• 콘크리트학회논문집
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• 제12권5호
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• pp.47-57
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• 2000

Experimental and numerical studies were done to investigate seismic performance of slender shear walls with no boundary confinement that are principal structural members of high0rise bearing wall buildings. 1/3 scale specimens that model the plastic region of long slender shear walls subjected to combined axial load and bending moment were tested to investigate strength, ductility, capacity of energy dissipation, and strain distribution, The experimental results show that the slender shear walls fail due to early crushing in the compressive boundary, and then have very low ductility. The measured maximum compressive strain is 0.0021, much less than 0.004 being commonly used for estimation of ductility. This result indicates that the maximum compressive strain is not a fixed value but is affected by moment gradient along the shear wall height and distance from the neutral axis to the extreme compressive fiber.

• Smart Structures and Systems
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• 제25권1호
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• pp.47-56
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• 2020

This paper proposes a model-based approach for structural damage identification and quantification. Using pseudo modal strain energy and mode shape vectors, a damage-sensitive objective function is introduced which is suitable for damage estimation and quantification in shear frames. Whale optimization algorithm (WOA) is used to solve the problem and report the optimal solution as damage detection results. To illustrate the capability of the proposed method, a numerical example of a shear frame under different damage patterns is studied in both ideal and noisy cases. Furthermore, the performance of the WOA is compared with particle swarm optimization algorithm, as one the widely-used optimization techniques. The applicability of the method is also experimentally investigated by studying a six-story shear frame tested on a shake table. Based on the obtained results, the proposed method is able to assess the health of the shear building structures with high level of accuracy.

• 한국지진공학회논문집
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• 제23권3호
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• pp.169-181
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• 2019

Seismic performance of ordinary reinforced concrete shear wall systems commonly used in high-rise residential buildings is evaluated. Three types of shear walls exceeding 60m in height are designed by performance-based seismic design. Then, incremental dynamic analysis is performed collapse probability is assessed in accordance with the procedure of FEMA P695. As a result, story drift, plastic rotation, and compressive strain are observed to be major failure modes, but shear failure occur little. Collapse probability and collapse margin ratio of performance groups do not meet requirement of FEMA P695. It is observed that critical wall elements fail due to excessive compressive strain. Therefore, the compressive strain of concrete at the boundary area of the shear wall needs to be evaluated with more conservative acceptance criteria.

• 한국지반환경공학회 논문집
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• 제12권1호
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• pp.27-33
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• 2011

직접전단시험이나 삼축압축시험 시 하중재하속도가 증가할수록 시료의 전단강도는 증가하는 것으로 알려져 있다. 본 연구에서는 점성토 지반의 거동특성에 영향을 미치는 중요한 두 가지 요인, 즉 전단속도와 실트함유량에 따른 점성토의 응력-변형률 거동특성을 규명하기 위하여 광양지역의 재생성 점성토를 대상으로 완속재하 상태로부터 급속재하 상태까지 재현함과 동시에 실트함유량 변화 시 그 거동 특성이 어떻게 변화되는지에 대한 연구를 수행하였다. 연구결과 동일변형률에서의 전단속도 증가에 따른 축차응력의 변화, 즉 등변형률선의 기울기는 양의 기울기를 가지며 일정변형률 이상에서는 기울기의 변화가 거의 없는 것으로 나타났다. 그리고 기울기 변화가 없는 지점의 값은 흙의 종류에 따라 달라지므로 그 흙이 가지는 고유 특성인 것으로 판단된다.

• 한국지반공학회지:지반
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• 제13권4호
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• pp.109-120
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• 1997

공용하중 상태에서 지반이 경험하는 변형률 크기는 0.1~1% 미만임이 밝혀지고 있다. 변형특성을 보다 엄밀히 평가하기 위하여는 미소변형률 영역에서의 신뢰성 있는 변형측정이 가능한 현장시험기기의 개발이 필요하다. 본 연구의 목적은 공내째하시험기(PMT)를 사용하여 지반의 미소변형률 전단탄성계수를 측정하는 것이다. 공내재하시험에서 시추공 설치에 따른 주위 지반의 교란효과를 제거하기 위하여 초기 하중재하단계가 아닌 역재하-재재하 단계에서 PMT 주위지 반의 응력상태 및 변형률 크기를 고려하여 미소변형률 잔단탄성계수를 결정하였다. 실내 토조에서 성형한 모래시료와 화강풍화토 현장지반에서 시험을 수행하였으며,시험결과로부터 본 연구 에서 사용한 PMT시험은 변형률 크기 10-2%~0.5% 범위에서 신뢰성 있는 전단탄성계수 측정이 가능하였다. 또한 변형률 크기를 고려하여 다른 실내외시험에서 결정된 전단탄성계수와 비교 하면 서로 잘일치하는 결과를 얻을 수 있었다.

• Structural Engineering and Mechanics
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• 제51권5호
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• pp.867-891
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• 2014

An equivalent single layer trigonometric shear deformation theory taking into account transverse shear deformation effect as well as transverse normal strain effect is presented for static flexure of cross-ply laminated composite and sandwich plates. The inplane displacement field uses sinusoidal function in terms of thickness coordinate to include the transverse shear deformation effect. The cosine function in thickness coordinate is used in transverse displacement to include the effect of transverse normal strain. The kinematics of the present theory is much richer than those of the other higher order shear deformation theories, because if the trigonometric term (involving thickness coordinate z) is expanded in power series, the kinematics of higher order theories (which are usually obtained by power series in thickness coordinate z) are implicitly taken into account to good deal of extent. Governing equations and boundary conditions of the theory are obtained using the principle of virtual work. The closed-form solutions of simply supported cross-ply laminated composite and sandwich plates have been obtained. The results of present theory are compared with those of the classical plate theory (CPT), first order shear deformation theory (FSDT), higher order shear deformation theory (HSDT) of Reddy and exact three dimensional elasticity theory wherever applicable. The results predicted by present theory are in good agreement with those of higher order shear deformation theory and the elasticity theory.

• Geomechanics and Engineering
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• 제1권4호
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• pp.263-274
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• 2009

The modified Cam clay (MCC) model is used to study the response of virgin compressed clay in undrained compression. The MCC deviatoric stress-strain relationship is obtained in closed form. Elastic and plastic deviatoric strains are taken into account in the analysis. For the determination of the elastic strain components, both a variable shear modulus and constant shear modulus are considered. Constitutive relationships are applied to the well-known London and Weald clays sheared in undrained compression.

• 한국지진공학회논문집
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• 제2권4호
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• pp.53-62
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• 1998

구조물의 내진 성능 향상을 위해 현재 종종 사용되어지고 있는 기초분리장치인 적층고베어링과 납-고무 베어링의 내진성능을 실험적으로 파악하였다 베어링의 전단 변형률 또는 가해진 수직 하중이 클수록 베어링의 전단 강성은 감소하며 가력 속도에 대한 영향을 무시할 만하다. 베어링은 순수압축력에는 강하며 인장력에는 그 반대이다.

• Geomechanics and Engineering
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• 제8권1호
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• pp.33-52
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• 2015

Based on the Mohr-Coulomb failure criterion, a gradient-dependent plastic model that considers the strain-softening behavior is presented in this study. Both triaxial shear tests on conventional specimen and precut-specimen, which were obtained from an ancient landslide, are performed to plot the post-peak stress-strain entire-process curves. According to the test results of the soil strength, which reduces from peak to residual strength, the Mohr-Coulomb criterion that considers strain-softening under gradient plastic theory is deduced, where strength reduction depends on the hardening parameter and the Laplacian thereof. The validity of the model is evaluated by the simulation of the results of triaxial shear test, and the computed and measured curves are consistent and independent of the adopted mesh. Finally, a progressive failure of the ancient landslide, which was triggered by slide of the toe, is simulated using this model, and the effects of the strain-softening process on the landslide stability are discussed.

• 한국공작기계학회논문집
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• 제10권1호
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• pp.127-132
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• 2001

By the use of a similar numerical method as the forming limit strain by coating method of coated sheet metals is investigated, in which the FEM is applied and J2G(J2-Gotohs Corner Theory) is utilized as the plasticity constitutive equa-tion. Circular bonded sheet metals with dissimilar sheets on both surface planes are stretched in a plane -strain state, with various work-hardening exponent n-values and thicknesses of each layer. Processes of shear-band formation in such com-posite sheets are clearly illustrated. It is concluded that, it the bonded state, the higher limiting strain of one layer is reduced due to the lower limiting strain of the other layer and vice versa, and does not necessarily obey the rule of linear combination of the limiting strain of each layer weighed according thickness.