• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.2
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• pp.150-156
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• 2015

In this study, the effects of different mix proportions and fire scenarios (exposure temperatures and post-fire-curing periods) on fire-damaged concrete were analyzed using a nonlinear resonance vibration method based on nonlinear acoustics. The hysteretic nonlinearity parameter was obtained, which can sensitively reflect the damage level of fire-damaged concrete. In addition, a splitting tensile strength test was performed on each fire-damaged specimen to evaluate the residual property. Using the results, a prediction model for estimating the residual strength of fire-damaged concrete was proposed on the basis of the correlation between the hysteretic nonlinearity parameter and the ratio of splitting tensile strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.3
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• pp.108-115
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• 2014

Mechanical properties of GFRP rebars significantly decrease due to high temperature as well as alkalinity of concrete. This study focuses on the long-term reduction of inter-laminar shear strength of pre-damaged GFRP rebars by high temperature. For this investigation, bare GFRP rebar specimens were exposed to $270^{\circ}C$ for 1hour and then immerged in alkali solution for several months and tested in shear. No thermally conditioned specimens were immerged and tested for the comparisons. In results, the reduction of thermally damaged GFRP rebars was greater than that of no thermally damaged ones. Based on the accelerated experimental test data, an polynomial equation is presented for prediction of long-term residual inter-laminar shear strength of GFRP rebars previously damaged by high temperature.

• Journal of the Society of Disaster Information
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• v.11 no.4
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• pp.589-596
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• 2015

As urbanization progressed along with quantitative expansion of the construction industry, concrete has developed diversely as a material that is the most extensively used in the construction industry. However, aggregate resources that are an essential element of concrete production are gradually being depleted and the phenomenon of aggregate shortage has been intensifying due to the reinforcement of regulations on environmental issues. Therefore, in the present study, environment friendly mortar was made by replacing aggregate with mud that is dumped when dredging sand is dumped. To identify the dynamic characteristics of the mortar and to identify its fire resistance efficiency, the mortar was heated and its residual compressive strength was measured. In the results, the residual compressive strength values of MM1, MM2, and MM3 were 45%, 95%, and 57.7% respectively and the mix MM2 showed the highest fire resistance efficiency.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.257-260
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• 2008

This study will make P-M interaction diagram of residual capacity at fire-damaged High strength concrete column with polypropylene fiber. Evaluating capacity of column decreasing spalling with P-M interaction diagram is important. because high strength concrete column with polypropylene fiber isn't section area loss. P-M interaction diagram that is made to analyze according to a various parameters is useful index for design and evaluating capacity of columns. In this study, spalling, temperature distribution of interior column, residual strength and movement of column in eccentric loading are studied with expose time of high temperature. For study fire test that is similar real act, and after cooling in normal condition residual strength of specimen is estimated. And this study use DIANA(Displacement Analyzer) for analyzing nonlinear analysis. with experiment temperature and strength data.

• Journal of Navigation and Port Research
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• v.38 no.4
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• pp.379-384
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• 2014

In case of sunken tankers, remaining-oil recovery operation should be conducted due to possible oil spill accident. However, the deep sea operation make difficulties in checking the completion of remaining oil recovery process, therefore the work termination procedure is very important. In this paper, a reasonable work termination procedure through the comparison and analysis of two cases(Youil No.1 and Osung No.3, Kyung-Shin) which were performed in different method, using disparate equipment. By investigating previously applied methods and techniques, work speed, safety and expenses were compared. The proposed ending procedure of the remaining-oil recovery project is to recover the remaining oil from each cargo tanks and to clean up such tanks whilst an independent surveyor proceeds to a confirmation procedure whereby said surveyor checks out whether any remaining oil exists by putting a stick in each cleaned up tanks and opening up the hatch cover of the tanks or the top place of the tanks to confirm the cleanness of oil. Such procedure shall be done through discussion by the ordering party, contractor and the independent surveyor all together with a flexible application.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.131-139
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• 2012

The lateral reinforcements of concrete such as hoops and spiral bars are known to confine concrete to compensate the strength loss due to fire by reducing explosive spalling and improving the capacity of ductility. In this context, a study was conducted to investigate the residual mechanical properties of confined and unconfined concrete($f_{ck}$=60MPa) after a single thermal cycle at 300, 600, $800^{\circ}C$. The main parameters required to establish the stress-strain relationship are the peak stress, the elastic modulus, and the strain at peak stress. The knowledge of the residual mechanical properties of concrete is necessary whenever the thermally damaged structure is required to bear a significant share of the loads, even after a severe thermal accident. Based on the results obtained in this study, the residual stress of confined concrete under thermal damage is higher according to the level of confinement and the larger strain made it to have better ductility. The decreasing ratio of elastic modulus from the relationship of stress and strain was also smaller than that of unconfined concrete.

• Journal of the KSME
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• v.28 no.4
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• pp.387-393
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• 1988

본 SP시험법은 사용되는 시편이 미소하다는 장점 때문에 재질의 평가나 더불어 비파괴검사의 일환으로서 이용할 수 있음을 서명해 왔다. 현존하고 있는 거대구조물들의 잔존수명평가가 요 구되는 있는 지금, 정량적인 경년변화측정방법으로서 SP시험법은 높은 가능성을 내포하고 있는 시험법으로 여겨지며, 이 방법을 현장에 정착시키기 위해선 산. 학. 연의 공동연구체제가 필요 하다고 할 수 있다.

• Journal of the Korea Concrete Institute
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• v.20 no.5
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• pp.583-592
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• 2008

Recently, the effects of high temperature on compressive strength, elastic modulus and strain at peak stress of high strength concrete were experimentally investigated. The present study is aimed to study the effect of elevated temperatures ranging from 20 to 700 on the material mechanical properties of high strength concrete of 40, 60, 80 MPa grade. In this study, the types of test were the stressed test and stressed residual test that the specimens are subjected to a 25% of ultimate compressive strength at room temperature and sustained during heating and when target temperature is reached, the specimens are loaded to failure. And another specimens are loaded to failure after 24 hour cooling time. Tests were conducted at various temperatures ($20{\sim}700^{\circ}C$) for concretes made with W/B ratios 46%, 32% and 25%. Test results showed that the relative values of compressive strength and elastic modulus decreased with increasing compressive strength grade of specimen and the axial strain at peak stress were influenced by the load before heating. Thermal strain of concrete at high temperature was affected by the preload level as well as the compressive strength. Finally, model equation for compressive strength and elastic modulus of heated high strength concrete proposed by result of this study.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.311-318
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• 2018

When reinforced concrete structures are exposed to fire, their mechanical properties such as compressive strength, elasticity coefficient and rebar yield strength, are degraded. Therefore, the structure's damage assessment is essential in determining whether to dismantle or augment the structure after a fire. In this study, the confinement effect of lateral reinforcement of RC column according to the numbers of fire exposure face and stirrup was verified by fire resistant test with the heating temperatures of $400^{\circ}C$, $600^{\circ}C$ and $800^{\circ}C$. The test results showed that the peak stress decreases and peak strain increases as the temperature is getting higher, also transverse ties are helpful in improving the compressive resistance of concrete subjected to high temperature. Based on the results of this study, the residual stress of confined concrete under thermal damage is higher at the condition of more lateral reinforcement ratio and less fire exposure faces. The decreasing ratio of elastic modulus of more confined and less exposure faces from the relationship of load and displacement was also smaller than that of opposite conditions.

• Journal of the Korea Concrete Institute
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• v.26 no.5
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• pp.643-650
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• 2014

Generally, the reinforced concrete slab has great fire resistance performance because concrete has excellent thermal material properties under fire. But, in the case of hollow slab, it will be expected that hollow slabs have different temperature distribution and fire endurance performance compare to reinforced concrete slab. Because hollow slab has internal void space that occurs decreasing regenerative effect of concrete and formation of internal air layer. Evaluation method for fire resistance performance of hollow slabs was proposed using $wickstr{\ddot{o}}m^{\prime}s$ method. For the casual use of evaluation, simplified method was proposed which was limited to solid slab and donut type hollow slab which was developed by authors of this research paper. Also, verification on proposed method was performed by comparing results of fire experiment for hollow slab and evaluation results. Proposed method of the results of this study was possible to predict the residual strength and temperature distribution of slabs under fire.