• 한국조경학회지
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• 제26권2호
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• pp.166-180
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• 1998

In a city where the greenery always lacks landscaping roofs of existing buildings offers a way to solve the problem. But the most serious problem that poses is the matter of load limit. At present most existing buildings have the loading capacity of 200 kg/$m^2$ or less on their roofs. If the natural soil is used the loading capacity is easily surpassed because it simply is too heavy. To alleviate this problem it is realized to introduce the light weight artificial soil. The specific gravity of light soil is 0.65 whereas the natural soil is 1.8 when wet. It is three times lighter than the natural soil, thus eases the burden to the roof. The next problem to be confronted is the plant species to plant. It is possible to plant trees but they soon outgrow the loading capacity by weighing 8 times heavier in 10 years. Therefore shrubs and perennials are suggested to be planted because they don't weigh much even when they reach the mature height. The last problem is the stress put on roofs by the weight of the users. By some unexpected event the crowd gathered on a weak roof can cause the structural damage or even the collapse of the roof. The avoid the possibility of collapse a plaza or big pocket should not be designed in a roof garden because they hold crowd. By following the suggested means the old roofs of existing buildings can turn into the urban oases in the sky.

• Computers and Concrete
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• 제31권5호
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• pp.371-384
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• 2023

Precast roofing systems employing prestressed elements often serve as smart structural solutions for the construction of industrial buildings. The precast concrete elements usually employed are highly engineered, and often consist in thin-walled members, characterised by a complex behaviour in fire. The present study was carried out after a fire event damaged a precast industrial building made with prestressed beam and roof elements, and non-prestressed curved barrel vault elements interposed in between the spaced roof elements. As a consequence of the exposure to the fire, the main elements were found standing, although some locally damaged and distorted, and the local collapse of few curved barrel vault elements was observed in one edge row only. In order to understand and interpret the observed structural performance of the roof system under fire, a full fire safety engineering process was carried out according to the following steps: (a) realistic temperature-time curves acting on the structural elements were simulated through computational fluid dynamics, (b) temperature distribution within the concrete elements was obtained with non-linear thermal analysis in variable regime, (c) strength and deformation of the concrete elements were checked with non-linear thermal-mechanical analysis. The analysis of the results allowed to identify the causes of the local collapses occurred, attributable to the distortion caused by temperature to the elements causing loss of support in early fire stage rather than to the material strength reduction due to the progressive exposure of the elements to fire. Finally, practical hints are provided to avoid such a phenomenon to occur when designing similar structures.

• Steel and Composite Structures
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• 제23권4호
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• pp.435-444
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• 2017

In the past, the progressive collapse resulting from local failures during accidents has caused many tragedies and loss of life. Although long-span spatial grid structures are characterised by a high degree of static indeterminacy, the sudden failure of key members may lead to a catastrophic progressive collapse. For this reason, it is especially necessary to research the progressive collapse resistance capacity of long-span spatial grid structures. This paper presents an evaluation method of important members and a novel dynamic analysis method for simulating the progressive collapse of long-span spatial grid structures. Engineering cases were analysed to validate these proposed method. These proposed methods were eventually implemented in the progressive collapse analysis of the main stadium for the Universiade Sports Center. The roof of the structure was concluded to have good resistance against progressive collapse. The novel methods provide results close to practice and are especially suitable for the progressive collapse analysis of long-span spatial grid structures.

• Steel and Composite Structures
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• 제26권5호
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• pp.549-556
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• 2018

Progressive building collapse occurs when failure of a structural component leads to the failure and collapse of surrounding members, possibly promoting additional failure. Global system collapse will occur if the damaged system is unable to reach a new static equilibrium configuration. The most common type of primary failure which led to the progressive collapse phenomenon, is the sudden removal of a column by various factors. In this study, a method is proposed to prevent progressive collapse phenomena in structures subjected to removal of a single column. A vierendeel peripheral frame at roof level is used to redistribute the removed column's load on other columns of the structure. For analysis, quasi-static approach is used which considers various load combinations. This method, while economically affordable is easily applicable (also for new structures as well as for existing structures and without causing damage to their architectural requirements). Special emphasis is focused on the evolution of vertical displacements of column removal point. Even though additional stresses and displacements are experienced by removal of a structural load bearing column, the proposed method considerably reduces the displacement at the mentioned point and prevents the collapse of the structural frame.

• 터널과지하공간
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• 제21권5호
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• pp.333-340
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• 2011

RMR은 국내터널의 지보재 설계를 위해 가장 빈번하게 사용되는 암반분류 방법이다. 그러나 설계당시의 검토된 지반조사를 통한 RMR값은 지반을 정확하게 대변할 수 없다. 터널 시공시 발생하는 붕괴 및 낙반사고를 사전에 예방하고 효율적인 지보 설계를 위해 붕괴위험도에 따라 기존 RMR 점수에 가중치를 적용한 Weighted-RMR(W-RMR)을 제안하고 터널에 적용하였다. 비재터널 현장에 W-RMR을 적용한 결과 막장 붕괴의 위험도에 따라 지보 설계를 탄력적으로 변경할 수 있었다.

• Structural Engineering and Mechanics
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• 제46권4호
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• pp.533-547
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• 2013

"Reciprocal Frame" refers to a self-supporting grid structure used both for floor and roof. Using Finite Element Methods for non-linear solid mechanics and frictional-contact, this paper intends to analytically and numerically investigate the collapse behaviour of a reciprocal frame structure made of fibre-reinforced concrete. Considering a simple 3-beam structure, it has been investigated using a solid finite element model. Once defined the collapse behaviour of the simple structure, the analysis has been generalized using a concentrated plasticity finite element method. Results provided will be useful for studying generic reciprocal frame structures with several beams.

• 대한지리학회지
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• 제43권4호
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• pp.466-476
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• 2008

한라산 북사면에 소재하는 구린굴의 천장이 함몰되고, 동굴 지상을 흐르던 병문천이 동굴 안으로 유입되면서 442m 길이의 구린굴 가운데 73m 구간이 하천 유로로 바뀌었다. 구린굴 유로의 폭과 높이는 각각 447cm 및 501cm이며, 벽면은 용암선반이 발달한 전형적인 용암동굴의 모습을 보이나 바닥에는 기반암 하도 특유의 마식지형이 나타난다. 거북등 모양의 절리가 발달한 동굴 천장의 암반 두께는 $30{\sim}60cm$에 불과하며, 이런 장소에서는 천장이 함몰하기 쉬워 유로 구간에는 전부 4개 지점에 윈도우가 발달한다. 구린굴 유로가 출현하기 이전의 지상 유로는 병문천의 지류로서 제4함몰 윈도우 지점을 지나 표고 660m 지점에서 구린굴 동쪽 유역으로부터 흘러나오는 본류에 합류하였다. 그러나 구린굴 지상 유로의 하상에 윈도우가 형성되면서 지상 유로는 구린굴 유로로 대체되고, 새로운 유로는 표고 660m 지점에서 본류에 합류하게 되었다. 이후 구린굴 상류 쪽으로 병문천 유역이 확대되면서 구린굴을 통과하는 유로가 본류로 바뀌었다. 그러나 홍수류가 발생하면 구린굴 지상 유로에도 유수가 발생하므로 병문천은 제4함몰 윈도우 지점에서 일시적으로 분기 하천의 형태를 이룬다. 제주도 용암동굴의 천장에서는 낙반 현상이 지속적으로 일어나고 있으므로 제주도의 수계 발달에 미치는 용암동굴의 영향은 현재 진행형이라고 할 수 있다.

• Geomechanics and Engineering
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• 제16권6호
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• pp.569-575
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• 2018

The stability of shallow cavities with an arbitrary profile is a difficult issue in geotechnical engineering. This paper investigates this problem on the basis of the upper bound theorem of limit analysis and the Hoek-Brown failure criterion. The influence of pore pressure is taken into consideration by regarding it as an external force acting on rock skeleton. An objective function is constructed by equating the internal energy dissipation to the external force work. Then the Lagrange variation approach is used to solve this function. The validity of the proposed method is demonstrated by comparing the analytical solutions with the published research. The relations between shallow and deep cavity are revealed as well. The detaching curve of cavity roof with elliptical profile is obtained. In order to facilitate the application of engineering practice, the numerical results are tabulated, which play an important role in tunnel design and stability analysis of roof. The influential factors on potential collapse are taken into consideration. From the results, the impact of various factors on the extent of detaching is seen intuitively.

• Structural Engineering and Mechanics
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• 제62권5호
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• pp.567-576
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• 2017

Structural failures are undesirable events that devastate the construction industry resulting in loss of life, injury, huge property loss, and also affect the economy of the region. Roof truss failures occur mainly due to excessive loading, improper fabrication, deterioration, inadequate repair, etc. Although very rare, a roof truss may even fail due to inappropriate location of supports. One such case was reported from the recent failure of a steel roof truss used in an indoor stadium at Kargil in India. Kargil region, being mountainous in nature, receives heavy snowfall and hence the steel roof trusses are designed for heavy snow loads. Due to inappropriate support location, the indoor stadium's steel roof truss had failed under heavy snow load for which it was designed and became an interesting structural engineering problem. The failure observed was primarily in terms of yielding of the bottom chord under the supports, leading to partial collapse of the roof truss. This paper summarizes the results of laboratory tests and analytical studies that focused on the validation of the proposed remedial measure for rehabilitating this distressed steel roof truss. The study presents the evaluation of (i) significant reduction in strength and stiffness of the distressed truss resulting in its failure, (ii) desired recovery in both strength and stiffness of the rectified truss contributed by the proposed remedial measure. Three types of models i.e., ideal truss model, as build truss model and rectified truss model were fabricated and tested under monotonic loading. The structural configuration and support condition varied in all the three models to represent the ideal truss, distressed truss and the rectified truss. To verify the accuracy of the experimental results, an analytical study was carried out and the results of this analytical study are compared with the experimental ones.

• 한국공간구조학회:학술대회논문집
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• 한국공간구조학회 2005년도 춘계학술발표회 및 정기총회 2권1호(통권2호)
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• pp.161-166
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• 2005

In spatial structures with large spaces, one important issue in structures with large spaces is how to carry the weight of the roof. A tensegrity cable dome structure is a kind of soft structural system using the tension cable and compression column as a main element. The tensegrity cable dome is built into a variety of shape around the world but then a collapse accident is increasing. Owing to a collapse accident we must grip of the collapse mechanism to prevent an accident and construct the structure with safety and economy. In this study, I investigated the unstable characteristics of the Geiger-type and Flower-type tcnsegrity cable dome structures, which is the lightweight hybrid structures using compression and tension elements continuously, according to the difference of loading conditions.