• Earthquakes and Structures
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• v.12 no.1
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• pp.135-144
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• 2017

Near-fault ground motions are characterized by high values of the ratio between the peak of vertical and horizontal ground accelerations, which can significantly affect the nonlinear response of a base-isolated structure. To check the effectiveness of different base-isolation systems for retrofitting a r.c. framed structure located in a near-fault area, a numerical investigation is carried out analyzing the nonlinear dynamic response of the fixed-base and isolated structures. For this purpose, a six-storey r.c. framed building is supposed to be retrofitted by insertion of an isolation system at the base for attaining performance levels imposed by current Italian code in a high-risk seismic zone. In particular, elastomeric (e.g., high-damping-laminated-rubber bearings, HDLRBs) and friction (e.g., steel-PTFE sliding bearings, SBs, or friction pendulum bearings, FPBs) isolators are considered, with reference to three cases of base isolation: HDLRBs acting alone (i.e., EBI structures); in-parallel combination of HDLRBs and SBs (i.e., EFBI structures); FPBs acting alone (i.e., FPBI structures). Different values of the stiffness ratio, defined as the ratio between the vertical and horizontal stiffnesses of the HDLRBs, sliding ratio, defined as the global sliding force divided by the maximum sliding force of the SBs, and in-plan distribution of friction coefficient for the FPs are investigated. The EBI, EFBI and FPBI base-isolation systems are designed assuming the same values of the fundamental vibration period and equivalent viscous damping ratio. The nonlinear dynamic analysis is carried out with reference to near-fault earthquakes, selected and scaled on the design hypotheses adopted for the test structures.

• Earthquakes and Structures
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• v.12 no.1
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• pp.67-77
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• 2017

In this paper, it is aimed to present a comparative study about the structural behavior of tall buildings consisting of different type of materials such as concrete, steel or timber using finite element analyses and experimental measurements on shaking table. For this purpose, two 1/60 scaled 28 and 30-stories wooden building models with $40{\times}40cm$ and $35{\times}35cm$ ground/floor area and 1.45 m-1.55 m total height are built in laboratory condition. Considering the frequency range, mode shapes, maximum displacements and relative story drifts for structural models as well as acceleration, displacement and weight limits for shaking table, to obtain the typical building response as soon as possible, balsa is selected as a material property, and additional masses are bonded to some floors. Finite element models of the building models are constituted in SAP2000 program. According to the main purposes of earthquake resistant design, three different earthquake records are used to simulate the weak, medium and strong ground motions. The displacement and acceleration time-histories are obtained for all earthquake records at the top of building models. To validate the numerical results, shaking table tests are performed. The selected earthquake records are applied to first mode (lateral) direction, and the responses are recorded by sensitive accelerometers. Comparisons between the numerical and experimental results show that shaking table tests are enough to identify the structural response of wooden buildings. Considering 20%, 10% and 5% damping rations, differences are obtained within the range 4.03-26.16%, 3.91-65.51% and 6.31-66.49% for acceleration, velocity and displacements in Model-1, respectively. Also, these differences are obtained as 0.49-31.15%, 6.03-6.66% and 16.97-66.41% for Model-2, respectively. It is thought that these differences are caused by anisotropic structural characteristic of the material due to changes in directions parallel and perpendicular to fibers, and should be minimized using the model updating procedure.

• Journal of the Korean Institute of Landscape Architecture
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• v.33 no.5 s.112
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• pp.15-30
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• 2005

A deserted town once vibrant with active commercial activities around a railroad station now tries to find a way to escape from depression and revive its life with a renewed civic pride. An open space adjacent to the Main Street, the commercial district of Buzzards Bay, Massachusetts, is waiting to be transformed and reconfigured to be a new ecological park to boost the economy of the community. Bridge Park is 26-acre land abutting the Cape Cod Canal with a railroad bridge as a backdrop. The existing condition of the site with a small salt marsh, woodland, lawn, and the vestige of old railroad easement along with the proximity to the commercial district poses an interesting question of how to make a medium scaled ecological park within an urban context. This paper examines the winning design proposals for the Bridge Park submitted to the International Design Competition held in April, 2005. Six winning proposals were introduced and discussed in terms of categories related to the trend of contemporary landscape design such as; 1) ecological ordinariness and geometric figures, 2) topography and spatial imagination, 3) minimal programs and open put 4) time and process oriented design, 5) park and economic effects and 6) diagrammatic plan and photo montage. Bridge Park Design Competition confirms the complex characteristics representing the contemporary landscape design overcoming the dichotomy between nature and culture and the 'pastoral ecological design' and 'landscape as an art'. The Park becomes the activating agent for the community rejecting the conventional and passive role as a romantic picturesque landscape. Bridge Park International Design Competition is a meaningful event to test the idea of new ecological urban park, and to fine-tune the trend of the contemporary urban park design.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.185-191
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• 1999

Mathematical morphology based on set theory has been applied to various areas in image processing. Pitas proposed a object recognition algorithm using Morphological Shape Decomposition(MSD), and a new representation scheme called Morphological Shape Representation(MSR). The Pitas's algorithm is a simple and adequate approach to recognize objects that are rotated 45 degree-units with respect to the model object. However, this recognition scheme fails in case of random rotation. This disadvantage may be compensated by defining small angle increments. However, this solution may greatly increase computational complexity because the smaller the step makes more number of rotations to be necessary. In this paper, we propose a new method for object recognition based on MSD. The first step of our method decomposes a binary shape into a union of simple binary shapes, and then a new tree structure is constructed which ran represent the relations of binary shapes in an object. finally, we obtain the feature informations invariant to the rotation, translation, and scaling from the tree and calculate matching scores using efficient matching measure. Because our method does not need to rotate the object to be tested, it could be more efficient than Pitas's one. MSR has an intricate structure so that it might be difficult to calculate matching scores even for a little complex object. But our tree has simpler structure than MSR, and easier to calculated the matchng score. We experimented 20 test images scaled, rotated, and translated versions of five kinds of automobile images. The simulation result using octagonal structure elements shows 95% correct recognition rate. The experimental results using approximated circular structure elements are examined. Also, the effect of noise on MSR scheme is considered.

• Tunnel and Underground Space
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• v.9 no.2
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• pp.114-130
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• 1999

It is very important to study on the structural behaviors of structurally damaged tunnel linings. A series of centrifuge model tests were performed in order to investigate different behaviors of tunnel linings. A 1/100-scaled aluminum horseshoe tunnel linings with a radius 5 cm, height 8 cm were buried in a depth with dry Joomunjin standard sand, the relative density of which was 86%. Such sectional forces as bending moments and thrusts along the tunnel circumference were measured by twelve strain gages. Earth pressures in soil mass and on the outside of lining model were estimated by pressure transducers, ground surface settlements at a center and edges by using LVDTs.

• Journal of the Korean GEO-environmental Society
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• v.7 no.5
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• pp.41-48
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• 2006

Crib wall is one of the segmental grid retaining walls using headers and stretchers to establish the framework of the wall. In this method, grids formed by the intersection of headers and stretchers are generally filled with the gravel to maintain the weight of the wall. Therefore, the construction can be carried out with higher speed and much economically when compared with the concrete retaining wall. Furthermore, it has high drain capacity, and environmentally friendly aspects also have been pointed out because the possibility of the planting at the front of the wall. However, in the crib wall method, the relative movement between the individual headers and stretchers was generally recognized, and stress redistribution in the gravel filling was also observed when subjected to the external loading and self-weight of filling. Therefore, it has been thought that the distribution of the earth pressure in the crib wall system differ from that of the concrete retaining wall. In this study, the surcharge tests using the scaled model crib wall was carried out to observe the distribution of the earth pressure in the segmental grid retaining wall. The earth pressure was measured in the six specified height of wall, and the distribution of the pressure was analyzed. Furthermore, the earth pressure by computation or by the test using the concrete retaining wall was also considered to make comparison.

• Journal of Broadcast Engineering
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• v.13 no.6
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• pp.796-803
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• 2008

In this paper, we present a depth scaling method for multiview images that could provide an 3D depth that a user prefers. Unlike previous works that change a camera configuration, the proposed method utilizes depth data in order to carry out the scaling of a depth range requested by users. From multivew images and their corresponding depth data, depth data is transformed into a disparity and the disparity is adjusted in order to control the perceived depth. In particular, our method can deal with multiview images captured by multiple cameras, and can be expanded from stereoscopic to multiview images. Based upon a DSCQS subjective evaluation test, our experimental results tested on an automultiscopic 3D display show that the perceived depth is appropriately scaled according to user's preferred depth.

• Economic and Environmental Geology
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• v.28 no.4
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• pp.405-414
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• 1995

An algorithm for monitoring geomorphological change using remote sensing data is investigated and tested using two LANDSAT TM data sets acquired over the Kyunggi Bay on April 15 1986 and September 22 1992, respectively. The algorithm exploits change vector analysis and tasseled cap transform. Although change vector analysis is effective for change detection, efficiency is decreased as the number of variables are increased. In this algorithm, we overcome the problem by utilizing the tasseled cap transform which can reduce six bands of LANDSAT TM data into only two components called Brightness and Greenness. The test results demonstrate that the algorithm is very effective in monitoring small-scaled changes over coastal area as well as significant changes in geomorphology. The resulting change vector image, however, is more sensitive to the changes occurred by human activities than by pure geological processes mainly because of relatively short time interval between two LANDSAT TM data sets.

• Explosives and Blasting
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• v.23 no.1
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• pp.65-77
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• 2005

Reflecting the fact that there are increasing number of old high-story apartment structures in urban area, it is expected that the demand of blasting demolition will increase in the near future. It is of great important to make up for the insufficient empirical knowledge in blasting demolition through priori method such as computer simulation. Computer simulation of the blasting demolition involves complicated process. In the past domestic researches, two-dimensional bonded particle model was used to examine the overall demolition behavior of a five-story simple structure. It was observed that the two-dimensional simulation did not properly simulate the collapsing behavior of a structure mainly due to the reduced degree of freedom. In this study, three-dimensional simulation was tried. It consumed a great amount of calculation time, which limited the extent of the study. A few parameters, such as delay times, amount of charge at each hole, ball properties, were modified in order to check oui; their effect on the collapsing behavior. The differences were observed as expected but the collapsing behavior did not exactly coincide with the test blasting with a scaled model.

• Journal of Korean Society on Water Environment
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• v.21 no.1
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• pp.59-65
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• 2005

A phosphate recovery system from artificial wastewater was developed using a completely mixed phosphorus crystallization reactor, in which powdered converter slag was used as a seeding crystal. In preliminary test, the optimal pH range for meta-stable hydroxyapatite crystallization for high phosphorus concentration was observed to be 6.0 to 7.0, which was different from the conventionally known pH range (8.0~9.5) for effective crystallization in relatively low phosphorus concentration less than 5 mg/L. The average phosphorus removal efficiency in a lab-scaled completely mixed crystallization system for artificial wastewater with about 100 mg/L of average $PO_4-P$ concentration was shown to be 60.9% for 40 days of lapsed time. XRD analysis exhibited that crystalline of hydroxyapatite formed on the surface of seed crystal, which was also observed in SEM analysis. In EDS mapping analysis, composition mole ratio (=Ca/P) of the crystalline was found to be 1.78, indicating the crystalline on the surface of seed crystal is likely to be hydroxyapatite. Particle size distribution analysis showed that average size of seed crystal increased from $28{\mu}m$ up to $50{\mu}m$, suggesting that phosphorus recycling from wastewater with high phosphorus concentration can be successfully obtained by using the phosphorus crystallization recovery system.