• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.301-312
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• 2007

A slab-column connection is susceptible to brittle punching shear failure, which may result in the necessity of shear reinforcement. In the present study, to investigate the earthquake resistance of newly developed lattice shear reinforcement, experimental study was performed for interior slab-column connections subjected to cyclic loading. For comparison, specimens with existing shear reinforcement method such as stud rail, shear band and stirrup were also tested. The test result showed that the structural capacity of the lattice shear reinforcement was superior to those of the existing methods and was greater than the code-specified strength. On the other hand, the existing methods did not significantly improve the shear strength of the specimens. The shear strengths of the existing methods were much less than the code-specified shear strength.

• Journal of the Korea Concrete Institute
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• v.22 no.4
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• pp.585-593
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• 2010

On the basis of the strain-based shear strength model developed in the previous study, a strength model was developed to predict the direct punching shear capacity and unbalanced moment-carrying capacity of interior and exterior slab-column connections. Since the connections are severely damaged by flexural cracking, punching shear was assumed to be resisted mainly by the compression zone of the slab critical section. Considering the interaction with the compressive normal stress developed by the flexural moment, the shear strength of the compression zone was derived on the basis of the material failure criteria of concrete subjected to multiple stresses. As a result, shear capacity of the critical section was defined according to the degree of flexural damage. Since the exterior slab-column connections have unsymmertical critical sections, the unbalanced moment-carrying capacity was defined according to the direction of unbalanced moment. The proposed strength model was applied to existing test specimens. The results showed that the proposed method predicted the strengths of the test specimens better than current design methods.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.391-398
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• 2012

This paper presents the shear capacities of biaxial hollow slab with donut type hollow sphere. Recently, various types of slab systems which can reduce self-weight of slabs have been studied for increasing constructions of taller and larger building structures. A biaxial hollow slab system is widely known as one of the effective slab system, which can reduce self-weight of slab. According to previous studies, the hollow slab has low shear strength, compared to solid slab. Also, the shear capacities of biaxial hollow slab are influenced by the shapes and materials of hollow spheres. However, the current code does not provide a clear computation method for the shear strength of hollow slab. To verify the shear capacities of this hollow slab, one-way shear tests were performed. Four test specimens were used for test parameters. One was conventional RC slab and others were hollow slabs. The test parameters included two different shapes and materials of plastic balls. The shape parameters were donut and non-donut forms and the material parameters were general plastic and glass fiber plastic. The results showed that the shear strengths varied depending on hollow shapes and materials used in the slab.

• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.347-358
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• 2009

Recently, it is getting into a good situation for the flat-plate slab system to be applied. The flat-plate slab without beam, however, is often too weak to control deflection properly compared to other typical slab-beam structures, for which the post-tension method is generally regarded as one of best solutions. The post-tension (PT) method can effectively control deflection without increase of slab thickness. Despite this good advantage, however, the application of PT method has been very limited due to cost increase, technical problems, and lack of experiences. Therefore, in order to reduce difficulties on applying full PT method under the current domestic circumstances and to enhance constructability of PT system, this research proposed the partial PT method with top jacking anchorage applied in a part of span as need. For the top jacking anchorage system, the efficiency of deflection control shall be considered in detail because it can vary widely depending on the location of anchorage that can be placed anywhere as need, and tensile stresses induced at back of the anchorage zone also shall be examined. Therefore, in this study, analysis were performed on the efficiency of deflection control depending on the location of anchorage and on tensile stresses or forces using finite element method and strut and tie model in the proposed top jacking anchorage system. The proposed jacking system were also applied to the floor slabs at a construction site to investigate its applicability and the analysis results of slab behavior were compared to the measured values obtained from the PT slab constructed by the partial PT method. The result of this study indicates that the partial PT method can be very efficiently applied with little cost increase to control deflection and tensile stresses in the region as a need basis where problem exists.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.867-870
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• 2008

Flat plate system has many advantages, story height reduction, a term of works shortening and changeableness of space, etc. However structures become a tendency of higher stories and when we use RC column, the size of column grow larger. For this reason the use of CFT column is increasing more and more. Accordingly, this study carried out the nonlinear finite element analysis. As a result of analysis moment strength of the connection increased but ductility decreased as the top reinforcement ratio in th effective width increased. And moment strength and ductility of the connection decreased as gravity load ratio decreased. In the case that shearhead length is not more than 0.27m, the effectiveness of shearhead length on the moment strength and ductility of the connection were small relatively to other variables. Initial stiffness and moment strength of connection increased as slab thickness increased

• Journal of Korean Society of Steel Construction
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• v.23 no.1
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• pp.125-135
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• 2011

To obtain a lower story height with a long span and better fire resistance, a new composite floor system using GFRP (glass-fiber-reinforced plastics) was proposed. This floor system consists of asymmetric steel with a web opening, a hollow core ball, concrete, and GFRP. To evaluate the flexural performance of the new composite floor system, an experiment was conducted. The test parameters were the presence of GFRP, the void ratio in relation to the hollow core balls, and the web opening. The test results showed that the resistance and stiffness of the specimen with GFRP were 10% higher than those of the reference specimen, and that fully composite action was accomplished up to the yielding point. After the attainment of the yield strength, the ductility of the specimen was reduced due to the stress concentration around the web openings. The slip between the concrete and steel beam, however, was small. Thus, in the design of the proposed new floor systems, it is desirable that the calculated resistance be reduced by 15%, for safety.