• Journal of Korean Society of Steel Construction
• /
• v.21 no.2
• /
• pp.135-144
• /
• 2009

This study aims to suggest an appropriate flexural reinforcement technique by evaluating the reinforcement capacity of specimens that underwent flexural reinforcement according to the post-tension method with the anchoring position of an unbonded tension member on the conventional SC composite beam and the applied tension level as variables. For the experiment, up to a predetermined yield load was applied to each type of specimen and then, unbounded post-tensioning was additionally conducted to examine its reinforcement capacity. The analysis of the said experiment showed that the post-reinforced SC composite beam was characterized by significantly improved yield stress and initial stiffness, compared with the pre-reinforced one and the experimental measurements/theoretical values of maximum stress ranged from 0.95 to 1.13 following reinforcement. There was little or no change depending on the maximum stress and tension in the specimen (D160, Class 240) whose neutral axis and upper part had anchoring devices mounted prior to reinforcement. Rather, the ductility decreased with the increasing tension. On the contrary, in the case of the other specimen (Class D120) whose neutral axis had anchoring devices mounted after reinforcement, both the maximum stress and ductility increased with increasing tension, which indicates that the latter tension reinforcement was reasonably appropriate and effective for the neutral axis reinforcement.

• Journal of the Korea Concrete Institute
• /
• v.16 no.5 s.83
• /
• pp.635-643
• /
• 2004

In this study, the tensile strength of 321 full-sized grout-filled splice steeve specimens were compared and analyzed in order to afford the data for a reasonable and economical design of this system. The experimental variables analyzed in this study were embedment length of reinforcing bars, compressive strength of grout, sleeve geometry, loading pattern and final failure mode of specimen. Following main conclusions are obtained : 1) The strength of grout-filled splice sleeve tends to be improved with increasing compressive strength of grout and embedment length of reinforcing bars. Specially this tendency appears apparent in specimens of bond failure rather than rebar failure. 2) The results of this study show that the sleeve geometry have influence on the bond strength of grout-filled splice sleeve. 3) The grout-filled splice sleeve of bond failure don't show the difference of tensile strength according to size of rebar. 4) It is verified that the tensile strength required in ACI and domestic code is retained either when the compressive strength of grout over 70 MPa is used with embedment length of reinforcing bars over 4.5d or when the compressive strength of grout over 80 MPa is used with embedment length of rebars over 3.9d. 5) It is verified that the tensile strength required in AIJ code is retained in case when the embedment length of reinforcing bars is 0.8 times the rebar diameter longer than in ACI code.

• Journal of Korean Society of Steel Construction
• /
• v.15 no.1
• /
• pp.87-96
• /
• 2003

The Ssteel-Cconcrete (SC) Ccomposite Ccolumn is a new Ccomposite Ccolunin system, where hoops are welded between flanges of H-shapesd steel and concrete is filled in spaces between flanges are filled with con crete. Tests of SC composite columns were performed previously to determine their compression, bending and shear strength, and it showed good structural behavior. But sSince a column is usually subjected to an axial compression force, and bending it ihas needed to be bent forevaluate its structural behavior to be evaluated when its axial load and bending isaresimultaneously applied to the SC composite column. In this paper, tests were conducted to investigate the bending strength of SC composite columns subjected to axial compression force and bending moment. The parameters of the tests were concrete, a stud bolt, a hoop and a magnitude of axial compression. The test results showed that the maximum bending strength and ductility of an SC composite column were increased by 33-42% and 33-63%, respectively, comparinged to those of a bare steel column. Also, the results obtained bywith the Korean Limit State Design Code (LSD) presents a considerably safe side value compared to those of the Eurocode-4 and the Japan Code. However, wWhen the axial compression force is was increased, however, there awere considerable differences between the maximum strength obtained by the test and the LSD analysis. For this reason, it is recommended tothe use of the Eurocode-4 is recommended when calculates the strength of an SC composite column is being calculated, since the Eurocode-4 gives us a better estimation.

• Journal of the Korea Concrete Institute
• /
• v.17 no.4 s.88
• /
• pp.513-520
• /
• 2005

The uniform truss mechanism is widely accepted as a shear transfer mechanism in reinforced concrete members. However, the uniform truss action cannot be expected when the bond stress distribution is not constant along longitudinal bars. A test method in which only the truss action takes place is developed and conducted to investigate the truss actions under various bond contributions. Based on the experimental results and analysis, the following findings can be obtained: 1) The bond stress distribution depends on the axial compression force, the amount of shear reinforcement and loading conditions. 2) The analysis using the combined truss model consisting of uniform and fan-shape trusses can predict the experimental results

• Journal of the Korea Concrete Institute
• /
• v.28 no.1
• /
• pp.95-104
• /
• 2016

Flexural strength of concrete ground slab reinforced with steel fiber is evaluated using the equivalent flexural strength ratio of steel fiber reinforced concrete based on the yield line theory. Recently, the European standard specifies that the tensile performance of the steel fiber reinforced concrete be evaluated directly from the residual flexural strength after the cracking of concrete. Thus, in the study, an experiment was carried out to evaluate the conventional equivalent flexural strength ratio and the residual flexural strength of the steel fiber reinforced concrete. Then the design flexural strength was investigated according to the location of a point load, based on the ratio of the radius of contact area of the load to the radius of relative stiffness. Design flexural capacity obtained from ACI 360R-10 was smaller than that from TR 34 (2003 & 2013). In addition, TR 34 (2013), which evaluates the design flexural capacity based on the residual flexural strength, showed slightly smaller value than TR 34 (2003).

• Journal of Korean Society of Steel Construction
• /
• v.12 no.6
• /
• pp.681-690
• /
• 2000

Recently, a long span is often required for the spacious building. Therefore the increase of stiffness is necessary to prevent floor vibration and control deformation of the building under earthquake and wind loads. For this purpose, steel beams with stiffened ends by reinforced concrete are effective. To realize such an effective reinforcement method, the smoothening of bending and shear stress transmission at the boundaries between middle-part of the steel beam and both end-parts of the steel beam with stiffened ends by reinforced concrete is required. Therefore, the fixed plate was installed at the boundary with the view of transferring the stress smoothly. This paper evaluates the method of effective transmission of bending and shear stress through the numerical analysis that is based on advanced experimental tests.

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.431-432
• /
• 2015

본 논문은 초고압 가스절연개폐장치의 메인 접점의 압점력에 따른 절연 특성에 대한 연구이다. 차단기 접점의 접촉이 잘 이루어지지 않는 현상이 발생하게 되면 접촉저항이 증가하여 차단기의 투입 및 개방 시에 전류에 의하여 접점에 손상이 발생한다. 그리고 차단기의 접점의 압점력이 커질수록 큰 조작력이 필요하므로 차단기의 동작에도 영향을 미치는 것은 많이 알려져 있다. 그러나 압점력과 절연 특성의 관계에 대한 연구가 미비하므로 이에 대한 연구가 필요하다. 본 연구는 초고압 가스절연개폐장치의 메인 접점의 압점력에 차이에 따른 전계를 해석하고, 고정측 접점의 쉴드 유무에 따른 절연 내력을 비교 및 분석하였다. 전계 해석 결과를 통해서 메인 접점의 압점력과 절연특성과 고정측 접점 쉴드의 영향을 비교함으로써 차단기 인터럽터 내부의 전계 분포를 확인하고, 전계 강도를 확인함으로 가스절연계폐장치의 적절한 절연내력 확보를 목적으로 한다.

• Journal of Korean Society of Steel Construction
• /
• v.20 no.1
• /
• pp.67-79
• /
• 2008

In this study, a bending test with three encased composite beams were carried out and analyzed using FEM in order to find how chemical adhesion, interface interlock, friction and composite action by shear studs contribute to stiffness, strength and composite action in the interface of encased compo site beams. The test and results of the FEM analysis showed that the difference in the ultimate moment capacity of the composite beams with and without studs is under 10%. The reason is that the effect of chemical adhesion, interface interlock, and friction in the interface on the composite action is so high that the encased beams have a moment capacity above some defined magnitude. Also, the increment of moment capacity up to plastic moment is not large and the increase of linearly proportioned.

• Journal of the Korea Concrete Institute
• /
• v.24 no.4
• /
• pp.399-406
• /
• 2012

Beam-column joints are generally recognized as the critical regions in the moment resisting reinforced concrete (RC) frames subjected to both lateral and vertical loads. As a result of severe lateral load such as seismic loading, the joint region is subjected to horizontal and vertical shear forces whose magnitudes are many times higher than in column and adjacent beam. Consequently, much larger bond and shear stresses are required to sustain these magnified forces. The critical deterioration of potential shear strength in the joint area should not occur until ductile capacity of adjacent beams reach the design demand. In this study, a method was provided to predict the deformability of reinforced concrete beam-column joints failing in shear after the plastic hinges developed at both ends of the adjacent beams. In order to verify the deformability estimated by the proposed method, an experimental study consisting of three joint specimens with varying tensile reinforcement ratios was carried out. The result between the observed and predicted behavior of the joints showed reasonably good agreement.

• Journal of Korean Society of Steel Construction
• /
• v.13 no.4
• /
• pp.419-431
• /
• 2001

This study was to investigate structural behavior of composite structure beams composed of end-RC. center-Steel according to respective reinforcing method for connection zone composed of different materials (SRC) while attaching main bars on steel-flange by welding. The main reinforcing methods are as follows ; non-reinforcing, vertical shear reinforcing (type-stirrup), inclined reinforcing(type-x), horizontal reinforcing(type-web, 0.3L), double horizontal reinforcing (type-web, 0.3L), vertical reinforcing (type-flange, 0.3L). Consequently, It showed little difference in structural properties like ductility and strength according to the attaching method of main bars. For Maximizing the structural properties of composite beam, the most effective methods were vertical reinforcing one and double horizontal reinforcing one.