• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.75-78
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• 2005

This study reports on the structural characteristics of slab-column connections using an ultra-high-strength-fiber-reinforced concrete. Compression tests were performed on two slab-column and four isolated column specimens. During the column load tests were performing on the slab-column specimens, the slab loads were also applied to consider actual confinement condition at the slab-column joint. The main parameter investigated was the ' puddling ' of ultra-high-strength-fiber-reinforced concrete. This paper also investigates the effects of some parameters on slab-column specimens and isolated column specimens without the surrounding slab for their ability to transmit axial loads from the ultra-high-strength concrete columns through slab-column connections. The beneficial effects of the ultra-high-strength-fiber-reinforced concrete puddling on the transmission of column loads through slab-column connections are demonstrated.

• KCI Concrete Journal
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• v.13 no.2
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• pp.49-57
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• 2001

Flat-plate buildings are commonly modeled as two-dimensional frames to calculate unbalanced moments, lateral drift and shear at slab-column connections. The slab-column frames under lateral loads are analyzed using effective beam width models, which is convenient for computer analysis. In this case, the accuracy of this approach depends on the exact values of effective beam width to account for the actual behavior of slab-column connections. In this parametric study, effective beam width coefficients for wide range of the variations are calculated on the several types of slab-column connections, and the results are compared with those of other researches. Also the formulas for effective beam width coefficients are proposed and verified by finite element analysis. The proposed formulas are founded to be more suitable than others for analyzing flat-plate buildings subjected to lateral loading.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.79-82
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• 2005

This study reports on the structural characteristics of slab-column connections using an ultra-high-strength-fiber-reinforced concrete from new and retrospective data. The parameters investigated were the ' puddling ' of ultra-high-strength-fiber-reinforced concrete and the use of high-strength concrete in the slab. The effects of these parameters on the punching shear capacity, negative moment cracking, and stiffness of the two-way slab specimens are investigated. Furthermore, the ACI Code (2002), the CSA Standard (1994), the BS Standard (1985) and the CEB-FIP Code (1990) predictions are compared to the experimental results obtained from some slab-column connections tested in this experiment and those tested by other investigators. The beneficial effects of the ultra-high-strength-fiber-reinforced concrete puddling and of the use of high-strength concrete are demonstrated. It is also concluded that the punching shear strength of slab-column connections is a function of the flexural reinforcement ratio.

• Structural Engineering and Mechanics
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• v.66 no.2
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• pp.203-215
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• 2018

A large body of experiments have been conducted to date to evaluate the punching shear strength of flat slab-column connections, but it is noted that only a few of them have been considered for the development of the ACI Code provisions. The limited test results used for the development of the code provisions fall short of predicting accurately the punching shear strength of such connections. In an effort to address this shortfall and to gain an insight into the factors that control the punching shear strength of flat slab-column connections, we report a qualified database of 650 punching shear test results in this article. All slabs examined in this database were tested under gravity loading and do not contain shear reinforcement. In order to justify including any test result for evaluation punching shear database, we have developed an approved set of criteria. Carefully established set of criteria represent the actual characteristics of structures that include minimum compressive strength, effective depths of slab, flexural and compression reinforcement ratio and column size. The key parameters that significantly affect the punching shear strength of flat slab-column connections are then examined using ACI 318-14 expression. The results reported here have paramount significance on the range of applicability of the ACI Code provision and seem to indicate that the ACI provisions do not sufficiently capture many trends identified through regression of the principal parameters, and fall on the unsafe side for the prediction of the punching shear strength of flat slab-column connections.

• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.209-216
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• 2007

This study reports on the structural characteristics of slab-column connections using fiber-reinforced ultra-high-strength concrete (UHSC). Compression tests were performed on two slab-column and four isolated column specimens. In the column load tests, slab loads were also applied on the slab-column specimens so that the actual confinement condition at the slab-column joint was considered. The main parameter investigated was the "puddling" of fiber-reinforced UHSC. This paper also investigates the effects of some parameters, such as confinement of slab concrete, steel fibers, and concrete strength of the joint, related to the ability of the slab-column specimens and isolated column specimens without the surrounding slab to transmit axial loads from the UHSC columns through slab-column connections. Furthermore, the ACI Code (2005) and the CSA Standard (2004) are compared to the experimental results. The beneficial effects of the puddling of fiber-reinforced UHSC on the transmission of column loads through slab-column connections are demonstrated.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.48-51
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• 2004

This paper is to study the response of flat plate slab-column connections consisting of various types of shear reinforcement and steel plate subjected to gravity loadings, mainly punching shear forces using the non-destructive testing, spectral analysis of surface waves and structural experiments. The base specimen failed due to punching shear generated from the gravity. The three other types of slab shear reinforcement and steel plate showed effective in resisting punching shear for these types of connections under gravity loading. This study has focused in evaluating the velocity response of a Surface wave during the early age as the poured concrete specimens have been hardened, the possibility of damage detection in the slab-column connection and the relationship between the punching shear forces and the surface wave velocities under the condition that the punching shear forces had gradually increased until the flat plate slab in slab-column connection had been failed.

• Computers and Concrete
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• v.22 no.1
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• pp.71-81
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• 2018

Introduction of prestressed concrete slabs based on post-tensioned (PT) method aids in constructing larger spans, more useful floor height, and reduces the total weight of the building. In the present paper, for the first time, simulation of 32 two-way PT slab-edge column connections is performed and verified by some existing experimental results which show good consistency. Finite element method is used to assess the performance of bonded and unbonded slab-column connections and the impact of different parameters on these connections. Parameters such as strand bonding conditions, presence or absence of a shear cap in the area of slab-column connection and the changes of concrete compressive strength are implied in the modeling. The results indicate that the addition of a shear cap increases the flexural capacity, further increases the shear strength and converts the failure mode of connections from shear rigidity to flexural ductility. Besides, the reduction of concrete compressive strength decreases the flexural capacity, further reduces the shear strength of connections and converts the failure mode of connections from flexural ductility to shear rigidity. Comparing the effect of high concrete compressive strengths versus the addition of a shear cap, shows that the latter increases the shear capacity more significantly.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.312-316
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• 1995

Flat-plate buildings are commonly modeled as two-dimensional frames to calculate lateral drift, unbalanced moments, and shear at slab-column connections. For gravity loads. the slab-column frames are analyzed using equivalent column approach, while equivalent beam approach is typical for lateral loads. The equivalent beam approach is convenient for computer analysis, but no rational procedure exists for determining the effective width of foor slabs. At present, the determination of the equivalent slab width and its stiffness is a matter of engineering judgement. To account for cracking, overly conservative assumptions are made regarding the stiffness of the slab. A rational approach is therefore needed to realistically estimate the equivalent slab width and its stiffness for unbalanced moment and lateral drift calculations. Based on the test results of 8 interior slab-column connections, an equivalent beam model is proposed in which columns are modeled conventionally as a function of column and slab aspect ratios and the magnitude of the gravity load. the proposed approach is verified with selected experimental results and is founded to be practical and convenient for analyzing flat-plate buildings subjected to gravity and lateral loading.

• Structural Engineering and Mechanics
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• v.5 no.5
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• pp.645-662
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• 1997

A nonlinear semi-three-dimensional layered finite element procedure is developed for cracking and failure analysis of reinforced concrete beams and the spandrel beam-column-slab connections of flat plates. The layered element approach takes the elasto-plastic failure behaviour and geometric nonlinearity into consideration. A strain-hardening plasticity concrete model and a smeared steel model are incorporated into the layered element formulation. Further, shear failure, transverse reinforcement, spandrel beams and columns are successfully modelled. The proposed method incorporating the nonlinear constitutive models for concrete and steel is implemented in a finite element program. Test specimens including a series of reinforced concrete beams and beam-column-slab connections of flat plates are analysed. Results confirm the effectiveness and accuracy of the layered procedure in predicting both flexural and shear cracking up to failure.

• Steel and Composite Structures
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• v.28 no.4
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• pp.471-482
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• 2018

The composite reinforced concrete and steel (RCS) structural systems have larger structural lateral stiffness, higher inherent structural damping, and faster construction speed than either traditional reinforcement concrete or steel structures. In this paper, four RCS subassemblies with or without the RC slab designed following a strong column-weak beam philosophy were constructed and tested under reversed-cyclic loading. Parameters including the width of slab and composite effect of the RC slab and beam were explored. The test results showed that all specimens performed in a ductile manner with plastic hinges formed in the beam ends near the column faces. The seismic responses of composite connections are influenced significantly by different width of slabs. Compared with that of the steel beam without the RC slab, it was found that the load carrying capacity of composite connections with the RC slab increased by 30% on average, and strength degradation, energy dissipation also had better performance, while the ductility of that were almost the same. Furthermore, the contribution of connection deformation to the overall specimen displacement was analyzed and compared. It decreased approximately 10% due to the coupling effect in the columns and beams with the RC slab. Based on the test result, some suggestions are presented for the design of composite RCS joints.