• Title/Summary/Keyword: Steel for Construction

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A identification of sprayed fire-resistive materials by near-infrared spectroscopy (근적외선 분광 분석법을 이용한 내화뿜칠재 일치성분석)

  • Cho, Nam-Wook;Shin, Hyun-Jun;Cho, Won-Bo;Lee, Seong-Hun;Rie, Dong-Ho;Kim, Hyo-Jin
    • Analytical Science and Technology
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    • v.24 no.2
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    • pp.85-93
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    • 2011
  • To protect the steel structure in a high story buildings from fire, the sprayed fire-resistive materials are applied during the construction. Current standard methods to check the quality of sprayed fire-resistive materials are real fire test in lab, which take a long time (several weeks) and expensive. In this study, a simple analytical method to check the quality of sprayed fire-resistive materials is developed using Near Infrared Spectroscopy (NIR). Total 9 kinds of sprayed fire-resisted materials and 3 kinds of normal sprayed material sets were used for the analysis. Each set of materials was 50 to 100 samples. Samples are grinded and make a fine powder. The spectral data acquisition was carried out using FT-NIR spectrometer with a integrating sphere. NIR methods successfully identify the sprayed fire resistive materials by a principle component analysis (PCA) after a vector normalization (SNV) pretreatment.

Study on the Structural Safety for the Non-Open excavation method by Using Steel Tubular Roof (대구경 강관을 이용한 비개착공법의 구조적 안전성에 대한 연구)

  • Kim, Kyong-Gon;Kim, Kyeong-Hwan;Kim, Hyo-Jin;Lee, Sang-Ho
    • Journal of Korean Society of societal Security
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    • v.2 no.4
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    • pp.49-57
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    • 2009
  • The development and use of underground space in the city have been expanded considerably worldwide due to the growing population and traffic. Because the construction of underground causes some problems including traffic jam and safety accidents, the non-open excavation construction method are commonly used. NTR (New Tubular Roof) method which is one of the non-open excavation method is investigated in this study. The structural safety of underground structures by using NTR method is evaluated by ANSYS 9.0. The tubular roof according to diameters are analysed by ANSYS 9.0 at critical construction step. Finally, according the diameter and thickness of tubular roof the stress nad dispacement are analyzed and then the The efficient use of tubular roof is suggested from relationship between tubular's thickness and stress condition.

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Effect of high-strength concrete on shear behavior of dry joints in precast concrete segmental bridges

  • Jiang, Haibo;Chen, Ying;Liu, Airong;Wang, Tianlong;Fang, Zhuangcheng
    • Steel and Composite Structures
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    • v.22 no.5
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    • pp.1019-1038
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    • 2016
  • The use of high-strength concrete (HSC) in precast concrete segmental bridges (PCSBs) can minimize the superstructure geometry and reduce beam weight, which can accelerate the construction speed. Dry joints between the segments in PCSBs introduce discontinuity and require special attention in design and construction. Cracks in dry joints initiate more easily than those in epoxy joints in construction period or in service. Due to the higher rupture strength of HSC, the higher cracking resistance can be achieved. In this study, shear behavior of dry joints in PCSBs was investigated by experiments, especially focusing on cracking resistance and shear strength of HSC dry joints. It can be concluded that the use of HSC can improve the cracking resistance, shear strength, and ductility of monolithic, single-keyed and three-keyed specimens. The experimental results obtained from tests were compared with the AASHTO 2003 design provisions. The AASHTO 2003 provision underestimates the shear capacity of single-keyed dry joint C50 and C70 HSC specimens, underestimates the shear strength of three-keyed dry joint C70 HSC specimens, and overestimates the shear capacity of three-keyed dry joint C50 HSC specimens.

Development of Ready-mixed Shotcrete I : Basic Study (레디믹스트 숏크리트 개발 I : 기초 연구)

  • Kim, Dong-Min;Ma, Sang-Joon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.31 no.5C
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    • pp.171-185
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    • 2011
  • Ready-mixed shotcrete that mixed with high quality aggregate and can improve construction quality is produced in a dry mortar plant and transported to construction sites. Because of using aggregate that produced in a special plant, Ready-mixed shotcrete has many advantages : good grain-size distribution, minimum stone powder, high quality and standardization material, etc. In this basic study different from the existing study that limited to additive and accelerator, the improvement of aggregate quality was tried to upgrade the shotcrete performance. The investigation about the construction conditions of shotcrete was performed and the result of an opinion poll was analyzed for a good grasp of the problems in domestic shotcrete quality. Pilot Plant Test was also performed to minimize the material segregation in plant manufacturing process. In additions, the field test was performed to find the optimum contents of synthetic fiber, appearing the same flexible toughness with that of steel fiber, and to find the optimum replacement ratio of blast furnace slag.

A Study on the Development of a Real-Time Schedule Progress Control System in Steel Structural Construction (철골골조공사의 실시간 진도관리 시스템 구축에 관한 연구)

  • Kim, Kyong-Hoon;Kim, Kyung-Hwan;Lee, Yoon-Sun;Kim, Jae-Jun
    • Proceedings of the Korean Institute Of Construction Engineering and Management
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    • 2007.11a
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    • pp.886-891
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    • 2007
  • All sorts of technique for schedule progress management is being developed recently. These can change and develop the abstractive concept model to a detailed model that describes the visual 3D image about a schedule plan. but, this technique is troublesome, because this requires the handwork by means of connection between 3D-CAD and scheduling Program. In this study, the process of real-time schedule progress control system using the integrated database by 3D-CAD object information system and schedule module is presented. This study present the process of a schedule progress management using IDEF0 model, and the process of real-time schedule progress management using RFID system. Through this study, we want to realize the rapid generation of estimated schedule information and to simulate and analyze actual schedule information by real-time.

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An Experimental of RC Beams Strengthened with Pultruded Glass Fiber and Steel strip (통기성 유리섬유-강판 인발성형 스트립으로 보강된 RC보의 실험적 거동분석)

  • Kim, Woonhak;Kang, Seokwon
    • Journal of the Society of Disaster Information
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    • v.9 no.3
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    • pp.315-323
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    • 2013
  • Recently, FRB is being used more as reinforcement of RC beam thanks to its material advantages in construction industry. The external attachment reinforcement of FRP is a construction method with advantages such as high strength, stiffness, excellent durability and construction practicability, despite of its weight. However, the reinforcement has a disadvantage to cause damage on permanent structure as its structure is water-tight by low water permeability reinforcement, preventing water from draining outside. The study attempted flexural failure test for GP of which material properties are equally same as the existing FRP and that with permeability, shows good binding with the concrete structure, durable performance and durability, comparably analyzing the improvement of durability and ductility according to changes of fiber contents of composite strip.

Investigation of Strength Characteristics of Ferrous Slag and Waste Concrete in Water Contacting Environment by Exposure to Raining Events

  • Kim, Byung-Gon;Shin, Hyunjin;Lee, Seunghak;Park, Junboum
    • Journal of Soil and Groundwater Environment
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    • v.21 no.2
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    • pp.1-7
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    • 2016
  • Ferrous slag is a by-product from steel making process and waste concrete is generated from construction activities. Large part of ferrous slag and waste concrete are recycled as construction materials. However, Ca2+ leaching out of ferrous slag and waste concrete in the water-contacting environment can cause a strength change. Strength can be reduced due to the dissolution of solid form of CaO which is one of the main contents of ferrous slag and waste concrete. On the other hand, strength can be enhanced due to the pozzolanic reaction of cementitious components with water. In this study, steelmaking slag, blast furnace slag, and waste concrete were aged by exposure to raining events, and the change of their compaction and shear strength characteristics was investigated. Optimum moisture content of all materials used in this study increased with aging period while maximum dry unit weight slightly decreased, implying that the relative contents of fine particles increased as the CaO solid particles were dissolved. Internal friction angle and shear strength of recycled materials also increased with aging period, indicating that the materials became denser by the decrease of void ratio attributed to the fine particles generated during the weathering process and the development of cementitious compounds increasing the bonding and interlocking forces between the particles. The results of this study demonstrated that mechanical strength of recycled materials used as construction materials has little chance to be deteriorated during their service life.

Power spectral density method performance in detecting damages by chloride attack on coastal RC bridge

  • Mehrdad, Hadizadeh-Bazaz;Ignacio J., Navarro;Victor, Yepes
    • Structural Engineering and Mechanics
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    • v.85 no.2
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    • pp.197-206
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    • 2023
  • The deterioration caused by chloride penetration and carbonation plays a significant role in a concrete structure in a marine environment. The chloride corrosion in some marine concrete structures is invisible but can be dangerous in a sudden collapse. Therefore, as a novelty, this research investigates the ability of a non-destructive damage detection method named the Power Spectral Density (PSD) to diagnose damages caused only by chloride ions in concrete structures. Furthermore, the accuracy of this method in estimating the amount of annual damage caused by chloride in various parts and positions exposed to seawater was investigated. For this purpose, the RC Arosa bridge in Spain, which connects the island to the mainland via seawater, was numerically modeled and analyzed. As the first step, each element's bridge position was calculated, along with the chloride corrosion percentage in the reinforcements. The next step predicted the existence, location, and timing of damage to the entire concrete part of the bridge based on the amount of rebar corrosion each year. The PSD method was used to monitor the annual loss of reinforcement cross-section area, changes in dynamic characteristics such as stiffness and mass, and each year of the bridge structure's life using sensitivity equations and the linear least squares algorithm. This study showed that using different approaches to the PSD method based on rebar chloride corrosion and assuming 10% errors in software analysis can help predict the location and almost exact amount of damage zones over time.

Development of Air Spring Damper System(ASDS) (공기 스프링 댐퍼 시스템(ASDS)의 개발)

  • Kim, Dong Baek;Park, Heung Sik
    • Journal of the Society of Disaster Information
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    • v.17 no.4
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    • pp.829-838
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    • 2021
  • Purpose: The Air Spring Damper System (ASDS) is proposed when existing concrete structures that have not been seismic resistant for economic and technical reasons or low-rise concrete structures that are difficult to earthquake. Method: To conduct a study on the damping force antigen in the kinetic equation of free vibration, we analyze whether this device has damping ability as a damper experimentally and theoretically, and examine the possibility of field application. Result: The air damper system is considered to be more economical than steel hysteresis dampers even if the number of dampers increases due to its easy manufacture and construction and low restrictions on shape, size, material, etc. Conclusion: In an air spring damper system, it is essential to reduce the diameter of the air inlet/outlet hole to improve the damping ratio, and in this case, if the diameter exceeds a certain lower limit, consideration of the compressibility of air is required, so further research is needed.

Corrosion-bond Strength Evaluation in OPC and Slag Concrete using Accelerated Corrosion Test (촉진부식실험을 이용한 OPC 및 슬래그 콘크리트의 부식-부착강도 평가)

  • Sang-Jin Oh;Hyeon-Woo Lee;Seung-Jun Kwon
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.12 no.1
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    • pp.1-7
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    • 2024
  • Concrete, as a porous construction material, permits chloride penetration from outside, which yields corrosion in embedded steel. In the study, an accelerated corrosion technique (ICM: Impressed current method) was adopted for rapid corrosion formation with 10 Volt of potential, and corrosion amou nt was controlled u p to 10.0 %. Corrosion amou nt had a linear relationship with cumulative corrosion current and increased with a quadratic function of accelerating period due to cracking. Regarding bond strength test, OPC concrete showed rapid drop of bond strength over 3.0 % of corrosion weight ratio, however slag concrete with 30 % replacement ratio showed a level of 51.4~71.6 % of corrosion ratio to OPC concrete with keeping residual bond strength.