• Title/Summary/Keyword: Interface shear strength

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Bi-Axial Stress Field Analysis on Shear-Friction in RC Members (2축-응력장 이론을 이용한 철근콘크리트 부재의 전단마찰 해석)

  • Kim, Min-Joong;Lee, Gi-Yeol;Lee, Jun-Seok;Kim, Woo
    • Journal of the Korea Concrete Institute
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    • v.24 no.1
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    • pp.25-35
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    • 2012
  • For a member subjected to direct shear forces, forces are transferred across interface concrete area and resisted by shear transfer capacity. Shear-friction equations in recent concrete structural design provisions are derived from experimental test results where shear-friction capacity is defined as a function of steel reinforcement area contained in the interface. This empirical equation gave too conservative values for concrete members with large amounts of reinforcement. This paper presents a method to evaluate shear transfer strengths and to define ultimate conditions which result in crushing of concrete struts after yielding of longitudinal reinforcement perpendicular to the interface concrete. This method is based on the bi-axial stress field theory where different constitutive laws are applied in various means to gain accurate shear strengths by considering softening effects of concrete struts based on the modified compression-field theory and the softened truss model. The validity of the proposed method is examined by applying to some selected test specimens in literatures and results are compared with recent design code provisions. A general agreement is observed between predicted and measured values at ultimate loading stages in initially uncracked normal-strength concrete test.

THE SHEAR BOND STRENGTH BETWEEN DICOR AND SEVERAL VENEERING PORCELAINS (Dicor와 수종 전장도재간의 전단결합강도)

  • Ryoo, Kyung-Hee;Lee, Sun-Hyung
    • The Journal of Korean Academy of Prosthodontics
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    • v.31 no.2
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    • pp.165-179
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    • 1993
  • Dicor has not been prescribed routinely, in spite of many advantages, because of esthetic limitations by excessive translucency and external shading. In an attempt to solve these problems, the technique of veneering Dicor by aluminous poreclain has been used and recently Dicor Plus system was developed. The purpose of this study was to evaluate the compatibility between Dicor and several veneering porcelains by measuring the shear bond strength and observing the failure mode and interface appearance with SEM. Total 55 Dicor disks(10.0mm diam. X 3.0mm thickness) were fabricated by lost wax technique and divided into five groups of 11. Veneering porcelains such as Dicor Plus, Vitadur Alpha, Vitadur N, Vivodent, and Ceramco II were built up over the center of the treated Dicor surface using paper tube(5.0mm diam. X 4.0mm height) and fired according to the manufacturesr’instructions. A representative sample from each group was completely embedded in epoxy resin and crosssectioned, and remaining 50 samples were embedded in epoxy resin with the bonded area perpendicular to table base. The shear bond strengths were measured by applying the shear load parallel to Dicor surface close to the bonded area. Failure modes and interface appearances were observed using SEM at 15 and 1000 magnification respectively. The obtained results were as follows : 1. The mean shear bond strengths showed Dicor-Dicor Plus(10.53 MPa); Dicor-Vitadur Alpha(8.84 MPa); Dicor-Vitadur N(7.37 MPa); Dicor-Vivodent(4.28 MPa); Dicor-Ceramco II(0.89 MPa). 2. The shear bond strength of Dicor-CeramcoII was significantly decreased compared with Dicor-Dicor Plus(p<0.01), but had no significant difference compared with Dicor-Vivodent(p>0.01). 3. The shear bond strengths of Dicor-Vitadur Alpha and Dicor-Vitadur N were not significantly different compared with Dicor-Dicor Plus(p>0.01). 4. SEM examination of bond failure modes revealed that Dicor-Dicor plus, Dicor-Vitadur Alpha, Dicor-Vitadur N exhibited cohesive failure within Dicor and Dicor-Vivodent exhibited adhesive failure. And Dicor-Ceramco III exhibited adhesive failure and cohesive failure within CeramcoIII together. 5. SEM examination of interfaces revealed that Dicor-Dicor Plus exhibited the most tight contact and Dicor-Vitadur Alpha, Dicor-Vitadur N exhibited acceptible contacts. But Vivodent exhibited discontinuous gap and Ceramco II exhibited large continuous gap.

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Evaluation of Mechanical Characteristic of Asphalt Pavement with usage of Trackless tack coat (부착방지 택코트 적용에 따른 아스팔트 포장 역학적 특성 평가)

  • Lim, Chisoo;Jeong, Hong-Gi;Jang, Daeseong;Park, Jin-Hoo;Lee, Jaejun
    • International Journal of Highway Engineering
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    • v.19 no.2
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    • pp.25-34
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    • 2017
  • PURPOSES: The purpose of this paper is to evaluate interface performance while using various tack coat materials for asphalt overlay. METHODS : The evaluation was conducted with tracking test, permeability, and interface bond strength. Tracking test was conducted using an image processing technique, to investigate the susceptibility of the tack coat materials. BBS and pull-off test were conducted to evaluate bond strength. The permeability test was conducted to evaluate the effect of tack coat materials. RESULTS : Results reveal that the trackless tack coat material demonstrates less tracking compared to other materials. Moreover, both BBS and pull-off tests can effectively evaluate the bond strength at the interface. RSC-4 was measured less bond strength. Moreover, tack coat prevents water penetration through the surface and aids the extension of the surface life of asphalt pavement. CONCLUSIONS : Trackless tack coat demonstrated a high and consistent bond strength performance. The tack coat types demonstrate marginally different performance as function of curing times. Field applicability was tested based on visual observation. Therefore, these should be considered when trackless tack coat is slightly enhanced the pavement performance based on limited this study results. Finally, it is necessary to allow reasonable time for the tack coat to completely cure.

A Shear Bond Chracteristics of Composite Slab with Closed-Shape Deckplate (폐쇄형 데크플레이트를 사용한 합성슬래브의 전단부착 특성에 관한 연구)

  • Ju, Gi Su;Park, Sung Moo
    • Journal of Korean Society of Steel Construction
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    • v.13 no.5
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    • pp.557-566
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    • 2001
  • Composite slab with deckplate needs sufficient bond strength between deckplate and concrete to conduct composite behavior Composite slab can transfer the shear by either chemical adhesion interface interlock, or active friction. There are several way of mechanical shear connection in composite slab. that is embossments shear connector shape of deckplate etc. Effect of mechanical interaction is deped on shape of deckplate which is to prevent peeling between deckplate and concrete and an amount of shear connector. The behavior and strength of the connection between the decking and the concrete slab due to embossments and end anchorage may be estimated using the push-off tests described in this paper We proposed the equation of shear bond strength in the composite slab It will be use to design by basic data in composite slab.

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Experimental studies of headed stud shear connectors in UHPC Steel composite slabs

  • Gao, Xiao-Long;Wang, Jun-Yan;Yan, Jia-Bao
    • Structural Engineering and Mechanics
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    • v.74 no.5
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    • pp.657-670
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    • 2020
  • Due to the high compressive and tensile strength of ultra-high performance concrete (UHPC), UHPC used in steel concrete composite structures provided thinner concrete layer compared to ordinary concrete. This leaded to the headed stud shear connectors embedded in UHPC had a low aspect ratio. In order to systematic investigate the effect of headed stud with low aspect ratio on the structural behaviors of steel UHPC composite structure s this paper firstly carried out a test program consisted of twelve push out specimens. The effects of stud height, aspect ratio and reinforcement bars in UHPC on the structural behaviors of headed studs were investigated. The push out test results shows that the increasing of stud height did not obviously influence the structural behaviors of headed studs and the aspect ratio of 2.16 was proved enough to take full advantage of the headed stud strength. Based on the test results, the equation considering the contribution of weld collar was modified to predict the shear strength of headed stud embedded in UHPC. The modified equation could accurately predict the shear strength of headed stud by comparing with the experimental results. On the basis of push out test results, bending tests consisted of three steel UHPC composite slabs were conducted to investigate the effect of shear connection degree on the structural behaviors of composite slabs. The bending test results revealed that the shear connection degree had a significantly influence on the failure modes and ultimate resistance of composite slabs and composite slab with connection degree of 96% in s hear span exhibited a ductile failure accompanied by the tensile yield of steel plate and crushing of UHPC. Finally, analytical model based on the failure mode of composite slabs was proposed to predict the ultimate resistance of steel UHPC composite slabs with different shear connection degrees at the interface.

Analysis of the Load Carrying Behavior of Shear Connection at the Interface of Encased Composite Beams (매입형 합성보의 전단합성거동에 대한 비교분석)

  • Shin, Hyun Seop;Heo, Byung Wook;Bae, Kyu Woong;Kim, Keung Hwan
    • Journal of Korean Society of Steel Construction
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    • v.20 no.1
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    • pp.67-79
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    • 2008
  • In this study, a bending test with three encased composite beams were carried out and analyzed using FEM in order to find how chemical adhesion, interface interlock, friction and composite action by shear studs contribute to stiffness, strength and composite action in the interface of encased compo site beams. The test and results of the FEM analysis showed that the difference in the ultimate moment capacity of the composite beams with and without studs is under 10%. The reason is that the effect of chemical adhesion, interface interlock, and friction in the interface on the composite action is so high that the encased beams have a moment capacity above some defined magnitude. Also, the increment of moment capacity up to plastic moment is not large and the increase of linearly proportioned.

Interlaminar Shear Strength of Carbon Fiber Epoxy Composite with Nickel Film (니켈 박막 첨가에 따른 탄소섬유 에폭시 복합재료의 층간 계면 특성)

  • Lee, Min-Kyung
    • Composites Research
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    • v.28 no.3
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    • pp.94-98
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    • 2015
  • This paper reports the effects of nickel film interleaves on the interlaminar shear strength(ILSS) of carbon fiber reinforced epoxy composites(CFRPs). A nickel thin film was deposited onto the prepreg by radio frequency(RF) sputtering at room temperature. The ILSS of the nickel film interleaved hybrid composites was increased compared to that of the composites without interleaves. To understand the mechanism of enhancement of the ILSS, the fracture surface of the tested specimens was examined by scanning electron microscopy(SEM). The metal interleaves were acted as a reinforcement for the matrix rich interface and the shear property of their composites improved by enhancing the resistance to matrix cracking.

Slant Shear Test for Determining the Interfacial Shear Strength of Concrete Strengthened with Ultra-High Performance Fiber Reinforced Concrete (초고성능 섬유보강 콘크리트로 보강된 콘크리트의 계면 전단강도 결정을 위한 경사전단 실험)

  • Lim, Woo-Young;Hong, Sung-Gul
    • Journal of the Korea Concrete Institute
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    • v.28 no.6
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    • pp.637-646
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    • 2016
  • In this study, slant shear tests for the prism specimens strengthened with ultra-high performance fiber reinforced concrete (UHPFRC), normal- and high-strength concrete were performed to evaluate the interfacial shear strength between old and new concrete substrate. Test parameters are the roughness of surface, concrete strength, and fiber volume fraction of UHPFRC. The surface of the concrete was roughened by shot blasting. Test results showed that the adhesion bond resistance of the specimen with a roughened surface was very large compared to that of the specimen with a smooth surface. In addition, the interfacial shear strength appeared to be affected by the concrete strength rather than the fiber volume fraction. For the roughened surface by shot-blasting method, interfacial shear resistance exceeded the upper limit which is presented in current design codes even if the shear-friction reinforcements are not provided. Based on the test results, it is applicable to use the current concrete design codes to achieve the shear-friction design for the interface between conventional concrete and UHPFRC. However, for the surface which is not processed, it would be appropriate to provide additional shear-friction reinforcement.

A comparison of the shear bond strength between porcelain repair systems and fractured surface of porcelain-fused-to-metal restorations (도재파절 양상에 따른 수종의 도재 수복용 레진의 결합력에 관한 실험적 연구)

  • Choi, Jeung Won;Han, Dong Hoo;Jeong, Chang Mo
    • The Journal of Korean Academy of Prosthodontics
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    • v.28 no.2
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    • pp.147-163
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    • 1990
  • Although dental porcelain demonstrates lasting esthetic results, it suffers from inherent brittle fractures. Various techniques and materials for intraoral porcelain repair has been suggested. This study investigated the in vitro shear strength of three porcelain repair systems according to aspects of the porcelain fractures. The purpose of this study was to evaluate the shear bond strength of three porcelain repair systems(All-bond, Clearfil, Scotchprime) according to fractured surface of porcelain - fused - to - metal restorations. For this study specimens were divided into five groups : group 1 represented fracture occurred at body porcelain layer, group 2 represented fracture occurred at opaque porcelain layer, group 3 represented fracture including 1/3 of metal exposure, group 4 represented fracture including 2/3 of metal exposure, and group 5 represented all metal surface was exposed. Specimens were stored in double deionized water(24Hr, $37^{\circ}C$) and thermocycling was performed(24Hr, 1080cycles), and subjected to a shear force parallel to the repair resin and porcelain interface by use of an University Testing Machine. The results of this study were obtained as follows : 1. In group 1 and 2, bond strength was relatively high, and bond strength showing reducing tendency as exposure of metal was increased. 2. In group 1, bond strength was relatively high, and no significant differences in porcelain repair system. 3. In group 2, 3 and 4, All-bond and Clearfil provided significantly higher bond strength than scotchprime. 4. In group 5, bond strength was the lowest among all groups and especially in case if Scotchprime. 5. Cohesive failure was observed in group 1 and 2, adhesive failure was observed in group 5, and cohesive / adhesive failures were observed in group 3 and 4.

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A study on the Interfacial Properties of Electrodeposited Single Carbon Fiber/Epoxy Composites Using Tensile and Compressive Fragmentation Tests

  • Park, Joung-Man;Kim, Jin-Won
    • Macromolecular Research
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    • v.10 no.1
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    • pp.24-33
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    • 2002
  • Interfacial and microfailure properties of carbon fiber/epoxy composites were evaluated using both tensile fragmentation and compressive Broutman tests. A monomeric and two polymeric coupling agents were applied via the electrodeposition (ED) and the dipping applications. A monomeric and a polymeric coupling agent showed significant and comparable improvements in interfacial shear strength (IFSS) compared to the untreated case under both tensile and compressive tests. Typical microfailure modes including cone-shaped fiber break, matrix cracking, and partial interlayer failure were observed under tension, whereas the diagonal slipped failure at both ends of the fractured fiber appeared under compression. Adsorption and shear displacement mechanisms at the interface were described in terms of electrical attraction and primary and secondary bonding forces.