• Smart Structures and Systems
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• v.6 no.8
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• pp.953-974
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• 2010

The performance of variable dampers for seismic protection of the benchmark highway bridge (phase I) under six real earthquake ground motions is presented. A simplified lumped mass finite-element model of the 91/5 highway bridge in Southern California is used for the investigation. A variable damper, developed from magnetorheological (MR) damper is used as a semi-active control device and its effectiveness with friction force schemes is investigated. A velocity-dependent damping model of variable damper is used. The effects of friction damping of the variable damper on the seismic response of the bridge are examined by taking different values of friction force, step-coefficient and transitional velocity of the damper. The seismic responses with variable dampers are compared with the corresponding uncontrolled case, and controlled by alternate sample control strategies. The results of investigation clearly indicate that the base shear, base moment and mid-span displacement are substantially reduced. In particular, the reduction in the bearing displacement is quite significant. The friction and the two-step friction force schemes of variable damper are found to be quite effective in reducing the peak response quantities of the bridge to a level similar to or better than that of the sample passive, semi-active and active controllers.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.10
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• pp.922-928
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• 2016

Bearing in mind that global climate change is a rising issue, the coastal community of Prek Thnaot, Cambodia has been put on severe effects about natural disasters caused from poor infrastructure and agriculture dependence. This paper proposes to provide and guide a strategic action for the sustainable development path of coastal community in a more continuous manner including a robust resilience to impacts of climate change, natural disasters, and other risks. In doing so, this paper will help environmentally sound management and coastal resources sustainability being sound for socially and economically inclusive development. Proposed fourteen strategic actions for the research should be accompanying with the participation of and cooperation from the local coastal community. Based on the proposed strategic actions, it is critical that the local authorities and other key stakeholders need to accomplish. Providing a good insight for the central government, the strategic action is expected to integrate and prepare a management strategy plan for the local coastal community level. Therefore, this information can be applied to other coastal areas to promote and ensure sustainable protection and management of coastal resources.

• Korean Journal of Metals and Materials
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• v.49 no.9
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• pp.671-677
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• 2011

Steel columns used in steel buildings are inclined to lose their strength when exposed to severe fire conditions, so fire resistance is required in most countries to protect against loss of life and building collapses. In Korea, the fire resistance of columns can be obtained by the fire test defined in KS F 2257-1, 7. The fire resistance of a steel column should be evaluated in terms of the column's conditions, such as various section types (H-section, hollow-section), the column's length and boundary conditions, and whether it is fixed or hinged. However, fire testing of steel columns is usually conducted on one standard-sized H-section over 3,000 mm, and the result is used as the column's fire resistance. This is not a reasonable way to ensure that a building can withstand fire conditions. In this study, to evaluate the possibility of calculating the fire resistance of steel columns with material properties of high tensile strength of SS 400, both load-bearing fire tests and calculation of steel temperatures were carried out. The results of temperature calculation were very similar to those obtained by fire test.

• Earthquakes and Structures
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• v.24 no.6
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• pp.415-428
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• 2023

Low-cost techniques with seismic isolation performance and excellent resilience need to be explored in the case of rural low-rise buildings because of the limited buying power of rural residents. As an inexpensive and eco-friendly isolation bearing, scrap tire pads (STPs) have the issue of poor resilience. Thus, a seismic isolation system under a column (SISC) integrated with STP needs to be designed for the seismic protection of low-rise rural buildings. The SISC, which is based on a simple exterior design, maintains excellent seismic performance, while the mechanical behavior of the internal STP provides elastic resilience. The horizontal behaviors of the SISC are studied through load tests, and its mechanical properties and the intrinsic mechanism of the reset ability are discussed. Results indicate that the average residual displacement ratio was 24.59%, and the reset capability was enhanced. Comparative experimental and finite element analysis results also show that the load-displacement relationship of the SISC was essentially consistent. The dynamic characteristics of isolated and fixed-base buildings were compared by numerical assessment of the response control effects, and the SISC was found to have great seismic isolation performance. SISC can be used as a low-cost base isolation device for rural buildings in developing countries.

• Journal of the Korean GEO-environmental Society
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• v.11 no.12
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• pp.47-56
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• 2010

The construction of new roads and the consistent extension of already-existing roads or the line-shape revision of those roads are increased with the governmental investment to SOC facilities currently. Accordingly, the road cut slopes are in the trend of rapidly increasing. As the road slope has increased, a lot of human and property damages has entailed consequently and in the local case, numerous studies have carried out aiming at minimizing this damages caused by the rockfall and landslide. In general, standard falling rock prevention facility has employed for most of the local road slope based on "Guide for Installation and Management of Road Safety Facilities" published by MLTM(the Ministry of Land, Transport, and Maritime Affairs) but profound doubt has raised as to whether this rockfall prevention facility would function properly enough to prevent rockfall efficiently without any damages in case of actual occurrence of rockfall. In addition, it is a reality that in most cases, such work is relied on overseas technology as a whole as the local technical level is low and in case of rockfall prevention net, it is judged that a study on rockfall prevention net that is able to endure more powerful rockfall energy is required as the problem including net bursting is taken place as a result of enough bearing force being failed to be demonstrated due to its partial weak point(not uniformly made). Under this background, in this study, three kinds of model depending on mesh size of expanded metal that is considered to have an adoptability as rockfall prevention net, as target are selected and characteristics depending on mesh size of expanded metal is intended to be researched through a pull-out test performance by using pull-out test equipment rockfall prevention net.

• Journal of Korean Medicine Rehabilitation
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• v.25 no.2
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• pp.15-35
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• 2015

Objectives This study was performed to investigate the effects of Bujasasim-tang ethanol extract (BST) on oxidative stress, inflammation and osteoarthritic rat model. Methods To ensure safety of BST, heavy metal levels were measured and cytotoxicity test was done. In vitro, To evaluate antioxidative effects of BST, total phenolic contents, 1,1-diphenyl-2-picryl-hydrazyl (DPPH), 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) scavenging activity, reactive oxygen species (ROS) levels were measured. Also, to evaluate anti-inflammatory effects of BST treated group, total nitric oxide (NO) and pro-inflammatory cytokines (IL-$1{\beta}$, IL-6, TNF-${\alpha}$) levels were measured in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. In vivo, We injected MIA $50{\mu}l$ (60 mg/ml) into knee joints of rats to induce osteoarthritis. Rats were divided into total 3 groups (normal, control, BST treated group, each n=7). Normal group was not treated at all without inducing osteoarthritis and taken normal diet. Control group was induced osteoarthritis by MIA and taken with 2 ml of distilled water once a day for 4 weeks. BST treated group was induced osteoarthritis by MIA and taken BST 2 ml (200 mg/kg/mouse) once a day for 4 weeks. We evaluated dynamic weight bearing with the Incapacitance Test Meter. At the end of experiment, the rats were sacrificed to observe the functions of liver and kidney, changes of WBC, neutrophil, lymphocyte, monocyte levels in blood, to evaluate the levels of pro-inflammatory cytokines, tissue inhibitor of metallopreteinases-1 (TIMP-1), matrix metalloproteinase-9 (MMP-9), prostaglandin $E_2$ ($PGE_2$), leukotriene $B_4$ ($LTB_4$) within serum. We observed change of articular structures by Hematoxylin & Eosin (H&E), safranin-O staining method and measured amount of cartilage by micro CT-arthrography. Statistical analysis was done by unpaired student's t-test with significance level at p<0.05 in SPSS 11.0 for windows. Results 1. Safety of the BST was identified. 2. AST, ALT, BUN, creatinine levels of BST treated group were within normal limit. In vitro, 1. DPPH and ABTS free radical scavenging activities of BST showed dose-dependent increase. 2. ROS production were significantly decreased. 3. Total nitric oxide (NO) and IL-$1{\beta}$ production were decreased. 4. IL-6 and TNF-${\alpha}$ production were significantly decreased. In vivo, 1. Weight bearing ability was significantly increased. 2. WBC, neutrophil, lymphocyte, monocyte levels in blood were decreased. 3. IL-$1{\beta}$ and TNF-${\alpha}$ levels in serum were significantly decreased. and the IL-6 level was decreased. 4. TIMP-1, MMP-9, $LTB_4$, $PGE_2$ levels in serum were significantly decreased. 5. Cartilage volume of BST treated group was significantly increased. Also changes of cartilage, synovial membrane, fibrous tissue were suppressed. Conclusions The results obtained in this study Bujasasim-tang have effects of antioxidative, anti-inflammatory, relieve pain and protection of cartilage. Therefore we expect that Bujasasim-tang is effective treatment for osteoarthritis.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.4
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• pp.51-63
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• 2002

This paper presents a hybrid control strategy for seismic protection of a benchmark cable-stayed bridge, which is provided as a testbed structure for the development of strategies for the control of cable-stayed bridges. This benchmark problem considers the cable-stayed bridge that is scheduled for completion in Cape Girardeau, Missouri, USA in 2003. Seismic considerations were strongly considered in the design of this bridge due to the location of the bridge in the New Madrid seismic zone and its critical role as a principal crossing of the Mississippi river. Based on detailed drawings of this cable-stayed bridge, a three-dimensional linearlized evaluation model has been developed to represent the complex behavior of the bridge. A set of eighteen evaluation criteria has been developed to evaluate the capabilities of each control strategy. In this study, a hybrid control system is composed of a passive control system to reduce the earthquake-induced forces in the structure and an active control system to further reduce the bridge responses, especially deck displacements. Conventional base isolation devices such as lead rubber bearings are used for the passive control design and Bouc-Wen model is used to simulate the nonlinear behavior of these devices For the active control design, ideal hydraulic actuators are used and on $H_2$/LQG control algorithm is adopted. Numerical simulation results show that the performance of the proposed hybrid control strategy is quite effective compared to that of the passive control strategy and slightly better than that of the active control strategy. The hybrid control method is also more reliable than the fully active control method due to the passive control part. Therefore, the proposed hybrid control strategy can effectively be used to seismically excited cable-stayed bridges.

• Journal of the Korean Geotechnical Society
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• v.35 no.11
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• pp.25-36
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• 2019

The safety barrier is installed on road embankment to prevent vehicles from falling into road side slope. Among the safety barrier, flexible guardrails are usually installed. The flexible guardrail generally consists of a protection cross-beam and supporting in-line piles. These guardrail piles are installed nearby slope edge of road embankment because the side area of the road is much narrow. The protection cross-beam absorbs impact energy caused by vehicle collision. The pile-soil interaction also absorbs the rest of the impact energy and then, finally, the flexible guardrail system resists the impact load. This paper aims to investigate the pile-soil interaction subjected to impact load using centrifuge model tests. In this study, a single pile was installed in compacted residual soil and loaded under lateral impact load. An impact loading system was designed and developed available on centrifuge tests. Using this loading system, a parametric study was performed and the parameters include types of loading and ground. Finally, the ultimate bearing capacity of supporting pile under impact load was analyzed using load-displacement curve and soil reaction pressure distributions at ultimate were evaluated and compared with previous studies.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.557-563
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• 2007

Rain-wind induced cable vibration can cause serious problems in cable-stayed bridge. External dampers attached to the cables have become widely accepted as an effective means for stay-cable vibration suppression. For very long stay-cables, however, such damper systems are rendered ineffective, as the dampers need be attached near the end of cables for aesthetic reasons. A recent study by the authors proposed that a movable anchorage system is replaced direct fixed support of the cable with a support through a bearing and damper. This paper extends the previous work by adding active control system to mitigate the cable vibration. The response of a cable with the proposed active control system is obtained and then compared to those of the cable with and without an external passive damper. The results show that the active control system can provide superior protection than the passive control system for a cable vibration.

• Journal of Society of Preventive Korean Medicine
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• v.6 no.1
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• pp.36-50
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• 2002

Health industry, a knowledge based high value-added industry, is being considered as a strategic area for the 21C and many advanced countries are making every endeavors for the promotion of health industry along with information technology, new materials, and mechatronics. Korean health industry, however, has been excluded from the governmental supports as well as bound by strict regulation so far, and there is a significant gap in technology compared with advanced countries. In 21C, technology is the main factor of national competitiveness and that is why the role of R&D institutes are so important in the high level of competition to cope with the technology protection policies of advanced countries. In this article, with Directory of Korean R&D Institutes published by Korea Industry Technology Association, I reviewed the trends of R&D institute of health industry. Main findings of the research can be summarized as follows. The portion of health industry R&D institute is 3.6% of total R&D institute but the amount of R&D investment is over than 5% This means health industry are knowledge based and R&D intensified industry, meanwhile the variations of same industry R&D institutes of health industry is huge in R&D investments and other activities. Regional distributions of health industry institutes show some kind of different patterns in each industry areas. Medical devices and Medical informatics's preference of metropolitan region are distinguished with other industry areas. Many of the institutes are located in same site of it's company rather than operating separate building for R&D specific uses. It is better for transforming ideas to products and close cooperation of research body with product lines, but it is a handicap for networking and communicating with other research institutions too. It takes 18.4yrs for bearing R&D institute on the average. For a long times 'copy products' or 'me too products' policies were easy way to maintain business entities. But recently, it is recognized that research activities are essential component of sustaining it's own business firms. This means technology itself is leading power of corporation itself in the high level of competition.