• Title, Summary, Keyword: punching shear failure

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Punching Shear Strength of Prestressed Precast Concrete Deck (프리스트레스를 도입한 프리캐스트 콘크리트 교량바닥판의 펀칭전단강도)

  • 정철헌;류형근;정운용;김인규
    • Journal of the Korea Concrete Institute
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    • v.14 no.5
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    • pp.653-659
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    • 2002
  • Recently, the failure case of the bridge deck slabs have been increasing in Korea and it was observed that the failure modes of most deck slabs collapsed were not caused by flexural moment but by local punching shear. The main reason of the failures was the punching shear failure of deck slabs under heavy truck traffics. This paper presents test results obtained from punching shear tests performed on prestressed precast deck specimens. Cracking patterns, failure modes, deflections, and stresses are included as well as discussion of the punching shear strength observed during punching shear tests. Static lest specimens had punching shear failures at loads much higher than predicted by the current codes. Tests results indicate that current code provisions appear to be conservative.

Comparison on the Failure Mechanism of Punching Shear in the Reinforced Concrete (철근 콘크리트의 뚫림전단 파괴메카니즘에 과한 비교)

  • 이주나;연규원;이호준;박찬수
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.533-538
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    • 2000
  • In R.C. flat slab system, a brittle punching failure is a very fatal problem. But there is no generally well-defined answer to the problem and there are wide differences in current practical design codes. therefore, in this study, the factors affecting to punching failure mechanism have been studied to find out the punching shear behavior in R.C. flat slabs by comparing other investigations and practical design codes. Therefore, In this study, the factors affecting to punching failure mechanism have been studied to find out the punching shear behavior in R.C. flat slabs by comparing other investigations and practical design codes. The conclusions in this study are summarized as follows; 1) The factors affecting to punching shear are concrete strength ($f_\alpha$), ratio of column side length to slab depth (c/d), ratio of distance from column center to radial contraflexure (l/d), yield strength of steel ($f_y$), flexural reinforcement ratio ($\rho$) and size effects. 2) It is shown that th use of $\surd{f_{ck}}$in applying($f_\alpha$ to punching shear strength estimation may be more sensitive in high concrete strength. 3) The effects of l/d, ($f_y$, size are no clear in the punching failure mechanism, so in the future, it should be investigated with the effects of various composed load.

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Progressive collapse resistance of flat slabs: modeling post-punching behavior

  • Mirzaeia, Yaser;Sasani, Mehrdad
    • Computers and Concrete
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    • v.12 no.3
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    • pp.351-375
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    • 2013
  • Post-punching resistance of a flat slab can help redistribute the gravity loads and resist progressive collapse of a structure following initial damage. One important difficulty with accounting for the post-punching strength of a slab is the discontinuity that develops following punching shear. A numerical simulation technique is proposed here to model and evaluate post-punching resistance of flat slabs. It is demonstrated that the simulation results of punching shear and post-punching response of the model of a slab on a single column are in good agreement with corresponding experimental data. It is also shown that progressive collapse due to a column removal (explosion) can lead to punching failure over an adjacent column. Such failure can propagate throughout the structure leading to the progressive collapse of the structure. Through post-punching modeling of the slab and accounting for the associated discontinuity, it is also demonstrated that the presence of an adequate amount of integrity reinforcement can provide an alternative load path and help resist progressive collapse.

A Study of Shear Reinforcement for Slab-Column Connection (슬래브-기둥 접합부의 전단보강상세에 관한 연구)

  • Baek, Sung-Woo;Kim, Jun-Seo;Choi, Hyun-Ki;Choi, Chang-Sik
    • 한국방재학회:학술대회논문집
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    • pp.37-40
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    • 2008
  • The study is an experimental test on full-scale flat plate slab-column interior connection. The punching shear on the flat plate slab-column connection can bring about the reason of the brittle punching shear failure which may result of collapsing the whole structure. From the development of residential flat plate system, the shear reinforcement is developed for preventing the punching shear. For making sure of the punching shear capacity, developed for shear reinforcement in slab-column connection, the structural test is performed. The dimension of the slabs was 2620*2725*180mm with square column (600*800mm). The slabs were tested up to failure monotonic vertical shear forces. The presences of S/S bar and wire mesh substantially increased the punching shear capacity and the ductility of the slab-column connections.

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Numerical study on effect of integrity reinforcement on punching shear of flat plate

  • Ahsan, Raquib;Zahura, Fatema T.
    • Computers and Concrete
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    • v.20 no.6
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    • pp.731-738
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    • 2017
  • Reinforced concrete flat plates consist of slabs supported directly on columns. The absence of beams makes these systems attractive due to advantages such as economical formwork, shorter construction time, less total building height with more clear space and architectural flexibility. Punching shear failure is usually the governing failure mode of flat plate structures. Punching failure is brittle in nature which induces more vulnerability to this type of structure. To analyze the flat plate behavior under punching shear, twelve finite element models of flat plate on a column with different parameters have been developed and verified with experimental results. The maximum range of variation of punching stress, obtained numerically, is within 10% of the experimental results. Additional finite element models have been developed to analyze the influence of integrity reinforcement, clear cover and column reinforcement. Variation of clear cover influences the punching capacity of flat plate. Proposed finite element model can be a substitute to mechanical model to understand the influence of clear cover. Variation of slab thickness along with column reinforcement has noteworthy impact on punching capacity. From the study it has been noted that integrity reinforcement can increase the punching capacity as much as 19 percent in terms of force and 101 percent in terms of deformation.

Estimation of Punching Shear Strength for Ultra High Performance Concrete Thin Slab (강섬유 보강 초고성능 콘크리트 슬래브의 뚫림 전단 성능 평가)

  • Park, Ji-Hyun;Hong, Sung-gul
    • Journal of Korean Association for Spatial Structures
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    • v.15 no.2
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    • pp.95-103
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    • 2015
  • UHPC(Ultra High Performance Concrete) is used widely with its remarkable performance, such as strength, ductility and durability. Since the fibers in the UHPC can control the tensile crack, the punching shear capacity of UHPC is higher than that of the conventional concrete. In this paper, seven slabs with different thickness and fiber volume ratio were tested. The ultimate punching shear strength was increased with the fiber volume ratio up to 1%. The shear capacity of specimens with the fiber content 1% and 1.5% do not have big differences. The thicker slab has higher punching shear strength and lower deformation capacity. The critical sections of punching shear failure were similar regardless of the fiber volume ratio, but it were larger in thicker slab.

Strength Model for Punching Shear of Flat Plate-Column Connections (플랫플레이트-기둥 접합부의 뚫림전단강도)

  • Choi Kyoung-Kyu;Park Hong-Gun
    • Journal of the Korea Concrete Institute
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    • v.16 no.2
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    • pp.163-174
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    • 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.

Crack constitutive model for the prediction of punching failure modes of fiber reinforced concrete laminar structures

  • Ventura-Gouveia, A.;Barros, Joaquim A.O.;Azevedo, Alvaro F.M.
    • Computers and Concrete
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    • v.8 no.6
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    • pp.735-755
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    • 2011
  • The capability of a multi-directional fixed smeared crack constitutive model to simulate the flexural/punching failure modes of fiber reinforced concrete (FRC) laminar structures is discussed. The constitutive model is implemented in a computer program based on the finite element method, where the FRC laminar structures were simulated according to the Reissner-Mindlin shell theory. The shell is discretized into layers for the simulation of the membrane, bending and out-of-plane shear nonlinear behavior. A stress-strain softening diagram is proposed to reproduce, after crack initiation, the evolution of the normal crack component. The in-plane shear crack component is obtained using the concept of shear retention factor, defined by a crack-strain dependent law. To capture the punching failure mode, a softening diagram is proposed to simulate the decrease of the out-of-plane shear stress components with the increase of the corresponding shear strain components, after crack initiation. With this relatively simple approach, accurate predictions of the behavior of FRC structures failing in bending and in shear can be obtained. To assess the predictive performance of the model, a punching experimental test of a module of a façade panel fabricated with steel fiber reinforced self-compacting concrete is numerically simulated. The influence of some parameters defining the softening diagrams is discussed.

Parametric studies on punching shear behavior of RC flat slabs without shear reinforcement

  • Elsamak, Galal;Fayed, Sabry
    • Computers and Concrete
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    • v.25 no.4
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    • pp.355-367
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    • 2020
  • This paper proposed a numerical investigation based on finite elements analysis (FEA) in order to study the punching shear behavior of reinforced concrete (RC) flat slabs using ABAQUS and SAP2000 programs. Firstly, the concrete and the steel reinforcements were modeled by hexahedral 3D solid and linear elements respectively, and the nonlinearity of the used materials was considered. In order to validate this model, experimental results considered in literature were compared with the proposed FE model. After validation, a parametric study was performed. The parameters include the slab thickness, the flexure reinforcement ratios and the axial membrane loads. Then, to reduce the time of FEA, a simplified modelling using 3D layered shell element and shear hinge concept was also induced. The effect of the footings settlement was studied using the proposed simplified nonlinear model as a case study. Results of numerical models showed that increase of the slab thickness by 185.7% enhanced the ultimate load by 439.1%, accompanied with a brittle punching failure. The punching failure occurred in one of the tested specimens when the tensile reinforcement ratio increased more than 0.65% and the punching capacity improved with increasing the horizontal flexural reinforcement; it decreased by 30% with the settlement of the outer footings.

Shear Strength Model for Interior Flat Plate-Column Connections (무량판 슬래브-기둥 내부 접합부에 대한 전단강도모델)

  • Choi, Kyoung-Kyu;Park, Hong-Gun
    • Journal of the Korea Concrete Institute
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    • v.22 no.3
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    • pp.345-356
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    • 2010
  • An alternative design method for interior flat plate-column connections subjected to punching shear and unbalanced moment was developed. Since the slab-column connections are severely damaged by flexural cracking before punching shear failure, punching shear was assumed to be resisted mainly by the compression zone of the slab critical section. Considering the interaction with the flexural moment of the slab, the punching shear strength of the compression zone was evaluated based on the material failure criteria of concrete subjected to multiple stresses. The punching shear strength was also used to evaluate the unbalanced moment capacity of the slab-column connections. For verification, the proposed strength model was applied to existing test specimens subjected to direct punching shear or combined punching shear and unbalanced moment. The results showed that the proposed method predicted the strengths of the test specimens better than current design methods in ACI 318 and Eurocode 2.