• 한국해양공학회지
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• 제34권2호
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• pp.110-119
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• 2020

Explosions and fires on offshore drilling units and process plants, which cause loss of life and environmental damage, have been studied extensively. However, research on drilling units increased only after the 2010 Deepwater Horizon accident in the Gulf of Mexico. A major reason for explosions and fires on a drilling unit is blowout, which is caused by a failure to control the high temperatures and pressures upstream of the offshore underwater well. The area susceptible to explosion and fire due to blowout is the drill floor, which supports the main drilling system. Structural instability and collapse of the drill floor can threaten the structural integrity of the entire unit. This study simulates the behavior of fire subsequent to blowout and assesses the thermal load. A heat transfer structure analysis of the drill floor was carried out using the assessed thermal load, and the risk was noted. In order to maintain the structural integrity of the drill floor, passive fire protection of certain areas was recommended.

• 국제초고층학회논문집
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• 제10권4호
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• pp.345-364
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• 2021

Developments in the understanding of fire behaviour for large open-plan spaces typical of tall buildings have been greatly outpaced by the rate at which these buildings are being constructed and their characteristics changed. Numerous high-profile fire-induced failures have highlighted the inadequacy of existing tools and standards for fire engineering when applied to highly-optimised modern tall buildings. With the continued increase in height and complexity of tall buildings, the risk to the occupants from fire-induced structural collapse increases, thus understanding the performance of complex structural systems under fire exposure is imperative. Therefore, an accurate representation of the design fire for open-plan compartments is required for the purposes of design. This will allow for knowledge-driven, quantifiable factors of safety to be used in the design of highly optimised modern tall buildings. In this paper, we review the state-of-the-art experimental research on large open-plan compartment fires from the past three decades. We have assimilated results collected from 37 large-scale compartment fire experiments of the open-plan type conducted from 1993 to 2019, covering a range of compartment and fuel characteristics. Spatial and temporal distributions of the heat fluxes imposed on compartment ceilings are estimated from the data. The complexity of the compartment fire dynamics is highlighted by the large differences in the data collected, which currently complicates the development of engineering tools based on physical models. Despite the large variability, this analysis shows that the orders of magnitude of the thermal exposure are defined by the ratio of flame spread and burnout front velocities (V_S / V_BO), which enables the grouping of open-plan compartment fires into three distinct modes of fire spread. Each mode is found to exhibit a characteristic order of magnitude and temporal distribution of thermal exposure. The results show that the magnitude of the thermal exposure for each mode are not consistent with existing performance-based design models, nevertheless, our analysis offers a new pathway for defining thermal exposure from realistic fire scenarios in large open-plan compartments.

• 한국산림과학회지
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• 제112권4호
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• pp.451-458
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• 2023

산불이 대형화됨에 따라 산불 예방 및 진화를 위해 임도시설의 중요성이 증가하고 있다. 산불 발생 시 임도가 제 역할을 수행하기 위해서는 적정한 노선 선정과 함께 구조적인 안정성을 확보해야 한다. 그동안의 연구는 산불 발생에 따른 임도의 효과와 노선 배치에 치중되어 있으며, 임도의 안전성 확보를 위한 연구는 수행되지 않은 실정이다. 따라서, 본 연구는 최근 3년간 초대형 산불 발생지 내의 임도 콘크리트 시설물을 대상으로 콘크리트 비파괴검사기법 중 하나인 반발경도법을 이용하여 산불 여부에 따라 그 강도를 비교하였다. 연구 결과, 산불 피해 콘크리트 시설물(15.4 MPa)은 미피해 콘크리트 시설물(18.0 MPa)에 비해 낮은 강도를 나타냈으며(p<0.001), 그 경향은 모든 대상 시설물에서 동일하게 나타났다. 따라서, 임도 시설의 강도 저하로 인한 임도의 2차 피해를 방지하기 위해 임도 시설물의 안전진단 기준이 마련되어야 할 것이다. 또한, 본 연구 결과에 대한 지속적인 모니터링과 실내 실험을 동반한 후속 연구가 진행되어 임도의 안정성을 제고해야 하며, 이를 통해 산불 예방과 진화를 위한 더 나은 전략을 마련할 수 있을 것이라 기대한다.

• 국제초고층학회논문집
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• 제7권4호
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• pp.375-387
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• 2018

This paper presents a review on progressive collapse mechanism of steel framed buildings exposed to fire. The influence of load ratios, strength of structural members (beam, column, slab, connection), fire scenarios, bracing systems, fire protections on the collapse mode and collapse time of structures is comprehensively reviewed. It is found that the key influencing factors include load ratio, fire scenario, bracing layout and fire protection. The application of strong beams, high load ratios, multi-compartment fires will lead to global downward collapse which is undesirable. The catenary action in beams and tensile membrane action in slabs contribute to the enhancement of structural collapse resistance, leading to a ductile collapse mechanism. It is recommended to increase the reinforcement ratio in the sagging and hogging region of slabs to not only enhance the tensile membrane action in the slab, but to prevent the failure of beam-to-column connections. It is also found that a frame may collapse in the cooling phase of compartment fires or under travelling fires. This is because that the steel members may experience maximum temperatures and maximum displacements under these two fire scenarios. An edge bay fire is more prone to induce the collapse of structures than a central bay fire. The progressive collapse of buildings can be effectively prevented by using bracing systems and fire protections. A combination of horizontal and vertical bracing systems as well as increasing the strength and stiffness of bracing members is recommended to enhance the collapse resistance. A protected frame dose not collapse immediately after the local failure but experiences a relatively long withstanding period of at least 60 mins. It is suggested to use three-dimensional models for accurate predictions of whether, when and how a structure collapses under various fire scenarios.

• Computers and Concrete
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• 제7권4호
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• pp.285-301
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• 2010

In this work we first review the statistical data on large fires in urban areas, presenting a detailed list of causes of fires, the type of damage to concrete and reinforced concrete structures. We also present the modern experimental approach for studying the fire-resistance of different structural components, along with the role of numerical modeling to provide more detailed information on quantifying the temperature and heat flux fields. In the last part of this work we provide the refined models for assessment of fire-induced damage in structures built of concrete and/or reinforced-concrete. We show that the refined models of this kind are needed to provide a more thorough explanation of damage and to complete the damage assessment and post-fire evaluations.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.771-776
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• 2007

Widespread propagation of failure can be triggered by localized damage to a structure because of fires, impact and explosion etc. In this paper, the progressive collapse analysis program is developed to automatically check the failed members and construct the modified structural model at each step. OpenSees, that is widely used in many research groups, was used for the developed progressive collapse analysis control program. The control program developed in this study automatically computes the damage indices of all the structural members and performance a progressive collapse analysis after the first failed member is selected. Using the developed program, we compared the progressive collapse behaviors of the example structures considering dynamic effects or not, and the difference of progressive collapse mechanism according to the modeling method of the failed members.

• Structural Engineering and Mechanics
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• 제32권6호
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• pp.771-786
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• 2009

In the past few decades, effects of natural hazards, such as earthquakes and wind, on existing structures have attracted the attention of researchers and designers. More recently, however, the phenomenon of progressive collapse is becoming more recognized in the field of structural engineering. In practice, the phenomenon can result from a number of abnormal loading events, such as bomb explosions, car bombs, accidental fires, accidental blast loadings, natural hazards, faulty design and construction practices, and premeditated terrorist acts. Progressive collapse can result not only in disproportionate structural failure, but also disproportionate loss of life and injuries. This paper provides an up-to-date comprehensive review of this phenomenon and its momentousness in structural engineering communities. The literature reveals that although the phenomenon of progressive collapse of buildings is receiving considerable attention in the professional engineering community, more research work is still needed in this field to develop a new methodology for efficient and inexpensive design to better protect buildings against progressive collapse.

• Steel and Composite Structures
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• 제36권4호
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• pp.383-398
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• 2020

This paper investigates the progressive collapse behavior of 3D steel-framed gravity buildings under fires with a cooling phase. The effect of fire protections and bracing systems on whether, how, and when a gravity building collapses is studied. It is found that whether a building collapses or not depends on the duration of the heating phase, and it may withstand a "short-hot" fire, but collapses under a mild fire or a "long-cool" fire. The collapse time can be conservatively determined by the time when the temperature of steel columns reaches a critical temperature of 550 ℃. It is also found that the application of a higher level of fire protection may prevent the collapse of a building, but may also lead to its collapse in the cooling phase due to the delayed temperature increment in the heated members. The tensile membrane action in a heated slab can be resisted by a tensile ring around its perimeter or by tensile yielding lines extended to the edge of the frame. It is recommended for practical design that hat bracing systems should be arranged on the whole top floor, and a combination of perimeter and internal vertical bracing systems be used to mitigate the fire-induced collapse of gravity buildings. It is also suggested that beam-to-column connections should be designed to resist high tensile forces (up to yielding force) during the cooling phase of a fire.

• 국제초고층학회논문집
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• 제2권1호
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• pp.11-21
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• 2013

The use of concrete filling offers a practical alternative for achieving the required stability of steel Hollow Structural Section (HSS) columns under fire conditions. However, current methods for evaluating fire resistance of Concrete Filled Hollow Structural Steel (CFHSS) columns are highly conservative as they are based on an elemental approach without due consideration to structural interactions that occur in framed structural systems. To overcome this limitation, a system level fire resistance analysis was carried out by treating CFHSS columns as part of an overall structural frame. In this analysis, an eight story steel-framed building was modeled under a range of standard and performance-based fire scenarios (including multi-story progressive burn-out fires) to evaluate the contribution of various structural members/assemblies to overall fire resistance. One of the primary factors considered was the use of concrete filling in HSS columns as an alternative to standard W-shape columns. Results from the analysis indicate that the use of CFHSS columns, in place of W-shape columns, in a performance-based environment can fully eliminate the need for applied fire protection to columns, while providing the required level of structural fire resistance.

• Steel and Composite Structures
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• 제7권2호
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• pp.105-118
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• 2007

On September $11^{th}$ 2001, the twin towers of the World Trade Center in New York City were struck by two hijacked airplanes. Despite severe local damage induced by the impact, the towers were able to sustain 102 and 56 minutes of the subsequent multi-storey fires before collapsing. The purpose of this study is to contribute to the understanding of the in-fire performance of composite trusses by examining the behaviour of the longer-span type used in the towers. It makes no attempt to be a forensic study of the actual events. Using the finite element package Vulcan, the structural mechanics of typical long-span composite floor trusses are explained, under a variety of scenarios, as the fire temperatures rise. Different boundary conditions, degrees of protection and loading are all covered, the results being presented mainly in the form of graphs of deflection and internal force of members against time.