A Case Study on Damage of Reinforced Earth Retaining Wall using Steel Bar

( Jong Nam Do ),( Nag Young Kim ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

Reinforced earth retaining walls were introduced in Korea at the end of the 1980s. Up to now, about 1200 have been constructed only on expressways. For the past 30 years, research on reinforced retaining walls has been carried out considerably. Various types of reinforced earth retaining wall front wall have been studied and reinforcement materials with various characteristics have been studied. This research was not completed by the research but it was applied to reinforced earth retaining wall in actual site and it was installed in every part of the highway. However, some of these reinforced retaining walls have been gradually causing problems. Damage occurred recently in reinforced earth retaining wall using reinforcement type reinforcing material. Most of the reinforcing materials of reinforced earth retaining walls are geosynthetics. However, the reinforced earth retaining wall where the damage occurred was especially made of steel bar. It is predicted that the construction applied to the reinforced earth retaining wall is applied to solve the problems occurring in the curved reinforced earth retaining wall because it is the curved portion of the wing wall of the abutment. However, the disadvantages of some construction methods, which were overlooked during construction, have been damaged. Therefore, in this study, the damage case of reinforced earth retaining wall using steel bar as reinforcing material was analyzed, and the field survey was introduced so that the repair and reinforcement plan could be presented.

Estimation Method of the Positions of Reinforcing Steel Bars by using Pulsed-Magnetization

Hori, Michitaka,Sana, Ryousuke,Komori, Mochimitsu 대한전기학회 2014 The Journal of International Council on Electrical Vol.4 No.4

Recently, the inspection of positions and depths of reinforcing steel bars in reinforced concrete structures is important. An electromagnetic induction method and an electromagnetic radiation radar method are used for inspection techniques of nondestructive. But, a general inspection technique also has the problem. Other techniques are actively researched now. Authors previously proposed a method of estimating position, depth and diameter of a single reinforcing steel bar by using the pulse-magnetization. In most cases reinforcing steel bars are usually found in more than one the reinforcing steel bars. Authors examined the method estimating the positions of reinforcing steel bars in more than one the reinforcing steel bars. The magnetization characteristic of the reinforcing steel bar was examined, Authors confirmed about the technique for estimating of the position of the reinforcing steel bar through the basic experiments and simulations, and report.

Effect of Different Environments on Bond Strength of Glass Fiber-Reinforced Polymer and Steel Reinforcing Bars

Jikai Zhou,Xudong Chen,Shixue Chen 대한토목학회 2012 KSCE JOURNAL OF CIVIL ENGINEERING Vol.16 No.6

The long-term durability of Glass Fiber-Reinforced Polymer (GFRP) bars in concrete need to be investigated and analyzed. This paper presents an experimental investigation into comparison of the durability of the bond between GFRP and steel reinforcing bars in concrete under different environment. For all bars, five environmental conditioning media were used. The bond strength after exposure was considered as a measure of durability of the bond between the bars and concrete. Ninety pullout specimens were used to study the effect of different environment on bond strength of GFRP and steel bars to concrete. Experimental results showed no indication of any bond degradation due to the continuous immersion in tap water, alkaline and salt solutions for ninety days. To the contrary the bond strength values of the conditioned specimens were comparable or slightly higher than the bond of the controlled specimens. The acid+chloride solutions have more detrimental effect on bond strength of GFRP bars in concrete. GFRP and steel bars have similar bond strength retention under alkaline environment. And the rate of bond degradation is very slow due to concrete reinforcement. The long-term durability of Glass Fiber-Reinforced Polymer (GFRP) bars in concrete need to be investigated and analyzed. This paper presents an experimental investigation into comparison of the durability of the bond between GFRP and steel reinforcing bars in concrete under different environment. For all bars, five environmental conditioning media were used. The bond strength after exposure was considered as a measure of durability of the bond between the bars and concrete. Ninety pullout specimens were used to study the effect of different environment on bond strength of GFRP and steel bars to concrete. Experimental results showed no indication of any bond degradation due to the continuous immersion in tap water, alkaline and salt solutions for ninety days. To the contrary the bond strength values of the conditioned specimens were comparable or slightly higher than the bond of the controlled specimens. The acid+chloride solutions have more detrimental effect on bond strength of GFRP bars in concrete. GFRP and steel bars have similar bond strength retention under alkaline environment. And the rate of bond degradation is very slow due to concrete reinforcement.

지지부재로 이형철근을 설치하는 띠형 강보강재의 인발성능 평가

정성규(Sung-gyu Jung),김주형(Juhyong Kim),조삼덕(Samdeok Cho),이광우(Kwangwu Lee) 한국지반신소재학회 2013 한국지반신소재학회 논문집 Vol.12 No.4

본 연구에서는 지지부재가 설치된 띠형 강보강재에 대한 실내인발시험을 수행하였다. 주문진 표준사를 사용하여 상대밀도 80%인 모형지반을 조성하였고, 지지부재의 개수를 0∼2개로 구분하여 실내인발시험을 수행하였다. 상재압은 50kN/m²∼200kN/m²까지 4단계로 구분하여 적용하였고, 1mm/min 속도로 강보강재를 인발하였다. 표면이 매끄러운 띠형 강보강재의 인발저항력은 보강재 표면과 지반 사이에서 마찰저항만 발현되기 때문에 인발 초기에 급격히 증가하다가 지속적으로 감소하는 경향을 나타낸다. 반면, 지지부재를 설치한 강보강재의 인발저항력은 마찰저항뿐만 아니라 수동저항도 함께 발현되므로 계속적으로 증가하는 것으로 나타났다. 보강재의 형태에 관계없이 최대인발저항은 상재압이 증가함에 따라 선형적으로 증가하는 것으로 나타났다. 지지부재를 1개 설치한 경우에 비해 지지부재를 2개 설치했을 때의 최대수동저항은 작게 나타났다. 이는 지지부재의 설치 간격 및 위치에 따라 지지부재에서 발현되는 수동저항의 크기가 다르기 때문에 나타나는 현상으로 판단되며, 지지부재 설치 위치 및 간격에 따른 추가 인발시험을 통해 확인할 필요가 있다. Laboratory pullout tests were conducted to evaluate pullout performance of steel strip reinforcements with deformed steel bars as transverse members. The steel strip reinforcement has an installation hole to assemble a deformed steel bar. Jumunjin standard sand is used to form a relative density of ground model to 80%. Frictional resistance of steel strip reinforcement without transverse member increases sharply at the initial displacement and quickly decreases with displacement. Maximum frictional resistance increases linearly as normal pressure increasing, and soil-reinforcement interaction friction angle(P_peak) of a steel strip reinforcement is estimated to 14.64°. Passive resistance increases with displacement and converge into maximum passive resistance in most cases. Maximum passive resistance increases linearly as normal pressure increasing irrespective of shape of the steel reinforcement. Pullout force of steel strip reinforcements with installation holes or transverse members largely increases about 4 to 7 times compared to frictional resistance force of steel strip reinforcements when embedment length(L_e) of steel strip reinforcements is 500 mm. In the case of using 2 transverse members, interference effect is observed due to the spacing of 2 transverse members and location of assembly holes and transverse members.

강섬유와 철근집합체 조합을 이용한 초고강도 섬유보강 철근 콘크리트 I형 보의 연성거동에 관한 실험

박진영,한상묵 한국구조물진단유지관리공학회 2016 한국구조물진단유지관리공학회 논문집 Vol.20 No.1

본 논문은 강섬유의 일부를 철근집합체로 대체하여 초고강도 섬유보강 철근 콘크리트 I 형보의 연성거동을 유도하는 것을 목적으 로 한다. 강섬유와 철근집합체의 조합을 가진 초고강도 콘크리트 I 형보 대한 휨거동 실험을 수행하였다. 강섬유의 혼입률은 0%, 0.7%, 1%, 1.5%, 2%이다. 철근집합체와 PS강연선 집합체가 압축구역에서 콘크리트를 구속하기 위해 사용되었다. 철근집합체와 강연선 집합체의 길이 도 실험요소 중 하나이다. 이러한 실험요소를 조합하여 9개의 초고강도 철근 콘크리트 I 형보를 제작하였다. 강섬유 뿐만 아니라 종방향의 철근 집합체도 초고강도 철근 콘크리트 I형 보의 연성거동을 유도하는데 효과를 가지고 있다. 강섬유 혼입률 0.7% 또는 1%와 철근집합체를 사용한 조합이 I형 보의 효과적인 연성 거동을 보여주고 있다. 하중과 처짐관계 및 균열양상 등이 좁은 간격을 가진 작은 직경의 종방향 철근 집합체의 유용성을 나타내고 있다. The purpose of this study is to induce the ductile behavior of the Ultra High Perfomance Concrete Reinforced I beam by substituting the part of steel fiber for bundle of reinforcing bars. Experiment of flexural behavior of the Ultra High Performance Concrete I shaped beam with the combination of the steel fiber and bundle of reinforcement bars was carried out. The volume fractions of steel fiber are 0%, 0.7%, 1%, 2%. The bundle of reinforcing bars and prestressing wire are used to restrain the concrete in compression zone. Length of bundle of reinforcing bar and prestressing wire is the one of test factors. The 9 Reinforced UHPC I shaped beam were made with these test factors. Not only steel fiber but also bundle of longitudinal reinforcing bar has effect to induce the ductile behavior of Reinforced UHPC I beam. The combination of 0.7% or 1.0% steel fiber and bundle of reinforcing bar showed the effective ductile behavior of I beam. The relationship of load-deflection and the crack pattern indicate the usefulness of the bundle of the longitudinal bar which has small diameter with close arrangement each other.

Investigation of Mechanical Properties of Ribbed Reinforcement Steel Bars: A Case Study on Ethiopian Construction Industry

Tariku Achamyeleh,Yusuf Şahin 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.5

This paper presents the annual report of the mechanical properties of ribbed reinforcement bars from construction sites taking projects as the case in and around Amhara, Ethiopia. Both imported and locally produced re-bars are used in the analysis without consideration of their varieties in the quality of the two sources. This paper focused on only with reinforcement bars of diameter 8, 10, 12 and 16 mm that accounted for 67% of the total tests. Using Universal Testing Machine, strength properties such as ultimate tensile strength (UTS), yield strength (YS), percentage elongation at fracture (%) and linear mass density property (kg/m) of steel reinforcing bars were analyzed for rebar diameters of 10, 12, 8 and 16 mm. Moreover, the results were analyzed by one-way analysis of variance (ANOVA). The results showed that the mean values of YS and UTS of all diameters surpassed the standard values recommended limit set by BS449: 1997 and ASTMA706. In addition, the mean values of percentage elongations for all tested steel products surpassed the 12% limit recommended by BS 449, 10% by ASTM A706 for all diameters. However, the mean mass per length values for 8, 10, 12 and 16 mm were below standard values set by ASTM A615/A615M. Furthermore, ANOVA indicated that the reinforced bars appeared to be dissimilar in terms of UTS and YS with 95% confi dence, but the reinforced bars were similar to the elongation percentage.

강섬유와 철근집합체 조합을 이용한 초고강도 섬유보강 철근 콘크리트 I형 보의연성거동에 관한 실험

박진영,한상묵 한국구조물진단유지관리공학회 2016 한국구조물진단유지관리공학회 논문집 Vol.20 No.1

The purpose of this study is to induce the ductile behavior of the Ultra High Perfomance Concrete Reinforced I beam by substituting thepart of steel fiber for bundle of reinforcing bars. Experiment of flexural behavior of the Ultra High Performance Concrete I shaped beam with thecombination of the steel fiber and bundle of reinforcement bars was carried out. The volume fractions of steel fiber are 0%, 0.7%, 1%, 2%. The bundleof reinforcing bars and prestressing wire are used to restrain the concrete in compression zone. Length of bundle of reinforcing bar and prestressingwire is the one of test factors. The 9 Reinforced UHPC I shaped beam were made with these test factors. Not only steel fiber but also bundle of longitudinalreinforcing bar has effect to induce the ductile behavior of Reinforced UHPC I beam. The combination of 0.7% or 1.0% steel fiber and bundle ofreinforcing bar showed the effective ductile behavior of I beam. The relationship of load-deflection and the crack pattern indicate the usefulness of thebundle of the longitudinal bar which has small diameter with close arrangement each other. 본 논문은 강섬유의 일부를 철근집합체로 대체하여 초고강도 섬유보강 철근 콘크리트 I 형보의 연성거동을 유도하는 것을 목적으로 한다. 강섬유와 철근집합체의 조합을 가진 초고강도 콘크리트 I 형보 대한 휨거동 실험을 수행하였다. 강섬유의 혼입률은 0%, 0.7%, 1%,1.5%, 2%이다. 철근집합체와 PS강연선 집합체가 압축구역에서 콘크리트를 구속하기 위해 사용되었다. 철근집합체와 강연선 집합체의 길이도 실험요소 중 하나이다. 이러한 실험요소를 조합하여 9개의 초고강도 철근 콘크리트 I 형보를 제작하였다. 강섬유 뿐만 아니라 종방향의 철근집합체도 초고강도 철근 콘크리트 I형 보의 연성거동을 유도하는데 효과를 가지고 있다. 강섬유 혼입률 0.7% 또는 1%와 철근집합체를 사용한조합이 I형 보의 효과적인 연성 거동을 보여주고 있다. 하중과 처짐관계 및 균열양상 등이 좁은 간격을 가진 작은 직경의 종방향 철근 집합체의유용성을 나타내고 있다.

Development Strength of Headed Reinforcing Bars for Steel Fiber Reinforced Concrete by Pullout Test

김승훈,백성철,이창용,육현웅,이용택 대한건축학회 2018 Architectural research Vol.20 No.4

In order to compare the development performance of headed reinforcing bar and straight reinforcing bar in tension for steel fiber reinforced concrete (SFRC), pullout test of specimens with reinforcing bar which was anchored on simple beam perpendicularly was conducted. The experimental variables were steel fiber volume ratio (VRsf), concrete compressive strength, and existence of head. As the result of test, splitting failure of concrete in the development direction of reinforcing bar in most specimens was observed. For development detail of headed reinforcing deformation bar, specimens with 1% VRsf showed approximately 63%~119% increase in pullout strength compare to specimens with 0% VRsf. Test result shows that SFRC is more effective in increasing pullout strength for headed reinforcing bars than increasing pullout strength of straight bars.

'Invited Paper' Computer-aided alloy designs of grade 600 MPa reinforced steel bars for seismic safety based on thermodynamic and kinetic calculations: Overview

Shim, Jae-Hyeok,Hwang, Byoungchul,Lee, Myoung-Gyu,Lee, Joonho Elsevier 2018 CALPHAD, computer coupling of phase diagrams and t Vol.62 No.-

<P><B>Abstract</B></P> <P>In order to satisfy the demands for both safety and global warming reduction, a high-strength seismic reinforced steel bar is required in the structural steel market. Recent developments in computational thermodynamics and related application software have made it possible to design a suitable material as well as support engineers of steel manufacturing companies in the production of the designed material with minimum benchmarks in practical operations. This paper reports our recent success in developing grade 600 MPa reinforced steel bars for seismic safety in South Korea. First, conventional alloy design based on CALPHAD-type computational thermodynamics was carried out. For this purpose, a typical alloy system of Fe-0.30C-0.23Si-1.37Mn-0.14V-0.22Cu (in wt%) was selected, and thermodynamic and kinetic calculations were carried out using MatCalc and JMatPro software. Second, in order to reduce V content in the steel for economic reasons, a cooling process designed using finite element (FE) simulation based on the thermodynamic database was performed. For this application, Fe-0.34C-0.22Si-1.34Mn-0.04 V (in wt%) alloy was chosen, and the FE software ABAQUS was applied for modeling the TempCore process. The mechanical properties of the steel products with a diameter of 32 mm produced based on the simulated results satisfy the required properties for grade 600 MPa seismic reinforced steel bars.</P>

Effects of Steel Fiber Reinforcement and the Number of Hooked Bars at R/C Exterior Joints

Choi, Ki-Bong Korea Concrete Institute 1999 KCI concrete journal Vol.11 No.3

An experimental study was performed on the Pull-out behavior of 90-deg standard hooks from the exterior beam-column connections. the effects of the number of hooked bars and fiber reinforcement of the joint area were investigated with the following conclusions : (1) Under the pull-out action of hooked bars. the damage and cracking of joint area the number of hooks pulling out from a joint increases; (2) Substitution of the transverse column (confining) reinforcement with steel fibers at the joint region effectively reduces the extent of cracking in exterior joints caused by the pull-out of hooked bars; (3) The pull-out strength and post-peak ductility of hooked bars are adversely influenced by the increase in number of hooks pulling out from an exterior joint. Current hooked bar anchorage design guidelines may be improved by considering the effect of the number of hooked bars on anchorage conditions at the exterior joints; and (4) The strength and ductility of hooked bars under pull-out forces are positively influenced by substituting the conventional confining reinforcement of exterior joints with steel fibers . The application of steel fibers to the exterior joints is an effective technique for improving the anchorage conditions of hooked bars, and also for reducing the congestion of reinforcement in the beam-column connections.