Evaluation of punching shear strength of voided slabs considering the effect of the ratio b₀/d

Chung, Joo-Hong,Bae, Baek-Il,Choi, Hyun-Ki,Jung, Hyung-Suk,Choi, Chang-Sik Elsevier 2018 ENGINEERING STRUCTURES Vol.164 No.-

<P><B>Abstract</B></P> <P>Voided slabs have been used as an effective technique to replace the heavy reinforced-concrete solid slabs. In voided slabs, the punching shear strength varies according to the arrangement of voids around the column because voids intersecting a failure surface anywhere along its radial length can directly reduce the punching shear strength and voids outside a failure surface can also reduce the punching shear strength by making the variation of shear stress around its perimeter. In this study, the punching shear strength of voided slabs was evaluated according to the arrangement of voids through experimental tests and numerical simulations. As a result, the factors on influencing the punching shear strength of voided slabs were determined as the void-based reduction of the cross-sectional area at the control perimeter and the ratio of the length of the control perimeter to the effective depth of the slab. Based on these influencing factors, a new method was developed to determine that the control perimeter section produces the smallest shear strength. This method can estimate the punching shear strength of voided slab systematically by assuming the location of the control perimeter at the solid region or voided region.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Test results of punching shear strength of voided slabs. </LI> <LI> Numerical investigation of the punching shear strength of voided slab. </LI> <LI> Punching shear strength evaluation of voided slabs which have affected by the arrangement of voids. </LI> <LI> Newly developed control perimeter calculation method for punching shear. </LI> </UL> </P>

PSC 바닥판의 뚫림전단강도 예측을 위한 단순트러스모델 개선 연구

박우진 ( Woo Jin Park ),황훈희 ( Hoon Hee Hwang ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.5

In this paper, the simple truss model was modified to predict the punching shear strength of long-span prestressed concrete (PSC) deck slabs under wheel load including the effects of transverse prestressing and long span length between girders. The strength of the compressive zone arounding punching cone was evaluated by the stiffness of inclined strut which was modified by considering aging effective modulus. The stiffness of springs which control lateral displacement of the roller supports consists of the steel reinforcement and prestressing which passed through the punching cone. Initial angle of struts was determined by the experimental observation to compensate for uncertainties in the complexities of the punching shear. The validity of computed punching shear strength by modified simple truss model was shown by comparing with experimental results and the experimental results were also compared with existing punching shear equations to determine level of predictability. The modified simple truss model appeared to better predict the punching shear strength of PSC deck slabs than other available equations. The punching shear strength, which was determined by snap-through critical load of modified simple truss model, can be used effectively to examine punching shear strength of long span PSC deck slabs.

Punching performance of RC slab-column connections with inner steel truss

Shi, Qingxuan,Ma, Ge,Guo, Jiangran,Ma, Chenchen Techno-Press 2022 Advances in concrete construction Vol.14 No.3

As a brittle failure mode, punching-shear failure can be widely found in traditional RC slab-column connections, which may lead to the entire collapse of a flat plate structure. In this paper, a novel RC slab-column connection with inner steel truss was proposed to enhance the punching strength. In the proposed connection, steel trusses, each of which was composed of four steel angles and a series of steel strips, were pre-assembled at the periphery of the column capital and behaved as transverse reinforcements. With the aim of exploring the punching behavior of this novel RC slab-column connection, a static punching test was conducted on two full-scaled RC slab specimens, and the crack patterns, failure modes, load-deflection and load-strain responses were thoroughly analyzed to explore the contribution of the applied inner steel trusses to the overall punching behavior. The test results indicated that all the test specimens suffered the typical punching-shear failure, and the higher punching strength and initial stiffness could be found in the specimen with inner steel trusses. The numerical models of tested specimens were analyzed in ABAQUS. These models were verified by comparing the results of the tests with the results of the analyzes, and subsequently the sensitivity of the punching capacity to different parameters was studied. Based on the test results, a modified critical shear crack theory, which could take the contribution of the steel trusses into account, was put forward to predict the punching strength of this novel RC slab-column connection, and the calculated results agreed well with the test results.

Punching-shear behaviors of RC-column footings with various reinforcement and strengthening details

Truong, Gia Toai,Choi, Kyoung-Kyu,Kim, Hee-Seung Elsevier 2017 Engineering structures Vol.151 No.-

<P><B>Abstract</B></P> <P>In this study, various reinforcement and strengthening details for the improvement of the punching-shear behavior of concrete footings were developed. Eight test specimens of reinforced-concrete (RC) footings were constructed and tested to investigate the punching-shear behavior of the concrete footings with the developed details. The test parameters include the additional placement of a longitudinal reinforcement around the column-footing connections, the inclination of the shear reinforcement, an additional cast of high-strength concrete, and an additional concrete cast with amorphous metallic fibers (AMFs). The test specimens were supported on a bed of steel car springs that simulate the elastic behavior of soil. The test results show that the punching strength was significantly enhanced by the additional placement of the longitudinal reinforcement around the column-footing connections and by the addition of the retrofit materials (high-strength concrete and AMF-reinforced concrete). Contrarily, the shear reinforcement that was placed around the connections did not significantly affect the punching-shear strength of the footings. The test results were also compared with strength predictions for which the current design codes and the existing theoretical models were used.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The punching shear behavior of RC column footings was investigated. </LI> <LI> A bed of steel car springs simulating the elastic behavior of soil was used. </LI> <LI> The effect of various reinforcing and strengthening methods on punching behavior of footings was analyzed. </LI> <LI> Contribution of AMF reinforced concrete on punching shear strength of footings was presented. </LI> <LI> The test results were compared with current design codes and theoretical models. </LI> </UL> </P>

초간편 강합성 바닥판의 펀칭 전단에 관한 실험적 연구

윤기용,이승열,이규세,김상섭 한국방재학회 2009 한국방재학회논문집 Vol.9 No.5

According to Korea Highway Bridge Design Code the bridge deck is designed by the strength design method and is regarded as a beam possessing the unit width based on the bending theory. By many researches it is revealed that the existing bridge deck is failed by punching shear. For evaluating the ultimate capacity of bridge deck it is important to estimate the behavior of bridge deck under the punching shear. For the punching strength it is difficult that the existing research results are applied to the simplified composite deck. In this study for comparing characteristics on punching shear the punching shear tests on simplified composite deck and RC deck are performed. The punching shear strength of simplified composite deck is compared with several bridge design codes. 현행 도로교설계기준의 바닥판에 대한 설계방법은 휨 이론에 따라 바닥판을 단위 폭의 보로 보고 강도설계법으로 설계하고 있다. 그러나 실제 교량 바닥판의 파괴 형태는 펀칭에 의한 파괴이므로 바닥판의 극한성능은 펀칭전단강도를 토대로 평가해야 할 것이다. 하지만 기존에 연구된 결과로는 초간편 강합성 바닥판의 펀칭전단강도를 산정하기 어려워 이에 대한 연구가 필요한 실정이다. 본 논문에서는 초간편 강합성 바닥판과 기존의 RC 바닥판에 대하여 펀칭전단강도실험을 실시하여 거동특성을 비교하였으며, 기존 RC 바닥판에 적용하고 있는 각국의 설계식들과 비교하였다.

Neuro-fuzzy optimisation to model the phenomenon of failure by punching of a slab-column connection without shear reinforcement

Mariam Hafidi,Fattoum Kharchi,Abdelouhab Lefkir 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.5

Two new predictive design methods are presented in this study. The first is a hybrid method, called neuro-fuzzy, based on neural networks with fuzzy learning. A total of 280 experimental datasets obtained from the literature concerning concentric punching shear tests of reinforced concrete slab-column connections without shear reinforcement were used to test the model (194 for experimentation and 86 for validation) and were endorsed by statistical validation criteria. The punching shear strength predicted by the neuro-fuzzy model was compared with those predicted by current models of punching shear, widely used in the design practice, such as ACI 318-08, SIA262 and CBA93. The neuro-fuzzy model showed high predictive accuracy of resistance to punching according to all of the relevant codes. A second, more userfriendly design method is presented based on a predictive linear regression model that supports all the geometric and material parameters involved in predicting punching shear. Despite its simplicity, this formulation showed accuracy equivalent to that of the neuro-fuzzy model.

A discrete element simulation of a punch-through shear test to investigate the confining pressure effects on the shear behaviour of concrete cracks

Alireza Bagher Shemirani,Vahab Sarfarazi,Hadi Haeri,Mohammad Fatehi Marji,Seyed shahin Hosseini 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.21 No.2

A discrete element approach is used to investigate the effects of confining stress on the shear behaviour of joint’s bridge area. A punch-through shear test is used to model the concrete cracks under different shear and confining stresses. Assuming a plane strain condition, special rectangular models are prepared with dimension of 75 mm×100 mm. Within the specimen model and near its four corners, four equally spaced vertical notches of the same depths are provided so that the central portion of the model remains intact. The lengths of notches are 35 mm. and these models are sequentially subjected to different confining pressures ranging from 2.5 to 15 MPa. The axial load is applied to the punch through the central portion of the model. This testing and models show that the failure process is mostly governed by the confining pressure. The shear strengths of the specimens are related to the fracture pattern and failure mechanism of the discontinuities. The shear behaviour of discontinuities is related to the number of induced shear bands which are increased by increasing the confining pressure while the cracks propagation lengths are decreased. The failure stress and the crack initiation stress both are increased due to confining pressure increase. As a whole, the mechanisms of brittle shear failure changes to that of the progressive failure by increasing the confining pressure.

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

Yaser Mirzaei,Mehrdad Sasani 사단법인 한국계산역학회 2013 Computers and Concrete, An International Journal Vol.12 No.3

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.

Neuro-fuzzy optimisation to model the phenomenon of failure by punching of a slab-column connection without shear reinforcement

Hafidi, Mariam,Kharchi, Fattoum,Lefkir, Abdelouhab Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.5

Two new predictive design methods are presented in this study. The first is a hybrid method, called neuro-fuzzy, based on neural networks with fuzzy learning. A total of 280 experimental datasets obtained from the literature concerning concentric punching shear tests of reinforced concrete slab-column connections without shear reinforcement were used to test the model (194 for experimentation and 86 for validation) and were endorsed by statistical validation criteria. The punching shear strength predicted by the neuro-fuzzy model was compared with those predicted by current models of punching shear, widely used in the design practice, such as ACI 318-08, SIA262 and CBA93. The neuro-fuzzy model showed high predictive accuracy of resistance to punching according to all of the relevant codes. A second, more user-friendly design method is presented based on a predictive linear regression model that supports all the geometric and material parameters involved in predicting punching shear. Despite its simplicity, this formulation showed accuracy equivalent to that of the neuro-fuzzy model.

절곡형 전단보강근을 사용한 슬래브-기둥 접합부의 이력 거동

이현호,이도범,이리형 한국구조물진단유지관리공학회 2006 한국구조물진단유지관리공학회 논문집 Vol.10 No.3

본 연구에서는 거주형 무량판 구조의 뚫림 전단을 방지하기 위한 연속 절곡된 전단 보강근을 개발하였다. 이를 적용한 슬래브-기둥 접합부에 있어 개발 전단 보강근의 뚫림 전단 성능을 평가하기 위하여, 구조 성능 실험을 수행하였다. 실험 변수는 전단보강근이 없는 경우, 개발 전단보강근을 사용한 경우, 헤드 스터드를 사용한 경우이다. 수평하중에 대한 저항성능을 평가하기 위하여 일정축력하에서의 이력 하중 실험을 수행하였다. 실험결과는 전체 변위 및 접합부 강도 등으로 평가되었다. 이러한 결과로부터, 개발된 전단보강근이 층간변위비 거동에 있어 우수한 성능을 보유함을 확인할 수 있었다. From the development of residential flat plate system, continuously bended shear reinforcement is developed for the prevention of punching shear. To know the punching shear capacity of developed shear reinforcement in slab-column joint, structural test is performed. The testing parameters are shear reinforcement types, such as no reinforcement, bended shear reinforcement, and head stud reinforcement. To verify the lateral capacity, cyclic load is applied under the constant vertical load condition. The results of tests are compared to as global displacement, slab-column joint strength. From the test results, the resisting capacity of developed shear reinforcement system has a good performance in the story drift ratio.