Comparative low-velocity impact response of textile-reinforced concrete and steel-fiber-reinforced concrete beams

Yoo, Doo-Yeol,Gohil, Udityasinh,Gries, Thomas,Yoon, Young-Soo SAGE Publications 2016 Journal of composite materials Vol.50 No.17

<P>In this study, the effect of the textile reinforcement type on the flexural response of textile-reinforced concrete beams under static and impact loads was investigated. In addition, to compare the flexural capacities with those of conventional steel-fiber-reinforced concrete, steel-fiber-reinforced concrete beams having similar compressive strength with that of textile-reinforced concrete were fabricated and tested according to the fiber content. Enhancements in the flexural capacities were obtained using polymer-coated textile reinforcement, and three-dimensional textile reinforcement resulted in slightly better flexural performance than two-dimensional textile reinforcement under both static and impact loads. Upon comparison with the results obtained from the steel-fiber-reinforced concrete beams, the textile-reinforced concrete specimen with polymer-coated textile reinforcement exhibited the best flexural performance in terms of the strength, toughness, and residual load carrying capacity (higher than or at least similar to those of the steel-fiber-reinforced concrete with a fiber volume content of 2%), whereas the textile-reinforced concrete specimens with uncoated textile reinforcement exhibited lower strength and toughness than those of the steel-fiber-reinforced concrete with a fiber volume content of 0.5%. Finally, the strain-rate sensitivity of the flexural strength for textile-reinforced concrete was found to be similar to that for steel-fiber-reinforced concrete.</P>

섬유보강 콘크리트의 역학적 특성에 대한 섬유 체적비와 길이의 영향

양근혁,오승진 한국건축시공학회 2008 한국건축시공학회지 Vol.8 No.1

Fifteen concrete specimens were mixed and tested to explore the significance and limitation of appling the polyvinyl alcohol (PVA) fiber and steel fiber with end hook to concrete. Main parameters investigated were volume fraction and length of the fibers. The measured mechanical properties of fiber reinforced concrete are analyzed according to the equivalent fiber amount index explaining the adding amount and length of fibers. Test results showed that compressive strength of fiber reinforced concrete was higher than that of concrete with no fiber by 10~20%. The normalized splitting tensile strength and flexural strength of PVA fiber reinforced concrete were similar to those of concrete with no fiber, whereas those of steel fiber reinforced concrete increased with the increase of the equivalent fiber amount index. In particular, much higher ductile behavior was observed in steel fiber reinforced concrete than in PVA reinforced concrete, indicating that the slope of descending branch of load-displacement relationship of steel fiber reinforced concrete decreased with the increase of the volume fraction and length of the fiber.

Seismic Performance Assessment of Hollow Reinforced Concrete and Prestressed Concrete Bridge Columns

Tae-Hoon Kim,Dai-Jeong Seong,Hyun Mock Shin 한국콘크리트학회 2012 International Journal of Concrete Structures and M Vol.6 No.3

The aim of this study is to assess the seismic performance of hollow reinforced concrete and prestressed concrete bridge columns, and to provide data for developing improved seismic design criteria. By using a sophisticated nonlinear finite element analysis program, the accuracy and objectivity of the assessment process can be enhanced. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), is used to analyze reinforced concrete and prestressed concrete structures. Tensile, compressive and shear models of cracked concrete and models of reinforcing and prestressing steel were used to account for the material nonlinearity of reinforced concrete and prestressed concrete. The smeared crack approach was incorporated. The proposed numerical method for the seismic performance assessment of hollow reinforced concrete and prestressed concrete bridge columns is verified by comparing it with the reliable experimental results. Additionally, the studies and discussions presented in this investigation provide an insight into the key behavioral aspects of hollow reinforced concrete and prestressed concrete bridge columns.

탄소섬유복합체 그리드 보강 콘크리트 기둥에 관한 연구 동향

윤현도(Yun, Hyun-Do),박완신(Park, Wan-Shin),김선우(Kim, Sun-Woo),김정은(Kim, Jeong-Eun) 대한건축학회 2022 대한건축학회논문집 Vol.38 No.11

Reinforced concrete is the most widely used construction material for building structures. However, the durability of this material is reduced due to various factors such as the cracking of concrete and corrosion of steel reinforcement. Fiber Reinforced Polymer (FRP) material, which is highly evaluated for its applicability as a concrete reinforcement, is known to be effective in enhancing the durability of structures. In this study, previous research on concrete column reinforced with carbon fiber reinforced polymer (CFRP) grid was reviewed. By analyzing these studies on replacing steel hoop, a concrete column reinforcement, with CFRP grid, it could provide reference data for future research on CFRP grid reinforced concrete columns and basic data necessary for designing CFRP grid reinforced concrete columns. The concrete column that replaced the steel hoop with the CFRP grid was divided into three categories: the column under concentric loading, the column subjected to bending and axial force, and the lateral confinement effect of the column. As a result, regarding behavior characteristics, there was no difference between ordinary steel hoop and CFRP grid; therefore, the possibility of substituting CFRP grid for ordinary steel reinforcement was confirmed. However, brittle fracture of the CFRP grid was observed during this experiment; further research on the improvement of joint strength of the CFRP grid edge joint is needed. Upon analyzing the proposed equation for the lateral confinement effect, it was found that the equations for estimating the ultimate strength of confinement concrete suggested by previous researchers could even be applied for the CFRP grid reinforced concrete column.

Corrosion Protection Method of Reinforcing Steel in Concrete by Using Corrosion Inhibitors

Bae Su-Ho,Chung Young-Soo,Kim Dae-Ho Korea Concrete Institute 2002 KCI concrete journal Vol.14 No.4

Reinforced concrete is inherently a durable composite material. When properly designed for the environment to be exposed and carefully constructed, reinforced concrete is capable of giving maintenance-free performance. However, unintentionally using improper materials such as non-washed sea sand having much salt together with poor controlled quality, or the concrete are placed in highly severe environment such as marine atmosphere, the corrosion of reinforcing steel in concrete becomes one of the most significant concerns of concrete. The purpose of this experimental research is to evaluate the performance of corrosion inhibitors for normal strength and high strength concrete, and to propose desirable measures for controlling corrosion of reinforcing steel in concrete. Test specimens in normal strength and high strength concrete were made with and without corrosion inhibitors. The accelerated corrosion test for reinforcing steel in concrete was adopted in accordance with JCI-SC3, which required the periodic 20 cycles for 140 days. One cycle includes 3 days for the wetting condition of $65^{\circ}C$ and $90\%$ RH, and 4 days for the drying condition of $15^{\circ}C\;and\;60\%$ RH. It was observed from the test that corrosion inhibitors in normal strength concrete and high strength concrete showed excellent corrosion resistance for reinforcing steel in concrete, but the silica fume in high strength concrete was found to have a negligible corrosion resistance if not used with corrosion inhibitors, since the chloride corrosion threshold limit in concrete containing silica fume without corrosion inhibitor was found to be considerably smaller than that of the case with corrosion inhibitor.

Seismic Performance Assessment of Hollow Reinforced Concrete and Prestressed Concrete Bridge Columns

Kim, Tae-Hoon,Seong, Dai-Jeong,Shin, Hyun Mock Korea Concrete Institute 2012 International Journal of Concrete Structures and M Vol.6 No.3

The aim of this study is to assess the seismic performance of hollow reinforced concrete and prestressed concrete bridge columns, and to provide data for developing improved seismic design criteria. By using a sophisticated nonlinear finite element analysis program, the accuracy and objectivity of the assessment process can be enhanced. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), is used to analyze reinforced concrete and prestressed concrete structures. Tensile, compressive and shear models of cracked concrete and models of reinforcing and prestressing steel were used to account for the material nonlinearity of reinforced concrete and prestressed concrete. The smeared crack approach was incorporated. The proposed numerical method for the seismic performance assessment of hollow reinforced concrete and prestressed concrete bridge columns is verified by comparing it with the reliable experimental results. Additionally, the studies and discussions presented in this investigation provide an insight into the key behavioral aspects of hollow reinforced concrete and prestressed concrete bridge columns.

Tensile Properties of Fiber Reinforced Concrete

Cho, Baik-Soon,Back, Sung-Yong,Park, Hyun-Jung Korea Concrete Institute 2000 KCI concrete journal Vol.12 No.2

Potentially significant mechanical improvements in tension can be achieved by the incorporation of randomly distributed, short discrete fibers in concrete. The improvements due to the incorporation fibers significantly influence the composite stress - strain ($\sigma$-$\varepsilon$) characteristics. In general incorporating fibers in a plain concrete has relatively small effect on its precracking behavior. It, however, alters its post-cracking behavior quite significantly, resulting in greatly improved ductility, crack controls, and energy absorption capacity (or toughness). Therefore, a thorough understanding the complete tensile stress - strain ($\sigma$-$\varepsilon$) response of fiber reinforced concrete is necessary for proper analysis while using structural components made with fiber reinforced concrete. Direct tensile stress applied to a specimen is in principle the simplest configuration for determining the tensile response of concrete. However, problems associated with testing brittle materials in tension include (i) the problem related to gripping of the specimen and (ii) the problem of ensuring centric loading. Routinely, indirect tension tests for plain concrete, flexural and split-cylinder tests, have been used as simpler alternatives to direct uniaxial tension test. They are assumed to suitable for fiber reinforced concrete since typically such composites comprise 98% by volume of plain concrete. Clearly since the post-cracking characteristics are significantly influenced by the reinforcing parameters and interface characteristics, it would be fundamentally incorrect to use indirect tensile tests for determining the tensile properties of fiber reinforced concrete. The present investigation represents a systematic look at the failure and toughening mechanisms and macroscopic stress - strain ($\sigma$-$\varepsilon$) characteristics of fiber reinforced concrete in the uniaxial tension test. Results from an experimental parametric study involving used fiber quantity, type, and mechanical properties in the uniaxial tension test are presented and discussed.

Interaction of magnetic water and polypropylene fiber on fresh and hardened properties of concrete

Mokhtar Ansari,Amir Safiey 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.39 No.3

Utilizing fibers is an effective way to avoid the brittle behavior of the conventional concrete and can enhance its ductility. In particular, propylene fibers can improve concrete properties, including energy absorption, physical and mechanical properties, controlling shrinkage cracks. The increase of fiber density leads to an increase of the overlapping surface of the fiber of concrete and, in turn, a decrease of cracks developed in the concrete. However, the workability of fiber reinforced concrete tends to be lower than the conventional concrete owing mainly to the hairline thickness and excessive concentration of fibers. The low slump of concrete impedes the construction of reinforced concrete members. In this research, we study if the utilization of magnetic water can alleviate the workability issue of young fiber reinforced concrete. To this end, the compressive and flexural strength of four types of concrete (conventional concrete, fiber reinforced concrete, magnetic concrete, magnetic fiber-reinforced concrete) is studied and compared at three different ages of 7, 14, and 28 days. In order to study the influence of the fiber density and length, a study on specimens with three different fiber density (1, 2, 5 kg of fiber in each cubic meter of concrete) and fiber length (6, 12, 18 mm) is undertaken. The result shows the magnetic fiber concrete can result in an increase of the flexural and compressive strength of concrete at higher ages.

Structural performance assessment of deteriorated reinforced concrete bridge piers

T.H. Kim 사단법인 한국계산역학회 2014 Computers and Concrete, An International Journal Vol.14 No.4

The aim of this study is to assess the structural performance of deteriorated reinforced concrete bridge piers, and to provide method for developing improved evaluation method. For a deteriorated bridge piers, once the cover spalls off and bond between the reinforcement and concrete has been lost, compressed reinforcements are likely to buckle. By using a sophisticated nonlinear finite element analysis program, the accuracy and objectivity of the assessment process can be enhanced. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), is used to analyze reinforced concrete structures. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. Advanced deteriorated material models are developed to predict behaviors of deteriorated reinforced concrete. The proposed numerical method for the structural performance assessment of deteriorated reinforced concrete bridge piers is verified by comparing it with reliable experimental results. Additionally, the studies and discussions presented in this investigation provide an insight into the key behavioral aspects of deteriorated reinforced concrete bridge piers.

Use of steel fibers as transverse reinforcement in diagonally reinforced coupling beams with normal- and high-strength concrete

Jang, Seok-Joon,Jeong, Gwon-Young,Yun, Hyun-Do Elsevier 2018 Construction & building materials Vol.187 No.-

<P><B>Abstract</B></P> <P>This study investigates the effects of using steel fibers as transverse reinforcement on the seismic performance of diagonally reinforced coupling beams that are composed of normal- and high-strength concrete. Four types of coupling beams were fabricated and tested under quasi-static reversed cyclic loading. A normal-strength reinforced concrete (RC) coupling beam with the compressive strength of 40 MPa was designed with the full confinement of a beam section according to ACI 318-14. A second RC coupling beam specimen with the same reinforcement details and concrete with the compressive strength of 80 MPa was fabricated also to evaluate the effects of strength. In addition, steel fiber was used in an attempt to simplify the complex details of transverse reinforcements for diagonally RC coupling beams. To this end, two fiber volume fractions of 1.0% and 1.25% were used for 40 MPa and 80 MPa steel fiber-reinforced concrete (SFRC) coupling beams, respectively. Test results indicated that the shear strength of the coupling beams increased with an increase in compressive strength, whereas the energy dissipation capacity was similar for the normal- and high-strength concrete RC coupling beams. Furthermore, this study found that the inclusion of steel fiber prevented buckling of the diagonal steel rebar as well as provided additional transverse reinforcement. The overall performance, including strength, stiffness degradation, and the energy dissipation capacity, of the SFRC coupling beams was similar to that of the conventional concrete coupling beams. Comparisons of the conventional concrete and SFRC beam specimens indicate that the use of steel fiber allows for the simplification of transverse reinforcement construction details for diagonally reinforced coupling beams.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The inclusion of steel fibers improves flexural behavior and toughness of concrete. </LI> <LI> SFRC significantly contributed to prevent the buckling of the diagonal reinforcement. </LI> <LI> Using fibers as transverse reinforcement improves constructability of coupling beam. </LI> <LI> Shear strength is well predicted considering contribution of diagonal concrete strut. </LI> </UL> </P>