• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.465-474
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• 2008

Generally design of frame structures composed of beam-column member is accomplished by stability evaluation of each member considering the effective buckling length. This study selects a member of the smallest non-dimension slenderness ratio using the buckling eigenvalue calculated by the elastic buckling eigen-value analysis and axial force of the each member, and decides the initial deflection quantity reflected geometric and material nonlinearities from a suggested equation on the base of standard strength curve of Korea Bridge Design Code. Second-order elastic analysis applying the initial deflection is executed and the stability of each member is evaluated and decides ultimate strength. Through examples of eight-stories and four-stories plane frame structures, the evaluation of the stability is compared with the existing method and ultimate strength of the suggested method is compared with ultimate strength by the nonlinear inelastic analysis. Through these procedures, the increasing of effective buckling length by elastic buckling eigenvalue analysis is prevented from a new design method that considers initial imperfections. And the validity of this method is proved.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.1
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• pp.13-24
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• 1993

The tangent stiffness matrices of the plane frame and the thin-walled space frame are derived by using the principle of virtual displacement. In case of the plane frame, the shape function and stiffness matrices are presented for the rigid-hinged condition. For the unsymmetric thin-walled space frame, the elastic and geometric stiffness matrices in three cases of the unrestrained torsion, the restrained torsion, and the restrained anti unrestrained torsion are evaluated by using the various Hermitian polynomials as the shape function. Numerical examples for the lateral buckling analysis of the space frames and the circular arch illustrate the accuracy and convergence characteristics of the derived formulations.

• Computational Structural Engineering
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• v.11 no.1
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• pp.46-57
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• 1998

노스리지 지진하의 모멘트 저항 강 뼈대 구조물에 대한 사례연구결과를 요약하면 다음과 같다. 1) 탄성과 비탄성 동적해석 방법의 신뢰도가 구조물의 동적거동의 모형화에 크게 영향을 받는다는 것을 알 수 있었고 구조물의 동적거동의 모형화를 위한 보다 개선된 지침과 기준의 필요성이 부각되었다. 2) 비탄성 횡방향 정적해석은 6층높이의 건물까지는 비탄성동적해석과 유사한 결과를 보였으나 10층 이상의 건물에서는 고차 모드 효과를 고려하지 못하여 상당히 상이한 결과를 나타냈다. 3) 응답스펙트럼 해석은 노스리지 지진하에서 탄성 시간이력 해석에 비하여 100%까지 상이한 결과를 보였다. 특정지진에 대한 구조물거동의 상세조사시 응답 스펙트럼 해석 대신 시간이력해석을 수행하는 것이 바람직하다. 4) 탄성 부재력의 저항능력 비와 소성 회전각 등의 거동지수 등은 현존하는 건물의 연결부 손상을 검사하기 위한 지침을 마련하는데 도움을 줄 수 있지만 특정 연결부를 검사에서 배제시키는 유일한 근거로 사용되어서는 안될 것으로 판단된다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.537-549
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• 2001

The effect of partially restrained(PR) connections and the uncertainties in them on the reliability of steel frames subjected to seismic loading is addressed. A stochastic finite element method(SFEM) is proposed combining the concepts of the response surface method(RSM), the finite element method(FEM), the first-order reliability method (FORM), and the iterative linear interpolation scheme. The behavior of PR connections is captured using moment-relative rotation curves, and is represented by the four-parameter Richard model. For seismic excitation, the loading, unloading, and reloading behavior at PR connections is modeled using moment-relative rotation curves and the Masing rule. The seismic loading is applied in the time domain for realistic representation. The reliability of steel frames in the presence of PR connections is calculated considering all major sources of nonlinearity. The algorithm is clarified with the help of an example.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.117-126
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• 2002

In this paper, 3-D fame design using second-orders plastic-hinge analysis accounting for lateral torsional buckling is developed. This analysis accounts for material and geometric nonlinearities of the structural system and its component members. Moreover, the problem associated with conventional second-order plastic-hinge analyses, which do not consider the degradation of the flexural strength caused by lateral torsional buckling, is overcome. Efficient ways of assessing steel frame behavior including gradual yielding associated with residual stresses and flexure, second-order effect, and geometric imperfections are presented. In this study, a model consisting of the unbraced length and cross-section shape is used to account for lateral torsional buckling. The proposed analysis is verified by the comparison of the LRFD results. A case studs shows that lateral torsional buckling is a very crucial element to be considered in second-order plastic-hinge analysis. The proposed analysis is shown to be an efficient reliable tool ready to be implemented into design practice.

• Journal of Korean Society of Steel Construction
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• v.14 no.1
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• pp.13-21
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• 2002

In this paper, 3-D frame design using refined plastic-hinge analysis accounting for local buckling is developed. This analysis accounts for material and geometric nonlinearities of the structural system and its component members. Moreover, the problem associated with conventional refined plastic-hinge analyses, which do not consider the degradation of the flexural strength caused by local buckling, is overcome. Efficient ways of assessing steel frame behavior including gradual yielding associated with residual stresses and flexure, second-order effect, and geometric imperfections are presented. In this study, a model consisting of the width-thickness ratio is used to account for local buckling. The proposed analysis is verified by the comparison of the LRFD results. A case study shows that local buckling is a very crucial element to be considered in second-order plastic-hinge analysis. The proposed analysis is shown to be an efficient, reliable tool ready to be implemented into design practice.

• Journal of Korean Society of Steel Construction
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• v.15 no.6 s.67
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• pp.661-672
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• 2003

The advanced analysis and optimal design of semi-rigid frame were presented. Advanced analysis can predict the combined nonlinear effects of connection, geometry, and material on the behavior and strength of semi-rigid frames. The Kishi-Chen power model was used to describe the nonlinear behavior of semi-rigid connections. Geometric nonlinearity was determined using stability functions. On the other hand, material nonlinearity was determined using the Column Research Council (CRC) tangent modulus and parabolic function. The direct search method proposed by Choi and Kim was used as optimization technique. The member with the largest unit value evaluated using the LRFD interaction equation was replaced one by one with an adjacent larger member selected from the database. The objective function was assumed as the weight of steel frame, with the constraint functions accounting for load-carrying capacities, deflections. inter-story drifts, and ductility requirement. Member sizes determined by the proposed method were compared with those derived using the conventional LRFD method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.443-453
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• 2013

The hybrid test is one of the most advanced test methods to predict the structural dynamic behavior with the interaction between a physical substructure and a numerical modeling in the hybrid control system. The purpose of this study is to perform the multi-directional dynamic test of a steel frame structure with the real-time hybrid system and to evaluate the validation of the results. In this study, FEAPH, nonlinear finite element analysis program for hybrid only, was developed and the hybrid control system was optimized. The inefficient computational time was improved with a fixed number iteration method and parallel computational techniques used in FEAPH. Furthermore, the previously used data communication method and the interface between a substructure and an analysis program were simplified in the control system. As the results, the total processing time in real-time hybrid test was shortened up to 10 times of actual measured seismic period. In order to verify the accuracy and validation of the hybrid system, the linear and nonlinear dynamic tests with a steel framed structure were carried out so that the trend of displacement responses was almost in accord with the numerical results. However, the maximum displacement responses had somewhat differences due to the analysis errors in material nonlinearities and the occurrence of permanent displacements. Therefore, if the proper material model and numerical algorithms are developed, the real-time hybrid system could be used to evaluate the structural dynamic behavior and would be an effective testing method as a substitute for a shaking table test.

• Journal of the Korean Institute of Gas
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• v.12 no.4
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• pp.41-45
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• 2008

This paper presents the numerical study on the strength safety and displacement behaviors of a helmet, which is to protect impact forces and to absorb the impact energy. Four different helmet models including a bead frame and a corrugation damper have been analyzed for the stress and the displacement characteristics by using the finite element method. The computed FEM results show that the bead frame on the summit area of the helmet is very useful to increase the strength safety of the helmet, and the corrugation damper on the lower part of the helmet may increase the energy absorption capacity. Thus, this paper recommends the bead frame and the corrugation damper as new design elements of the helmets.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.2
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• pp.123-133
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• 2006

The main objective of this study is to develop an optimization algorithm of framed structures with rigid and various semi-rigid connections using the multilevel dynamic programming and the sequential unconstrained minimization techniques (SUMT). The second-order elastic analysis is performed for steel framed structures. The second order elastic analysis is developed based on nonlinear beam-column theory considering the bowing effect. The following semi-rigid connections are considered; double web angle, top-seat angle and top-seat angle with web angle. We considered the three connection models, such as modified exponential, polynomial and three parameter model. The total weight of the structural steel is used as the objective function in the optimization process. The dimensions of steel cross section are selected as the design variables. The design constraints consist of strength requirements for axial, shear and flexural resistance and serviceability requirements.