• 제목/요약/키워드: shear key failure

검색결과 144건 처리시간 0.03초

Experimental study on the shear failure model for concrete under compression-shear loading

  • Shu, Xiaojuan;Luo, Yili;Zhao, Chao;Dai, Zhicheng;Zhong, Xingu;Zhang, Tianyu
    • Computers and Concrete
    • /
    • 제29권2호
    • /
    • pp.81-92
    • /
    • 2022
  • The influence of normal stress perpendicular to the potential shear plane was always neglected in existing researches, which may lead to a serious deviation of the shear strength of concrete members in practice designs and numerical analyses. In this study, a series of experimental studies are carried out in this paper, which serves to investigate the shear behavior of concrete under compression shear loading. Based on the test results, a three-phase shear failure model for cohesive elements are developed, which is able to take into consideration the influence of normal stress on the shear strength of concrete. To identify the accuracy and applicability of the proposed model, numerical models of a double-noted concrete plate are developed and compared with experimental results. Results show that the proposed constitutive model is able to take into consideration the influence of normal stress on the shear strength of concrete materials, and is effective and accurate for describing the complex fracture of concrete, especially the failure modes under compression shear loadings.

탄소섬유쉬트로 보강된 철근콘크리트 보의 휨거동에 전단키와 U 스터립이 미치는 영향 (Effect of Shear Key and U strip on Flexural Behavior of Reinforced Concrete Beams Strengthened by CFS(Carbon Fiber Sheet))

  • 최홍식;이진용;이성태;이시우;허권
    • 한국콘크리트학회:학술대회논문집
    • /
    • 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
    • /
    • pp.88-91
    • /
    • 2004
  • It is generally known that the bonding strength of RC(Reinforced Concrete) flexural members strengthened by fiber sheet composites are sufficient and the bonding failure does not occur until the sheet failed. However, many researchers have been reported that, before the failure of the sheet, the bonding failure happens even though the bonding length is sufficient. This study was carried out to evaluate the effectiveness of shear key and U strip on flexural behavior of reinforced concrete beam structures. The ply number of CFS(Carbon Fiber Sheet), location of shear key, and existence or not of U strip were selected as the main test variables. Test results show that the behavior of a beam of which shear key is located in the nearby. of support and U strip is not existent, and having CFS of 1 ply is mostly improved.

  • PDF

Mechanical properties and failure mechanism of gravelly soils in large scale direct shear test using DEM

  • Tu, Yiliang;Wang, Xingchi;Lan, Yuzhou;Wang, Junbao;Liao, Qian
    • Geomechanics and Engineering
    • /
    • 제30권1호
    • /
    • pp.27-44
    • /
    • 2022
  • Gravelly soil is a kind of special geotechnical material, which is widely used in the subgrade engineering of railway, highway and airport. Its mechanical properties are very complex, and will greatly influence the stability of subgrade engineering. To investigate the mechanical properties and failure mechanism of gravelly soils, this paper introduced and verified a new discrete element method (DEM) of gravelly soils in large scale direct shear test, which considers the actual shape and broken characteristics of gravels. Then, the stress and strain characteristics, particle interaction, particle contact force, crack development and energy conversion in gravelly soils during the shear process were analyzed using this method. Moreover, the effects of gravel content (GC) on the mechanical properties and failure characteristics were discussed. The results reveal that as GC increases, the shear stress becomes more fluctuating, the peak shear stress increases, the volumetric strain tends to dilate, the average particle contact force increases, the cumulative number of cracks increases, and the shear failure plane becomes coarser. Higher GC will change the friction angle with a trend of "stability", "increase", and "stability". Differently, it affects the cohesion with a law of "increase", "stability" and "increase".

Classification method for failure modes of RC columns based on key characteristic parameters

  • Yu, Bo;Yu, Zecheng;Li, Qiming;Li, Bing
    • Structural Engineering and Mechanics
    • /
    • 제84권1호
    • /
    • pp.1-16
    • /
    • 2022
  • An efficient and accurate classification method for failure modes of reinforced concrete (RC) columns was proposed based on key characteristic parameters. The weight coefficients of seven characteristic parameters for failure modes of RC columns were determined first based on the support vector machine-recursive feature elimination. Then key characteristic parameters for classifying flexure, flexure-shear and shear failure modes of RC columns were selected respectively. Subsequently, a support vector machine with key characteristic parameters (SVM-K) was proposed to classify three types of failure modes of RC columns. The optimal parameters of SVM-K were determined by using the ten-fold cross-validation and the grid-search algorithm based on 270 sets of available experimental data. Results indicate that the proposed SVM-K has high overall accuracy, recall and precision (e.g., accuracy>95%, recall>90%, precision>90%), which means that the proposed SVM-K has superior performance for classification of failure modes of RC columns. Based on the selected key characteristic parameters for different types of failure modes of RC columns, the accuracy of SVM-K is improved and the decision function of SVM-K is simplified by reducing the dimensions and number of support vectors.

전단저항키 실험 및 내진성능평가 (Experimental and Analytical Evaluation of Seismic Performance of Shear-Resistance Key)

  • 박종철;강형택;박찬민
    • 한국콘크리트학회:학술대회논문집
    • /
    • 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
    • /
    • pp.523-528
    • /
    • 2000
  • In multi-span bridges, a shear key is often used to distribute the seismic force to the case, the shear key is sometimes required to be reinforced to withstand the seismic force. To improve the strength of shear key, the strength and failure mode of shear key have to be carefully estimated and the proper reinforcement scheme should be elaborated. The test results show that the strength of shear key is 2.5 times higher than the strength calculated by PCI design handbook. Also the strength of shear key is greatly improved by placing PT bars into shear key. In this study, the analytical method to evaluate the strength of sheat key and the reinforcement scheme are proposed.

  • PDF

토사지반에 설치된 역 T형 옹벽의 저판형상이 활동거동에 미치는 영향 (Effects of Base Shape of Cantilever Retaining Wall in Soil Foundation on the Sliding Behavior)

  • 유남재;이명욱;김영길;이종호
    • 산업기술연구
    • /
    • 제19권
    • /
    • pp.135-145
    • /
    • 1999
  • This thesis is to investigate the sliding behavior of cantilever retaining wall by using the commercially available program of FLAC to simulate its behavior numerically. Cantilever retaining walls with flat base, sloped base and base with shear key, uniform surcharges being applied on the surface of backfill, were investigated to figure out appropriate location of shear key beneath the base of wall and, thus, its applicability to field condition was assessed by comparing the analyzed results to each other. On the other hand, previously performed centrifuge model test results (Eum, 1996) were analyzed numerically with FLAC to compare test results with respect to characteristics of load-settlement of surcharges and load-lateral movement of wall. Based on the failure mechanism observed during centrifuge tests, limit equilibrium method of finding the ultimate load inducing the sliding failure of wall was used to compare with values of the ultimate load obtained from conventional method of limit equilibrium method. Therefore, appropriate location of shear key was determined to mobilize the maximum resistance against sliding failure of wall.

  • PDF

Numerical simulation of the effect of bedding layer geometrical properties on the shear failure mechanism using PFC3D

  • Haeri, Hadi;Sarfarazi, Vahab;Zhu, Zheming;Marji, Mohammad Fatehi
    • Smart Structures and Systems
    • /
    • 제22권5호
    • /
    • pp.611-620
    • /
    • 2018
  • In this research the effect of bedding layer angle and bedding layer thickness on the shear failure mechanism of concrete has been investigated using PFC3D. For this purpose, firstly calibration of PFC3d was performed using Brazilian tensile strength. Secondly shear test was performed on the bedding layer. Thickness of layers were 5 mm, 10 mm and 20 mm. in each thickness layer, layer angles changes from $0^{\circ}$ to $90^{\circ}$ with increment of $25^{\circ}$. Totally 15 model were simulated and tested by loading rate of 0.016 mm/s. The results shows that when layer angle is less than $50^{\circ}$, tensile cracks initiates between the layers and propagate till coalesce with model boundary. Its trace is too high. With increasing the layer angle, less layer mobilize in failure process. Also the failure trace is very short. It's to be note that number of cracks decrease with increasing the layer thickness. The minimum shear test strength was occurred when layer angle is more than $50^{\circ}$. The maximum value occurred in $0^{\circ}$. Also, the shear test tensile strength was increased by increasing the layer thickness.

Numerical simulations of fracture shear test in anisotropy rocks with bedding layers

  • Haeri, Hadi;Sarfarazi, Vahab;Zhu, Zheming;Nejati, Hamid Reza
    • Advances in concrete construction
    • /
    • 제7권4호
    • /
    • pp.241-247
    • /
    • 2019
  • In this paper the effect of bedding layer on the failure mechanism of rock in direct shear test has been investigated using particle flow code, PFC. For this purpose, firstly calibration of pfc2d was performed using Brazilian tensile strength. Secondly direct shear test consisting bedding layer was simulated numerically. Thickness of layers was 10 mm and rock bridge length was 10 mm, 40 mm and 60 mm. In each rock bridge length, bedding layer angles changes from $0^{\circ}$ to $90^{\circ}$ with increment of $15^{\circ}$. Totally 21 models were simulated and tested. The results show that two types of cracks develop within the model. Shear cracks and tensile cracks. Also failure pattern is affected by bridge length while shear strength is controlled by failure pattern. It's to be noted that bedding layer has not any effect on the failure pattern because the layer interface strength is too high.

Behaviors of novel sandwich composite beams with normal weight concrete

  • Yan, Jia-Bao;Dong, Xin;Wang, Tao
    • Steel and Composite Structures
    • /
    • 제38권5호
    • /
    • pp.599-615
    • /
    • 2021
  • The ultimate strength behaviour of sandwich composite beams with J-hooks and normal weight concrete (SCSSBJNs) are studied through two-point loading tests on ten full-scale SCSSBJNs. The test results show that the SCSSBJN with different parameters under two-point loads exhibits three types of failure modes, i.e., flexure, shear, and combined shear and flexure mode. SCSSBJN failed in different failure modes exhibits different load-deflection behaviours, and the main difference of these three types of behaviours exist in their last working stages. The influences of thickness of steel faceplate, shear span ratio, concrete core strength, and spacing of J-hooks on structural behaviours of SCSSBJN are discussed and analysed. These test results show that the failure mode of SCSSBJN was sensitive to the thickness of steel faceplate, shear span ratio, and concrete core strength. Theoretical models are developed to estimate the cracking, yielding, and ultimate bending resistance of SCSSBJN as well as its transverse cross-sectional shear resistance. The validations of predictions by these theoretical models proved that they are capable of estimating strengths of novel SCSSBJNs.

압축하중을 받는 1/12.5 축소모형 강관 연결부의 부착전단 거동에 대한 실험적 연구 (Experimental Study on Bond Behavior of 1/12.5 Scale Model of the Steel Tubular Joint Connection Subjected to Compressive Loads)

  • 오홍섭
    • 한국구조물진단유지관리공학회 논문집
    • /
    • 제28권3호
    • /
    • pp.19-26
    • /
    • 2024
  • 본 연구에서는 풍력타워 지지구조 연결부 1/12.5 축소모형 실험체의 압축거동을 실험적으로 분석하였다. 압축강도 140MPa의 고성능 시멘트계 그라우트를 연결부에 충전하였으며, 전단키 간격, 형상과 연결부 길이를 변수로 하여 실험을 수행하였다. 연결부 내의 전단키의 개수가 동일한 경우 연결부 길이보단 전단키의 간격이 작을수록 부착전단강도가 높게 나타났으며, 동일한 간격과 연결부 길이에서는 전단키의 높이가 높을수록 강도가 높게 나타났다. 또한 연결부 슬립량 1.0mm 내외까지 선형거동을 한 후 하중이 증가함에 따라 비선형 거동을 한후 7.0mm 내외의 슬립에서 최대 강도에 도달하는 것으로 나타났다. 전단키의 형상과 간격 등에 따라 강도가 증가함에 따라 파괴형태는 계면전단파괴에서 그라우트 파괴로 변화하는 것으로 나타났으며, 강섬유에 의해 취성적인 파괴는 발생하지 않는 것으로 나타났다.