• Steel and Composite Structures
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• v.29 no.6
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• pp.735-748
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• 2018

In this paper, the cyclic behavior of steel beam-concrete encased steel (CES) column joints was investigated experimentally and numerically. Three frame middle joint samples with varying concrete slab widths were constructed. Anti-symmetrical low-frequency cyclic load was applied at two beam ends to simulate the earthquake action. The failure modes, hysteretic behavior, ultimate load, stiffness degradation, load carrying capacity degradation, displacement ductility and strain response were investigated in details. The three composite joints exhibited excellent seismic performance in experimental tests, showing high load-carrying capacity, good ductility and superior energy dissipation ability. All three joint samples reached their ultimate loads due to shear failure. Numerical results from ABAQUS modelling agreed well with the test results. Finally, the effect of the concrete slab on ultimate load was analyzed through a parametric study on concrete strength, slab thickness, as well as slab width. Numerical simulation showed that slab width and thickness played an important role in the load-carrying capacity of such joints. As a comparison, the influence of concrete grade was not significant.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.1
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• pp.97-105
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• 2006

The reinforced concrete flat plate system provides architectural flexibility, clear space, reduced building height, simple formwork, which consequently enhance constructibility. One of the serious problem in the flat plate system is brittle punching shear failure due to transfer of shear force and unbalanced moments in column-slab connection. Since the use of high strength concrete recently has become in practice for reinforced concrete structures, it is highly desired to establish the structural design method for flat plate construction using high strength concrete. In this paper, interior column-slab connection constructed with high strength concrete were tested under lateral and gravity loads to evaluate their strength and behavior. The test parameters were slab reinforcement ratio and the gravity load levels.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.339-344
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• 1995

In the design of ductile moment-resisting frames (DMRFs) following the strong column-weak beam dsign philosophy, it is desirable that the joint and column remain essentially elastic in order to insure proper energy dissipation and lateral stability of the structure. The joint has been identified as the "weak link" in DMRFs because any stiffness or strength deterioration in this region can lead to substantial drifts and the possibility of collapse due to P-delta effects. Moreover, the engineer is faced with the difficult task of detailing an element whose size is determined by the framing members, but which must resist a set of loads very different from those used in the design of the beams and columns. Four 2/3-scale beam-column-slab joint assemblies were designed according to existing code requirements of ACI 318-89, representing interior joints of DMRFs with reinforced high strength concrete. The influence on aseismic behavior of beam-column joints due to monolithic slab, has been investigated.estigated.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.107-110
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• 2005

In general, post tensioned (PT) flat plate slab systems have been used as a Gravity Load Resisting System (GLRS) in buildings. Thus, these systems should be constructed with Lateral Force Resisting Systems (LFRS) such as shear walls and moment resisting frames. When lateral loads such as winds or earthquakes occur, lateral load resisting systems undergo displacement by which connected gravity systems experience lateral displacement. Therefore, GLRS should have some lateral displacement capacity in order to hold gravity loads under severe earthquakes and winds. Since there are the limited number of researches on PT flat plate slab systems, the behavior of the systems have not been well defined. This study investigated the cyclic behavior of post tensioned flat plate slab systems. For this purpose, an experimental test was carried out using 4 interior PT flat plate slab-column specimens. All specimens have bottom reinforcement in the slab around the slab-column connection. Test variables of this experimental study are vertical load level and tendon distribution patterns.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.307-310
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• 2005

The PCS system, which consists of precast concrete column and steel beam, has been under development. Experimental test has been carried out to investigate the structural performance of the system under earthquake. Two types of test specimens of beam-column joints are designed in order to compare the performances. One is the system with reinforced concrete slab and the other is without slab. It is found that the system with slab could satisfy all of the requirements from ACI Criteria such as strength, stiffness degradation and energy dissipation capacity except initial stiffness. It is also investigated that the stiffness of the joint is belong to rigid joint type according to Bjorhovde criterion. And it is observed that the partial-composite system between beam and slab is more effective than full-composite system in the respect of the energy dissipation capacity of the system.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.757-762
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• 2000

The purpose of this study is to investigate the performance of slab-beam-column subassemblage in the Ordinary Moment Frame(OMF). For this purpose, 3-story building was designed according to UBC and ACI building code(ACI 318-99) and the subassemblages of in the first story were constructed. The subassemblages were classified into interior and exterior. Each interior and exterior subassemblage is modeled by the 2/3 scale experimental specimens. All the specimens have the transverse beam and the columns on the slab have the lap splice as the typical exterior and interior slab-beam-column subassemblage. The interior subassemblage was tested under the constant axial force, while the exterior subassemblage was tested under the fluctuating axial force. Based on the results of the experiments, the performance of each subassemblage is evaluated and the failure mode is investigated.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.239-242
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• 2005

The purpose of this research was focused on substantiating an effects of tendon-layouts and compressed stress($=f_{pc}$) induced by post-tensioning on seismic performance of post-tensioned flat plate slab-column connection designed as non-participating system. To accomplish this purpose, an experimental research of flat plate exterior slab-column connections subjected to gravity load and reversed lateral displacement history are presented. As a result, tendon-layout is a main variable to influence failure mechanism, dissipated energy and lateral deformation capacity. Furthermore, compressed stress ($=f_{pc}$) induced by post-tensioning enhanced the seismic performance of flat plate slab.

• Journal of the Korea Concrete Institute
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• v.29 no.1
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• pp.77-84
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• 2017

In this study, the structural performance of high strength concrete (HSC) column-normal strength concrete (NSC) slab connection was investigated according to confinement effects, aspect ratio (h/c) and strength ratio ($f^{\prime}_{cc}/f_{cs}$). The study was conducted by using finite element analysis. To verify the analysis methods, the experiments and analyses results were compared. The specimens were classified by connection types including interior column, edge column, corner column and isolated column. As a result, ultimate strength of interior column was larger than other specimens. Also, the axial stresses of connection were decreased when the aspect ratio was increased. As the strength ratio between column and slab was increased, the ultimate strength of specimens was also increased until the strength ratio was reached to 1.83.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.53-56
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• 2004

Recently, post tension flat plate slab system is widely used for a new slab structural system. Slab-column connections may fail in brittle manner by punching shear. Flat plate slabs have been widely used for gravity load resisting system in buildings. Lateral resistance usually provided by shear walls or moment resisting frames. Since plat plates move together with lateral loading system during earthquake or wind, it is important to evaluate the gravity resistance under a drift experienced by lateral force resisting system during either design earthquake or wind. Thus, this study investigated post tension flat plate slab systems whether they have sufficient strength and deformability to resist gravity loads during specified drift levels. Experimental research was carried out.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.26-29
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• 2006

A flat plate-column connection is susceptible to brittle punching shear failure, which may result in the necessity of shear reinforcement. In present study, experimental tests were performed to study the capacity of slab-column connections strengthened with lattice, stud rail, shear band and stirrup under gravity and cyclic lateral load. Among them, the capacity of the specimens with lattice are superior to the others due to the truss action of the lattice bars and dowel action of the longitudinal bars as well as the shear resistance of the web re-bar. On the other hand, the strengths of the specimens with stud rail, shear band and stirrup are lower than the estimated strength by the ACI, therefore design formulas of the ACI are needed to revise.