improve objectivity in future studies. Further research on various arbitration methods that maximize the effect of intervention will be needed.

• Journal of the Korea Concrete Institute
• /
• v.16 no.2 s.80
• /
• pp.221-228
• /
• 2004

In recent years building floors become larger and more spacious due to the development of new design methods and high strength and light weight materials. However, such long span floor systems may provide smaller amount of damping and have a longer period so that they may be more vulnerable to the floor vertical vibration. In Korea when floors are to be checked against the floor vertical vibration, the provisions developed in foreign countries have been used. However these guidelines have been developed based on human perception, which may vary from country to country. Also, Korea have particular floor systems, such as flat plate floor system of apartment building. This study attempts to evaluate the vibration performance of the floors in typical apartment buildings. Two different floors with the area of $28 m^2$ and $32 m^2$ were investigated. The criteria provided by ATC-1(1999), AISC-11(1997), AIJ(1991) and the local criteria developed in the previous study(Han, 2003) was used to check the acceptability of the floor vertical vibration.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.27 no.2
• /
• pp.109-114
• /
• 2021

The characteristics of vibrational stress (shock and vibration) during transport and the possibility of damage to the packaged pears by functional PLA tray were investigated. And this study was conducted to analyze how environmental conditions by simulated transport environment affect quality factors such as weight loss (%) and soluble solid content (SSC, %), and firmness (bioyield strength, kPa) of packaged pears by PLA tray and Expanded PET foam pad (Group 1), EPE cushion cup pad and net (Group 2) for exporting. Pears with or without vibration stress were stored for 30 days at low temperatures (5 ± 0.8℃, 80 ± 5% relative humidity). There was the statistically significant difference (p ≤ 0.05) between pears with and without vibration stress for weight loss, soluble solid content, and firmness (bioyield strength) after 30 days storage. Vibration stress accelerated pear quality deterioration during storage, resulting in increased weight loss, soluble solids content, and reduced hardness. The firmness (bioyield strength) and weight changes of pears with PLA trays were smaller than those of conventional packaging box systems. It was determined that the firmness of agricultural products was a quality factor closely related to the storage period and that PLA could be applied.