전단파, 전자기파 및 콘 관입저항력을 이용한 직접전단실험시 전단영역 특성 평가

변용훈,이종섭,쭝꽝홍,짠밍콰 한국지반공학회 2011 한국지반공학회논문집 Vol.27 No.2

The characteristics of shear zone in granular soils largely affect the stability of geo-structures. The goal of this study is to evaluate shear zone in a direct shear test using shear wave, electrical resistivity, and cone tip resistance. Bender elements and electrical resistivity probe are embedded into the wall of a direct shear box made of transparent acrylic material to estimate the shear wave velocities and the electrical resistivity at shear and non-shear zones. At the point of peak and residual strength, micro cone penetration test which can be available to measure tip resistance has been performed. Experimental results show that the shear wave velocities at upper shear zone increase during shearing while the values remain constant at bottom and lower shear zone. Also, resistivities at lower shear zone depend on relative density while resistivities at bottom remain constant. The results of cone penetration test demonstrate the correlation of the cone tip resistance and small strain shear modulus at shear zone. This study suggests that the application of the modified direct shear box including shear wave, electrical resistivity and the micro cone tip resistance may become effective tools for analyzing the characteristics of a shear zone.

Shear resistance behaviors of a newly puzzle shape of crestbond rib shear connector: An experimental study

Thi Hai Vinh Chu,Duy Kien Dao,Duc Vinh Bui,Van Phuoc Nhan Le,김인태,안진희 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.5

A newly puzzle shape of crestbond rib shear connector is a type of ductile perfobond rib shear connector. This shear connector has some advantages, including relatively easy rebar installation and cutting, as well as the higher shear resistance strength. Thus, this study proposed a newly puzzle shape of crestbond rib with a "Ʊ" shape, and its shear resistance behaviors and shear strengths were examined using push-out tests. Five main parameters were considered in the push-out specimens to evaluate the effects of shear resistance parameters such as the dimensions of the crestbond rib, transverse rebars in the crestbond dowel, concrete strength, rebar strength, and dowel action on the shear strength. The shear loading test results were used to compare the changes in the shear behaviors, failure modes, and shear strengths. It was found that the concrete strength and number of transverse rebars in the crestbond rib were significantly related to its shear resistance. After the initial bearing resistance behavior of the concrete dowel, a relative slip occurred in all the specimens. However, its rigid behavior to shear loading decreased the ductility of the shear connection. The cross-sectional area of the crestbond rib was also shown to have a minor effect on the shear resistance of the crestbond rib shear connector. The failure mechanism of the crestbond rib shear connector was complex, and included compression, shear, and tension. As a failure mode, a crack was initiated in the middle of the concrete slab in a vertical direction, and propagated with increasing shear load. Then, horizontal cracks occurred and propagated to the front and rear faces of the specimens. Based on the results of this study, a design shear strength equation was proposed and compared with previously suggested equations.

Shear and tensile behaviors of headed stud connectors in double skin composite shear wall

Jia-Bao Yan,Zhe Wang,Tao Wang,Xiao-Ting Wang 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.26 No.6

This paper studies shear and tensile behaviors of headed stud connectors in double skin composite (DSC) structure. Firstly, 11 push-out tests and 11 tensile tests were performed to investigate the ultimate shear and tensile behaviors of headed stud in DSC shear wall, respectively. The main parameters investigated in this test program were height and layout of headed stud connectors. The test results reported the representative failure modes of headed studs in DSC structures subjected to shear and tension. The shear-slip and tension-elongation behaviors of headed studs in DSC structures were also reported. Influences of different parameters on these shear-slip and tension-elongation behaviors of headed studs were discussed and analyzed. Analytical models were also developed to predict the ultimate shear and tensile resistances of headed stud connectors in DSC shear walls. The developed analytical model incorporated the influence of the dense layout of headed studs in DSC shear walls. The validations of analytical predictions against 22 test results confirmed the accuracy of developed analytical models.

Experimental Verification of Resistance-Demand Approach for Shear of HSC Beams

Ahmed K. El-Sayed,Ahmed B. Shuraim 한국콘크리트학회 2016 International Journal of Concrete Structures and M Vol.10 No.4

The resistance-demand approach has emerged as an effective approach for determining the shear capacity of reinforced concrete beams. This approach is based on the fact that both the shear resistance and shear demand are correlated with flexural tensile strain from compatibility and equilibrium requirements. The basic shear strength, under a given loading is determined from the intersection of the demand and resistance curves. This paper verifies the applicability of resistance-demand procedure for predicting the shear capacity of high strength concrete beams without web reinforcement. A total of 18 beams were constructed and tested in four-point bending up to failure. The test variables included the longitudinal reinforcement ratio, the shear span to depth ratio, and the beam depth. The shear capacity of the beams was predicted using the proposed procedure and compared with the experimental values. The results of the comparison showed good prediction capability and can be useful to design practice.

Experimental Verification of Resistance-Demand Approach for Shear of HSC Beams

El-Sayed, Ahmed K.,Shuraim, Ahmed B. Korea Concrete Institute 2016 International Journal of Concrete Structures and M Vol.10 No.4

The resistance-demand approach has emerged as an effective approach for determining the shear capacity of reinforced concrete beams. This approach is based on the fact that both the shear resistance and shear demand are correlated with flexural tensile strain from compatibility and equilibrium requirements. The basic shear strength, under a given loading is determined from the intersection of the demand and resistance curves. This paper verifies the applicability of resistance-demand procedure for predicting the shear capacity of high strength concrete beams without web reinforcement. A total of 18 beams were constructed and tested in four-point bending up to failure. The test variables included the longitudinal reinforcement ratio, the shear span to depth ratio, and the beam depth. The shear capacity of the beams was predicted using the proposed procedure and compared with the experimental values. The results of the comparison showed good prediction capability and can be useful to design practice.

Effects of STF and Fiber Characteristics on Quasi-Static Stab Resistant Properties of Shear Thickening Fluid (STF)-Impregnated UHMWPE/Kevlar Composite Fabrics

Ting-Ting Li,Wenna Dai,Liwei Wu,Hao-Kai Peng,Xiayun Zhang,Bing-Chiuan Shiu,Jia-Horng Lin,Ching-Wen Lou 한국섬유공학회 2019 Fibers and polymers Vol.20 No.2

In order to deeply explore the fiber characteristics influencing on stab resistance of shear thickening fluid (STF)-impregnated fabrics, two different weaving fabrics, ultra-high molecular weight polyethylene (UHMWPE) fabric and Kevlar fabrics are saturate the various concentrations and particle size of STFs. Result shows that, SiO2/PEG-200 blends demonstrate quick shear-thickening property, and the critical shear rate lowers to 1.2-45 s-1 with higher concentration of 75 nm SiO2. STF concentration and particle size significantly affect spike puncture resistance property, but the knife stab resistance mainly depends on fiber characteristics. Comparatively, STF-UHMWPE composite fabrics exhibit better knife stab resistance but weaker spike puncture resistance than STF-Kevlar fabrics. This study can provide an optimization for structure design of stab resistance armors in the future.

풍화된 암반에 근입된 현장타설말뚝의 주면지지력

권오성(Kwon Oh Sung),김명모(Kim Myoung Mo) 대한토목학회 2008 대한토목학회논문집 C Vol.28 No.4

본 연구에서는 암반의 풍화상태가 암반에 근입된 현장타설콘크리트 말뚝의 주면지지력에 미치는 영향을 분석하였다. 이를 위해 먼저 총 4부지의 풍화된 화강암/편마암 지역에 시공된 현장타설말뚝 14본(직경 400~1500 ㎜)에 대한 축방향 정재하 시험 및 하중전이 계측결과, 그리고 대상암반에 대한 엄밀한 지반조사 결과를 포함하는 데이터베이스를 구축하고, 암반 주면부의 거동과 암반물성치의 상관관계를 분석하였다. 풍화암/연암에 근입된 대상말뚝의 경우 주면지지력과 신선암편의 일축압축강도와의 상관관계 분석 결과 일관적인 상관성을 찾을 수 없었다. 그러나 Hoek-Brown 파괴규준을 이용해 추정한 암반강도는 주면지지력과 좋은 상관관계를 가지는 것으로 나타났다. 암반의 풍화 및 절리상태를 대변한다고 판단되는 암반물성치 (e.g. E<SUB>m</SUB>, E<SUB>ur</SUB>, P<SUB>lm</SUB>, RMR, RQD, j)들과 주면지지력의 상관성 분석을 통해 얻은 최적회귀곡선의 상관계수 또한 대부분의 경우 0.75 이상으로 좋은 상관성을 가지는 것으로 나타났다. 추가적으로, 본 연구의 결과를 이용하여 기존의 주면지지력 추정 방법의 풍화암/연암에의 적용성을 재하시험결과와의 비교를 통해 고찰하였다. 암반상태를 고려한 기존의 주면지지력 추정방법은 각각 암체계수(j) 0.15 이상, RQD 60 이상의 비교적 상태가 양호한 암반에 대해서만 제안되어 있으므로, 암체계수 0.15 이하, RQD 0~50인 연암 및 풍화암에 대한 본 연구의 결과를 이용하여 암반상태가 불량한 암반까지 이들 방법의 적용정을 보완 및 확장하였다. In this research, the effect of rock mass weathering on the side shear resistance of drilled shaft socketed into igneous-metamorphic rock was investigated. For that, 23 cast-in-place concrete piles with diameters varying from 400㎜ to 1,500㎜ were constructed at four different sites, and the static axial load tests were performed to examine the resistant behavior of the piles. A comprehensive field/laboratory testing program at the field test site was also performed to describe the in situ rock mass conditions quantitatively. The side shear resistance of rock socketed piles was found to have no intimate correlation with the compressive strength of the intact rock. However, the global rock mass strength, which was calculated by the Hoek and Brown criteria, was found to closely correlate to the side shear resistance. The ground investigation data regarding the rock mass conditions (e.g. E<SUB>m</SUB>, E<SUB>ur</SUB>, P<SUB>lm</SUB>, RMR, RQD, j) were also found to be highly correlated with the side shear resistance, showing the coefficients of correlation greater than 0.75 in most cases. Additionally, the applicability of existing methods for the side shear resistance of weathered granite-gneiss was verified by comparison with the field test data. The existing methods which consider the effect of rock mass condition were modified and/or extended for weathered rock mass where mass factor j is lower than 0.15, and RQD is below 50%.

셀식 구조물의 전단저항력 해석기법에 관한 연구

정삼동(Jung Sam Dong),원종화(Won Jong Hwa),조우연(Cho Woo Yeon),김문겸(Kim Moon Kyum) 대한토목학회 2007 대한토목학회논문집 A Vol.27 No.4A

셀식 구조물은 대표적인 불연속 구조체로서 일반적인 연속체 해석기법의 적용이 난해하여 전단저항력에 관한 평가기법이 명확하게 확립되어 있지 않다. 본 연구에서는 셀식 구조물의 내부채움재에서 발생하는 전단저항력을 정량적으로 평가하기 위한 전단저항력 해석기법을 제안하고 전단변형실험을 통하여 제안된 해석기법의 적용성에 대하여 검토하였다. 전단저항력 해석기법은 개별요소법을 도입함으로써 연속체에서 불연속체 거동까지의 일련의 과정에 대하여 모형화가 가능하고 이들의 정동적 해석을 수행할 수 있다. 또한 내부마찰각과 상재하중을 전단저항력의 주요영향인자로 선정하고 케이스별 해석을 설시하여 이들이 전단저항력에 미치는 영향을 분석하였으며, 이는 실험 결과와 매우 유사한 거동을 보임을 확인하였다. It is rather difficult to apply finite element methods to a cellular structure due to the fact that it is a typical model of discontinuous structures, and there are no clearly established evaluation techniques regarding its shear resistance. This paper presents an analytical approach on the shear resistance force of fill materials in a cellular structure. In order to solve the issue, shear resistance analysis was performed by introducing displacement incremental analysis into the distinct element method, which enabled it to modelize not only continuous but also discontinuous structures for static and dynamic analyses. Also, friction angle and vertical load were selected as main factors influencing shear resistance, and their effect on shear resistance was analyzed through a case study. This approach has led to a conclusion in which the computational results are in close agreement with the experimental ones.

Experimental Study of Steel Plate Composite Shear Wall Units under Cyclic Load

Zhen Guo,Yingshu Yuan 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.3

A novel type of steel plate composite shear wall that was assembled by using a steel plate and precast cement-based concrete plate is presented in this paper. The steel plate shear wall, which differs from normal steel plate shear walls, was trilaterally constrained with an elastic restraint side. The precast concrete slab was designed to prevent steel plate buckling. Six steel plate shear wall specimens were tested by using a hydraulic servo actuator. The failure mode, shear resistance, lateral stiffness, and buckling mode were investigated through an experimental study. The results indicate that the width-thickness ratio of the steel plate affected the shear-carrying capacity and failure mode. A low width-thickness ratio of steel plate required adequate bonding to prevent boundary failure. The precast concrete slabs enhanced the lateral stiffness and improved the buckling strength or shear resistance of the steel plate. The material workable capability of steel plate was fully developed with a composite buckling-restraint by using the composite shear wall; similarly, the earthquake-resistant behavior of the structural system would likewise be enhanced further.

경화 지연제 혼입 콘크리트의 부착전단강도 및 부식내구성 평가

손진수 ( Jin-su Son ),이진영 ( Jin-young Lee ) 한국농공학회 2023 한국농공학회 학술대회초록집 Vol.2023 No.0

In this study, the bond shear strength and corrosion resistance of concrete with setting retarder were evaluated. To investigate the bond shear strength and corrosion resistance of concrete with setting retarder, slant shear tests, bi-surface tests, and accelerated corrosion tests were carried out. Variables considered included the proportion of setting retarder (0, 1%), surface treatments of concrete (as-cast, chipping, brushing), curing hours (8, 16, 24h), and concrete cover depths (20, 30, 45mm). As a result, the bond shear strength of concrete with retarder showed higher value compared to normal concrete. Moreover, an increase in curing hours resulted in a higher value of bond shear strength. Furthermore, the addition of a retarder in concrete demonstrated an increase in corrosion resistance. Based on the test results, it is deemed that the addition of a setting retarder can be a suitable solution to address the bond shear strength and durability issues that may arise at the interface of delayed concrete placement.