• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1331-1344
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• 2021

This study is to evaluate the seismic capacity of the fire-damaged cabinet facility in a nuclear power plant (NPP). A prototype of an electrical cabinet is modeled using OpenSees for the numerical simulation. To capture the nonlinear behavior of the cabinet, the constitutive law of the material model under the fire environment is considered. The experimental record from the impact hammer test is extracted trough the frequency-domain decomposition (FDD) method, which is used to verify the effectiveness of the numerical model through modal assurance criteria (MAC). Assuming different temperatures, the nonlinear time history analysis is conducted using a set of fifty earthquakes and the seismic outputs are investigated by the fragility analysis. To get a threshold of intensity measure, the Monte Carlo Simulation (MCS) is adopted for uncertainty reduction purposes. Finally, a capacity estimation model has been proposed through the investigation, which will be helpful for the engineer or NPP operator to evaluate the fire-damaged cabinet strength under seismic excitation. This capacity model is presented in terms of the High Confidence of Low Probability of Failure (HCLPF) point. The results are validated by the proper judgment and can be used to analyze the influences of fire on the electrical cabinet.

• 한국공간구조학회논문집
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• 제23권2호
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• pp.61-68
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• 2023

A two-hour fire-resistance PC hollow slab for residential use was developed to secure structural and fire-resistance performance and to be applied to the general building and apartment housing markets. Compared to the existing hollow slab, in order to secure the same or better structural performance and economic feasibility by reducing the quantity, it was attempted to secure the fire resistance performance by reducing the concrete filling rate in the cross section and adjusting the thickness of the upper and lower flanges by optimizing the hollow shape in the cross section of the slab. For structural performance evaluation, experiments were performed on PC hollow slabs by varying the member thickness and the presence or absence of overlaid concrete, and all of the experimental results showed that the design strength was sufficiently exhibited and that stability during construction was possible. The developed synthetic PC hollow slab has secured fire resistance and residential performance so that it can be applied to all buildings, and it is intended to be immediately applied to the field.

• 한국화재소방학회논문지
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• 제22권4호
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• pp.65-69
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• 2008

인화점의 정보를 확보하는 것은 화재 및 폭발의 예방을 위해 대단히 중요하다. 본 연구에서는 n-propanol+formic acid 계의 하부 인화점을 Penskey-Martens 밀폐식 장치를 이용하여 측정하였다. 이성분계 혼합물은 최소 인화점 현상(MFPB)을 보였다. 실험값은 Raoult의 법칙과 최적화 기법에 의해 추산된 값과 비교하였다. 그 결과, 최접화 기법에 의한 추산값이 Raoult의 법칙에 의한 추산값 보다 실험값에 더욱 근접하였다.

• 한국안전학회지
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• 제27권2호
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• pp.65-71
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• 2012

Changes in the styles of communities are leading of increases in the number of high-rise apartments and commercial-apartment structures. Tall high-rise structures, while presenting unique economies of scale and cost effectiveness, tend to be highly engineered and complex structures. In the event of a fire, this complexity in design also results in a complexity in the behavior of fire propagation and control. High-rise structures are among the most potentially dangerous due to the high population density in the building, and the inherent limitations on evacuation and on fire control services. One of the most critical points of fire propagation is the movement of fire through the outer wall structures. Controlling such propagation is essential in controlling the spread of the fire throughout the building itself, as well as controlling the potential for its spread to adjacent buildings. In this study, we will be examining the potential for fire control design and effects mitigation using a 1/4.5 scale model. The primary focus of the study will be the effects of extended balconies into the structure of high-rise apartments. The authors will also consider the effectiveness of reduced-scale model tests.

• 한국강구조학회 논문집
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• 제22권6호
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• pp.523-532
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• 2010

콘크리트가 충전된 각형강관기둥(이하, 각형 CFT기둥)은 높은 내화성능과 하중저항능력을 보유하고 있지만, CFT기둥의 외부에 내화피복을 함으로써 기둥의 내화성능을 향상시킬 필요가 있다. 본 연구는 내화 피복된 각형 CFT기둥의 온도분포에 대한 실험결과이다. 실험을 위하여 특수 제작된 전기로를 이용하여 축소모형 시험체의 재하가열실험을 수행하였다. 축하중을 받는 내화 피복된 각형 CFT기둥의 온도 분포 특성을 파악하기 위하여 내화피복의 종류와 두께, 강관의 두께 및 가열시간 등을 변수로 설정하였다. 실험결과 전기로의 온도에 따른 시험체별 온도분포와 콘크리트와 강재의 온도분포 특성을 파악하였다. 또한 시험체의 온도변화에 따른 축변위와 국부좌굴 등의 거동을 파악하였다.

• Structural Engineering and Mechanics
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• 제50권6호
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• pp.755-772
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• 2014

A simplistic approach towards evaluation of complete load deflection response of Reinforced Concrete (RC) flexural members under post fire (residual) scenario is presented in this paper. The cross-section of the RC flexural member is divided into a number of sectors. Thermal analysis is performed to determine the temperature distribution across the section, for given fire duration. Temperature-dependent stress-strain curves for concrete and steel are then utilized to perform a moment-curvature analysis. The moment-curvature relationships are obtained for beams exposed to different fire durations. These are then utilized to obtain the load-deflection plots following pushover analysis. Moreover one of the important issues of modeling the initial stiffness giving due consideration to stiffness degradation due to material degradation and thermal cracking has also been addressed in a rational manner. The approach is straightforward and can be easily programmed in spreadsheets. The presented approach has been validated against the experiments, available in literature, on RC beam subjected to different fire durations viz. 1hr, 1.5hrs and 2hrs. Complete load-deflection curves have been obtained and compared with experimentally reported counterparts. The results also show a good match with the results obtained using more complicated approaches such as those involving Finite element (FE) modeling and conducting a transient thermal stress analysis. Further evaluation of the beams during fire (at elevated temperatures) was performed and a comparison of the mechanical behavior of RC beams under post fire and during fire scenarios is made. Detailed formulations, assumptions and step by step approach are reported in the paper. Due to the simplicity and ease of implementation, this approach can be used for evaluation of global performance of fire affected structures.

• 한국화재소방학회논문지
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• 제24권1호
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• pp.40-45
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• 2010

비대칭 H형강을 활용한 합성보는 1970년대 후반 이후 스웨덴에서 Thor beam(Hat beam)으로 발표되었으며 British Steel과 SCI는 슬림플로어 보를 개발하였다. 슬림플로어 공법은 1990년대 초반부터 유럽의 주요 선진국에서 많은 관심을 갖고 개발하여 온 건축 구조 부재의 한 형태로 2000년대에 영국에서는 열간압연 형강 그리고 핀란드에서는 비대칭 용접 형강의 관심이 집중되고 있다. 슬림플로어 공법의 가장 큰 장점은 층고 감소를 토대로 도심 건축물의 최대 10% 내외의 연면적 증가 효과와 각종 내 외장재 절감 및 자원의 절약 폐기물 감소효과 등이며 일반 합성보에 비하여 철골보의 노출면이 적어 내화 성능에서도 우수한 장점이 있다. 본 연구는 비대칭 H형강을 사용한 슬림플로어 보의 화재시 구조 성능에 관한 연구로 표준화재조건에서 강재 단면의 형상 변화를 통한 구조물의 내화 거동과 재하 하중비를 변수로 화재시 구조물의 온도 분포와 처짐을 비교 분석하는 것을 목적으로 한다.

• Steel and Composite Structures
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• 제33권1호
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• pp.111-122
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• 2019

This paper presents an experimental work on the post-fire behavior of two kinds of innovative composite stub columns under eccentric compression. The partially precast steel reinforced concrete (PPSRC) column is composed of a precast outer-part cast using steel fiber reinforced reactive powder concrete (RPC) and a cast-in-place inner-part cast using conventional concrete. Based on the PPSRC column, the hollow precast steel reinforced concrete (HPSRC) column has a hollow column core. With the aim to investigate the post-fire performance of these composite columns, six stub column specimens, including three HPSRC stub columns and three PPSRC stub columns, were exposed to the ISO834 standard fire. Then, the cooling specimens and a control specimen unexposed to fire were eccentrically loaded to explore the residual capacity. The test parameters include the section shape, concrete strength of inner-part, eccentricity ratio and heating time. The test results indicated that the precast RPC shell could effectively confine the steel shape and longitudinal reinforcements after fire, and the PPSRC stub columns experienced lower core temperature in fire and exhibited higher post-fire residual strength as compared with the HPSRC stub columns due to the insulating effect of core concrete. The residual capacity increased with the increasing of inner concrete strength and with the decreasing of heating time and load eccentricity. Based on the test results, a FEA model was established to simulate the temperature field of test specimens, and the predicted results agreed well with the test results.

• Computers and Concrete
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• 제20권2호
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• pp.177-184
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• 2017

The characteristics of lightweight aggregate (LWA) with a low specific gravity and high water absorption will significantly change the properties of lightweight aggregate concrete (LWAC). This study aimed at exploring the effect of presoaking degree of LWA on the strength degeneracy of LWAC and flexural behavior of LWAC members exposed to elevated temperatures. The residual mechanical properties of the LWAC subjected to elevated temperatures were first conducted. Then, the residual load tests of LWAC members (beams and slabs) after exposure to elevated temperatures were carried out. The test results showed that with increasing temperature, the decreasing trend of elastic modulus for LWAC was considerably more serious than the compressive strength. Besides, the presoaking degree of LWA had a significant influence on the residual compressive strength and elastic modulus for LWAC after exposure to $800^{\circ}C$. Moreover, owing to different types of heating, the residual load bearing capacity of the slab specimens were significantly different from those of the beam specimens.

• Steel and Composite Structures
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• 제20권1호
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• pp.185-203
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• 2016

Shear connectors are key components to ensure the efficient composite action and satisfactory transfer of shear forces at the steel-concrete interface in composite beams. Under hazardous circumstances, such as fire in a building, the performance of a composite beam significantly relies on the performance of shear connectors. Studies on the behavior of shear connectors subjected to elevated temperatures performed in the last decade are reviewed in this paper. The experimental testing of push-out specimens, the design approaches provided by researchers and different codes, the major failure modes, and the finite element modeling of shear connectors are highlighted. The critical research review showed that the strength of a shear connector decreases proportionally with the increase in temperature. Compared with the volume of work published on shear connectors at ambient temperatures, a few studies on the behavior of shear connectors under fire have been conducted. Several areas where additional research is needed are also identified in this paper.