• Title/Summary/Keyword: Spalling analysis

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Development of performance assessment criterion for structures of shield TBM tunnel (쉴드 TBM 터널의 구조물 성능 평가 기준 개발)

  • Seong, Joo-Hyun;Lee, Yu-Seok;Hong, Eun-Soo;Byun, Yo-Seph
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.17 no.5
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    • pp.553-561
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    • 2015
  • In this study, the performance assessment criterion for reasonable maintenance of shield TBM tunnel was presented. The performance assessment items such as crack, leakage, breakage, spalling, exfoliation/detachment, efflorescence, quality condition, exposure of steel, carbonation, faulting step, bolts condition, drainage condition, ground condition, contact section condition and conduit condition were selected by analyzing domestic and foreign performance assessment criterions and investigating segment lining deterioration cases through the site investigation and in-depth inspection analysis result on the shield TBM tunnel. In addition, the reasonable weight using AHP (Analytic Hierarchy Process) were estimated.

Fire Resistance of High-Strength Concrete Corresponding to the Finishing Material Kinds and Thickness (마감재 종류 및 두께 변화에 따른 고강도 콘크리드의 내화특성)

  • Jung, Hong-Keun;Pei, Chang-Chun;Lee, Seong-Yeun;Han, Chang-Peng;Han, Min-Cheol;Han, Cheon-Goo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2009.05a
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    • pp.473-474
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    • 2009
  • In this study, a column member of an existing architecture finished with gypsum board was assumed to examine fire resistance characteristics according to the type and thickness of finishing material. All specimens showed spalling to the reinforcing part after fire resistance test. For temperature characteristics, rapid temperature increase of 100${\sim}$200 $^{\circ}C$ was shown between 35 ${\sim}$ 60 minutes in the sequence of 9.5 T, 9.5 T (2 pieces), 12.5 T, 15 T and fire resistant 12.5 T. The analysis suggested that finishing materials with better fire resistance are necessary.

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An Experimental Study on the Evaluation of Fire-Resist Performance of High-Strength Concrete Filled steel Tube Column at Fire (화재가열을 받은 고강도 콘크리트를 충전한 CFT 기둥의 내화성능 평가에 관한 실험적 연구)

  • Lee, Hyoung-Jun;Lee, Tae-Gyu;Kim, Young-Sun;Han, Hee-Chul;Kim, Gyu-Yong;Kim, Moo-Han
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2008.05a
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    • pp.193-197
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    • 2008
  • Recently, it increases in use of CFT(Concrete filled steel tube, below CFT) that is an excellent internal force and deformation capacity because material and method are required to be diversification and High-Performance according to increase the super-high structure. And it is proposed to use high-strength Concrete Filled steel Tube Column. But it is difficult quantitative evaluation about fire-resist performance of CFT because steel tube bind concrete. Also, the case of high strength CFT is feared that spalling occur inside. Therefore, this study made CFT specimen that determine the factor(which is strength of concrete) and then CFT column was exposed to heating controlled as closely as possible the ISO-834 standard fire curve. Also, it tried to analyze internal temperature through nonlinear transient heat flow analysis.

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Effect of Lubricant Additives on the Surface Fatigue Performance of Gear Oils

  • Hong, Hyun-Soo;Huston, Michael E.;Stadnyk, Nicholas M.
    • Tribology and Lubricants
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    • v.11 no.5
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    • pp.136-143
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    • 1995
  • The effect of additive chemistry on the serface fatigue of gears was investigated using the FZG gear tester and fluids based on an API GL-5 grade oil. Surface fatigue lives were determined as a function of load and additive chemistry. At 1.52 GPa, the removal of the primary extreme pressure additive (EP) from the fully formulated gear oil decreased the fatigue life of gears slightly (4%), however, the removal of the primary antiwear additive (AW) decreased the fatigue life of gears significantly (83%). At 1.86 GPa, the removal of the EP additive from the fully formulated gear oil decresed the gear fatigue life 27%, however, the removal of the primary AW additive decreased the fatigue life of gears significantly (75%). Micropitting was the dominant surface morphology in the dedendum of gears tested With two oils at load stage: one using the complete additive package, and a second where the EP additive has been removed. However, spalling is the primary failure mode of gears tested without an AW additive independent of whether an EP agent was present. Surface analysis of pinion gears showed the formation of a mixed phosphate/phosphite-oxide layer on the surface of gears tested with fluids containing an AW. Formation of this layer seems to be key to long fatigue life.

Structural performance of novel SCARC column under axial and eccentric loads

  • Zhou, Chunheng;Chen, Zongping;Li, Junhua;Cai, Liping;Huang, Zhenhua
    • Steel and Composite Structures
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    • v.37 no.5
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    • pp.503-516
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    • 2020
  • A novel spiral confined angle-steel reinforced concrete (SCARC) column was developed in this study. A total of 16 specimens were prepared and tested (eight of them were tested under axial loading, the other eight were tested under eccentric loading). The failure processes and load-displacement relationships of specimens under axial and eccentric loads were examined, respectively. The load-carrying capacity and ductility were evaluated by parametric analysis. A calculation approach was developed to predict the axial and eccentric load-carrying capacity of these novel columns. Results showed that the spiral reinforcement provided enough confinement in SCARC columns under axial and low eccentric loads, but was not effective in that under high eccentric loads. The axial load-carrying capacity and ductility of SCARC columns were improved significantly due to the satisfactory confinement from spirals. The outer reinforcement and other construction measures were necessary for SCARC columns to prevent premature spalling of the concrete cover. The proposed calculation approach provided a reliable prediction of the load-carrying capacity of SCARC columns.

Fire Resistance Behaviour of High Strength Concrete Members with Vapor Pressure and Creep Models (증기압 및 크리프 모델을 사용한 고강도콘크리트 부재의 내화성능평가)

  • Lee, Tae-Gyu
    • Fire Science and Engineering
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    • v.24 no.4
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    • pp.33-40
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    • 2010
  • A numerical model considering the vapor pressure and the creep models, in the form of a analytical program, for tracing the behavior of high strength concrete (HSC) members exposed to fire is presented. The two stages, i.e., spalling procedure and fire resistance time, associated with the thermal, moisture flow, creep and structural analysis, for the prediction of fire resistance behavior are explained. The use of the analytical program for tracing the response of HSC member from the initial pre-loading stage to collapse, due to fire, is demonstrated. The validity of the numerical model used in this program is established by comparing the predictions from this program with results from others fire resistance tests. The analytical program can be used to predict the fire resistance of HSC members for any value of the significant parameters, such as load, sectional dimensions, member length, and concrete strength.

Earthquake resistance of structural walls confined by conventional tie hoops and steel fiber reinforced concrete

  • Eom, Taesung;Kang, Sumin;Kim, Okkyue
    • Earthquakes and Structures
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    • v.7 no.5
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    • pp.843-859
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    • 2014
  • In the present study, the seismic performance of structural walls with boundary elements confined by conventional tie hoops and steel fiber concrete (SFC) was investigated. Cyclic lateral loading tests on four wall specimens under constant axial load were performed. The primary test parameters considered were the spacing of boundary element transverse reinforcement and the use of steel fiber concrete. Test results showed that the wall specimen with boundary elements complying with ACI 318-11 21.9.6 failed at a high drift ratio of 4.5% due to concrete crushing and re-bar buckling. For the specimens where SFC was selectively used in the plastic hinge region, the spalling and crushing of concrete were substantially alleviated. However, sliding shear failure occurred at the interface of SFC and plain concrete at a moderate drift ratio of 3.0% as tensile plastic strains of longitudinal bars were accumulated during cyclic loading. The behaviors of wall specimens were examined through nonlinear section analysis adopting the stress-strain relationships of confined concrete and SFC.

Thermal Shock Behavior of TiN Coating Surface by a Pulse Laser Ablation Method

  • Noh, Taimin;Choi, Youngkue;Jeon, Min-Seok;Shin, Hyun-Gyoo;Lee, Heesoo
    • Korean Journal of Metals and Materials
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    • v.50 no.7
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    • pp.539-544
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    • 2012
  • Thermal shock behavior of TiN-coated SUS 304 substrate was investigated using a laser ablation method. By short surface ablation with a pulse Nd-YAG laser, considerable surface crack and spalling were observed, whereas there were few oxidation phenomena, such as grain growth of TiN crystallites, nucleation and growth of $TiO_2$ crystallites, which were observed from the coatings quenched from $700^{\circ}C$ in a chamber. The oxygen concentration of the ablated coating surface with the pulse laser also had a lower value than that of the quenched coating surface by Auger electron spectroscopy and electron probe micro analysis. These results were attributed to the fact that the properties of the pulse laser method have a very short heating time and so the diffusion time for oxidation was insufficient. Consequently, it was verified that the laser thermal shock test provides a way to evaluate the influence of the thermal shock load reduced oxidation effect.

Experimental analysis of blast loading effects on security check-post

  • Muhammed Rizvan Akram;Ali Yesilyurt
    • Structural Engineering and Mechanics
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    • v.87 no.3
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    • pp.273-282
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    • 2023
  • Concrete construction, one of the oldest building practices, is commonly used in all parts of the world. Concrete is the primary building material for both residential and commercial constructions. The challenge of protecting the buildings, hence nation, against the attack of terrorism has raised the importance to explore the understanding of building materials against the explosion. In this research, a security check-post (reinforced concrete frame filled with plain cement concrete) has been chosen to study the behavior of structural elements under blast loading. Eight nitroglycerines-based dynamite blasts with varying amounts of explosive charge, up to 17 kg weight has been carried out at various scale distances. Pressure and acceleration time history records are measured using blast measuring instruments. Security check post after being exposed by explosive loading are photographed to view cracking/failure patterns on the structural elements. It is noted that with the increase of quantity of explosive, the dimensions of spalling and crack patterns increase on the front panels. Simple empirical analyses are conducted using ConWep and other design manuals such as UFC 3-340-02 (2008) and AASTP-1 (2010) for the purpose of comparison of blast parameters with the experimental records. The results of experimental workings are also compared with earlier researchers to check the compatibility of developed equations. It is believed that the current study presents the simple and preliminary procedure for calculating the air blast and ground shock parameters on the structures exposed to blast explosion.

A Study on Thermal Analysis with Strength Characteristics of HPC Column with Fiber Cocktail in KS Fire Curve (표준화재조건에서 Fiber Cocktail을 혼입한 고강도 콘크리트 기둥의 강도별 전열특성에 관한 연구)

  • Kim, Heung-Youl;Chae, Han-Sik;Kim, Hyung-Jun;Jeon, Hyun-Kyu;Youm, Kwang-Soo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.397-400
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    • 2008
  • To carry out this study efficiently, the material, physical and mechanical properties of the existing high temperature area was identified and the thermal transportation of structural elements was carried out through the finite element analysis method(ABAQUS) for 40 to 100 MPa high strength concrete based on Fiber Cocktail mixing. The results are as follows. First, it was analyzed that 40, 50 and 60 MPa high strength concretes have a thermal transportation properties similar to the analysis model of 30 MPa normal concrete. Second, it was analyzed that the analysis model of 80 and 100 MPa high strength concrete have slightly lower thermal transportation properties compared to normal model. Third, this study didn't consider the explosive spalling by the pore pressure within high strength concrete. If the properties for the pore pressure within high strength concrete is considered and database by strength and by inner temperature of various high strength concrete and steel materials are established in the future, it is interpreted that the technical foundation will be laid for performance-based design of fire-resistant construction.

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