• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.6
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• pp.505-512
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• 2012

In this paper, an efficient yet accurate method for the thermal stress analysis using a first order shear deformation theory(FSDT) is presented. The main objective herein is to systematically modify transverse shear strain energy through the mixed variational theorem(MVT). In the mixed formulation, independent transverse shear stresses are taken from the efficient higher-order zigzag plate theory, and the in-plane displacements are assumed to be those of the FSDT. Moreover, a smooth parabolic distribution through the thickness is assumed in the transverse normal displacement field in order to consider a transverse normal deformation. The resulting strain energy expression is referred to as an enhanced first order shear deformation theory, which is obtained via the mixed variational theorem with transverse normal deformation effect(EFSDTM_TN). The EFSDTM_TN has the same computational advantage as the FSDT_TN(FSDT with transverse normal deformation effect) does, which allows us to improve the through-the-thickness distributions of displacements and stresses via the recovery procedure. The thermal stresses obtained by the present theory are compared with those of the FSDT_TN and three-dimensional elasticity.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.14-17
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• 2010

본 논문에서는 국내에서 주상복합건물에 주로 건설되는 철근콘크리트 전단벽과 무량판 골조 기둥 시스템의 횡저항 거동을 조사, 분석하였다. 이 시스템의 내진설계 시 건물골조시스템을 적용하게 되는데 전단벽 설계는 큰 어려움이 없으나 골조의 경우 변형의 적합성을 고려해야 할 경우에 상세하고 명확한 지침이 마련되어 있지 않아 그 적용이 쉽지 않다. 이를 해결하기 위하여 예제 건물을 선정하여 기준에 따라 설계한 후 비선형정적 해석을 수행하여 철근콘크리트 전단벽과 무량판 골조 기둥의 비선형 거동을 조사하였다. 그 결과 무량판 골조 기둥의 거동은 전단벽에 종속되었고 변형의 적합성을 고려하기 위해 골조의 모멘트를 증폭하더라도 기둥의 단면 변화가 크지 않으므로 실무적으로 큰 어려움이 없는 것으로 나타났다. 다만 강도뿐만 아니라 변형 능력에 대해서도 추가적인 연구가 필요하다.

• Journal of Korean Society of Steel Construction
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• v.23 no.4
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• pp.475-481
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• 2011

In this study, a simplified method of improving not only transverse shear stress but also shear strain based on the first-order shear deformation theory was developed. Unlike many established methods, such as the higher-order shear deformation and layerwise theories, this method can easily apply to finite elements as only $C^0$ continuity is necessary and the formulation of equations is very simple. The basic concept in this method, however, must be corrected:the distribution of the transverse shear stresses and shear strains through the thickness from the formulation based on the higher-order shear deformation theory. Therefore, the shear correction factors are no longer required, based on the first-order shear deformation theory. Numerical analyses were conducted to verify the validity of the proposed formulations. The solutions based on the simplified method were in very good agreement with the results considering the higher-order shear deformation theory.

• Journal of the Korea Concrete Institute
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• v.26 no.2
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• pp.159-169
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• 2014

This study generalizes the lateral load-displacement relationship of reinforced concrete shear walls from the section analysis for moment-curvature response to straightforwardly evaluate the flexural capacity and ductility of such members. Moment and curvature at different selected points including the first flexural crack, yielding of tensile reinforcing bar, maximum strength, 80% of the maximum strength at descending branch, and fracture of tensile reinforcing bar are calculated based on the strain compatibility and equilibrium of internal forces. The strain at extreme compressive fiber to determine the curvature at the descending branch is formulated as a function of reduction factor of maximum stress of concrete and volumetric index of lateral reinforcement using the stress-strain model of confined concrete proposed by Razvi and Saatcioglu. The moment prediction models are simply formulated as a function of tensile reinforcement index, vertical reinforcement index, and axial load index from an extensive parametric study. Lateral displacement is calculated by using the moment area method of idealized curvature distribution along the wall height. The generalized lateral load-displacement relationship is in good agreement with test result, even at the descending branch after ultimate strength of shear walls.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.3
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• pp.249-257
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• 2011

In this paper, an systematic approach is presented, in which the mixed variational theorem is employed to incorporate independent transverse shear stresses into a classical higher-order shear deformation theory(HSDT). The HSDT displacement field is taken to amplify the benefits of using a classical shear deformation theory such as simple and straightforward calculation and numerical efficiency. Those independent transverse shear stresses are taken from the fifth-order polynomial-based zig-zag theory where the fourth-order transverse shear strains can be obtained. The classical displacement field and independent transverse shear stresses are systematically blended via the mixed variational theorem. Resulting strain energy expressions are named as an enhanced higher-order shear deformation theory via mixed variational theorem(EHSDTM). The EHSDTM possess the same computational advantage as the classical HSDT while allowing for improved through-the-thickness stress and displacement variations via the post-processing procedure. Displacement and stress distributions obtained herein are compared to those of the classical HSDT, three-dimensional elasticity, and available data in literature.

• Computational Structural Engineering
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• v.11 no.4
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• pp.287-294
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• 1998

입면의 형태가 임의의 층에서 큰 차이를 보이는 3차원 비정형 setback 구조물의 동적 거동 특성과 이들 구조물의 동적 거동에 미치는 바닥 슬래브의 면내 변형 효과를 분석하였다. 비정형 setback 구조물의 전반적인 동적 거동특성을 분석하기 위하여 베이스 부분의 평면적과 타워 부분의 평면적 비(R?), setback 발생위치(L?)등을 매개 변수로 사용하였다. 48개의 비정형 setback 구조물들에 대한 해석 수행 결과 setback 구조물은 정형 구조물에 비해 횡방향 1차 모드의 유효 모드 중량(effective modal weight)이 작게 나타나는 경향을 보이기 때문에 setback 구조물의 동적 거동을 파악하기 위해서는 등가 정적 해석법 대신에 동적 해석을 수행할 필요가 있음을 알 수 있었다. 바닥슬래브의 면내 변형은 보다 긴 구조물의 고유 진동 주기값을 가져오며 모드 순서 및 모드 형상에도 변화를 준다. 이러한 사실은 바닥슬래브의 면내 변형으로 인하여 횡방향 저항 요소들간의 전단력 분포와 층 변위가 영향을 받을 수 있다는 것을 의미한다. 이러한 현상은 횡방향 저항 요소들간의 강성 차가 심한 프레임-전단벽 시스템에서 두드러지게 나타난다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.4
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• pp.99-108
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• 2007

In the flat-plate slab design of the KCI and ACI building code, the punching shear strength of connections with shear reinforcement can increase one and half times to that of connections without shear reinforcement. And the ACI-ASCE committee 352 recommendations propose limiting the direct shear ratio $V_g$/$V_c$ on interior connections to 0.4 to insure adequate drift capacity. In this study, four interior column-slab connections were tested to look into the punching shear strength and the lateral displacement capacity of the flat-plate slab with and without shear reinforcement under cyclic lateral loading. Based on the test results, it is found that the provision about punching shear strength in the codes may appropriate for the gravity loading only whereas it is unconservative for the lateral loading and that the limit of ACI-ASCE committee 352 appears conservative.

• Journal of Korean Society of Steel Construction
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• v.9 no.1 s.30
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• pp.149-157
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• 1997

철골 모멘트 접합부를 헌치로서 보강할 경우 내진거동이 크게 증진됨이 최근의 실물대 시험에서 입증되고 있다. 본 연구에서는 헌치로서 보강된 철골 모멘트 접합부가 골조의 탄성 횡변위 거동에 미치는 영향을 해석적으로 평가하는 방안을 제시하였다. 즉 내부의 보-기둥 부분골조를 대상으로 기둥, 보 및 이중패널존에서 기인하는 탄성 횡변위 성분을 해석적으로 유도하였다. 핵심이 되는 내용은 헌치 보강시 생성되는 이중패널존의 전단변형을 고려하는 것이었다. 제시된 방안에 의한 예측치는 3차원 유한요소해석에 의한 결과와 잘 부합하였다. 본 연구에서 수행한 사례연구에 의할 때 헌치의 도입으로 패널존의 강성증대가 가장 현저하여서 패널존의 전단변형에서 기인하는 탄성 횡변위가 50%정도 감소되었다. 본 연구의 결과는 아직 잘 알려지지 않은 헌치 보강에 따른 부차효과(side effects)의 이해에 도움이 될 수 있을 것이다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.3
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• pp.259-266
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• 2015

In this paper, transverse shear spacing and effective depth of wide beams were considered as parameters to evaluate the shear capacity of wide beam according to transverse spacing of steel plates with openings in experimental way. The eight specimens were composed of: five specimens of shear reinforced by steel plates with openings and three non-reinforced specimens. Crack, failure mode, strain and load-displacement curve of specimens were analysed. Shear contribution of shear reinforcement is evaluated and maximum transverse spacing of shear reinforcement was proposed. Shear strength of the specimen that reinforced with three stirrup legs was higher than shear strength of the specimen that reinforced with two stirrup legs. And as the effective depth increased, shear strength was increased.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.4 s.74
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• pp.407-418
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• 2006

In this paper, an efficient yet accurate stress analysis based on the first-order shear deformation theory (FSDT) is presented. The transverse shear strain energy is modified via the mixed variational theorem, so that the shear correction factors are automatically involved in the formulation. In the mixed variational formulation, the transverse stresses are taken to be functions subject to variations. The transverse shear stresses based on an efficient higher order plate theory (EHOPT, Cho and Parmerter, 1993) are utilized and modified, while the transverse normal stress is assumed to be the third-order polynomial of thickness coordinates, which satisfies both zero transverse shear stresses and prescribed surface fractions in top and bottom surfaces. On the other hand, the displacements are assumed to be those of the FSDT Resulting strain energy expressions are referred to as an EFSDTM3D that stands for an enhanced first-order shear deformation theory based on the mixed formulation for three dimensional elasticity, The developed EFSDTM3D preserves the computational advantage of the classical FSDT while allowing for important local through-the-thickness variations of displacements and stresses through the recovery procedure that is based on the least square minimization of in-plane stresses. Comparisons of displacements and stresses of both laminated and sandwich plates using the present theory are made with the classical FSDT, three-dimensional exact solutions, and available data in the literature.