• Journal of the Korea Concrete Institute
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• v.17 no.3 s.87
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• pp.435-444
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• 2005

This paper predicted the shear behavior of reinforced concrete columns using Transformation Angle Truss Model (TATM) considered the effects of bending moment and axial force. Nine columns with various shear span- to-depth ratios and axial force ratios were tested to verify the theoretical results obtained from TATM. Fine linear displacement transducers (LVDT) were attached to a side of the column near the shear critical region to measure the curvature, the longitudinal and transverse axial deformations, and the shear deformation of the column. The test was terminated when the value of the applied load dropped to about $85\%$ of the maximum-recorded load in the post-peak descending branch. All the columns were failed in shear before yielding of the flexural steel. The shear strength and the stiffness of the columns increased, as the axial force increased and the shear span-to-depth ratio decreased. Shear stress-shear strain and shear stress-strain of shear reinforcement curves obtained from TATM were agreed well with the test results in comparison to other truss models (MCFT, RA-STM, and FA-STM).

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.1-8
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• 2020

This study presents a shear strength estimation model, in which the shear failure of a reinforced concrete (RC) member is assumed to be governed by the flexure-shear mechanism. Two shear demand curves and corresponding potential capacity curves for cracked tension and uncracked compression zones are derived, for which the bond mechanism developed between reinforcing bars and surrounding concrete is considered in flexural analysis. The shear crack concentration factor is also addressed to consider the so-called size effect induced in large RC members. In addition,unlike exising methods, a new formulation was addressed to consider the interaction between the shear contributions of concrete and stirrup. To verify the proposed method, an extensive shear database was established, and it appeared that the proposed method can capture the shear strengths of the collected test specimens regardless of their material properties, geometrical features, presence of stirrups, and bond characteristics.

• Computational Structural Engineering
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• v.3 no.3
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• pp.20-24
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• 1990

현재까지의 철근콘크리트(R/C)부재의 이력거동을 예측하기 위한 이론적 연구는 대부분이 휨 변위량이 전체 변위량을 지배한다는 가정하에 휨 해석을 행하고 있다. 그러나 지진과 같은 탄성한계를 벗어난 강한 동적반복하중을 받는 경우 철근 콘크리트 부재의 변위량은 휨 변위량 뿐만 아니라 전단 변위량 및 부재연결부에서의 회전 변위량에 의해 지배됨이 많은 연구를 통해 밝혀졌다. 전단이력거동은 강성과 강도저하가 심하게 나타나고 낮은 에너지 발산능력을 갖는 특징에 의해 휨 이력거동과는 구별되며 반복하중이 계속되면 강성이 저하되는 경향때문에 전단변형이 R/C부재의 거동을 지배하게 된다. 이러한 부재거동의 특징에 견주어 볼 때 현재 사용되고 있는 해석모델을 이용하여 동적응답을 예측하고, 해석하여 설계된 기존의 R/C부재는 강한 동적하중을 받을 경우 해석적으로는 전혀 예측치 못하게 되는 결과를 초래하게 된다.

• Journal of Korean Society of Steel Construction
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• v.24 no.5
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• pp.535-547
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• 2012

PSRC column is a concrete encased steel angle column. In the PSRC column, the steel angles placed at the corner of the cross-section resists bending moment and compression load. The lateral re-bars welded to steel angles resist the column shear and the bond between the steel angle and concrete. In the present study, current design procedures in KBC 2009 were applied to the flexure-compression, shear, and bond design of the PSRC composite column. To verify the validity of the design method and failure mode, simply supported 2/3 scaled PSRC and correlated SRC beams were tested under two point loading. The test parameters were the steel angle ratio and lateral bar spacing. The test results showed that the bending, shear, and bond strengths predicted by KBC 2009 correlated well with the test results. The flexural strength of the PSRC specimens was much greater than that of the SRC specimen with the same steel ratio because the steel angles were placed at the corner of the column section. However, when the bond resistance between the steel angle and concrete was not sufficient, brittle failures such as bond failure of the angle, spalling of cover concrete, and the tensile fracture of lateral re-bar occurred before the development of the yield strength of PSRC composite section. Further, if the weldability and toughness of the steel angle were insufficient, the specimen was failed by the fracture of the steel angle at the weld joint between the angle and lateral bars.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.3
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• pp.77-84
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• 2021

In this study, flexural tests of prestressed high strength spun concrete (PHC) piles reinforced with infilled concrete and longitudinal rebars were conducted, where the longitudinal rebar ratio and the presence of sludge formed on the inner surface of PHC pile were set as key test variables. A total of six PHC pile specimens were manufactured, and their flexural behaviors including failure mode, crack pattern, longitudinal strain distribution in a section and end slip between external PHC pile and infilled concrete were measured and discussed in detail. The test results revealed that the flexural stiffness and strength increased as the longitudinal rebar ratio became larger, and that the sludge formed on the inner surface of PHC pile did not show any detrimental effect on the flexural performance. In addition to the experimental approach, this study presents a nonlinear flexural analysis model considering compatibility conditions and strain and stress distributions of the PHC piles and infilled concrete. The rationality of the nonlinear flexural analysis model was verified by comparing it with test results, and it appeared that the proposed model well evaluated the flexural behavior of PHC piles reinforced with infilled concrete and longitudinal rebars with a good accuracy.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.934-941
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• 2002

It is important to consider the effect of member size when estimating the ultimate strength of a concrete flexural member because the strength always decreases with an increase of member size. In this study, the size effect of a reinforced concrete (RC) beam was experimentally investigated. For this purpose, a series of beam specimens subjected to four-point loading were tested. More specifically, three different effective depth (d$\approx$15, 30, and 60 cm) reinforced concrete beams were tested to investigate the size effect. The shear-span to depth ratio (a/d=3) and thickness (20 cm) of the specimens were kept constant where the size effect in out-of-plane direction is not considered. The test results are curve fitted using least square method (LSM) to obtain parameters for the modified size effect law (MSEL). The analysis results show that the flexural compressive strength and the ultimate strain decrease as the specimen size increases. In the future study, since $\beta_1$ value suggested by design code and ultimate strain change with specimen size variation, a more detailed analysis should be performed. Finally, parameters for MSEL are also suggested.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.4
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• pp.9-14
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• 1989

A strain rate-dependent element model was used to study the loading rate-sensitivity of R/C beams and columns with different design factors. Conclusions were derived regarding the differences between the element axial/flexural performance under impulsive and quasi-static loads. Practical design formalas for predicting the loading rate-dependent axial and flexural strengths of R/C elements were also suggested.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.9-10
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• 2015

Generally significant reinforcement is used in nuclear power plant structures and may cause potential problems when concrete is poured. In particular pouring concrete into structural member joint area is more difficult than other areas since the joint area is very congested due to the crossed bars and the embedded plates, The purpose of this study is to solve these problems by applying Gr.80(550MPa) shear bars to containment structures of nuclear power plant. In order to apply them to containment structures, it is necessary to change ASME-CC code (ASME Sec.III Div.2). The structural performance tests of wall & beam have been done to compare Gr.80(550Mpa) with Gr.60(420MPa) shear bars. The test results and code change proposal were presented to ASME-CC Committee last year and the discussion for code change will be expected to proceed in the near future.

• Journal of Korean Society of Steel Construction
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• v.24 no.2
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• pp.137-147
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• 2012

This paper describes an experimental study on the mechanical characteristic and behavior of a structure that has a joint between the reinforced concrete (RC) member and steel plate concrete (SC) member. An out-of-plane flexural test on an L-type test specimen and in-plane shear test on an I-type test specimen were carried out by means of repeated cyclic loading until their failure. Based on the results, the former showed pull-out failure mode of anchored vertical bars while the latter exhibited flexural failure mode of the basement member. These results reveal that the maximum capacity of the specimens is 96% and 82%, respectively, compared with the theoretical value.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.136-143
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• 2015

Galvanizing is one of the method used to solve the problem of corrosion of reinforcement in concrete structures. There few research reported in the literature regarding the effect of galvanized coating on the behavior of lap splices in concrete beams. The objective of this study was to determine whether galvanized rebar adversely affects lap splice behavior and bond strength. Concrete beams reinforced with black or galvanized rebar were tested in flexure. The test variables included the presence of galvanized rebar steel diameter, and lengths of lap splices. The study concentrated on comparing crack, failure pattern, and bond strength. The ultimate behavior of beams reinforced with galvanized rebar was not significantly different from that of black steel reinforced beams. Therefore, the test results indicated that the use of galvanizing-coated rebar had no adverse effect on behavior in lap splices of rebar compared to the use of black rebar.