고강도 콘크리트를 사용한 플랫 플레이트 구조의 기둥-슬래브 접합부 강성에 관한 연구

김형기,유제준 대한건축학회 2005 大韓建築學會論文集 : 構造系 Vol.21 No.2

In this study, the four column-slab connections in flat plate system using high strength concrete exceeding 60㎫, modeled after a typical reinforced concrete flat plate building, were tested under combined gravity and lateral loadings. The variables selected for this study were the slab reinforcement ratio and the level of slab gravity load. The test results were compared with the stiffness predictions of elastic finite element analysis, the ACI equivalent frame method and the AIJ method. The followings were found: 1) The stiffness of column-slab connection under gravity loading reduced as the slab gravity load increased. At the level of service gravity load, the gravity stiffness was about 70 percent of initial stiffness. 2) The lateral stiffness of column-slab connection decreased with increasing the lateral deflection and was dependent on the level of slab gravity "load and slab reinforcement percentage. 3) The initial lateral stiffness was about 50 percent of elastic finite element analysis in lateral drift ratio of 0.0625 percent. This was attributed to the accelerated slab cracking around the connection as a result of the increased gravity load moments. 4) The lateral stiffness varied from 24 to 37 percent of elastic finite element analysis and from 17 to 26 percent of ACI equivalent frame method in lateral drift ratio of 0.2 percent. This result gave agreement with other researcher's test result of column-slab connection in flat plate system using normal strength concrete.

Development and evaluation of punching shear database for flat slab-column connections without shear reinforcement

Derogar, Shahram,Ince, Ceren,Mandal, Parthasarathi Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.2

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.

Development and evaluation of punching shear database for flat slab-column connections without shear reinforcement

Shahram Derogar,Ceren Ince,Parthasarathi Mandal 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.2

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.

Enhancing the performance of UHSC columns intersected by weaker slabs

Shin, H.O.,Yoon, Y.S.,Cook, W.D.,Mitchell, D. Elsevier 2016 ENGINEERING STRUCTURES Vol.127 No.-

This paper presents strategies for enhancing the transmission of ultra-high-strength concrete (UHSC) column loads through normal-strength concrete (NSC) slabs in the joint of slab-column connections. Parameters of the investigation were the ratio of column concrete strength to slab concrete strength (f<SUB>cc</SUB><SUP>'</SUP>/f<SUB>cs</SUB><SUP>'</SUP>), as well as the placement of steel fiber-reinforced concrete, and the installations of high-strength dowel bars and special structural steel inserts in the weak slab joint. The beneficial effects of using high-strength dowel bars and high-strength structural steel inserts on the ability to transmit axial loads from the UHSC columns through the weaker slabs were demonstrated. The benefits of placing steel fiber-reinforced concrete in the joint are not as significant as the additional high-strength steel reinforcement. Predictions of the effective concrete strengths using current code approaches and using equations proposed in the literature were compared to the experimental results. The results indicate that the design approach in the CSA Standard (CSA A23.3-14) and the method proposed by Kayani (1992), which is based on the a data fitting approach, provide reasonable lower bound predictions of the effective strength for the UHSC columns with weaker slab layers.

슬래브-기둥 접합부의 구속도 및 드롭패널에 따른 방폭 성능 평가

임광모,이주하 대한토목학회 2017 대한토목학회논문집 Vol.37 No.2

The numerical analysis was conducted to evaluate the behavior of slab-column connection subjected to blast loads using LS-DYNA. The typical form of slab-interior column connection for analysis was considered as a reference specimen and the drop panel slab-interior column was designed to verify the effects of drop panel. The slab-column connections, which were composed of interior, edge and corner column, were additionally analyzed to compare their confinement effects of specimens. Analysis results were contained the failure shape of connection, behavior of member and so on. From the results, the blast-resistant capacities of slab-column connection would be enhanced by reinforcing the drop panel. In addition, the performance of connections could be improved, when the confinement effects were enhanced. 본 연구에서는 폭발하중을 받는 슬래브-기둥 접합부의 거동을 해석적으로 분석하였다. 슬래브-기둥의 거동을 분석하기 위해 유한요소해석프로그램 LS-DYNA를 사용하여 폭발해석을 수행하였다. 대상 접합부의 형태는 일반적인 내부기둥형태의 슬래브-기둥 접합부와 기둥주위에 드롭패널(drop panel)을 보강한 접합부로 설정하였다. 또한, 슬래브에 의한 기둥의 구속도에 따라 내부기둥, 외부기둥 그리고 모서리기둥 시험체를 모델링하여 비교분석이 수행되었다. 해석결과는 접합부의 파괴형상, 단위부재의 거동 등을 포함하고 있다. 해석결과 드롭패널을 보강한 경우 슬래브-기둥 접합부의 거동이 향상되는 것을 확인하였으며 슬래브에 의한 기둥의 구속도가 감소할수록 거동이 저하되는 것을 확인하였다

Effect of Embedded Pipelines within Slab Thickness on Punching Shear Capacity of Flat Slabs

Haider Ali Al-Tameemi,Mohsen A. Habelalmateen,Ahmed A. Alalikhan 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.1

Frequently, construction requirements demand to provide service pipelines passing laterally within slab thickness near the slab-column connections of flat slabs. The flat slabs including such conducted pipelines are expected to undergo a significant reduction in the punching shear capacity. For this purpose, experimental program was conducted in this study incorporating 10 specimens of reinforced concrete flat slab. One slab specimen was solid slab with no pipeline as a reference specimen and the other nine slab specimens were fabricated with either single or double pipelines passing through the slab thickness at different locations. Test results indicated that including pipelines within the slab thickness at a horizontal distance equal to or less than one-half of the slab thickness from the face of the column led to a substantial reduction in the ultimate load and the stiffness of the flat slabs. It was also found that the structural performance of a flat slab with double small pipelines horizontally aligned near tension face was more desirable than that of a flat slab with a single large pipeline. Furthermore, a modification is suggested to be introduced to the punching shear equation of Eurocode 2 to include the effect of the embedded pipelines in flat slabs.

래티스 철근 보강 슬래브-기둥 접합부에 대한 주기하중실험

김유니,강수민,박홍근 대한건축학회 2011 大韓建築學會論文集 : 構造系 Vol.27 No.10

An experimental study was performed to investigate the unbalanced moment–carrying capacity of slab–column connections reinforced with lattice reinforcement. In the lattice reinforcement, top and bottom longitudinal bars are weld-connected with web bars. The web bars are used as shear reinforcement. The top and bottom bars provide flexural resistance and the anchorage for the web bars. In this test, six specimens of slab-column connection including a shear-unreinforced specimen were tested under cyclic loading, maintaining a direct punching shear force. The test parameters were the length of the lattice bars and the shape of the layout. For the layout, cruciform, combined cruciform and corner reinforcement, and parallel layouts were used. The length of the lattice bars from the column face was 3.0 ~ 8.0 times the slab depth. According to the test results, the lattice reinforcement improved the load-carrying capacity and deformation capacity of the slab-column connection. However, the effect of the lattice reinforcement significantly varied with the length and the layout of the lattice-reinforcement. The combined cruciform and corner reinforcement layout showed the best performance even with a short length, 3.0 times the slab depth. The contributions of the lattice reinforcement to the flexural moment capacity and the eccentric shear capacity were discussed.

Modification of the ACI 318 Design Method for Slab-Column Connections Subjected to Unbalanced Moment

Choi, Kyoung-Kyu,Shin, Dong-Woo,Park, Hong-Gun MULTI SCIENCE 2014 ADVANCES IN STRUCTURAL ENGINEERING Vol. No.

<P> In the ACI 318-11 design method for slab-column connections subjected to unbalanced moment, the contribution factors assigning the proportion of the connection unbalanced moment to be resisted by the slab flexural reinforcement and by eccentric vertical shear stresses are prescribed by only considering the aspect ratio of columns. However, the validity of the prescribed contribution factors have not been completely verified by extensive test results, and the strength prediction by the design method using the contribution factors does not agree well with existing test results. In the present study, a modified strength model was proposed without prescribing the contribution factors. In the proposed model, the contribution of flexural moment is directly calculated using the slab reinforcement ratio, and the contribution of eccentric shear is calculated based on the conventional eccentric shear stress model. The proposed method was verified by comparing its prediction with existing test results. The results showed that the proposed method predicts the test results with reasonable accuracy, and it corresponds with the fundamental mechanics of the punching shear of slab-column connections as investigated in previous studies. </P>

Experimental investigation on the seismic behavior of reinforced concrete column-steel beam subassemblies

Liquan Xiong,Jinjie Men,Ruyue Ren,Mengke Lei 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.28 No.4

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.

Punching Shear Strength of Slab-Column Connections

Choi, Kyoung-Kyu,Cho, Seung-Ho,Park, Hong-Gun,Lee, Sang-Hyun,Chung, Lan 단국대 부설 리모델링연구소 2009 리모델링 연구소 논문집 Vol.7 No.1

A improved strength model was developed to predict the punching shear strength of interior slab-column connections without shear reinforcement. Considering the damage due to flexural cracking at slab-column connections damaged by flexural cracking, the punchingshear force was assumed to be resisted mainly by the compression zone of the critical section. The punching shear strength was defined by using the material failure criteria of concrete. In the evaluation of the punching shear strength, the interaction between the shear stress and the compressive normal stress developed by the flexural moment of the slab was considered. The proposed strength model was verified by existing test specimens.