• Structural Engineering and Mechanics
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• 제59권3호
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• pp.455-473
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• 2016

Methods for the seismic demands evaluation of structures require iterative procedures. Many studies dealt with the development of different inelastic spectra with the aim to simplify the evaluation of inelastic deformations and performance of structures. Recently, the concept of inelastic spectra has been adopted in the global scheme of the Performance-Based Seismic Design (PBSD) through Capacity-Spectrum Method (CSM). For instance, the Modal Pushover Analysis (MPA) has been proved to provide accurate results for inelastic buildings to a similar degree of accuracy than the Response Spectrum Analysis (RSA) in estimating peak response for elastic buildings. In this paper, a simplified nonlinear procedure for evaluation of the seismic demand of structures is proposed with its applicability to multi-degree-of-freedom (MDOF) systems. The basic concept is to write the equation of motion of (MDOF) system into series of normal modes based on an inelastic modal decomposition in terms of ductility factor. The accuracy of the proposed procedure is verified against the Nonlinear Time History Analysis (NL-THA) results and Uncoupled Modal Response History Analysis (UMRHA) of a 9-story steel building subjected to El-Centro 1940 (N/S) as a first application. The comparison shows that the new theoretical approach is capable to provide accurate peak response with those obtained when using the NL-THA analysis. After that, a simplified nonlinear spectral analysis is proposed and illustrated by examples in order to describe inelastic response spectra and to relate it to the capacity curve (Pushover curve) by a new parameter of control, called normalized yield strength coefficient (${\eta}$). In the second application, the proposed procedure is verified against the NL-THA analysis results of two buildings for 80 selected real ground motions.

• 한국공간구조학회논문집
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• 제6권2호
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• pp.131-136
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• 2006

It is important to evaluate energy absorption capacity of frames required during a design earthquake. An inelastic computer analysis based on mathematical modelling of energy absorbing frames and elements makes it possible to evaluate required energy absorption capacity. But such an analysis sometimes consumes much computation time particularly in case of complicated structural system. This paper presents a proposal to predict energy absorption of multi-bent steel frames by simple equivalent linear method.

• Structural Engineering and Mechanics
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• 제4권2호
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• pp.139-148
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• 1996

Vector algorithms and the relative importance of the four basic modules (computation of element stiffness matrices, assembly of the global stiffness matrix, solution of the system of linear simultaneous equations, and calculation of stresses and strains) of a finite element computer program for inelastic analysis of reinforced concrete shells are presented. Performance of the vector program is compared with a scalar program. For a cooling tower problem, the speedup factor from the scalar to the vector program is 34 for the element stiffness matrices calculation, 25.3 for the assembly of global stiffness matrix, 27.5 for the equation solver, and 37.8 for stresses, strains and nodal forces computations on a Gray Y-MP. The overall speedup factor is 30.9. When the equation solver alone is vectorized, which is computationally the most intensive part of a finite element program, a speedup factor of only 1.9 is achieved. When the rest of the program is also vectorized, a large additional speedup factor of 15.9 is attained. Therefore, it is very important that all the modules in a nonlinear program are vectorized to gain the full potential of the supercomputers. The vector finite element computer program for inelastic analysis of RC shells with layered elements developed in the present study enabled us to perform mesh convergence studies. The vector program can be used for studying the ultimate behavior of RC shells and used as a design tool.

• 한국전산구조공학회논문집
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• 제18권2호
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• pp.169-179
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• 2005

탄성 및 비탄성좌굴 고유치해석법을 이용하여 강절프레임의 보-기둥부재의 유효좌굴길이를 산정하는 개선된 방법을 제시한다. 이를 위하여 먼저 설계기준에 제시된 압축재의 내하력 곡선식으로부터 접선계수이론(tangent modulus theory)에 근거하여 세장비-접선계수(tangent modulus), 응력-변형률 곡선식을 유도한다. 이때 안정함수를 이용하여 보-기둥요소의 접선강성행렬을 얻고, 비탄성 좌굴 고유치해석법을 제시하며 이를 이용하여 유효좌굴길이를 산정하는 방법을 제시한다. 해석예제를 통하여 강절프레임에 탄성 및 비탄성좌굴해석법에 의한 유효좌굴길이 비교결과를 제시하고, 매개변수 연구 결과를 제시한다.

• 한국강구조학회 논문집
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• 제11권3호통권40호
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• pp.271-279
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• 1999

보와 기둥과의 반강접에 관한 최근 연구로서 기둥 면과 T-stub 플랜지 사이에 격리재를 설치하는 개량된 T-stub 요소를 개발하고 있다. 개량된 T-stub에 대한 비탄성 해석을 수행하였으며, 그 결과를 실험값과 비교 분석하였다. 비탄성 해석 방법은 기둥 면과 격리재 사이에 간격요소(gap element)를 적용하고, 고력볼트에 초기 응력을 부여하여 실험값과 잘 일치하는 결과를 보인다. 실무에서의 설계와 해석에 적용할 수 있는 약산식으로서 T-stub의 초기 강성도와 압축하중에 의한 소성내력에 관한 설계식을 제시한다.

• Computers and Concrete
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• 제18권6호
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• pp.1113-1134
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• 2016

A methodology using neural networks has been proposed for rapid prediction of inelastic bending moments in reinforced concrete continuous beams subjected to service load. The closed form expressions obtained from the trained neural networks take into account cracking in concrete at in-span and at near the internal supports and tension stiffening effect. The expressions predict the inelastic moments (considering the concrete cracking) from the elastic moments (neglecting the concrete cracking) at supports. Three separate neural networks are trained since these have been postulated to represent all the beams having any number of spans. The training, validating, and testing data sets for the neural networks are generated using an analytical-numerical procedure of analysis. The proposed expressions are verified for example beams of different number of spans and cross-section properties and the errors are found to be small. The proposed expressions, at minimal input data and computation effort, yield results that are close to FEM results. The expressions can be used in preliminary every day design as they enable a rapid prediction of inelastic moments and require a computational effort that is a fraction of that required for the available methods in literature.

• 전산구조공학
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• 제5권1호
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• pp.83-89
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• 1992

사용하중하의 철근콘크리트 스래브의 비탄성 처짐을 산정하는 실용적인 방법을 제시하였다. 선형 유한요소 해석의 탄성해석결과와 설계된 철근량을 이용하여 비탄성 처짐계수(.betha.)를 결정하고, 이를 이용하여 설계된 슬리브의 사용성을 검토하기 위한 사용하중하의 처짐을 구할 수 있도록 하였다. 모서리에 지지된 슬래브 예에서 제시한 방법으로 구한 비탄성처짐과 실험 및 비선형해석 결과와 비교해 본 결과 서로 매우 잘 일치함을 보여주었다. 제시된 방법을 비정형 슬래브 설계에 응용한 문제도 고려하였다.

• Structural Engineering and Mechanics
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• 제36권2호
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• pp.165-179
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• 2010

Maximum deflection in a beam is a design criteria and occurs generally at or close to the mid-span. Neural networks have been developed for the continuous composite beams to predict the inelastic mid-span deflections (typically for 20 years, considering cracking, and time effects, i.e., creep and shrinkage, in concrete) from the elastic moments and elastic mid-span deflections (neglecting instantaneous cracking and time effects). The training and testing data for the neural networks is generated using a hybrid analytical-numerical procedure of analysis. The neural networks have been validated for four example beams and the errors are shown to be small. This methodology, of using networks enables a rapid estimation of inelastic mid-span deflections and requires a computational effort almost equal to that required for the simple elastic analysis. The neural networks can be extended for the composite building frames that would result in huge saving in computational time.

• 한국지진공학회논문집
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• 제5권2호
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• pp.113-124
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• 2001

이 연구는 철근콘크리트 구조물의 비탄성 거동을 파악하고 합리적이면서 경제적인 내진설계기준의 개발을 위한 자료를 제공하는데 그 목적이 있다. 정학하고 올바른 내진성능의 파악을 위하여 비탄선 해석프로그램을 사용하였다. 사용된 프로그램은 철근콘크리트 구조물의 해석을 위해서 유한요소법을 이용하여 개발된 RCAHEST이다. 재료적 비선형성에 대해서는 균열콘크리트에 대한 인장, 압축 전단모델과 콘크리트 소에 있는 철근모델을 조합하여 고려하였다. 이에 대한 콘크리트 균열모델로서는 분산균열모델을 사용하였다. 또한, 횡방향 구속철근으로 인한 강도의 증가 효과를 고려하였다.

• 콘크리트학회논문집
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• 제12권4호
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• pp.59-67
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• 2000

With increased height of structure, the effect of column shortening need special consideration in the design and construction of high-rise buildings. The shortening of each column affects nonstructural members such as partitions, cladding, and M/E systems, which are not designed to carry gravity forces. The slabs and beams will tilt due to the cumulative differential shortening of adeacent vertical members. The main purpose of estimating the total shortening of vertical structural member is to compensate the differential shortening between adeacent members. This paper presents effect of parameters for phenomenon of column shortening in vertical members. The paper presents effect of parameters for phenomenon of column shortening in vertical members. The conclusions obtained from this study are follow as ; Strength of concrete and steel ratio effected on column shortening caused by elastic and inelastic shortening. Also, it is known that Ultimate-shrinkage-Value, Specific-Creep-Value, and volume to surface ratio effected on inelastic shortening only. Particularly, Ultimate-Shrinkage-Value and Specific-Creep-Value effected considerable on the amount of total column shortening.