• Proceedings of the Korea Concrete Institute Conference
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• 1990.04a
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• pp.122-127
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• 1990

The transfer of forces across the interface by bond between concrete and steel is of fundamental importance to many aspects of reinforced concrete behavior. Bond stress - slip relationships were studied using a symmetrical tension test specimen. This type of test is intented to simulate conditions in the tension zone of a concrete beam between primary cracks and below the neutral axis. These relationships between local bond stress and local slip are quite different at different locations along the bar. The present study allows more accurate analysis of reinforced concrete structures by employing more realistic bond stress-slip relations.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.357-360
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• 2002

A in-situ experiment was performed to evaluate the pullout resistance capacity of chains which is used as a reinforcement of reinforced earth wall. It was also considered that chain was combined with a bar or L-type steel angle by the transverse reinforcement member in the experiment. As a result of experiment, it is expected that chain can be safely used as reinforcements of reinforced earth wall, although it is concerned that a theoretical estimation of the pullout resistance capability of chain is too conservative.

• Advances in concrete construction
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• v.14 no.1
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• pp.45-55
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• 2022

In this article, the flexural and shear capacity of ultra-high-performance fiber-reinforced concrete beams (UHPFRC) using two kinds of rebars, including GFRP and steel rebars, are experimentally investigated. For this purpose, six UHPFRC beams (250 × 300 × 1650 mm) with three reinforcement ratios (ρ) of 0.64, 1.05, and 1.45 were constructed using 2% steel fibers by volume. Half of the specimens were made of UHPFRC reinforced with GFRP rebars, while the other half were reinforced with conventional steel rebars. All specimens were tested to failure in four-point bending. Both the load-deformation at mid-span and the failure pattern were studied. The results showed that utilizing GFRP bars increases the flexural strength of UHPFRC beams in comparison to those made of steel bars, but at the same time, it reduces the post-cracking strain hardening. Furthermore, by increasing the percentage of longitudinal bars, both the post-cracking strain hardening and load-bearing capacity increase. Comparing the experiment results with some of the available equations and provisions cited in the valid design codes reveals that some of the equations to predict the flexural strength of UHPFRC beams reinforced with conventional steel and GFRP bars are reasonably conservative, while Khalil and Tayfur model is un-conservative. This issue makes it essential to modify the presented equations in this research for predicting the flexural strength of UHPFRC beams using GFRP bars.

• Journal of Ocean Engineering and Technology
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• v.20 no.6 s.73
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• pp.1-6
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• 2006

Corrosion of reinforcing steel bars is a major concern for ocean engineers when reinforced concrete structures are exposed to marine environments. Evaluating the degree of corrosion and corrosion-induced defects is extremely necessary to pursue a proper retrofit or rehabilitation plan for reinforced concrete structures. A promising inspection should be carried out for the evaluation, otherwise the retrofit or rehabilitation process would be useless. Nowadays, ultrasonic guided wave-based inspection techniques become quite promising for the inspection, mainly because of their long-range propagation capability and their sensitivity to different types of defects or conditions. Evaluating haw the guided waves response to the different types of defects or conditions is quite challenging and important. This study shows how surface conditions of reinforcing bars and a corrosion-induced defect, separation, affect guided wave propagation in reinforced concrete. Experiments and associated signal analysis show the sensitivity of guided waves to the surface conditions, as well as the amounts of separation at the interface between. concrete and steel bar.

• Steel and Composite Structures
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• v.12 no.3
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• pp.261-273
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• 2012

This study proposes and examines a circular composite bridge pier for seismic resistance. The axial and flexural strengths of the proposed bridge pier are provided by the longitudinal reinforcing bars and the concrete, while the transverse reinforcements used in the conventional reinforced concrete pier are replaced by the steel tube. The shear strength of this composite pier relies on the steel tube and the concrete. This system is similar to the steel jacketing method which strengthens the existing reinforced concrete bridge piers. However, no transverse shear reinforcing bar is used in the proposed composite bridge pier. A series of experimental studies is conducted to investigate the seismic resistant characteristics of the proposed circular composite pier. The effects of the longitudinal reinforcing bars, the shear span-to-diameter ratio, and the thickness of the steel tube on the performance of strength, ductility, and energy dissipation of the proposed pier are discussed. The experimental results show that the strength of the proposed circular composite bridge pier can be predicted accurately by the similar method used in the reinforced concrete piers with minor modification. From these experimental studies, it is found that the proposed circular composite bridge pier not only simplifies the construction work greatly but also provides excellent ductility and energy dissipation capacity under seismic lateral force.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.126-127
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• 2018

Rebar work is important in terms of cost and process of reinforced concrete construction along with formwork and concrete construction, and the quality of reinforced concrete construction has a great influence on the safety and durability of the structure. Therefore it is important to thoroughly inspect the steel reinforcement after casting the concrete because it is difficult to confirm the actual condition of the reinforcement. The purpose of this study is to develop an augmented reality system to visualize the records of bar placing work, which is increasingly utilized in the construction field. In order to improve maintenance of reinforced concrete, this study suggests a plan to effectively manage the drawing information including the structural drawing, the placing drawing, and the photographed image at the construction and inspection stage, and develop a system that utilizes augmented reality technology that can display the state of the inside of a concrete structure by superimposing it on actual environment.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.187-188
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• 2023

In this study, the analysis of concrete cracks was conducted with a total of three variables: coating thickness, oxygen diffusion rate, and reinforced diameter of reinforced concrete structures. Cracks occurred after about 3, 4, and 6 years at the coating thickness of 30, 40, and 50mm when the coating thickness was used as a variable, and cracks occurred after about 4, 5, and 10 years at oxygen diffusivity of 2e-9, 2e-11, and 2e-12 (m²/s) when the oxygen diffusion rate was used as a variable. In the case of reinforcing bar diameters, cracks occurred after about 4, 3, and 2 years on the reinforcing bar diameters of D10, D19, and D25.

• Earthquakes and Structures
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• v.17 no.2
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• pp.205-219
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• 2019

In Peru, construction of dwellings using confined masonry walls (CM) has a high percentage of acceptance within many sectors of the population. It is estimated that only in Lima, 80% of the constructions use CM and at least 70% of these are informal constructions. This mean that they are built without proper technical advice and generally have a high seismic vulnerability. One way to reduce this vulnerability is by reinforcing the walls. However, despite the existence of some reinforcement methods in the market, not all of them can be applied massively because there are other parameters to take into account, as economical, criteria for seismic improvement, reinforcement ratio, etc. Therefore, in this paper the feasibility of using five reinforcement techniques has been studied and compared. These reinforcements are: welded mesh (WM), glass fiber reinforced polymer (GFRP), carbon fiber reinforced polymer (CFRP), steel bar wire mesh (CSM), steel reinforced grout (SRG). The Multi-Criteria Decision Making (MCDM) method can be useful to evaluate the most optimal strengthening technique for a fast, effective and massive use plan in Peru. The results of using MCDM with 10 criteria indicate that the Carbon Fiber Reinforced Polymer (CFRP) and Steel Reinforced Grout (SRG) methods are the most suitable for a massive reinforcement application in Lima.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.3
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• pp.19-25
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• 2019

The purpose of this study was to evaluate bending performance of concrete filled soldier pile for temporary retaining wall. Structural performance tests were conducted on total number of four specimens. Each specimen had a unique characteristics with combination of the following variables, existence of reinforcing bar and locations of reinforcing steel plates. The results of this study were as follows; concrete filled steel tubes with being reinforced bar and flange rather than non-bar showed better performance. Higher yield, tensile strength and sufficient plastic strain were archived and maximum moment observed in experiments exceeded theoretical maximum moment in both allowable stress design and limit state design at all specimens.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.3
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• pp.33-41
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• 2016

Concrete is inherently a good fire-resistance material among all other constrcution materials and protects the reinforcing steel inside. This study investigates the material characteristics of concrete and steel bar inside the full scale reinforced concrete(RC) beam exposed to fire test. The fire test specimen was 4 m long and the test was conducted under no loading condition following KS F 2257. Fire source is simulated by ISO 834 and number of thermocouples were installed to measure temperature variation of surfaces and inside of the beam. The measured compressive strength of cored specimen, which was exposed to fire test, was 11 MPa, about 66% lower than the strength before exposure. The yielding strength of steel bar also decreased about 75 MPa, about 17% lower. The measured temperature of protected steel bar was around $649^{\circ}C$, the critical limit, after 4 hour exposure.