• Journal of the Korea Institute of Building Construction
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• v.17 no.2
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• pp.141-147
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• 2017

The purpose of this study is to develop an inorganic filling adhesive using MKP and borax based on Dead-burn magnesia and fly ash. First, basic experiments was conducted to derive the proper addition rate of MKP. And this experiment was carried out according to addition ratio of borax. The test items are measured for pot life, flexural strength, compressive strength, adhesive strength, tensile strength, ratio of temperature change, ratio of hardening shrinkage, radon gas and formaldehyde emission. As a result, the proper addition rate of phosphate was 35%. The pot time is about 10minutes, 15minutes and 25minutes according to addition rate of borax. The flexural strength and compressive strength were obtained at 12hours for minimum flexural strength of 8.0MPa and minimum compressive strength of 31.0MPa. The tensile strength was the least 4.1MPa, and the ratio of hardening shrinkage was maximum 2.4% and ratio of heat change was maximum - 0.3%, which satisfied all of the quality standards of 'KS F 4923' (epoxy resin for repairing concrete structures). Both Radon gas and formaldehyde emission was not detected.

• Journal of the Korean Institute of Gas
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• v.2 no.2
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• pp.1-11
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• 1998

A quantitative risk assessment and consequence analysis for PBL(Poly Butadiene Latex) reaction processes were performed. As a result of the Quantitative risk assessment, for the accident probability of PBL reactors causing a reaction runaway, was calculated as $9.197{\times}10^{-5}/yr$ The most important factor that affected the accident probability of PBL reactor was the relief device. When the reactor exploded, peak overpressure at the target point was $5.066{\times}10^5(Pa)$ and the range of effects windows to be broken occurred in almost all of the factory areas. The maximum radius of effect was 27m, in which workers could be die by the direct for eardrum damage was calculated at 77m. When the PBL reactor exploded, the extent of structural damage to buildings was calculated from the center of the explosion to a range of 52m. The results of the study's assessment have provided a direction for facility's improvement as well as effective safety investment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.1
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• pp.81-88
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• 2022

In the NRC (New paradigm Reinforced Concrete) beam, steel forms, main angles used as main reinforcements, and shear angles used as basic shear reinforcements are welded and assembled in the form of vierendeel truss structures in a steel factory. After the NRC truss frame is installed at the site, additional main reinforcement and shear reinforcement are distributed. In this study, the shear performance evaluation of the NRC beam was conducted through shear tests in accordance with the type of shear reinforcement of the NRC beam (shear angle, inclined shear reinforcing bar, and U-type cover bar). As a result of the test, the initial stiffness was similar before the initial cracking of each specimen, and all specimens were shear fractured.The shear reinforcements of the specimens exhibited a yielding behavior at the time of the maximum sheat force, and the shear strengths of the specimens increased as the amount of reinforcement of the shear reinforcement increased. These results show that NRC shear reinforcements exhibit shear performance corresponding to their shear strength contribution. As a result of calculating the nominal shear strengths according to KDS 14 20 22, the experimental shear strengths of the NRC beam specimens with shear reinforcement was 37~146% larger than the nominal shear strengths, so It was evaluated as a safety side.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.262-269
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• 2021

This paper conducts an evaluation of the structural performance of the lap splice detail of SD700 headed bar experiment for developing an RC beam with different depths joint details. The experiment variable is lap splice length, yield strength, and end anchorage of main reinforcements. For all specimens, a headed bar was applied to the main reinforcement of the beam with low depth (B2), and the beam with high depth (B1) was applied to the main reinforcement with two splice methods: straight headed bar and 90° hooked-headed bar. The experimental results were that specimens of applying SD500 and SD600 had the results of flexural fracture at the lap splice location, which maximum load was similar. For specimens of appling SD500, the 90° hooked-headed bar of B1, suppressed horizontal cracks in the lap splice section compared to the straight headed bar. Specimens of applying an SD 700 headed bar had the results of brittle anchorage failure. In addition, maximum load was increased with the lap splice length increasing. For specimens of applying SD700 headed bar, test for test maximum load/theoretical load for test development length/design development length were estimated to be 1.30~1.48 for the ACI 318-19 equation, and 1.14~1.30 for the KDS-2021 equation. Thus, ACI 318-19 equation had conservatively greater safety factors as estimated development lengththened.

• Journal of Korean Society of societal Security
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• v.3 no.2
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• pp.65-71
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• 2010

This study was conducted to provide a method for fire suppression in a central area inside the roof of a wooden cultural property using a gas extinguishing apparatus, which is used as one of fire suppression methods with view to preventing valuable wooden properties inherited from ancestors from being destructed by fire. For a wooden property, it is very difficult to suppress fire when combustion spreads to a central area inside its roof, so it is impossible to put out a fire without destructing it. Such a fire fighting apparatus as a sprinkler, etc., installed in modern structures, is very effective, but the possibility of damaging a cultural property is highly probable after installment and operation, which leads to its low adaptability to a wooden property. Thus, the necessity of developing a fire suppress ion apparatus was raised to minimize the said problem and to obtain the desired results, and the need of making a plan on the installment was also raised based on the results of a test whose validity was proven. The central area inside a roof is a traditional - architectural style which is found in Korean wooden structures only, so it is impossible to discover similar cases in foreign countries. For this reason, this study was conducted to verify the effectiveness by developing a fixed fire suppression apparatus designed considering the speed and effectiveness in fire suppression. This study was sequentially carried out in the following steps. First, a frame for this study was made and the specific plan on a fire suppression method was established. Then, a fire suppression apparatus was installed. In the first step, the effectiveness for fire suppression was tested by installing valve open - punched - main water pores, and in the second step, the same effectiveness was tested by valve opened - punched - injection ports. For a wooden property similar to "Sungnyemun"(Gate of Exalted Ceremonies), its central area of the roof decides whether the fire suppression is successful or not, so the opinions on how to put out a fire were presented in this study, and thus the objective data to establish a method on fire suppression in a wooden structure(cultural property) was secured. Lastly, a scientific verification in the effectiveness for fire suppression measures was presented by installing a gas - fixed fire suppression apparatus.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.4
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• pp.86-95
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• 2019

Recently, the applications of carbon fiber have been broader than ever when it comes to such industrials as automobiles, ships, aerospace, civil engineering and architecture because of their lightweight-ness and high mechanical properties. This study analyzed mechanical properties and flexural behavior of carbon fiber reinforced cement composites(CFRC) with different fiber contents and fiber lengths, and also impact resistance by natural drop test on mortar specimens was compared and examined. In addition, contents of carbon fiber(CF) were varied by 0.5%, 1.0%, 2.0% and 3.0%. Fiber lengths was used for 6 mm and 12 mm, respectively. As a result of the test, the flow value was very disadvantageous in terms of fluidity due to the carbon fiber ball phenomenon, and the unit weight was slightly reduced. In particular, the compressive strength was decreased with increasing carbon fiber contents. On the other hand, the flexural strength was the highest with 12 mm fiber length and 2% fiber content. As the results of the impact resistance test, the specimens of plain mortar takes about 2~3 times to final fracture, while the specimens of CFRC is somewhat different depending on the increase of the fiber contents. However, when the fiber length is 12 mm and the fiber content is 2%, the impact resistance was the highest.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.3
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• pp.12-20
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• 2023

This study presents basic data on how to secure stability by analyzing the change in tensile force of steel rod and the inclination characteristics of PSC BOX in the "Temporary fixation system using internal prestressing tendon", which is mainly applied to construction of superstructures by FCM. To date, it has been difficult to confirm the changes in tension force of the steel rod and the inclination of the PSC BOX because the steel rod was installed vertically inside the pier and the PSC BOX. Therefore, measurement of the change in length of the steel rod and the displacement of PSC BOX were performed using a micro-measured FBG sensor. Comparisons of the calculated tensile force and the residual tensile force of the steel rod revealed that the safety factor decreased in all bridges. The cause was mainly identified to be the loss of tensile force in fixation~1segment, and countermeasures are suggested. The analysis of the inclination characteristics showed that the inclination increased with the segment progresses even in bridges with sufficient safety factor, and the difference before and after the segment was confirmed. In addition, the increase in inclination was related to the loss of tension force in the steel rod, and the stress on the opposite sides of the inclination was further reduced. It is believed that upward tensile force is generated in the steel rod on the opposite side of the inclined side due to the unbalanced moment, causing the difference in stress of the steel rod between the two sides.

• Fire Science and Engineering
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• v.26 no.1
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• pp.43-48
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• 2012

Recently, evacuation safety of building resident become the major concern, as the building has been higher and more complicated. Required evacuation time using stairway is longer in high-rise buildings, moreover it is impossible for the disabled to evacuate by using stairway. For this reason the study on the effectiveness of using elevator for evacuation is progressing. This study shows the flow coefficient of hoistway when elevator is moving. The results of this study can be used for the study of elevator piston effect as basic data. Experiments were performed in 5 different hoistways at 3-story and 2-story buildings. According to the result of flow coefficient experiments, average flow coefficient is 0.954. Considering the $4{\sigma}$ to guarantee 99.99 % reliance, it is 0.86. This result is 3.6 % bigger than 0.83 that Klote and Tamura suggested. It represents that the maximum critical pressure is decreased about 7 % on the same condition of elevator and elevator shaft. When the smoke control performance of high-rise building is evaluated, the result is significant economically by applying a more realistic and less value of elevator piston effect.

• Spatial Information Research
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• v.20 no.2
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• pp.155-164
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• 2012

Indoor fire simulators have been used to analyse building safety in the events of emergency evacuation. These applications are primarily focused on simulating evacuation behaviors for the purpose of checking building structural problems in normal time rather than in real time situations. Therefore, they have limitations in handling real-time evacuation events with the following reasons. First, the existing models mostly experiment the artificial situations using randomly generated evacuees while real world requires actual data. Second, they take too long time in operation to generate real time data. Third, they do not produce optimal results to be used in rescueing or evacuation guidance. In order to solve these limitations, we suggest a method to build an evacuation simulation system that can be used in real-world emergency situations. The system performs numerous simulations in advance according to varying distributions of occupants. Then the resulting data are stored in DBMS. The actual person data captured in infrared sensor network are compared with the simulation data in DBMS and the querried data most closely is provided to the user. The developed system is tested using a campus building and the suggested processes are illustrated.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.3
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• pp.196-201
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• 2014

As political circumstances in oversea countries and Korea varies, the risk of vulnerability from unexpected extreme loading conditions, such as explosions or extreme impacts, also increased. In addition, construction companies in Korea recently have taken chances of overseas expansion to countries where their domestic situations are not in rest. Therefore, the resistance of construction materials for blast or impact loading become taking more consideration from engineering field. This study is a part of the research to develop a high performance fiber reinforced cementitious composite materials with high volume steel fibers and primary purpose of this study is to find an optimum mix proportions of in-fill slurry. In order to accomplish the tasks this study performed experimental investigations on the slurry for consistency, compressive strength, flowability, J-penetration, bleeding and rheology properties as well as mechanical properties, compressive and flexural strength, with respect to different mix proportions.