• Journal of the Korea Concrete Institute
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• v.13 no.1
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• pp.46-53
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• 2001

Two full scale precast pretensioned dapped ended rectangular beams designed by PCI design handbook for a major domestic live load of market and parking building - 500kgf/㎡ and 1,200kgf/㎡ were investigated experimentally. The bottom length of beams was 60cm which was same to the length of rectangular column in the base of five-story market or parking buildings. The height of dap was web hight plus half of the flange height within the allowable limit of PCI method. Shear tests were performed on four beam ends. Followings were obtained from the experimental study. All of the specimens were fully complied with the PCI design handbook. Two of four specimens which were designed for live load of 1,200kgf/㎡ showed crackings at the re-entrant corner of dap before the full service loadings, and failed by direct shear at the load level much less than their calculated nominal strength. The specimens designed for live load of 1,200kgf/㎡ failed at 772 tonf and 78.36tonf by direct shear crackings. This strength was less than PCI limit of 81.9 tonf and higher than ACI limit of 65.62tonf. Thus, the limit suggested by ACI seems more reasonable in regard of safety in view of this test results. According to load-strain curves, the strain of hanger reinforcement reached almost yield strain. It is recommended to use more inclined hanger reinforcement of improve the strength and serviceability.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.5
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• pp.621-640
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• 2019

Quantitative stability assessment of underground cavities can be presented as a factor of safety based on the Shear Strength Reduction Method (SSRM). Also, SSRM is one of the stability evaluation methods commonly used in slope stability analysis. However, there is a lack of research that considers the relationship between the probability of occurrence of cavities in the ground and the potential failure surface of the slope at the same time. In this study, the effect of small underground cavities on the failure behavior of the slope was analyzed by using SSRM. Considering some of the glaciology studies, there is a case that suggests that there is a cavity effect inside the glacier in the condition that the glacier slides. In this study, the stability evaluation of underground cavities and slope stability analysis, where SSRM is used in geotechnical engineering field, was carried out considering simultaneous conditions. The slope stability analysis according to the shape and position change of underground cavities which are likely to occur in the lower part of a mountain road was analyzed by using SSRM in FLAC3D software and the influence of underground cavities on the slope factor of safety was confirmed. If there are underground cavities near slope potential failure surface, it will affect the calculation of a factor of safety. The results of this study are expected to be basic data on slope stability analysis with small underground cavities.

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.1 s.16
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• pp.69-76
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• 2005

The pull-out capacity of expansion anchor(heavy duty anchor and wedge anchor) was studied experimentally in this paper. Loading conditions included tension, shear, and combined tension and shear. The heavy duty anchor and wedge anchor were manufactured in domestic and installed In plain concrete. The failure mode of steel and concrete were studied carefully for the analytical formula of the anchorage design and the experimental data were compared with different models for the interaction of tension and shear capacities. Based on the research, the following conclusion may be drawn : The interaction of forces is well-described by an elliptical interaction relationship.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.3
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• pp.391-399
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• 2001

Three-dimensional dynamic analysis of underground openings subjected to explosive loadings considering the effects of water saturation is carried out in this study. The surrounding rock mass is assumed to be the limestone with 13.5% of porosity. Two calculations are compared using as identical explosive charge; the first in dry rock of 13.5% porosity, the second in the identical rock, but in a fully saturated condition. It is shown that velocity, displacement, and stress time histories are higher in saturated rock than those in dry rock through numerical studies. It is also shown that underground openings in saturated rock masses could be significantly more vulnerable to the potential damages associated with shear failure than those in dry medium.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.151-160
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• 2003

The stability of the designed rock slope is analysed based on two kinds of shear strength model. Besides the deterministic analysis, a probabilistic approach on Monte Carlo simulation is proposed to deal with the uncertain characteristics of the discontinuity and the results obtained from two models are compared to each other. To carry out the research of characteristics of the discontinuity, BIPS, DOM Scanline survey data and direct shear test data are used, and chi-square test is used for determining the probability distribution function. The rock slope is evaluated to be stable in the deterministic analysis, but in the probabilistic analysis, the probability of failure is more than 5%, so, it is considered that the rock slope is unstable. In the shear strength models, the probability of the failure based on the Mohr-Coulomb model(linear model) is higher than that of the Barton model. It is supported by the fact that the Mohr-Coulomb model is more sensitive to block size than the Barton model. In fact, there is no reliable way to estimate the unit cohesion of the Mohr-Coulomb model except f3r back analysis and in the case of small block failure in the slope, Mohr-Coulomb model may excessively evaluate the factor of the safety. So, the Barton model of which parameters are easily acquired using the geological survey is more reasonable for the stability of the studied slope. Also, the selection of the proper shear strength model is an important factor for slope failure analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.335-341
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• 2020

This study examined the shear bond strength between the zirconia core and pressed lithium disilicate veneering ceramics. The Schmitz-Schulmeyer test method was used to investigate the core-veneer shear bond strength of industrially manufactured zirconia core ceramic (Zirtooth, HASS, Gangneung, Korea) and pressed veneer ceramic (IPS e.max Zirpress, Vita PM9, GC Initial IQ, HASS Rosetta SM) (N=40). Data were statistically analyzed using one-way ANOVA and Tukey's test (a=0.05). The fractured surfaces of the specimens were examined to determine the failure pattern using a digital microscope. The mean ± SD shear bond strength in MPa were 16.69±3.11, 14.21±3.63, 11.17±2.92, and 27.90±5.71 for IPS e.max Zirpress, VITA PM9, GC Initial IQ, and HASS Rosetta SM, respectively. The average shear bond strength was largest for HASS Rosetta SM, followed by IPS e.max Zirpress, Vita PM9, and GC Initial IQ(p<0.05). The digital microscopy examination of the fracture surface showed adhesive and cohesive failure in pressed lithium disilicate veneering ceramics. The use of lithium disilicate veneer ceramic produced a significantly higher shear bond strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.3
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• pp.108-115
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• 2014

Mechanical properties of GFRP rebars significantly decrease due to high temperature as well as alkalinity of concrete. This study focuses on the long-term reduction of inter-laminar shear strength of pre-damaged GFRP rebars by high temperature. For this investigation, bare GFRP rebar specimens were exposed to $270^{\circ}C$ for 1hour and then immerged in alkali solution for several months and tested in shear. No thermally conditioned specimens were immerged and tested for the comparisons. In results, the reduction of thermally damaged GFRP rebars was greater than that of no thermally damaged ones. Based on the accelerated experimental test data, an polynomial equation is presented for prediction of long-term residual inter-laminar shear strength of GFRP rebars previously damaged by high temperature.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.4
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• pp.39-49
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• 2002

In this paper, the characteristics of RB(rubber bearing) were studied by various prototype tests on RB with low hardness rubber. The characteristics of RB were tested on displacements, repeated cycles, frequencies, vertical pressures, temperature, vertical stiffness and the capability of shear deformation. The prototype test showed that the displacement and vertical pressures were the most governing factors influencing on characteristics of RB. The effective stiffness and equivalent damping of RB showed small increment in high frequency range. After the repeated cyclic test with 50's cycles, the effective stiffness and equivalent damping of RB were almost constant compared with those of the 1st cycles due to low hysteretic damping. The shear modulus of RB was reduced after large deformation, and this value of RB was partly recovered after 40 days. Finally, the shear failure test of RB was conducted, the prototype was failed over 490% of shear strain, and real size RB was failed over 430% of shear strain.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.481-482
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• 2010

There is disagreement among researchers in many areas of FRP RC design code except flexural. So a new efficient and reliable shear strength equation which show a high accuracy and a consistent variation in predicting failure modes and shear strength was proposed.

• Magazine of the Korea Concrete Institute
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• v.2 no.1
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• pp.101-108
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• 1990

An experimental and analytical invest.igation was conducted regarding the behavior of reinforced concrete skew bridge decb with Ontario-type reinforcement. A full-scale model repmsenting the essential behavior of a full skew bridge was built and tested. The test specimen had details similar to those required by the Ontario Highway Bridge Design Code, modified as recommended by the Texas State Highway Dopartment. The skuw bridge deck performed sati:,factorily under the current AASHTO design load le"els as well as the overload conditions(about :3 times the current AASHTO design wheel load). The skew edges failed by shear ; the center by punching shear. The calculated flexural capacity considering arching action always far exceeded the actual failure load (shear or punching shear) at each test location. To check the experimental results a detailed finite element model of the specimen was developed using a general-purpose structural analysis pmgram. Analytical predictions and exper'imental results agreed c1osuly.