• 토지주택연구
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• 제8권3호
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• pp.211-221
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• 2017

This study proposed hybrid coupled shear wall in the steel plate insertion method, which is capable of reinforcing the shear strength of the entire wall without increasing wall thickness in the wall-slab apartment buildings. The proposed hybrid coupled shear wall was tested for its effectiveness, shear strength and seismic behavior in experiment. As a test result, the shear strength improvement by the proposed hybrid coupled shear was found effective. Integral-type of steel plate insertion was found more effective than separate-type steel plate insertion. In this case, if the stud enforcement method proposed in this study was used, the shear strength of hybrid coupled shear wall was recommended to calculate using the KBC2016 0709.4.1(3) method. The steel plate inserted in the proposed method was found to have no significant impact on the final fracture behavior and bending strength of hybrid coupled shear wall. The shear strength at the final destruction of the wall was merely about 1/50 of the entire design shear strength. Thus, it is deemed that the wall was over excessively designed regarding the shear force in the existing design method. This finding indicates further study on wall designing to ensure effective and economic designing based on appropriate strength estimation under the destruction mechanism.

• 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.

• Geomechanics and Engineering
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• 제21권3호
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• pp.247-258
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• 2020

The shear strength of unsaturated soils, a research hotspot in geotechnical engineering, has great guiding significance for geotechnical engineering design. Although kinds of calculation models for the shear strength of unsaturated soil have been put forward by predecessors, there is still need for new models to extensively consider the nonlinear variation of shear strength, particularly for the nonlinear effect of the net normal stress on the shear strength of unsaturated soil. Here, the shear strength of unsaturated soils is explored to study the nonlinear effects of net normal stress with the introduction of a general nonlinear Mohr-Coulomb (M-C) strength criterion, and the relationship between the matric suction (or suction stress) and degree of saturation (DOS) constructed by the soil-water characteristics curve (SWCC) of van Genuchten is also applied for unsaturated soil. Then, two calculation models (i.e., an envelope shell model and an effective stress model) are established for the shear strength of unsaturated soils under the nonlinear strength theory. In these two models, the curve of the shear strength of unsaturated soils versus the net normal stress exhibits a tendency to gently. Moreover, the proposed formulas have flexibility and convenience with five parameters (for the effective stress model) or six parameters (for the envelope shell model), which are from the M-C strength parameters of the saturated soil and fitting parameters of SWCC of van Genuchten. Thereafter, by comparison with the classical theory of the shear strength of unsaturated soils from some actual cases, the rationality and accuracy of the present models were verified.

• 한국지진공학회논문집
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• 제13권6호
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• pp.1-9
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• 2009

본 연구는 아라미드 섬유 보강 폴리머(Aramid Fiber Reinforced Polymers, 이하 AFRP)rebar로 보강된 콘크리트 깊은보의 전단강도를 평가하기 위하여 전단경간비, 보강비, 유효깊이, 주근을 변수로 총 8본의 시험체에 대한 전단 실험을 수행하였다. ACI 318-08의 스트럿-타이 모델(이하 STM)을 이용한 전단강도와 아치작용을 고려한 제안식에 의한 전단강도를 비교-평가하였으며, 그 결과 AFRP rebar로 보강한 경우, Steel rebar로 보강한 경우보다 전단강도가 증가하는 것으로 나타났다. 전단강도 산정에 있어 ACI 318-08 STM을 이용한 해석이 상대적으로 정확했으며, 실험결과를 토대로 스트럿의 크기효과를 고려한 유효압축강도 산정 모델을 제안하였다. 이를 본 실험에 적용시킨 결과 기존 기준 및 제안식을 이용한 전단강도 산정방법보다 합리적인 결과를 얻을 수 있었다.

• Computers and Concrete
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• 제9권2호
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• pp.133-151
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• 2012

This paper presents an analytical procedure for the analysis of high strength steel fiber reinforced concrete members considering the cracking effect in the serviceability loading range. Modifications to a previously proposed formula for the effective moment of inertia are presented. Shear deformation effect is also taken into account in the analysis, and the variation of shear stiffness in the cracked regions of members has been considered by reduced shear stiffness model. The effect of steel fibers on the behavior of reinforced concrete members have been investigated by the developed computer program based on the aforementioned procedure. The inclusion of steel fibers into high strength concrete beams and columns enhances the effective moment of inertia and consequently reduces the deflection reinforced concrete members. The contribution of the shear deformation to the total vertical deflection of the beams is found to be lower for beams with fibers than that of beams with no fibers. Verification of the proposed procedure has been confirmed from series of reinforced concrete beam and column tests available in the literature. The analytical procedure can provide an accurate and efficient prediction of deflections of high strength steel fiber reinforced concrete members due to cracking under service loads. This procedure also forms the basis for the three dimensional analysis of frames with steel fiber reinforced concrete members.

• Structural Engineering and Mechanics
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• 제61권5호
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• pp.605-615
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• 2017

Shear failure of reinforced concrete (RC) beams is a major concern for structural engineers. It has been shown through various studies that the shear strength and ductility of RC beams can be improved by adding steel fibers to the concrete. An accurate model predicting the shear strength of steel fiber reinforced concrete (SFRC) beams will help SFRC to become widely used. An artificial neural network (ANN) model consisting of an input layer, a hidden layer of six neurons and an output layer was developed to predict the shear strength of SFRC slender beams without stirrups, where the input parameters are concrete compressive strength, tensile reinforcement ratio, shear span-to-depth ratio, effective depth, volume fraction of fibers, aspect ratio of fibers and fiber bond factor, and the output is an estimate of shear strength. It is shown that the model is superior to fourteen equations proposed by various researchers in predicting the shear strength of SFRC beams considered in this study and it is verified through a parametric study that the model has a good generalization capability.

• 한국지반공학회논문집
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• 제31권9호
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• pp.17-27
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• 2015

벤더엘리먼트가 장착된 삼축압축시험장비를 이용하여 모래에 대한 일련의 압밀배수시험을 수행하였다. 상대밀도 및 유효구속응력 조건을 달리하여 각각의 조건별 응력-변형률 관계를 측정하였으며, 압밀이 종료된 시점에서의 전단파 속도를 측정함으로써 전단파 속도와 간극비, 유효응력, 그리고 전단강도와의 상관관계를 분석하였다. 분석 결과, 미소변형률에서의 전단파 속도로부터 계산된 최대전단탄성계수와 파괴 시의 축응력과 압밀 시의 구속응력의 합으로 정의되는 유효수직응력간에는 고유한 상관관계가 존재하는 것으로 나타났다. 도출된 전단탄성계수와 유효수직응력간의 상관관계는 유효구속응력을 정규화시킴으로써 정확도를 향상시켰다. 본 연구를 통해 제시된 상관관계를 통해 전단강도 및 내부 마찰각을 예측하였을 시, 실제 실내 시험을 통해 산출된 내부 마찰각을 정확하게 예측할 수 있는 것으로 나타났다. 이는 미소변형률에서의 전단파 속도를 기반으로 신뢰성 높은 파괴 시 전단강도, 나아가 내부 마찰각까지 예측이 가능하다는 것을 의미하며 기존 SPT-N value와 경험식을 통해 내부 마찰각을 예측하여 설계에 적용하는 방식의 불확실성을 개선해 줄 수 있는 매우 유용한 방법이라고 판단된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.73-80
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• 2001

The shear strength of jointed rock is influenced by effective normal stress, joint wall compressive strength, joint roughness and so on. Since joint roughness makes considerable influences on shear strength of jointed rock, many studies tried to get quantitative joint roughness parameter. Until now, Joint Roughness Coefficient, JRC proposed by Barton has been prevalently used as a rock joint roughness parameter In spite of its disadvantages. In this study, a quantification of rock joint roughness is performed using surface roughness parameter, Rs. Proposed method is applied to rock core specimens, field joint surfaces, and JRC profiles. The scale of fluctuation is introduced to extend the suggested method to the large scale field joint surface roughness. Based on the quantification of joint surface roughness, joint shear tests are performed with the portable shear box. The relationship between joint surface roughness and joint shear strength is investigated and finally, a rock joint shear strength equation is derived from these results. The equation has considerable credibility and originality in that it is obtained from laboratory tests and expressed with quantified parameter.

• 한국지반공학회논문집
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• 제19권6호
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• pp.7-14
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• 2003

본 연구에서는 굴패각 혼합토의 전단강도 특성을 파악하고자 해성토에 굴패각 혼합율 0%, 25% 그리고 50%로 달리 한 후 $K_o$ 비배수 삼축압축 실험을 실시하였다. 또한 각 혼합비에 따라 유효 연직압을 200kPa, 300kPa 그리고 400kPa로 적용하였고, 유효 연직압 300kPa에 대해서 전단속도를 세가지로 달리하여 그에 따른 혼합토의 전단강도 특성을 알아보았다. 일련의 실험결과로부터 굴패각 혼합비가 증가할수록 굴패각 입자의 파쇄로 인해 전단강도가 증가함을 볼 수 있었으며, 전단속도는 굴패각 혼합토의 전단강도에 큰 영향을 미치지 못함을 확인하였다. 굴패각 혼합토의 실내실험과 Mayne, Bishop의 경험식을 토대로 비교 분석한 결과 비배수 전단강도는 실험값과 비슷한 경향을 나타내고 있다. 그러나 간극수압계수 예측은 혼합비 0%에서 경험식이 실험값과 보다 과대 평가를 보이고 있다.

• 한국구조물진단유지관리공학회 논문집
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• 제18권2호
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• pp.90-98
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• 2014

철근콘크리트 구조물의 전단거동은 수년간의 많은 연구에도 불구하고, 이론적으로 명확하게 규명하기에 어려운 문제중에 하나이다. 중공 슬래브의 휨강도와 전단강도는 중공부로 인하여 감소되기 때문에, 이에 따른 구조물의 성능을 예측하는 것은 중요한 문제라 할 수 있다. 현재 각국의 중공슬래브 전단설계기준은 실험에 의한 기준식을 제시하고 있다. 따라서 본 연구에서는 철근비에 따른 일방향 중공슬래브 전단강도 산정방법에 관한 연구를 수행하기 위해 실험결과를 분석하고, 전단강도 산정식들을 비교, 분석하였다.