• Advances in concrete construction
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• v.16 no.1
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• pp.1-20
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• 2023

This study presents the experimental results performed to evaluate the effects of Polyvinyl-alcohol (PVA) and Polypropylene (PP) fibers on the fresh and residual mechanical properties of the hybrid fiber reinforced SCC before and after the exposure of 250℃, 500℃ and 750℃ temperatures. The compressive and splitting tensile strength, modulus of rupture (MOR), ultrasonic pulse velocity (UPV) as well as toughness and weight loss were investigated at different temperatures. PVA and PP fibers were added into SCC mixtures having only macro steel fiber and also having binary hybridization of both macro and micro steel fiber. The results showed that the use of micro steel fiber replaced by macro steel fiber improved the fresh and hardened properties compared to the use of only macro steel fiber. Moreover, it was emphasized that PVA or PP enhanced the residual flexural performance of SCC, generally, while it negatively influenced the workability, weight loss, UPV and the residual strengths with regards to the use of single steel fiber and binary steel fiber hybridization. Compared to the effect of synthetic fibers, PP had slightly more positive effect in the view of workability while PVA enhanced the residual mechanical properties more.

• Journal of the Korea Institute of Building Construction
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• v.9 no.4
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• pp.63-73
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• 2009

Recently, the use of lightweight panels in building structures has been increasing. Of the various lightweight panel types, styrofoam sandwich panels are inexpensive and are excellent in terms of their insulation capacity and their constructability. However, sandwich panels that include organic material are quite vulnerable to fire, and thus can numerous casualties in the event of a fire due to the lack of time to vacate and their emission of poisonous gas. On the other hand, lightweight foamed concrete is excellent, both in terms of its insulation ability and its fire resistance, due to its Inner pores. The properties of lightweight concrete is influenced by foaming agent type. Accordingly, this study investigates the insulation properties by foaming agent type, to evaluate the possibility of using light-weight foamed concrete instead of styrene foam. Our research found thatnon-heating zone temperature of lightweight foamed concrete using AP (Aluminum Powder) and FP (animal protein foaming agent) are lower than that of light-weight foamed concrete using AES (alkyl ether lactic acid ester). Lightweight foamed concrete using AES and FP satisfied fire performance requirements of two hours at a foam ratio 50, 100. Lightweight foamed concrete using AP satisfied fire performance requirements of two hours at AP ratio 0.1, 0.15. The insulation properties were better in closed pore foamed concrete by made AP, FP than with open pore foamed concrete made using AES.

• Journal of Korean Society of Forest Science
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• v.100 no.1
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• pp.112-117
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• 2011

This study was conducted for searching the functional feeding groups, and community stability of the macroinvertebrate on forest fire area of Uljin-gun. The samples were collected from 2 sites of control area and 2 sites of experimental area during 2007 to 2009. The identified species were 89 belonged to 47 families, 16 order, 6 class, and 4 phylum in control area. And 84 belonged to 43 families, 16 order, 6 class, and 4 phylum were identified in experimental area. As a result of changes in species and individuals of E.P.T. taxa investigated in experimental area by year, Ephemeroptera was 21 species, $2,434.6inds./m^2$, Plecoptera was 3 species, $199.8inds./m^2$, and Trichoptera 14 species, $540.2inds./m^2$ in 2007. And in 2009, Ephemeroptera was 9 species, $296inds./m^2$, Trichoptera was 4 species, $44.4inds./m^2$, and Plecoptera was none, showing that species and individuals belonging to E.P.T. taxa decrease rapidly every year. Community analysis by year, in 2008 when the water system started to be influenced by the fire directly, it showed a trend that H' and RI decreased in the experimental area. Functional feeding group by year, it showed a trend that species and individuals of GC type which is a functional group picking up and eating FPOM (fine particulate organic matter) from deposits in the bottom of water or benthic areas and performs an important function of material circulation in ecosystem decrease every year. Community stability by year, an environment of water system in forest fire area started to be somewhat destroyed, from 2008, it is shown that both species in I area which have great ability of resistance and recovery and species in III area which live in relatively stable water system decreased a little.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.81-89
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• 2018

Austenitic stainless steels have excellent corrosion resistance, durability and fire resistance. Especially, since STS304L among austenitic types is a low-carbon variation of STS304 and has excellent intergranular corrosion resistance, it can often be used under the welded condition without heat treatment after field welding. This paper investigated ultimate behaviors such as ultimate strength and weld metal fracture mechanism of STS304L fillet-welded connections with TIG(tungsten inert gas) welding through test results. Main variables of specimens are weld length and welding direction against loading. Fracture of specimens are classified into three modes(tensile fracture, shear fracture and block shear fracture). Ultimate strengths were compared according to the welding direction and weld length and TFW series with transverse fillet weld had the highest strength compared with other types(LFW series with longitudinal fillet weld and FW series with all round weld). It is known that current design specifications such as KBC 2016 and AISC2010 underestimated the strength of TFW and LFW specimens and provided unconservative estimates for FW specimens. Finally, strength equations were proposed considering material properties of STS 304L material.

• Journal of the Korea Concrete Institute
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• v.28 no.6
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• pp.673-683
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• 2016

In recent years, frequent terror or military attack by explosion, impact, fire accidents have occurred. Particularly, World Trade Center collapse and US Department of Defense Pentagon attack on Sept. 11 of 2001. Also, nuclear power plant incident on Mar. 11 of 2011. These attacks and incidents were raised public concerns and anxiety of potential terrorist attacks on major infrastructures and structures. Therefore, the extreme loading researches were performed of prestressed concrete (PSC) member, which widely used for nuclear containment vessel and gas tank. In this paper, to evaluate the blast resistance capacity and its protective performance of bi-directional unbonded prestressed concrete member, blast tests were carried out on $1,400{\times}1,000{\times}300mm$ for reinforced concrete (RC), prestressed concrete without rebar (PSC), prestressed concrete with rebar (PSRC) specimens. The applied blast load was generated by the detonation of 55 lbs ANFO explosive charge at 1.0 m standoff distance. The data acquisitions not only included blast waves of incident pressure, reflected pressure, and impulse, but also included displacement, acceleration, and strains at steel, concrete, PS tendon. The results can be used as basic research references for related research areas, which include protective design and blast simulation under blast loading.

• Composites Research
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• v.33 no.4
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• pp.177-184
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• 2020

Flame retardant(FR) clothes prohibit additional fire diffusion and make the personnel do their tasks without a hitch in a flammable environment. The existing FR clothes, however, are heavy and give high thermal fatigue. Therefore, it is strongly demanded to develop a light, convenient, and eco-friendly clothes. Recently, many works have been reported to make FR fabrics with phosphorus compounds, but their performance could not satisfy the specified criteria in appraisal standards of domestic and American FR clothes or combat uniforms. In this paper, two kinds of phosphorus compounds were applied to cotton fabric. Graphene oxide functionalized with a phosphorus-rich deep eutectic solvent and ammonium polyphosphate were coated on cotton fabric by eco-friendly padding procedure. The coated fabrics were analyzed with thermogravimetric analysis, vertical flame resistance test(ASTM D6413), cone calorimeter test(ISO 5660-1), and method of test for limited flame spread(ISO 15025). It was revealed that the as-made cotton with those two materials simultaneously had better flame resistance than the cottons with each one. Furthermore, an additional coating for hydrophobicity on the FR cotton was tried for better washing fastness.

• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.157-165
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• 2016

It is possible to achieve high strength ranging from 40 MPa to 70 MPa in alkali-activated slag concrete (AASC), and AASC is also known to have a finer pore structure due to its high latent hydraulicity and fineness of slag cement, which makes it difficult for chloride ions to penetrate. Electrophoresis is mostly used to calculate the effective diffusion coefficient of chloride ions, and then to evaluate resistance to salt damage. Few studies have been conducted on the fixation capacity of chloride ions in AASC. For this reason, in this study the chloride fixation within the hardened paste was evaluated according to the type and the amount of alkaline activators. As a result, it was revealed that among the test specimens, the chloride fixation was greatest in the paste containing $Na_2SiO_3$. In addition, it was found that as more activator was added, a higher level of chloride fixation was observed. Through this analysis, it can be concluded that the type and the amount of alkaline activators have a high correlation with the amount of C-S-H produced.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.3
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• pp.189-196
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• 2013

In order for efficient recycling and eco-friendly treatment of construction waste, there is a need to apply a building separation and dismantling technique early on in the stage of waste generation. This study was conducted to analyze the relevant domestic circumstances and propose the applicable range of buildings in order to introduce a building separation and dismantling system to Korea. For this purpose, related policies and systems implemented overseas and the current situation of buildings were examined, and the workability of separation and dismantling of buildings according to their uses was compared. Also, the economic impact of the separation and dismantling system was examined and a survey was conducted, seeking the opinions of the relevant companies regarding the need for the system and the selection criteria for eligible buildings. Based on the results, it was determined that it would be impossible to apply the separation and dismantling system to all buildings in Korea, considering the current technical power and economic situation, and that the system should be introduced in phases, according to the building classification determined based on floor area and use, as the cost may vary depending on a number of variables including the level of difficulty and field conditions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.688-695
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• 2017

Compared to metal, CFRP has excellent mechanical characteristics in terms of intensity, hardness, and heat resistance as well as its light weight that it is used widely in various fields. Therefore, this material has been used recently in the aerospace field. On the other hand, the material has shortcomings in terms of its extreme vulnerability to damage occurring internally from an external impact. This study examined the intensity up to its destruction from repeated use with the internal impact of a CFRP laminated plate that had also been exposed to external impact obtain design data for the external plate of aircraft used in the aerospace field. For the experimental method, regarding the quasi-isotopic type CFRP specimen and orthotropic CFRP specimen that are produced with a different layer structure, steel spheres with a diameter of 5 mm were collided to observe the resulting impact damage. Through a 3-point flexural fatigue experiment, the progress of internal layer separation and impact damage was observed. Measurements of the flexural fatigue strength after the flexural fatigue experiment until internal damage occurs and the surface impacted by the steel spheres revealed the quasi-isotopic layer structure to have a higher intensity for both cases.

• Journal of Korean Society of Disaster and Security
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• v.10 no.1
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• pp.85-90
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• 2017

The purpose of this study is to investigate the effect of vertical and horizontal refraction on the lower part of the power supply and control system of various facilities and machinery that use electricity, so that the power distribution system, which is an important electric facility installed in buildings and public facilities, Type earthquake resistant pads to protect the substructure and prevent short-circuiting on the upper part of the system. The GR-63-CORE (Scale 8.3 class) It is earthquake disaster prevention and disaster prevention technology that satisfies seismic performance. As a research result, it is possible to protect the electricity and communication infrastructure, which can contribute to shortening the time for recovering the electric facilities to the normal state in case of an earthquake, and preventing the fire caused by the destruction of the electricity supply facility in case of an earthquake. As a result, it is possible to minimize the spread of fire that occurs when a large-scale earthquake occurs and to minimize the damage of people and damage to property, and it can contribute to the securing of electric infrastructure that enables citizens to quickly recover to daily life even after suffering a major earthquake. In addition, the technology can be applied to ensure the seismic resistance of the equipment in the communication and computer room, and it can be applied to various fields where the facility function can be stopped due to the shaking of the earthquake base.