• Journal of the Korea Concrete Institute
• /
• v.18 no.2 s.92
• /
• pp.257-266
• /
• 2006

Flat-plate building systems are utilized extensively for construction of apartments, hotels and office buildings because of short construction period, low floor-to-floor height and flexibility in plan design. Recently, to increase lateral seismic resistance of flat-plate building systems, wall-columns are used frequently. Therefore, to estimate strength of flat-plate column connection accurately, the effect of column section shape on the behavior of flat-plate column connection should be considered properly, In the present study, a numerical analysis was performed for interior connections of continuous flat-plate to analyze the effect of column section shape. For the purpose, a computer program for nonlinear FE analysis was developed, and the validity was verified. Through the parametric study, the variations of shear stress distribution around the connection were investigated. According to the result of numerical analysis, as the length of the cross section of column in the direction of lateral load increases, the effective area and the maximum shear strength providing the torsional resistance decrease considerably. Therefore, these effects should be considered properly to estimate the strength of flat-plate connection accurately.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.11 no.6
• /
• pp.23-32
• /
• 2007

This study developed an analytical model for predicting nonlinear behavior of PT flat plate frames having slab-column connections with and without slab bottom reinforcement passing through the column. The developed model can predict the failure sequence until punching failure occurs. For verifying the analytical model, the test results of PT flat plate slab-column connections were compared with the results of the analysis. Moreover, the results of static pushover test and shaking table test of 2 story PT flat plate frame were compared with analysis results. For evaluating seismic performance of PT flat plate frame, this study conducted nonlinear response history analysis of the 2 story PT flat plate frame with and without slab bottom reinforcement passing through the column under 1940 El Centro ground motion scaled to have pseudo spectral acceleration of 0.3, 0.5, and 0.7g at the fundamental period of the frame. This study observed that as ground motion is more intense, seismic demands for the frame having the connections without slab bottom reinforcement passing through the column are larger than those without slab bottom reinforcement.

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

• Journal of the Korea Concrete Institute
• /
• v.18 no.3 s.93
• /
• pp.405-414
• /
• 2006

In the present study, a numerical analysis was performed for interior connections of continuous flat plate to analyze the effect of design parameters such as column section shape, gravity load and slab span on the behavioral characteristics of the connections. For the purpose, a computer program for nonlinear FE analysis was developed, and the validity was verified. Through the parametric study, the variations of shear stress distribution around the connection were investigated. According to the result of numerical analysis, as the length of the cross section of column in the direction of lateral load increases and gravity load increases, the effective area and the maximum shear strength providing the torsional resistance decrease considerably. And as the slab span loaded with relatively large gravity load increases, the negative moment around the connection increases and therefore the strength of connection against unbalanced moment decreases. By considering the effect of design parameters on the strength of the connections, the effective shear strength to calculate the torsional moment capacity of connection was proposed and the effectiveness of the proposed shear strength was verified.

• Journal of the Korea Concrete Institute
• /
• v.16 no.2 s.80
• /
• pp.229-240
• /
• 2004

Many experiments have been performed to investigate eccentric shear strength and unbalanced moment-carrying capacity of flat plate-column connections under combined gravity and lateral load. However, each existing experiment used different test setup, and the shear strength of the connection was different depending on the test setup. Current design methods which were based on the experimental results might not accurately explain the shear strength of the flat plate. In a companion study, based on results of nonlinear finite element analyses, an alternative design method for the plate-column connection was developed. However, in this method, eccentric shear strength of the connection which was required for assessing unbalanced moment-carrying capacity was evaluated by an empirical formula. In the present study, a theoratical approach using Rankine's failure criterion was attemped to investigate failure mechanism of the eccentric shear. Based on the results, an improved strength model of the eccentric shear was developed, and it was verified by comparison with the existing experimental results. By means of the strength model, the design method developed in the companion study was re-verified.

• Journal of the Korea Concrete Institute
• /
• v.16 no.2 s.80
• /
• pp.163-174
• /
• 2004

A number of experiments were performed to investigate the punching shear strength of flat plate-column connections. According to the experiments, the punching shear strength varies significantly with design parameters such as the column size of the connection, reinforcement ratio, and boundary condition. However, current design methods do not properly address the effects of such design parameters. In the present study, a theoratical approach using Rankine's failure cirterion was attempted to define the failure mechanism of the punching shear According to the study, the failure mechanism can be classified into the compression-controlled and the tension-controlled, depending on the amount of bottom re-bars placed at the connection, and the punching shear strength is also significantly affected by the flexural damage of slab. Based on the finding, a new strength model of punching shear was developed, and verified by the comparisons with existing experiments and nonlinear finite element analyses. The comparisons show that the proposed strength model addressing the effects of various design parameters can predict accurately the punching shear strength, compared to the existing strength models.

• Journal of the Korea Concrete Institute
• /
• v.14 no.6
• /
• pp.949-960
• /
• 2002

Flat plate structures under lateral load are susceptible to punching shear failure of the slab-column connection. To prevent such brittle failure, strength and ductility of the connection should be ensured. However, due to complexity in the behavior and difficulty in simulating the actual load and boundary conditions of the flat plate system, it is not easy to obtain reliable data regarding to the strength and ductility from the previous experimental studies. In the present study, a numerical study was performed for interior connections of continuous flat plate. For the purpose, a computer program for nonlinear FE analyses was developed, and the validity was verified by comparisons with the existing experimental results. Through the parametric studies, the variations of bending moment, shear, and torsional moment around the connection were investigated. Based on the findings of the numerical studies, the aspects which need to be improved in current design methods were discussed. The results of the present study will be used for developing a design method for the flat plate-column connection in the companion paper.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.14 no.3
• /
• pp.31-38
• /
• 2010

The purpose of this study is to evaluate the seismic performance of gravity-designed post tensioned (PT) flat plate frames with and without slab bottom reinforcement passing through the column. In low and moderate seismic regions, buildings are often designed considering only gravity loads. This study focuses on the seismic performance of gravity load designed PT flat plate frames. For this purpose, 3-, 6- and 9-story PT flat plate frames are designed considering only gravity loads. For reinforced concrete flat plate frames, continuous slab bottom reinforcement (integrity reinforcement) passing through the column should be placed to prevent progressive collapse; however, for the PT flat plate frames, the slab bottom reinforcement is often omitted since the requirement for the slab bottom reinforcement for PT flat plates is not clearly specified in ACI 318-08. This study evaluates the seismic performance of the model frames, which was evaluated by conducting nonlinear time history analyses. For conducting nonlinear time history analyses, six sets of ground motions are used as input ground motions, which represent two different hazard levels (return periods of 475 and 2475 years) and three different locations (Boston, Seattle, and L.A.). This study shows that gravity designed PT flat plate frames have some seismic resistance. In addition, the seismic performance of PT flat plate frames is significantly improved by the placement of slab bottom reinforcement passing through the column.

• Journal of the Korea Concrete Institute
• /
• v.29 no.2
• /
• pp.209-216
• /
• 2017

One of the important considerations in structural designing the flat plate system is ensuring the resistance to punching shear caused by axial loads and the ductile ability to follow horizontal deformation under earthquake. In this study, the ECC (Engineered Cementitious Composite) has been placed in the critical section zone of punching shear at slab-column joint to improve ductility and the advanced details of shear reinforced area nearby critical section zone has been developed using stud and steel fiber. The shear performance tests were performed on the specimens with parameters of fiber type mixed with ECC, stud and steel fiber set into the shear reinforced area in which the failure pattern, joint strength, displacement and strain of the specimen were compared and analyzed. The test results showed that the strength and ductility of specimens with ECC applied to joint were better than those of RC flat plate system. Also, the shear reinforcement effect of stud and the ductility improvement of steel fiber concrete were confirmed in the shear reinforcement area.

• Journal of the Korea Concrete Institute
• /
• v.14 no.6
• /
• pp.961-972
• /
• 2002

Flat plate structures under lateral load are susceptible to the brittle shear failure of plate-column connection. To prevent such brittle failure, strength and ductility of the connection should be ensured. However, according to previous studies, current design methods do not accurately estimate the strength of plate-column connection. In the present study, parametric study using nonlinear finite element analysis was performed for interior connections. Based on the numerical results, a design method for the connection was developed. At the critical sections around the connection coexist flexural moment and shear developed by lateral and gravity loads, and maximum allowable eccentric shear stresses were proposed based on the interactions between the flexural moment and shear, The proposed method can precisely predict the strength of the connection, compared with the current design provisions. The predictability of the proposed method was verified by the comparisons with existing experiments and nonlinear numerical analyses.