• Structural Engineering and Mechanics
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• v.44 no.5
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• pp.649-661
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• 2012

An experimental research was conducted to investigate the strength of biaxially loaded short and slender reinforced concrete columns with high strength concrete. In the study, square and L-shaped section reinforced concrete columns were constructed and tested to obtain the load-deformation behaviour and strength of columns. The test results of column specimens were analysed with a theoretical method based on the fiber element technique. The theoretical ultimate strength capacities and the test results of column specimens have been compared and discussed in the paper. Besides this, observed failure mode and experimental and theoretical load-lateral deflection behaviour of the column specimens are presented.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.202-205
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• 2006

Three reinforced concrete shear wall and infilled shear wall using retrofitting system were constructed and tested under both vertical and cyclic loadings, Experimental programs were carried out to evaluate and improve the seismic performance of such test specimens, such as the hysteretic behavior, the maximum horizontal strength, crack propagation, and ductility etc. under load reversals. All the specimens were modeled in one-third scale size. For specimens(RWAHC, RWXHC) designed by the improving of seismic performance using the high ductile fiber composite mortar, anchoring, and advanced detailing system for the reinforced concrete shear wall load-carrying capacities were increased $1.1{\sim}1.22$ times in comparison with the standard specimen(SRW).

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.295-299
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• 1996

Intrinsic Fabry-Perot Optical fiber sensors were embedded to tensile side of the 20cm$\times$20cm$\times$150cm cement concrete structures. The sensors were attached to the reinforcing steels and then, the cement concretes were applied. It took 30 days for curing the specimens. After that, the specimens were tested with 4-point bending method by universal testing machine. Strains were measured and recorded by the strain gauges embedded near optical fiber sensors. Output data of fiber sensor showed good linearity to the strain data from the strain gauges up 2000microstrain. The optical fiber sensors showed good response after yielding of structure while embedded metal film strain gauges did not show any response. We also specimens were broken down. In conclusion, the optical fiber sensors can be used as elements of health monitoring systems for cement concrete infra-structures.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.890-895
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• 2003

The purpose of this experimental study is to investigate the influence of shear span-to-depth ratio on the minimum shear reinforcement ratio of reinforced concrete beams. In this study, 7 reinforced concrete beam specimens were tested. The parameters of experiment are shear span-to-depth ratio(a/d=2.0, 3.0, 4.0) and shear reinforcement ratio($p_v$=0%, 0.183%, and 0.233%). The section of all secimens was 350mm width and 450mm depth. The observed results were compared with the calculated results by the current ACI 318-02 Building Code and the proposed equation. The safety rate of the specimens, L5S2A, L5S3A, L5S4A, and L5S4P specimens were 1.80, 1.25, 1.38, and 1.56 respectively. The test results indicated that the shear behavior of reinforced concrete beams with the minimum shear reinforcement was influenced by the shear span-to-depth ratio.

• Journal of the Korea Institute of Building Construction
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• v.4 no.2
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• pp.89-95
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• 2004

1) As result of specimen with shear reinforcing bar of reinforced concrete beam, ductile coefficient of specimen was high in specimen containing Cockle shells based on non-mixed specimen. In increase rate of specimens, yield strength was similar in specimens containing Cockle shells and non-mixed specimens and maximum strength was higher in specimen containing Cockle shells. 2) To sum up the above experimental results, it is found that using splitted Cockle shells as aggregate for concrete by 10%～ 15% showed the same or higher compressive strength and shear strength as concretes using general aggregate and it can be used as substitute aggregate of concrete. It is considered that for future use of splitted Cockle shells as substitute concrete aggregate, continuous researches of its durability, applicability and economy are needed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.2
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• pp.93-102
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• 2001

The objective of this experimental study is to evaluate the strengthening effects of concrete compression confined with Epoxy-boned compound fiber sheets. An analytical model is proposed to construct a stress-strain relationship for confined concrete. Test results are summarized as followed. While non-FRP lateral confinement specimens appeared sudden failure after shell concrete was torn off, specimens confined laterally with FRP were showed that their failure. Specially, Glass fiber lateral confined specimens occurred obviously increase ductility ability. Hence, concrete specimen with lateral confinement by Hi-carborn and Aramide. Glass fiber simultaneously can be increased in not only strength but also a lot of ductility ability.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.127-130
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• 2005

The purpose of this study is to investigate the flexural behavior of reinforced concrete beam members exposed to high temperature. In order to study the flexural behaviors, the 17 specimens have been tested with variables of reinforcement ratios($0.5\rho_{max},\rho_{min}$), heating conditions(nonheating, 400$^{circ}C$, 600$^{circ}C$, 800$^{circ}C$ heating and 1 hour preservation) and loading state(stressed and residual state). The results show that the stiffness and strength of specimens are lower when they are exposed to higher temperature and the pattern of crack and color of specimens exposed to fire are different from ordinary concrete members.

• Structural Engineering and Mechanics
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• v.87 no.3
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• pp.201-210
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• 2023

This paper investigates the flexural behavior of reinforced recycled aggregates concrete (RRAC) beams after exposed to high temperatures. The experimental results from 17 specimens were present and compared with temperatures, recycled coarse aggregate (RCA) replacement percentages, and concrete strength as variables. It was found that the high temperature would not cause an observable change in the failure pattern. However, high temperature can significantly reduce the stiffness and ductility, and accelerate the damage degradation of specimens. After exposure to 600℃, the ultimate bearing capacity of the specimens decreased by 20%-30% The mechanical properties of RRAC beams after high temperatures were barely impacted by the replacement percentages. Increasing the concrete strength of RCA could effectively improve the bearing capacity and peak deflection of RRAC beams after exposed to high temperatures. Furthermore, the calculation method of the bending bearing capacity and deflection of RRAC beams was also discussed.

• Structural Engineering and Mechanics
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• v.64 no.2
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• pp.243-257
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• 2017

Investigating the properties and durability of high-strength concrete exposed to sulfuric acid attack for the purpose of its application in structures exposed to this acid is of outmost importance. In this research, the resistance and durability of high-strength concrete containing macro-polymeric or steel fibers together with the pozzolans of silica fume or nano-silica against sulfuric acid attack are explored. To accomplish this goal, in total, 108 high-strength concrete specimens were made with 9 different mix designs containing macro-polymeric and steel fibers at the volume fractions of 0.5, 0.75, and 1.0%, as well as the pozzolans of silica fume and nano-silica with the replacement levels of 10 and 2%, respectively. After placing the specimens inside a 5% sulfuric acid solution in the periods of 7, 21, and 63 days of immersion, the effect of adding the fibers and pozzolans on the compressive properties, ultrasonic pulse velocity (UPV), and weight loss of high-strength concrete was investigated and the respective results were compared with those of the reference specimens. The obtained results suggest the dependency of the resistance and durability loss of high-strength concrete against sulfuric acid attack to the properties of fibers as well as their fraction in concrete volume. Moreover, compared with using nano-silica, using silica fume in the fibrous concrete mix leads to more durable specimens against sulfuric acid attack. Finally, an optimum solution for the design parameters where the crushing load of high-strength fibrous concrete is maximized was found using response surface method (RSM).

• Advances in concrete construction
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• v.6 no.2
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• pp.199-220
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• 2018

In this study, the effects of sulphuric acid on the mechanical performance and the durability of Engineered Cementitious Composites (ECC) specimens were investigated. The carbon fiber reinforced polymer (CFRP) and basalt fiber reinforced polymer (BFRP) fabrics were used to evaluate the performances of the confined and unconfined ECC specimens under static and cyclic loading in the acidic environment. In addition, the use of CFRP and BFRP fabrics as a rehabilitation technique was also studied for the specimens exposed to the sulphuric acid environment. The polyvinyl alcohol (PVA) fiber with a fraction of 2% was used in the research. Two different PVA-ECC concretes were produced using low lime fly ash (LCFA) and high lime fly ash (HCFA) with the fly ash-to-OPC ratio of 1.2. Unwrapped PVA-ECC specimens were also produced as a reference concrete and all concrete specimens were continuously immersed in 5% sulphuric acid solution ($H_2SO_4$). The mechanical performance and the durability of specimens were evaluated by means of the visual inspection, weight change, static and cyclic loading, and failure mode. In addition, microscopic changes of the PVA-ECC specimens due to sulphuric acid attack were also assessed using scanning electron microscopy (SEM) to understand the macroscale behavior of the specimens. Results indicated that PVA-ECC specimens produced with low lime fly ash (LCFA) showed superior performance than the specimens produced with high lime fly ash (HCFA) in the acidic environment. In addition, confinement of ECC specimens with BFRP and CFRP fabrics significantly improved compressive strength, ductility, and durability of the specimens. PVA-ECC specimens wrapped with carbon FRP fabric showed better mechanical performance and durability properties than the specimens wrapped with basalt FRP fabric. Both FRP materials can be used as a rehabilitation material in the acidic environment.