• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.267-272
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• 1995

The objective of this study is to investigate the effect of concrete strength on the stirrup effectiveness factor(K) of reinforced concrete beams with stirrup based on previous test results(a/d$\geq$2.5). In the procedure of the estimation of K, it was assumed that the ultimate shear strength for beams without stirrup is equal to the concrete contribution to shear strength for beam with stirrup. A model equation for calculation the stirrup of compressive strength of concrete. It was shown that the stirrup effective factor of compressive strength of concrete. It wah shown that the stirrup effective factor is greater than 1.0 up to compressive strength 85MPa. Therefore the current ACI Code equation for predicting the shear strength and the stirrup effectiveness factor of 1.0 is conservative for nomal and high stength concrete beams with stirrup.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.275-278
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• 2005

This paper presents a model for evaluating the contribution by arch action and frame action to shear resistance in shear-critical reinforced concrete beams without stirrup. The rotating angle softened truss model is employed to calculate the shear deformation of the web and the relative axial displacement of the compression and tension chord by the shear flow are also calculated. From this shear compatibility condition in a beam, the shear contribution by the arch action is numerically decoupled. The transverse strain obtained from the proposed model is selected for shear failure criterion. Using the failure criterion, shear strength of RC slender beams without stirrup is predicted.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.891-896
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• 2000

It is necessary to drill new opening in an existing R.C beam either for service ducts and pipes or the determination of in place concrete strength. Therefore, to simulate in this study, 18-R.C beams were fabricated with circular openings. The major parameters considered are the sizes, location of opening and cut-off stirrup. These beams are tested shear failure and capacity under a point loading. The sizes of opening are changed 0.11, 0.2, 0.3 times of beam-depth and the locations of opening are divided into $X_1$ zone, $X_2$ zone, $X_3$zone. Loads are applied up to failure to observe the cracking initiation and propagation, initial diagonal cracking, midspan deflection. As a result, the sizes of opening with 0.11D and 0.2D in R.C beams without cutoff stirrup are profitable in $X_1$ and $X_3$zone. R.C beams with 0.3D and cutoff stirrup are advantageous in $X_3$zone.

• Magazine of the Korea Concrete Institute
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• v.8 no.6
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• pp.173-182
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• 1996

An experimental research was carried out to investigate the effect of thc compressive strength of concrete on the stirrup effectiveness in shear behavior of concrete beams. For this purpose. total 24 beams of section dimension of $300{\times}600mm$ were tested: 4 specimens without web reinforcement and 20 specimens with web reinforcement in the form of vertical stirrups. Main variables were two levels(norma1 and high strength) of the compressive strength of concrete and six types of t h e shear rcinfor.cement ratios. Prior to experiment, for given sections and assumed material constants, the reference shear reinforcement ratio(${\rho}_vACI$) which leads to the flexure failure using the provisions of the ACI Building Code(AC1 318-95) was calculated. and the shear reinforcement ratios were relatively selected from the value of ${\rho}_vACI$. From test results, it was shown that thc safety factor of ACI eyuation for p1,ediction of shear strength was decreased with increasing the compressive strength of concrete in beams without stirrups. However. it was observed that as the amount of' stirrup is increased, the safety factor for high strength conci,ete beams with high stirrup ratio is ensured more than that for normal strength concrete beams. Therefore i t appears that the stirrup effectiveness of high strength concrete beams is greater than that of normal strength concrete beams.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.6
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• pp.142-152
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• 2010

In this study, eleven reinforced concrete beams, without stirrup, using high ductile fiber-reinforced mortar with ground granulated blast furnace slag(SHF Series, SHFSC Series) and standard specimens without or with stirrup(SSS, BSS) were constructed and tested under monotonic loading. Experimental programs were carried out to improve and evaluate the shear performance of such test specimens, such as the load-displacement, the failure mode, the maximum strength, and shear strength. All the specimens were modeled in scale-down size. Test results showed that test specimens(SHF Series, SHFSC Series) was increased respectively the shear strength carrying capacity by 26%, 20% and the ductility capacity by 5.27, 5.75 times in comparison with the standard specimen without stirrup(SSS). And the specimens(SHF Series, SHFSC Series) showed enough ductile behavior and stable flexural failure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.3
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• pp.47-57
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• 2023

In this study, pull-out tests were performed to investigate the effects of stirrup spacing, rebar diameter, and corrosion rate on bond strength of deformed bars in reinforced concrete. Twelve pull-out specimens with different stirrup spacing, rebar diameter, and corrosion rate were prepared following the RILEM RC6 guidelines. The test results showed that the bond strength of specimens with stirrups increased when the corrosion rate was less than 3%, whereas it decreased when the corrosion rate was more than 3%. On the other hand, the bond strength of specimens without stirrups decreased as the corrosion rate increased. The effect of rebar diameter was less significant compared to those of stirrup spacing and corrosion rate. A bond strength model for pull-out specimens was proposed considering stirrup ratio and corrosion rate, and the model showed the lowest error among the previous models.

• Earthquakes and Structures
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• v.18 no.5
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• pp.581-598
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• 2020

This paper aims to investigate the seismic behavior and influence parameters of the large-scaled thin-walled reinforced concrete (RC) tubular columns in air-cooled supporting structures of thermal power plants (TPPs). Cyclic loading tests and finite element analysis were performed on 1/8-scaled specimens considering the influence of wall diameter ratio, axial compression ratio, longitudinal reinforcement ratio, stirrup reinforcement ratio and adding steel diagonal braces (SDBs). The research results showed that the cracks mainly occurred on the lower half part of RC tubular columns during the cyclic loading test; the specimen with the minimum wall diameter ratio presented the earlier cracking and had the most cracks; the failure mode of RC tubular columns was large bias compression failure; increasing the axial compression ratio could increase the lateral bearing capacity and energy dissipation capacity, but also weaken the ductility and aggravate the lateral stiffness deterioration; increasing the longitudinal reinforcement ratio could efficiently enhance the seismic behavior; increasing the stirrup reinforcement ratio was favorable to the ductility; RC tubular columns with SDBs had a much higher bearing capacity and lateral stiffness than those without SDBs, and with the decrease of the angle between columns and SDBs, both bearing capacity and lateral stiffness increased significantly.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.205-215
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• 2005

The main objective of this study is to investigate the behavior of NSC and HSC beams with stirrups. Main variables were the concrete compressive strength and amount of vertical stirrups. A total of 24 beams was tested; 4 beams without web reinforcement and 20 beams with web reinforcement in the form of vertical stirrups. Main variables were 2 different compressive strengths of concrete of 26.9MPa and 63.5MPa, 5 different spacing of stirrups of 200, 150, 120, 100 and 90mm. Therefore, the results were compared with the strengths predicted by the equations of ACI code 318-99 and other researchers. The shear reinforcement ratio, where the test beams were failed simultaneously under flexure and shear, were $0.63{\rho}_{vmax}$ for NSC beams and $0.53{\rho}_{vmax}$ for HSC beams, respectively. The ACI code equation was found to be very conservative for shear design.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.407-410
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• 2005

This paper describes an evaluation of reinforcement tension in RC beams using the variable truss models. The models were examined with the beam test results by Kim, Kim and White. Consequently, a fixed inclination $\theta$ at the support un-explains global state of internal force flow in cracked reinforced concrete beams subjected to shear and bending. Accordingly, we must introduce the arch factor for development of consistent model in reinforced concrete beams subjected to shear and bending

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.671-679
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• 2008

The near surface mounted (NSM) FRP strengthening method has been conventionally applied for strengthening the deteriorated concrete structures. The NSM strengthening method, however, has been issued with the problem of limitation of the cutting depth which is usually considered as concrete cover depth. This may be related with degradation of bonding performance in long-term service state. To improve the debonding problem, in this study, the Stirrup partial-cutting NSM (SCNSM) strengthening method using CFRP plate was newly developed. SCNSM strengthening method can be effectively applied to the deteriorated concrete structure without any troubles of insufficient cutting depth. To experimentally verify the structural behavior, the flexural test of the concrete beam by using the SCNSM strengthening method was conducted with the test variable as the strengthening length (32%, 48%, 70%, 80%, 96% of span length). In the result of the test, the NSM and SCNSM strengthened specimen showed similar structural behavior with load-deflection, mode of failure. Additionally, there was no apparent structural degradation by the stirrup partial-cutting. Consequently, it was evaluated that the SCNSM strengthening method can be useful for seriously damaged concrete structures that is hard to apply the conventional NSM strengthening method for increasing the structural capacity.