• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.4
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• pp.139-146
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• 2002

A analysis of crack behavior in RC member was performed by nonlinear finite element method. Two crack models were used in F.E.M.(finite element method): one was FCM (the fixed crack model) and the other was RCM (the rotated crack model). Based on parametric study, the ratio of shear steel, strength of concrete, and a/d(shear span/effective depth) were compared with test results of references. According to the test results, when the member behavior was affected by the shear or diagonal tension, RCM was reasonable. However, when the behavior was affected by the flexibility, FCM was more appropriate. In addition, each crack model behavior for the change of shear steel ratio, the increase of strain energy was constant in FCM, but it was different in RCM because of diagonal crack distribution and crack width. Since the strength of concrete is affected not only by shear but also by flexural strength, each crack model behavior yields similar results.

• Structural Engineering and Mechanics
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• v.15 no.2
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• pp.181-198
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• 2003

Six large scale models of conventionally reinforced concrete coupling beams with span/depth ratios ranging from 1.17 to 2.00 were tested under monotonically applied shear loads to study their nonlinear behavior using a newly developed test method that maintained equal rotations at the two ends of the coupling beam specimen and allowed for local deformations at the beam-wall joints. By conducting the tests under displacement control, the post-peak behavior and complete load-deflection curves of the coupling beams were obtained for investigation. It was found that after the appearance of flexural and shear cracks, a deep coupling beam would gradually transform itself from an ordinary beam to a truss composed of diagonal concrete struts and longitudinal and transverse steel reinforcement bars. Moreover, in a deep coupling beam, the local deformations at the beam-wall joints could contribute significantly (up to the order of 50%) to the total deflection of the coupling beam, especially at the post-peak stage. Finally, although a coupling beam failing in shear would have a relatively low ductility ratio of only 5 or even lower, a coupling beam failing in flexure could have a relatively high ductility ratio of 10 or higher.

• Advances in concrete construction
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• v.13 no.3
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• pp.243-254
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• 2022

Reinforced concrete (RC) deep beams are critical structural elements used in offshore pile caps, rectangular cross-section water tanks, silo structures, transfer beams in high-rise buildings, and bent caps. As a result of the low shear span ratio to effective depth (a/d) in deep beams, arch action occurs, which leads to shear failure. Several studies have been carried out to improve the shear resistance of RC deep beams and avoid brittle fracture behavior in recent years. This study was performed to investigate the behavior of RC deep beams numerically and experimentally with different reinforcement arrangements. Deep beams with four different reinforcement arrangements were produced and tested under monotonic static loading in the study's scope. The horizontal and vertical shear reinforcement members were changed in the test specimens to obtain the effects of different reinforcement arrangements. However, the rebars used for tension and the vertical shear reinforcement ratio were constant. In addition, the behavior of each deep beam was obtained numerically with commercial finite element analysis (FEA) software ABAQUS, and the findings were compared with the experimental results. The results showed that the reinforcements placed diagonally significantly increased the load-carrying and energy absorption capacities of RC deep beams. Moreover, an apparent plastic plateau was seen in the load-displacement curves of these test specimens in question (DE-2 and DE-3). This finding also indicated that diagonally located reinforcements improve displacement ductility. Also, the numerical results showed that the FEM method could be used to accurately predict RC deep beams'behavior with different reinforcement arrangements.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.46-55
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• 2016

Three small scale hollow circular reinforced concrete columns(4.5 aspect ratio) were tested under cyclic lateral load with constant axial load. Diameter of section is 400 mm, hollow diameter is 200 mm. The selected test variable are transverse steel ratio. Volumetric ratio of spirals of all the columns is 0.302~0.604% in the plastic hinge region. It corresponds to 45.9~91.8% of the minimum requirement of confining steel by Korean Bridge Design Specifications, which represent existing columns not designed by the current seismic design specifications or designed by seismic concept. The final objectives of this study are to provide quantitative reference data and tendency for performance or damage assessment based on the performance levels such as cracking, yielding, steel fracture, etc. In this paper, describes mainly failure behavior, strength degradation behaviour, displacement ductility of circular reinforced concrete bridge columns with respect to test variables.

• Journal of Korean Society of Steel Construction
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• v.14 no.1
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• pp.87-94
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• 2002

In the preceding study, a series of results was presented according to factors like as attaching method of main bar, shear span to depth ratio, reinforcing method for different types of region among various factors, which could determine the properties of composite beams. Based on these results, this study was planned to investigate the structural behaviors of according to attaching method of main bar for composite beams(end-reinforced concrete(RC), center-steel concrete (SC)) varying ratio of tensile bar to steel mainly. Consequently, there were little difference according to attaching method of main bar. And as the ratio of tensile bar to steel increase, the efficiency of strength was high, but ductile capacity of beams could deteriorate. Therefore, to maximize the structural properties of composite beams, it was considered that the ratio of tensile bar to steel should be limited.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.851-854
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• 2008

Using the recycled aggregate not only saves landfill space but also reduces the demand for extraction of natural raw material for new construction activity. However few investigations have been carried out to study the shear behaviors of RC beams with recycled aggregates such as low absorption of recycled aggregate and full-scale specimens. In this study, six reinforced concrete beams were tested to evaluate the effects of shear strength, and shear behavior on the replacement level (0, 30, 60, and 100%) of recycled coarse aggregate and different amounts of shear reinforcement. The results showed that the beams with recycled coarse aggregates present the similar shear strength and deflections as the beam with natural aggregate on an equal amount of shear reinforcement. the reinforced concrete beams with recycled coarse aggregates present the Influence of shear span-to-depth ratio, effective depth, tension reinforcement ratio and compressive strength as the beams with natural aggregate. Shear strength were compared with the provisions in current code (KCI2007) and the equation proposed by Zsutty. The KCI equations were conservative and subsequently can be used for the shear design of recycled aggregate concrete beam.

• Journal of the Korea Concrete Institute
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• v.25 no.4
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• pp.389-400
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• 2013

Little investigations have been carried out to study the shear behaviors of RC beams with recycled aggregates. So, this experiment investigates the shear performance and suggests the possible application of Recycled Concrete Aggregate (RCA) for building structures. In general, shear strength of reinforced concrete beam without stirrups is dependent on the compressive strength of concrete, the longitudinal steel ratio, and the shear span-to-depth ratio. In this study, total 28 recycled aggregate concrete beams without shear reinforcement were tested by two-point load and all beams were singly reinforced. The variables studied in this investigation are shear span-to-depth ratios (a/d=2, 3 and 4), RCA replacement ratios (0, 15, 30 and 50%) and longitudinal steel ratios (0.80, 1.27 and 1.84%). The designed concrete compressive strength with a 30 MPa is used. This research will play an important role toward the establishment of the structural design standard for RCA concrete.

• Journal of the Korea Concrete Institute
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• v.29 no.4
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• pp.335-343
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• 2017

This paper aims at investigating the bending strength of high-strength concrete beams with compressive strength of 80 MPa. The experimental parameters included nominal yielding strength of rebar with 400 and 600 MPa, rebar ratio ranging from 0.98 to 1.97%, and shear span-effective depth ratios (a/d) of 6.0 and 4.8. Experimental results were discussed regarding load-deflection relationship, ductility, bending strength, and prediction of bending strength of beams. Test results indicate that the use of high-strength rebar increased bending strength but decreased ductility. As span-effective depth ratio increased, the ductility of test beams decreased. In addition, test results of bending strength were compared with predictions from the current KCI code, Eurocode 2 and Korean Highway Design Specification (KHDC). The design code predictions for bending strength underestimated the experimental results. Therefore, the current design code predictions for bending strength of high-strength concrete beams would provide conservative design. Predictions of bending strength from KCI code using strength reduction factors and those from Eurocode 2 as well as KHDC using material factors were similar each other.

• Journal of the Korea Concrete Institute
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• v.13 no.6
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• pp.619-628
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• 2001

In building construction, openings of the story-height deep beams are usually required for accessibility and service lines such as air conditioning ducts, drain pipes and electric units. It is known that the main parameters affecting the load bearing capacity of deep beams with web openings are size, shape, location and reinforcements of openings. However, there have been no pertinent theories and national design codes for predicting ultimate shear strength of reinforced concrete deep beams with web openings. In this study, the shear behavior of simply supported reinforced concrete deep beams with web openings subject to concentrated loads has been scrutinized experimentally. A total of 34 specimens, the geometry of openings, its reinforcements and shear span to depth ratio, being taken as the experimental variables, has been cast and tested in the laboratory. The effects of these structural parameters on the shear strength and crack initiation and propagation have been carefully checked and analyzed. From the tests, it has been observed that the failures of all specimens were due to shear mechanism and the ultimate strength of specimens varies according to the location of openings, by which the formation of compression struts between the loading points and supports are deterred. All of the test results of specimens have been compared with the formulas proposed by previous researchers. The results were closely coincident with the formulas given by Ray and Kong's equation except for some X series specimens having a larger dimension of openings beyond the geometric limits of proposed equations.

• Magazine of the Korea Concrete Institute
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• v.9 no.4
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• pp.167-176
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• 1997

The current study is a part of series of research about the evaluation method of the unbonded tendon stress in prestressed concrete member at flexural failure. As the first part. previous design equations were examined in oder to find whether any modifications may be needed. A total of 167 experimental results tested for more than 40 years were gathered to build D/B and then previous proposed and codified equations were evaluated with the experimental relsults. The ACI Code equation and Naaman, Harajli, and Chakrabarti's equations were chosen for the purpose of examination. Then, the followings were obtained from the analytical examination. It is desirable to compute the tendon stress with the member analysis method instead of the sectional analysis method which has been used in the current ACI Code. The tendon stress may also be influenced significantly by the amount of ordinary bonded reinforcements and the loading types. And the current ACI Code overestimated the effect of span/depth ratio. As results, it was concluded that the revision of the ACi Code equation should be considered positively. Then, a new design has to be proposed with the reasonable and comprehensive investigation about influential factors on the tendon stress variation.