• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.3
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• pp.243-250
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• 2004

In SPS system, steel beams are used as not only temporary struts supporting the wale but main flexural members of building. Previous experimental works show that RC wale-steel beam joints have some flexural rigidity. In this paper, nonlinear analysis is performed using DRAIN-2DX program to investigate the behaviors of the underground composite frames constructed with SPS system when the rigidity of RC wale-steel beam joints change. Analysis variables are the procedure of construction, magnitude of lateral forces, and flexural rigidity of the RC wale-steel beam joint with stud connector. Analysis results show the effects of joint rigidity for the yielding process of frame and the moment and deflection at the mid-span of beam.

• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.719-725
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• 2010

The analysis and experimental program of reinforced concrete (RC) structures for resistance against such extreme loads as earthquake, blast, and impact have been carried by many researchers and designers. Under the extreme loads, a large amount of energy is suddenly exerted to the structure, hence if the structure fails to absorb the impact energy, catastrophic collapse may occur. To prevent catastrophic collapse of structures, reinforced concrete must have adeguate toughness or it needs to be strengthened. The FRP strengthening method and SFRC are studied widely in resistance of impact load because of their high energy absorption capacity. In this study, drop weight impact tests were implemented to evaluate the impact resistance of SFRC and FRP strengthened RC beam while the total steel fiber volume fractions was fixed at 0.75% carbon FRP flexural strengthened RC beams. Futhermore, to prevent the shear-plug cracks when the impact load strikes the beams, additional FRP shear strengthening method are applied. The experimental, results showed that the FRP strengthened RC SFRC beams has high resistance of shear-plug cracks and crack width and SFRC has high resistance of concrete spalling failure compared to normal RC beams. The FRP flexural and shear strengthening RC beams has weakness in the spalling failure because the impact load concentrated the concrete face which is not strengthened with FRP sheets.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.3
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• pp.189-196
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• 2004

The RC wale-steel beam stud connection may have smaller moment and shear resistance because the tensile and shear capacity of the studs are limited by the depth of RC beam. Especially, they are subjected to compressive axial load. This paper describes the experimental works to develop the connection details of RC wale-steel beam joints subjected to shear and axial loads. Shear connectors developed in this study are closed C type deformed bar, opened C type deformed bar, and U type deformed bar. From shear test, the shear performance of RC wale-steel beam joint with the developed connectors are compared with the stud connection. Test results indicated that the developed connectors were very effiecive to increase the shear strength.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.734-741
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• 2002

An experimental study was carried out for beam-column joints composed of RC column and RS beams. The purpose of this study is to examine the inelastic seismic behavior for the RC-RS connection. Two interior and one exterior beam-column assemblies with variable moment ratios were tested. Experimental results showed that strength and deformability except stiffness were satisfactory. It is considered that the lack of stiffness was due to the slipping of steel beam from RS beam. The behavioral characteristics of the RC-RS connection were evaluated according to the quideline suggested by Hawkins et al. Nominal strength at 5 ％ joint distortion was not satisfactory, but all the other requirements, such as strength preserving capability, energy dissipation, and initial stiffness and strength ratios after peak load were satisfactory compared with the guideline. Thus it was concluded that the RC-RS connections can maintain ductility with excellent energy-dissipating capacity if being provided with appropriate reinforced structural system such as RC core wall for the initial lateral stiffness.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.9-14
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• 2017

In the present work, a mechanical performances under cyclic loading in RC (Reinforced Concrete) beams with normal steel and FRPH (Fiber Reinforced Plastic Hybrid) bar are investigated. For the work, RC beam members with $200{\times}200{\times}2175mm$ of geometry and 24 Mpa of design strength are prepared, and 4-point-bending tests are performed for evaluation of cracking, yielding, and ultimate loads. Through static loading test, 48.9kN and 36.0 kN of yielding loads are measured for normal RC and FRPH beam, respectively. They have almost same ultimate load of 50.0 kN. Typical tension hardening behavior is observed in FRPH beam, which is caused by the behavior of FRPH bar with tension hardening. In cyclic loading conditions, FRPH beam has more smaller crack width and scattered crack pattern, and it shows more elastic recovery than normal RC beam. The energy dissipation ratio in FRPH beam is 0.83, which is greater than 0.62 in normal RC beam and it shows more effective resistance to cyclic loadings.

• Journal of Korean Society of Steel Construction
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• v.19 no.3
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• pp.259-270
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• 2007

This paper presents an analytical method of evaluating the flexural behavior of RC (reinforced concrete) beams strengthened with high-strengh bars. The former experimental results were used to compare with the analytical results. The experimental results also outline the advantages of externally strengtheng method with high-strenght bars. To evaluate the flexural behavior of RC beams strenghtend with unbonded high-strength bars, this paper proposes a method involving a simple strength-summation method. This method basically assumes that the total strength of RC beams strengthened with high-strength bars is equal to the sum of the strengths of the RC beams and the high-strength bars. This analytical method also includes the effects of compressive force due to the tension from high-strength bars. A comparison of the analytical and experimental results leads to the conclusion that the simple strength-summation mothod can simulate the flexural behavior of RC beams strengthened with high-strength bars with a good level of accuracy.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.4
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• pp.1-8
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• 2008

RC beam of existing structures often encounter shear problems for various reasons. The shear failure of RC beam is sudden and brittle. Strengthening technique jacketing with external bonding of steel plates(or CFRP and CFS) with epoxy is many use to in practice. This study presents test results on strengthening shear deficient RC beams by external bonding of slit type steel plates. Test parameters are width, interval, length, thickness and angle of slit in steel plates. The purpose was to evaluate the reinforcing effects, failure modes and shear capacities for RC beams of strengthened with various slit type steel plates. The test result confirmed that all slit steel plates improved the stiffness and strength of the specimens significantly. Failure modes of SV series and SD series showed shear fractures and flexure fractures at ultimate state respectively. SD series were ductile rather than SV series.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.5
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• pp.79-86
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• 2010

This study was performed to evaluate the flexural behavior of Hybrid fiber sheet (HFC) and Hybrid fiber bar (HFB) strengthened reinforced concrete (RC) beams. According to test results, Hybrid fiber reinforcement strengthened RC beams showed approximately 60 to 200% higher reinforcing effects than that of un-reinforced specimens. In addition, the reinforced beams showed the ideal failure pattern, which is failed presenting the ductile behavior after yielding of the reinforcing bar. More specifically, in the case of HFB reinforced RC beams, the difference with puttying method was not apparent since HFB beams reinforced using the injection of epoxy and bonding of putty showed the similar failure patterns.

• Journal of the Korea Concrete Institute
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• v.22 no.4
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• pp.527-534
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• 2010

This study presents a simple method to improve the bond performance of reinforced concrete (RC) beams having high-strength shear reinforcement. In general, the yield strength and the ratio of shear reinforcements are the main parameters governing the shear capacity of RC beams. The yield strength of shear reinforcement, however, has little influence on the bond capacity of RC beams. Therefore, a sudden bond failure of the members with high-strength shear reinforcement can occur before flexural failure. To estimate the structural performance of the proposed method, four RC beams were cast and tested. The main test parameters were the yield strength, ratio, and reinforcing types of shear reinforcements. The experimental results indicated that the proposed method was able to effectively improve the bond performance of RC beams with high-strength shear reinforcement.

• Journal of Korean Association for Spatial Structures
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• v.11 no.1
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• pp.57-66
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• 2011

For the lateral load resistance of a RC frame in a medium risk seismic zone, the strength of lower story beams and columns should be larger than those of the upper stories. However, the lateral loads can be accommodated by redistributing design beam moments vertically as well as horizontally so all beams end up with identical strengths. This paper looks at the impact of the vertical redistribution of beam moments to provide identical beam strength over as many floors as possible. Two-bay six-story RC frame was designed with and without vertical beam moment redistribution and its seismic performance were evaluated by using push-over limit analysis and by non-linear time history dynamic analysis. Analytical results show that with the use of vertical beam moment redistribution the increase in the ductility demand is similar to the proportion of moment redistribution applied, but this additional demand is below the ductility capacity of well detailed RC members.