• 대한치과기공학회지
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• 제38권4호
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• pp.291-298
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• 2016

Purpose: This study was to evaluate the effect of coloring liquids on the shear bond strength between zirconia and veneering ceramic. Methods: Zirconia(15 mm in diameter, 2.5 mm in thickness; n=40) used in the experiment were divided into 5 groups depending on the coloring liquid. Each specimen were polished using a polishing machine(LaboPol-2, Struers, UK). A cylinder of veneering porcelain(6 mm in diameter, 3 mm in thickness) was fabricated and fired on zirconia surfaces. The shear bond strength was measured using a universal testing machine(Model 4302, Instron, USA). All data were analyzed statistically using a one-way ANOVA and Tukey's multiple comparisons test. After the shear bond test, fracture surfaces were examined by SEM. Results: Colored zirconia showed a higher shear bonding strength than that of uncolored zirconia except for colored zirconia immersed in Zirkonzahn coloring liquid. In particular, colored zirconia immersed in Kuwotech coloring liquid showed the highest shear bond strength. After the shear bond test, mixed failure patterns were mainly observed in the failure between zirconia and veneering ceramic. Conclusion: Coloring liquid enhanced the shear bond strength zirconia and veneering ceramic than uncolored zirconia.

• Structural Engineering and Mechanics
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• 제78권4호
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• pp.413-423
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• 2021

Piers are the main lateral force-resisting members of high-speed railway (HSR) bridges used in China and are characterized by low axial load ratios, low longitudinal reinforcement ratios, low stirrup ratios, and high shear span ratios. It is well known that flexural, flexural-shear, and shear failures of piers may occur during an earthquake. In this study, a new shear strength model was developed to simulate the seismic failure of HSR solid piers accurately. First, low cyclic-loading test data of solid piers obtained in recent years were collected to set up a database for model verification. Second, based on the test database, the applicability of existing shear strength models was evaluated. Finally, a new shear strength model for HSR solid piers with round-ended cross-sections was derived based on the truss model and ultimate equilibrium theory. In comparison with existing models, it was demonstrated that the proposed model could be used to predict the shear strength of HSR piers more accurately.

• Steel and Composite Structures
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• 제48권2호
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• pp.131-143
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• 2023

The CFRP bar was used to achieve more ductile and durable headed-stud shear connectors in composite components. Three series of push-out tests were firstly conducted, including specimens reinforced with pure steel fibers, steel and CFRP bars. The distributed stress was measured by the commercial PPP-BOTDA (Pre-Pump-Pulse Brillouin optical time domain analysis) optical fiber sensor with high spatial resolution. A series of numerical analyses using non-linear FE models were also made to study the shear force transfer mechanism and crack response based on the test results. Test results show that the CFRP bar increases the shear strength and stiffness of the large diameter headed-stud shear connection, and it has equivalent reinforcing effects on the stud shear capacity as the commonly used steel bar. The embedded CFRP bar can also largely improve the shear force transfer mechanism and decrease the tensile stress in the transverse direction. The parametric study shows that low content steel fibers could delay the crack initiation of slab around the large diameter stud, and the CFRP bar with normal elastic modulus and the standard reinforcement ratio has good resistance to splitting crack growth in headed stud shear connectors.

• Structural Engineering and Mechanics
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• 제66권2호
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• pp.203-215
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• 2018

A large body of experiments have been conducted to date to evaluate the punching shear strength of flat slab-column connections, but it is noted that only a few of them have been considered for the development of the ACI Code provisions. The limited test results used for the development of the code provisions fall short of predicting accurately the punching shear strength of such connections. In an effort to address this shortfall and to gain an insight into the factors that control the punching shear strength of flat slab-column connections, we report a qualified database of 650 punching shear test results in this article. All slabs examined in this database were tested under gravity loading and do not contain shear reinforcement. In order to justify including any test result for evaluation punching shear database, we have developed an approved set of criteria. Carefully established set of criteria represent the actual characteristics of structures that include minimum compressive strength, effective depths of slab, flexural and compression reinforcement ratio and column size. The key parameters that significantly affect the punching shear strength of flat slab-column connections are then examined using ACI 318-14 expression. The results reported here have paramount significance on the range of applicability of the ACI Code provision and seem to indicate that the ACI provisions do not sufficiently capture many trends identified through regression of the principal parameters, and fall on the unsafe side for the prediction of the punching shear strength of flat slab-column connections.

• 콘크리트학회논문집
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• 제17권6호
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• pp.963-974
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• 2005

본 논문은 고강도 콘크리트로 타설된 2개의 대형 프리스트레스트 콘크리트 보로부터 얻어진 4개의 전단실험 결과를 고찰하였다. 특히 경사진 프리스트레싱 긴장재가 부재의 전단거동에 미치는 영향을 세밀히 분석하였다. 본 실험에서 경사진 프리스트레싱 긴장재를 사용한 부재는 직선 프리스트레싱 긴장재를 사용한 부재에 비해 높은 초기전단균열강도와 전단강도를 가졌다. 또한 실험 결과는 경사진 프리스트레싱 긴장재의 사용이 부재 단부에서 긴장재의 미끄러짐을 감소시켜주는 것으로 관찰되어 부재 단부에서 크게 요구되는 단부 정착력을 분산시키는데 효과적임을 보여주었다. 실험 결과로부터 얻어진 부재의 전단강도는 ACI 318-02와 AASHTO LRFD의 전단설계기준에 의하여 계산된 값과 비교 분석되었다. 두 전단설계기준은 모든 시험체에 대해 안정적인 전단강도를 제공하였으며, 특히 경사진 프리스트레싱 긴장재를 가진 부재들에 대해서 실험결과에 비해 매우 낮은 전단강도를 제공하였다.

• 한국방재학회 논문집
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• 제9권1호
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• pp.27-32
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• 2009

본 연구의 주목적은 아스팔트 포장층간의 접착전단강도를 측정하는 실험법과 평가 방법을 개발하고 배수성 포장에 사용되는 택코트 재료의 특성과 적정 살포량을 평가하고자 하였다. 실험에는 두 종류(RSC-4, 개질유화)의 유화아스팔트와 가열 아스팔트바인더 타입(HM-1) 한 종류로 실시하였으며, HM-1은 배수성 포장에 사용하기 위해 새로 개발된 제품이다. 접착전단강도를 측정하기 위해 직접전단실험을 다양한 실험 조건에서 수행하였다. 실험을 통해 얻은 접착전단강도 값은 결과의 변별력이 떨어 졌으며 하중-변위 곡선의 면적인 터프니스가 접착전단강도를 평가하는데 보다 유용한 것을 확인 할 수 있었다. 배수성 포장의 경우 RSC-4의 경우는 $0.8l/m^2$ 이상, 개질유화아스팔트의 경우는 $0.5{\sim}0.6l/m^2$의 살포량이 적당한 것으로 나타났다. Trackless 성능이 우수한 HM-1은 유화 아스팔트 택코트에 비해 월등히 좋은 접착전단성능을 발휘하는 것으로 나타났다.

• Steel and Composite Structures
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• 제36권1호
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• pp.103-118
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• 2020

The static behavior of grouped large-headed studs (d = 30 mm) embedded in ultra-high performance concrete (UHPC) was investigated by conducting push-out tests and numerical analysis. In the push-out test, no splitting cracks were found in the UHPC slab, and the shank failure control the shear capacity, indicating the large-headed stud matches well with the mechanical properties of UHPC. Besides, it is found that the shear resistance of the stud embedded in UHPC is 11.4% higher than that embedded in normal strength concrete, indicating that the shear resistance was improved. Regarding the numerical analysis, the parametric study was conducted to investigate the influence of the concrete strength, aspect ratio of stud, stud diameter, and the spacing of stud in the direction of shear force on the shear performance of the large-headed stud. It is found that the stud diameter and stud spacing have an obvious influence on the shear resistance. Based on the test and numerical analysis results, a formula was established to predict the load-slip relationship. The comparison indicates that the predicted results agree well with the test results. To accurately predict the shear resistance of the stud embedded in UHPC, a design equation for shear strength is proposed. The ratio of the calculation results to the test results is 0.99.

• 대한토목학회논문집
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• 제26권2C호
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• pp.73-80
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• 2006

4종류 토목섬유 조합으로 구성된 4가지 토목섬유 접촉면의 정적 및 동적 하중 상태에서의 전단거동을 평가하였다. 정적하중 조건에서 경사판 시험과 직접전단 시험을 수행하였으며, 두가지 시험 결과를 상호 비교하였다. 비교 결과 직접전단 시험의 경우, 직접전단 시험이 수행되지 아니한 낮은 응력 단계에서의 접촉면 전단강도를 실제보다 크게 예측할 가능성이 높은 것으로 나타났다. 또한 정적상태에서 수행된 두 종류 시험을 통해 산정된 전단강도를 이용하여 곡선형태의 파괴 포락선식을 구할 수 있었다. 한편 정적 전단강도와 진동대시험을 통해 동적 하중 상태에서 구한 접촉면 전단강도를 비교하여, 하중 특성과 가해진 응력 크기에 따라 각기 다른 마찰 특성을 보임을 확인하였다. 따라서 토목섬유 사이의 접촉면 전단강도를 정확히 평가하기 위해서는 실제 현장에 설치되는 재료를 대상으로 예상되는 응력의 크기와 하중 유형을 고려하여 시험이 수행되어야 할 것이다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 연약지반처리위원회 학술세미나
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• pp.71-78
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• 2000

SHANSEP method involves the consolidation to stresses in excess of the preconsolidation pressure in order to overcome sample disturbance effect. The concept of SHANSEP is based on an approach to laboratory test which attempts to reproduce the in-situ conditions more closely than is possible in routine tests and evaluates normalized strength parameters for the soil as a function of OCR. But SHANSEP method can be applied only to fairly uniform clay deposits, and is unsuitable for a random deposit. In this study, CK/sub o/U triaxial compression test and incremental loading consolidation test were performed for the application of SHANSEP method on Yangsan clay. During the K/sub o/-consolidation, triaxial specimens were consolidated to stress equal to two times the in-situ vertical effective stress. And for overconsolidated condition, the specimens were swelled to a known vertical effective stress in order to have the desired OCR. With the results of CK/sub o/U triaxial compression test using the block samples, the relationship between c/sub u//σ/sub vc/' and OCR on Yangsan clay was established. For evaluating the undrained shear strength of Yangsan clay with depth, CK/sub o/U triaxial compression test was performed using the piston samples taken from Yangsan site. And also undrained shear strength was analyzed from the in-situ test such as Cone Penetration Test(CPT), Dilatometer Test(DMT), and Field Vane Test(FVT) and was compared with that of CK/sub o/U triaxial compression test.

• Architectural research
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• 제20권3호
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• pp.75-82
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• 2018

The aim of the study is to evaluate the concrete shear strength and structural behavior of two general beams and eight shape memory alloys (SMAs)-reinforced beams under the flexural test. This work compares the existing reference formula for concrete shear strength with test result to provide the basic data for the design of highly intelligent reinforced concrete (hereinafter, HIRC) beams. The evaluation of the concrete shear strength was performed with effective depth (d=65, 70, 80), SMA diameter change (ø=2.0, 2.5) as the main variables of the specimens. For the relationship between the effective depth and the $V_{\exp}/V_{cal}$, the test result shows that the concrete shear strength gradually approaches 1.0 as the effective depth length increase. For the AIJ formula, the specimens are approached evenly for comparison between $V_{\exp}/V_{cal}$ and the by-product (garnet, fly-ash) reinforced specimen; however, other formulas indicate a deviation.