냉간성형한 ㄷ 형강 전단연결재의 Push-out 실험

최인락(In-Rak Choi) 호서대학교 공업기술연구소 2020 공업기술연구 논문집 Vol.39 No.1

이 연구에서는 U튜브 합성보에 적용하기 위하여 개발된 냉간성형한 ㄷ형강 앵커의 전단성능을 평가하기 위하여 Push-out 실험을 진행하였다. Push-out 실험체는 총 4개로, 주요 실험변수는 앵커의 길이와 앵커가 설치된 강재보의 종류 (H형강, U튜브 단면)이다. Push-out 실험결과 냉간성형한 ㄷ형강 앵커를 적용한 경우 앵커가 설치된 강재 단면 형상과 상관없이 항복점 도달 이후에 전단내력이 지속적으로 증가하는 형태를 보였다. ㄷ형강 앵커에 대한 건축물 강구조 설계기준(KDS 41 31 00)의 전단강도 평가식을 기준으로 실험체의 전단강도를 평가하였으며, 실험결과를 토대로 냉간성형한 ㄷ형강 앵커를 적용한 경우 전단강도식을 수정하여 평가하였다. U튜브 합성보의 경우 적용한 ㄷ형강 앵커의 전단강도와 콘크리트의 수평전단강도의 합으로 실험체의 전단강도를 근사적으로 예측할 수 있었다. In this study, push-out tests were conducted to evaluate shear strength of cold-formed C-channel anchor developed for U-tube composite beam. Total 4 specimens were prepared for push-out test. Test parameters were length of C-channel anchor and types of steel section (H-shape or U-tube shape). Test results show that, specimens with cold-formed C-channel anchor reached its maximum load by the shear strength increased continuously after reaching the yield point, regardless of steel section with anchor installed. Shear strength of C-channel anchor used in test specimens was evaluated using the equations in Korean Building Code for Steel Structures (KDS 41 31 00). Also, based on the test results, shear strength equations were modified and it was reevaluated. Using the modified equations, summation of shear strength of steel anchors and horizontal shear strength of concrete, shear strength of U-tube composite beam can be approximately estimated.

U-튜브 플랜지 H-Beam에 적용된 Z-Bar 전단연결재의 Push-out 실험

최인락,김영훈,정석재,이재환 한국강구조학회 2019 韓國鋼構造學會 論文集 Vol.31 No.6

이 연구에서는 UH합성보에 적용하기 위하여 개발된 Z-bar 앵커의 전단성능을 평가하기 위하여 push-out 실험을 진행하였다. Push-out 실험체는 총 9개로, 주요 실험변수는 강재앵커의 종류(Z-bar 앵커, 스터드앵커)와 사용된 Z-bar 앵커의 길이, 상부 U튜브의 절곡방향, U튜브의 깊이이다. 실험결과의 상대적 비교를 위하여 동일 단면에 스터드앵커를 적용한 실험을 추가하였다. 실험결과UH단면에 Z-bar 앵커를 적용한 경우 스터드앵커와 다르게 항복점 도달 이후에 충분한 항복구간 없이 최대하중에 도달하였으며 이후급격한 하중 저하를 보였다. 건축물 강구조 설계기준(KDS 41 31 00)에 의한 전단강도 평가식을 기준으로 실험체의 전단강도를 평가하였으며, 실험결과를 토대로 UH 단면에 Z-bar 앵커를 적용한 경우 전단강도식을 수정하여 평가하였다. UH단면의 경우 Z-bar 앵커의 전단강도와 콘크리트의 수평전단강도의 합으로 실험체의 전단강도를 근사적으로 예측할 수 있었다. In this study, push-out tests were conducted to evaluate shear strength of Z-bar anchor developed for U-tube flange H-composite beam. Total 9 specimens were prepared for push-out test. Test parameters were types of steel anchor (Z-bar anchor or stud anchor), length of Z-bar anchor, and bending direction or depth of upper U-tube section. For comparison, the same steel sections using stud anchor were also tested. Test results show that, unlike using the stud anchor, UH sections with Z-bar anchor reached its maximum load without sufficient yield plateau, and then the load was suddenly decreased. Shear strength of steel anchors used in UH section was evaluated using the equations in Korean Building Code for Steel Structures (KDS 41 31 00). Also, based on the test results, shear strength equations were modified and it was reevaluated. Using the modified equations, summation of shear strength of steel anchors and concrete, shear strength of UH section can be approximately estimated.

다양한 레진시멘트로 합착한 섬유포스트의 결합강도 비교

이현아,조영곤 大韓齒科保存學會 2008 Restorative Dentistry & Endodontics Vol.33 No.6

이 연구는 다양한 접착시스템을 사용하는 6가지 레진시멘트를 이용하여 근관에 합착한 섬유포스트를 push-out 검사에 의해 포스트와 치근 상아질 간의 결합강도를 상호 비교하기 위하여 시행되었다. 발거된 하악 소구치의 치관부를 제거하고 치근부를 근관충전한 후 9 mm의 포스트 룸을 형성하였다. 사용된 레진시멘트의 종류에 따라서 무작위로 6개씩 선택하여 Duo-Link 군 Variolink Ⅱ 군, Panavia F 군, Multilink Automix 군, RelyX Unicem 군, Maxcem 군으로 분류하였다. 제조사의 지시에 따라서 각각의 레진시멘트를 Uni-dose needle tip을 이용하여 근단부에서부터 주입하여 광투과성 섬유 포스트인 no. 2 DT Light Post를 근관에 합착하였다. 증류수에 24시간동안 보관한 후, 주수 하에 저속의 Diamond Wheel Saw를 이용하여 각 치근을 횡단면으로 1 mm두께로 절단하여 연속적인 절편 6개를 얻었다. 각 군의 시편을 universal testing machine에 고정하고 push-out 검사를 시행하여 push-out 강도를 통계 분석한 결과, 서로 다른 접착시스템을 사용한 레진시멘트 군 간의 push-out 강도는 유의한 차이가 나타나지 않았다 (p>0.05). The purpose of this study was to compare the push-out strength of a fiber post cemented with various resin cements. Newly extracted 36 human mandibular premolars which had single root canal were selected and their crown portions were removed. The root canal was instrumented using PROTAPER^(TM) system and obturated using continuous wave technique, In each root, a 9-mm deep post space was prepared. #2 translucent fiber post (DT Light post, Bisco Inc., Schaumburg, IL, U.S.A.) was cemented using injection technique with Uni-dose needle tip (Bisco) and six different resin cements. The tested resin cements were Duo-Link(Bisco Inc., Schaumburg, IL, U.S.A.), Variolink Ⅱ (Ivoclar-Vivadent AG, Schann, Liechtenstein), Panavia F (Kuraray Medical Inc., Okayama, Japan), Multilink Automix (Ivoclar-Vivadent AG, Schann, Liechtenstein), RelyX Unicem (3M ESPE Dental Products, St. Paul, MN, U.S.A.), and Maxcem (Kerr Co.,CA, U.S.A.). After storage in distilled water for 24 hours, each root was transversally sectioned into approximately 1-mm thick sections. This procedure resulted in 6 serial sections per root. Push-out test was performed using a universal testing machine (EZ Test, Shimadzu Co.) with a crosshead speed of 1 mm/min. The data were analyzed with one-way ANOVA and Tukey HSD (p=0.05). The push-out strength of the groups which cemented fiber post with Panavia F and Multilink Automix were lower than those of the other groups. But, there were no statistically significant difference among groups at a probability level of 0.05.

부분 매립형 역T형강 합성바닥판의 전단강도 평가

최준혁(Choi Jun Hyeok),김성훈(Kim Sung Hoon),박승열(Park Seung Ryul),이승용(Lee Seung Yong) 대한토목학회 2007 대한토목학회논문집 A Vol.27 No.6A

본 연구에서는 부분 매립형 합성바닥판의 전단강도 평가를 위한 push-out시험 결과를 나타내었다. 대상 바닥판은 상부는 철근콘크리트이며 하부는 역 T형강으로 구성되어 있다. 시험은 총 16개의 push-out 시험체에 대하여 시험하였으며, 시험변수는 강재 보의 구멍의 간격 및 직경, 철근의 강도이다. 이 결과로부터 각 시험변수들에 대한 영향정도와 강재와 콘크리트 사이의 전단력을 분석하였다. 또한 합성바닥판의 전단강도를 예측하기 위하여 강재와 콘크리트와의 부착력, 구멍에 의한 콘크리트 다웰 작용에 의한 전단력 그리고 관통철근에 의한 전단력의 합으로 나타낸 실험식을 제시하였다. This paper presented the results of push-out test for evaluation of shear strength of partially filled composite deck. The deck consists of reinforced concrete in the upper part and inverted T-shaped steel in the lower part. A total of 16 push-out test specimens were tested. The test parameters were the spacing and the size of holes and the bar strength. From the results, the effect of the test parameters and the shear force between steel and concrete were investigated. An empirical expression consisted of the sum of the contact shear force, the dowel action of concrete and the reinforcing bars effect was proposed for predicting of shear strength in composite deck.

Investigation of pipe shear connectors using push out test

Saeed Nasrollahi,Shervin Maleki,Mahdi Shariati,Aminaton Marto,Majid Khorami 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.27 No.5

Mechanical shear connectors are commonly used to transfer longitudinal shear forces across the steel-concrete interface in composite beams. Steel pipe as a new shear connector is proposed in this research and its performance to achieve composite strength is investigated. Experimental monotonic push-out tests were carried out for this connector. Then, a nonlinear finite element model of the push-out specimens is developed and verified against test results. Further, the finite element model is used to investigate the effects of pipe thickness, length and diameter on the shear strength of the connectors. The ultimate strengths of these connectors are reported and their respective failure modes are discussed. This paper comprises of the push-out tests of ten specimens on this shear connector in both the vertical and horizontal positions in different reinforced concretes. The results of experimental tests are given as load-deformation plots. It is concluded that the use of these connectors is very effective and economical in the medium shear demand range of 150-350 KN. The dominant failure modes observed were either failure of concrete block (crushing and splitting) or shear failure of pipe connector. It is shown that the horizontal pipe is not as effective as vertical pipe shear connector and is not recommended for practical use. It is shown that pipe connectors are more effective in transferring shear forces than channel and stud connectors. Moreover, based on the parametric study, a formula is presented to predict the pipe shear connectors' capacity.

Comparison of Static and Fatigue Behaviors between Stud and Perfobond Shear Connectors

Bing Wang,Qiao Huang,Xiaoling Liu 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.1

This paper presents an experimental evaluation for comparison of the behaviors of stud and Perfobond shear connectors under static and fatigue loading based on 20 push-out tests. The push-out tests for each type of shear connectors including three series: static tests, fatigue endurance tests and residual mechanical properties test, respectively. In static tests, the failure modes of two types of connectors are different. The elastic stiffness and ultimate slip in the load-slip curves of the Perfobond are larger than that of stud. In fatigue endurance tests, the fatigue life of the studs is 2.68 million, while the Perfobond specimens do not fail after 3.0 million numbers of cycles under the same test conditions as studs'. Compared with the stud, the relative-slip of Perfobond increased sharply in the early period. In residual mechanical properties tests, the residual bearing capacity, shear stiffness and ductility are presented and discussed. The variation rules of these three indexes for two types of connectors are the same, while the indexes of Perfobond are much larger than stud’s throughout the process. The results indicate that Perfobond connector has good ductility, better fatigue resistance and higher safety reliability. However, the economy of Perfobond connectors is not as good as studs’.

Push-out bond strength of a self-adhesive resin cement used as endodontic sealer

Gurgel-Filho, Eduardo Diogo,Lima, Felipe Coelho,Saboia, Vicente De Paula Aragao,Coutinho-Filho, Tauby De Souza,Neves, Aline De Almeida,da Silva, Emmanuel Joao Nogueira Leal The Korean Academy of Conservative Dentistry 2014 Restorative Dentistry & Endodontics Vol.39 No.4

Objectives: The aim of the present study was to investigate the bond strength of RelyX Unicem (3M) to root canal dentin when used as an endodontic sealer. Materials and Methods: Samples of 24 single-rooted teeth were prepared with Gates Glidden drills and K3 files. After that, the roots were randomly assigned to three experimental groups (n = 8) according to the filling material, (1) AH Plus (Dentsply De Trey GmbH)/Gutta-Percha cone; (2) Epiphany SE (Pentron)/Resilon cone; (3) RelyX Unicem/Gutta-Percha cone. All roots were filled using a single cone technique associated to vertical condensation. After the filling procedures, each tooth was prepared for a push-out bond strenght test by cutting 1 mm-thick root slices. Loading was performed on a universal testing machine at a speed of 0.5 mm/min. One-way analysis of variance and Tukey test for multiple comparisons were used to compare the results among the experimental groups. Results: Epiphany SE/Resilon showed significantly lower push-out bond strength than both AH Plus/Gutta-Percha and RelyX Unicem/Gutta-Percha (p < 0.05). There was no significant difference in bond strength between AH Plus/Gutta-Percha and RelyX Unicem/Gutta-Percha (p > 0.05). Conclusions: Under the present in vitro conditions, bond strength to root dentin promoted by RelyX Unicem was similar to AH Plus. Epiphany SE/Resilon resulted in lower bond strength values when compared to both materials.

Push-out resistance of concrete-filled spiral-welded mild-steel and stainless-steel tubes

Chi K. Loke,Yasoja K.R. Gunawardena,Farhad Aslani,Brian Uy 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.33 No.6

Spiral welded tubes (SWTs) are fabricated by helically bending a steel plate and welding the resulting abutting edges. The cost-effectiveness of concrete-filled steel tube (CFST) columns can be enhanced by utilising such SWTs rather than the more conventional longitudinal seam welded tubes. Even though the steel-concrete interface bond strength of such concrete-filled spiralwelded steel tubes (CF-SWSTs) is an important consideration in relation to ensuring composite behaviour of such elements, especially at connections, it has not been investigated in detail to date. CF-SWSTs warrant separate consideration of their bond behaviour to CFSTs of other tube types due to the distinct weld seam geometry and fabrication induced surface imperfection patterns of SWTs. To address this research gap, axial push-out tests on forty CF-SWSTs were carried out where the effects of tube material, outside diameter (D), outside diameter to wall thickness (D/t), length of the steel-concrete interface (L) and concrete strength grade (f'c) were investigated. D, D/t and L/D values in the range 102-305 mm, 51-152.5 and 1.8-5.9 were considered while two nominal concrete grades, 20 MPa and 50 MPa, were used for the tests. The test results showed that the push-out bond strengths of CF-SWSTs of both mild-steel and stainless-steel were either similar to or greater than those of comparable CFSTs of other tube types. The bond strengths obtained experimentally for the tested CF-SWSTs, irrespective of the tube material type, were found to be well predicted by the guidelines contained in AISC-360.

Perfobond rib 전단연결재의 전단강도 및 잔류강도 평가

안진희(Ahn Jin Hee),김상효(Kim Sang Hyo),구현본(Koo Hyun-Bon),강균희(Kang Gyun Hee) 대한토목학회 2007 대한토목학회논문집 A Vol.27 No.2A

본 논문에서는 실험적 연구를 통해 perfobond 전단연결재의 전단거동 특성과 피로하중에 따른 잔류강도 변화를 평가하였다. 이를 위해 총 18개의 perfobond 전단연결재 시험체를 제작하였으며, 이들 시험체에 대한 정적 및 피로 직접전단실험을 실시하여 홀 관통철근콘크리트 다웰효과반복하중 작용 등이 전단강도에 미치는 영향을 분석하였다. 실험결과, perfobond 전단연결재의 전단강도에서 콘크리트 다웰효과는 최대전단강도의 약 65%를 차지하고, perfobond 전단연결재 홀에 배치된 관통철근은 전단강도를 100% 이상 증가시키는 것으로 나타났다. 특히, 홀 관통철근은 전단연결부 파괴시 하중-슬립 거동의 연성을 현저히 향상시키는 것으로 나타났다. 두 종류의 피로하중(도로교설계기준에 명시된 설계하중과 설계하중의 50%)을 일정횟수 반복재하한 후 정적 직접전단실험을 통해 측정한 perfobond 전단연결재의 잔류강도는, 홀 관통철근이 없는 시험체의 잔류강도는 최대전단강도의 약 65% 수준으로 저하되었으나, 홀 관통철근이 설치된 시험체의 잔류강도는 반복재하하중에 의하여 크게 감소되지 않음을 확인할 수 있었다. 따라서, 교량과 같이 피로하중이 빈번히 작용하는 구조물에 perfobond 전단연결재를 사용할 경우, 전단강도의 저하를 방지하기 위해 홀 관통철근 배근이 필요한 것으로 나타났다. This paper deals with the static shear strength and residual strength after cyclic loading of perfobond rib shear connectors. A total of eighteen push-out specimens with perfobond rib shear connectors were fabricated and a series of static and residual push-out tests were conducted. Then, the influences of hole crossing bars, concrete dowel, and cyclic loading on the shear strength were evaluated experimentally. As a results of this study, it is proved that the concrete dowel action is charge of 65% in ultimate shear strength of perfobond shear connectors, and the hole crossing bars increase the shear strength of that in two times. Especially, at the time of failure of shear connectors, the hole crossing bars significantly increase ductility of load-slip behavior. According to the residual push-out tests applying two types of cyclic loadings, design load and 50% of design load specified in Korean Highway Bridge Design Code, the residual strength, which was drawn by static push-out test after cyclic loadings, of the specimens without hole crossing bars were reduced to 65% of ultimate strength. However, the residual strength of the hole crossing bars were not reduced significantly. Therefore, as the perfobond shear connectors are applied to the Bridges which are frequently subjected to the fatigue loadings, it is designable to install hole crossing bar in order to prevent reducing of shear strength by fatigue loadings.

Push-Out Behavior of Short Headed Stud Connectors in Steel-Ultra High Performance Concrete Composite Deck

Qiu Zhao,Guanming Huang,Chen Xu,Yunfan Peng 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.7

A steel-ultra high performance concrete (UHPC) composite deck has good fatigue performancewhile the thin UHPC slab leaves a very limited space for the connector configuration. This is actually crucial to achieve the composite action. Current literatures concerning the short stud behavior are still limited for a general mechanism understanding. Therefore, a series of push-tests containing 15 specimens were conducted for investigating the mechanical behavior of short studs with various diameters and lengths in UHPC composite deck. And a parametric FEM analysis with nonlinear material constitutions was conducted as well for the bearing performance understanding. The push-out tests showed the shear fracture near stud roots is the leading dominant failure mode, and a longer stud length might introduce a higher percentage of stud shank bending deformation. It explained longer stud length could be helpful to improve the shear strength of stud in UHPC. Meanwhile, the shear stiffness of the push-out specimens were all increased with a larger stud diameter or length. On the other side, the analysis results showed that a pull-out failure could happen when the stud length was less than 25 mm in UHPC and the failure mode of stud could also be affected by the concrete strength. In addition to the tests and analysis, the safety redundancies of strength evaluations of short stud in UHPC based on several civil codes were discussed in terms of the comparison works.