• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.2
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• pp.69-80
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• 2008

In this study, improved capacity spectrum method (CSM) is proposed. The method can account for higher mode contribution to the seismic response of MDOF systems. The CSM has been conveniently used for determining maximum roof displacement using both demand spectrum and capacity curve of equivalent SDOF system. Unlike the conventional CSM, the maximum roof displacement is determined without iteration using inelastic displacement ratio and R factor calculated from demand spectrum and capacity curve. Three moment resisting steel frames of 3-, 9- and 20-stories are considered to test the accuracy of the proposed method. Nonlinear response history analysis (NL-RHA) for three frames is also conducted, which is considered as an exact solution. SAC LA 10/50 and 2/50 sets of ground motions are used. Moreover, this study estimates maximum story drift ratios (IDR) using ATC-40 CSM and N2-method and compared with those from the proposed method and NL-RHA. It shows that the proposed CSM estimates the maximum IDR accurately better than the previous methods.

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.374-381
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• 2000

본 논문에서는 지진 발생시, LRB가 설치된 교량의 시간이력 해석을 수행하였다 이를 위해 LRB의 비선형 거동특성을 Bi-linear로 모형화 하였으며, 기존의 방법인 등가선형으로 모형화된 해석결과와 비교하였다. 또한 LRB받침만 설치된 경우와, LRB받침과 일반탄성받침이 함께 사용된 경우를 해석하여, 받침이 혼합된 경우, 상시하중과 지진하중시 발생할 수 있는 문제점을 검토하였다. 4경간 연속교량에 적용된 해석결과를 보면, LRB만을 설치한 경우, Pot-Bearing만 설치된 경우에 .비해, 고유주기 상승과 이력감쇠에 의한 지진력의 감소와 함께, 지진력의 효과적인 분배를 볼 수 있었으며, 일반탄성받침과의 적절한 조합에 의해서도, 충분한 면진성능을 얻을 수 있었다. 또한 LRB의 등가선형 모델이 Bi-linear 모델에 비해 보수적인 해석결과를 나타내었다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.2
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• pp.145-154
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• 2020

Steel set is a structure that stabilize the NATM tunnel until the installation of shotcrete, and it is combined after the shotcrete is installed to improve stability. In this study, determination approach for the equivalent elastic modulus of shotcrete-lattice girder composite is newly suggested for tunneling simulation. Also, a method was presented to calibrate the equivalent elastic modulus through the comparison of the full 3D model and equivalent model. When the conventional equivalent elastic modulus is used for shotcrete-lattice girder composite, the flexural strength of equivalent model is 130% smaller than that of full 3D model. Equivalent elastic modulus is adjusted considering the error of flexural strength. It is found that the error of flexural strength obtained from adjusted equivalent model using adjusted equivalent elastic modulus is reduced less than 1%.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2411-2425
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• 2013

In the design of pile foundation on the rock layer in the stratified structure with sedimentary and rock layers, the structural analysis of the stratified rock layer is required to determine the failure modes (flexural failure, punching shear failure or end bearing failure) and the bearing capacity of the rock layer. However, the existing usable Elastic Plate Analysis Method (EPAM) suggested by ACI committee 436 and Korean Code Requirements for Structural Foundation Design is very complex, and engineers have many difficulties in using it. Therefore, in this research, we proposed the relatively simple Circular Foundation Analysis Method (CFAM) with the concept and the equation of the equivalent effective width (radius) instead of the complex EPM, and the related equations of bending moment and shear force to be equal to the analysis results of EPAM. As a result, the proposed CFAM using the equivalent effective width (radius) is simple and convenient to use, and the analysis results of it are very good in their accuracies comparing those of EPAM and Finite Element Method.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.2
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• pp.169-187
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• 2008

Performance-based approaches as an alternative method of the existing force-based approach have gradually become recognized tools for the seismic design and evaluation. The maximum inelastic displacement response using capacity spectrum method (CSM) with elastic response spectrum is estimated from seismic response of equivalent linear system converted from nonlinear system. The purpose of this paper is to evaluate accuracy of capacity spectrum method using the equivalent SDOF methods of 4 types and the equivalent damping methods of 5 types for RC wall structure. In order to evaluate accuracy of capacity spectrum analysis, the shaking table test results for RC wall structures are compared with those by the capacity spectrum analysis. Also, the effect of bilinear capacity curves by two bilinear approximation methods for capacity spectrum analysis is compared.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.454-457
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• 2011

본 논문에서는 국내에서 아직 기준이 마련되지 않은 제진설계에 대한 접근을 소개하였다. ASCE 7-05 기준에 근거하여 국내 5층 규모의 철근콘크리트 신축 건물에 제진 설계를 수행하였다. 우리나라의 현행 기준을 만족하면서 효과적인 제진 시스템 설계를 위한 방법을 소개한다. ASCE 7-05 기준에서는 제진 구조물 해석 시 부재력이 공칭강도의 1.5배를 초과하지 않은 경우 경계비선형 해석을 허용하고 있다. 이 때의 제진 설계 프로세스는 기존의 중력하중 및 등가정적하중의 75%에 의한 단면을 가정하여 부재설계를 실시하고, 선형 시간이력 해석을 통해 제진장치 및 가새를 설계한다. 이후 우리나라 실정에 맞도록 보정된 인공 지진파를 입력하여 경계비선형 해석을 실시하고, 밑면 전단력 및 층간변위 등의 만족여부를 검토한다. 이 때 목표성능을 완전탄성설계 또는 유사탄성설계로 정하여 목표성능을 만족하는지도 검토하여야 한다. 본 논문에 적용한 신축 건물은 유사탄성 설계를 위해 경계비선형 해석을 실시하였고, 가장 효과적인 제진 설계를 위해 댐퍼의 종류, 설치방법, 개수, 변위 증폭비 등을 변수로 한 case study를 진행하였다. 해석 결과 목표성능을 만족하는 범위 내에서 가장 효과적인 제진 설계는 점성댐퍼, 이층 토글형태, 증폭비 2.0, 총 8개의 댐퍼를 설치하는 것으로 나타났다.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.2
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• pp.35-44
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• 2004

In the capacity spectrum method(CSM) using a linear response spectrum, the peak response of an inelastic system under a given earthquake load is estimated transforming the system into the equivalent elastic one. The CSM for estimating the peak inelastic response is evaluated in this paper. The equivalent period and damping ratio are calculated using the ATC-40, G lkan, Kowalsky, and Iwan methods, and the performance points are obtained according to the procedure B of ATC-40. Analysis results indicate that the ATC-40 method generally underestimates the peak response resulting in the unsafe design, while the G lkan and Kowalsky methods overestimate the responses. The Iwan method produces the values between those by the ATC-40 method and the G lkan and Kowalsky methods, and estimates the responses relatively closer to the exact ones. Further, it is found that the Kowalsky method gives the negative equivalent damping ratios depending on the hardening ratios, and thereby can not be used to estimate the responses in some cases.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.6
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• pp.71-80
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• 2003

Though a nonlinear time history analysis may be provided to estimate more exactly the seismic performance of building structure, approximation methods are still needed in the aspect of practicality and simplicity, In converting a multi-story structure to an equivalent SDOF system, the mode vectors of the multi-story structure are assumed as the mode shape in elastic state regardless of elastic or elastic-plastic state. However, the characteristics of displacement mode are also changed after the yielding made in the structural elements, because the structure becomes inelastic in each incremental load step. In this research, a method of converting MDOF system to ESDOF system is presented by using nonlinear displacement mode considering the mode change of structures after the yielding. Also, the accuracy and efficiency of the method of the nonlinear displacement mode method of the estimate of seismic response of Mixed Building Structures were examined by comparing the displacements of the roof level of the multi-story building structures estimated from this converted displacement response of ESDOF with the displacement of the roof level through the nonlinear dynamic analysis of the multi-story building structures subjected to an actual earthquake excitation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.4
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• pp.621-629
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• 1992

This study is concerned with an application of the Boundary Element Method to 2-dimensional elastoplastic stress analysis on the material nonlinearities. The boundary integral formulation adopted an initial stress equation in the inelastic term. In order to determine the initial stress increment, the increment of initial elastic strain energy due to elastic increment in stressstrain curve was used as the convergence criterion during iterative process. For the validity of this procedure, the results of B.E.M. with constant elements and NISA with linear elements where compared on the thin plate with 2 edge v-notches under static tension and the thick cylinder under internal pressure. And this paper compared the results of using unmedical integral with the results of using semi-analytical integral on the plastic domain integral.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.8
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• pp.740-746
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• 2008

In this paper, robust structural design of the PEMFC stack gasket is pursued with Taguchi method by considering the noise factor in stack assembly. The study of noise problem in stacking is required to secure the safety and performance improvement of PEMFC stack. The design parameters in the Taguchi method are selected so that the structural responses are insensitive to the noise factors. In the gasket analysis, a Mooney-Rivlin strain energy function is used to consider hyperelasticity between load and displacement. By uni-axial and equi-biaxial tension tests of the gasket, the material properties are determined for the use in robust design of PEMFC gasket. The robust design of the PEMFC stack may provide structural reliability.