• Steel and Composite Structures
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• 제4권3호
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• pp.211-226
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• 2004

This paper presents a study on the structural behaviour of modular steel scaffolds through both experimental and numerical investigations. Three one-storey and three two-storey modular steel scaffolds were built and tested to failure in order to examine the structural behaviour of typical modular steel scaffolds. Details of the tests and their test results were presented in this paper. Moreover, an advanced non-linear analysis method was employed to evaluate the load carrying capacities of these scaffolds under different support conditions. Comparisons between the experimental and the numerical results on the structural behaviour of these modular steel scaffolds were also presented. Moreover, the restraining effects of external supports in practical situations were also studied through finite element methods. The predicted load carrying capacities and deformations at failure of these models under partially restrained conditions were found to be close to the experimental results. A codified design method for column buckling with modified slenderness ratios was adopted for practical design of modular steel scaffolds.

• Steel and Composite Structures
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• 제9권6호
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• pp.499-518
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• 2009

The present paper investigates the stochastic seismic responses of steel structure systems with Partially Restrained (PR) connections by using Perturbation based Stochastic Finite Element (PSFEM) method. A stiffness matrix formulation of steel systems with PR connections and PSFEM and MCS formulations of structural systems are given. Based on the formulations, a computer program in FORTRAN language has been developed, and stochastic seismic analyses of steel frame and bridge systems have been performed for different types of connections. The connection parameters, material and geometrical properties are assumed to be random variables in the analyses. The Kocaeli earthquake occurred in 1999 is considered as a ground motion. The connection parameters, material and geometrical properties are considered to be random variables. The efficiency and accuracy of the proposed SFEM algorithm are validated by comparison with results of Monte Carlo simulation (MCS) method.

• Steel and Composite Structures
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• 제8권1호
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• pp.35-52
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• 2008

The paper investigates the seismic performance of a Partially-Restrained (PR) steel-concrete composite frame using the probabilistic approach. The analysed frame was tested at the ELSA laboratory of the Joint Research Centre of Ispra (Italy), while the representative beam-to-column composite connections were tested at the Universities of Pisa, Milan and Trento (Italy). The component modelling of both interior and exterior composite joints is described first, including the experimental-numerical validation. The Latin Hypercube method has been used to draw the probabilistic distribution curves of joints, and then the whole PR composite frame has been analysed. Pushover and incremental dynamic analyses have been carried out using the non-linear FE code SAP2000 version 9.1. The fragility and performance curves of the PR composite frame have been determined for four damage limit states.

• 한국강구조학회 논문집
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• 제19권5호
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• pp.503-513
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• 2007

구조물의 지진응답은 구조물의 강성도에 영향을 미치는 접합부의 특성에 영향을 받는다. 본 연구에서는 합성반강접 접합부를 갖는 2차원 8층 비가새 철골구조물에 대하여 동적 비선형 해석 프로그램을 이용한 푸쉬오버 해석과 시간이력해석을 실시하여 구조물의 거동을 예측하였다. 접합부 비선형 모멘트-회전 특성, 합성보 및 철골기둥의 재료 비선형 특성을 고려하여 구조해석을 실시하였다. 합성반강접 접합부를 완전 강접합부로 이상화하면 푸쉬오버 해석에서 구조물의 초기강성도와 종국강도가 증가되었고 시간이력해석에서는 밑면전단력, 최대층간변위, 보 및 기둥에 발생되는 최대 휨모멘트가 접합부 강성 및 이력거동의 영향을 받았다. 최대지반가속도가 0.4g인 지진파에 대하여 합성반강접 구조물에서는 FEMA 273의 최대 층간변위에 대한 인명손상방지 기준을 만족하였으며 보와 기둥이 비탄성 거동을 경험하지 않은 반면 완전 강접합부로 이상화한 구조물에서는 보 및 기둥이 비탄성 거동을 경험하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 가을 학술발표회 논문집
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• pp.19-28
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• 1996

본 논문에서는 유연 연결부를 갖고 있는 이차원 구조물의 비탄성 좌굴해석을 연구하였다. 본 해석을 통하여 구조물의 기하학적, 및 재료적 비선형 뿐만 아니라 유연 연결부의 비선형 효과가 구조물의 거동과 강도에 미치는 영향을 예측할 수 있다. 본 해석 결과는 실험 결과와 비교하였으며 예제해석도 수행하였다.

• Structural Engineering and Mechanics
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• 제67권5호
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• pp.439-455
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• 2018

Within a probabilistic framework, this paper addresses the determination of the static structural response of beams and frames with partially restrained (semi-rigid) connections. The flexibility of the nodal connections is incorporated via an idealized linear-elastic behavior of the beam constraints through the use of rotational springs, which are here considered uncertain for taking into account the largely scattered results observed in experimental findings. The analysis is conducted via the Probabilistic Transformation Method, by modelling the spring stiffness terms (or equivalently, the fixity factors of the beam) as uniformly distributed random variables. The limit values of the Eurocode 3 fixity factors for steel semi-rigid connections are assumed. The exact probability density function of a few indicators of the structural response is derived and discussed in order to identify to what extent the uncertainty of the beam constraints affects the resulting beam response. Some design considerations arise which point out the paramount importance of probability-based approaches whenever a comprehensive experimental background regarding the stiffness of the beam connection is lacking, for example in steel frames with semi-rigid connections or in precast reinforced concrete framed structures. Indeed, it is demonstrated that resorting to deterministic approaches may lead to misleading (and in some cases non-conservative) outcomes from a design viewpoint.

• Structural Engineering and Mechanics
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• 제9권3호
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• pp.241-256
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• 2000

The major sources of energy dissipation in steel frames with partially restrained (PR) connections are evaluated. Available experimental results are used to verify the mathematical model used in this study. The verified model is then used to quantify the energy dissipation in PR connections due to hysteretic behavior, due to viscous damping and at plastic hinges if they are formed. Observations are made for two load conditions: a sinusoidal load applied at the top of the frame, and a sinusoidal ground acceleration applied at the base of the frame representing a seismic loading condition. This analytical study confirms the general behavior, observed during experimental investigations, that PR connections reduce the overall stiffness of frames, but add a major source of energy dissipation. As the connections become stiffer, the contribution of PR connections in dissipating energy becomes less significant. A connection with a T ratio (representing its stiffness) of at least 0.9 should not be considered as fully restrained as is commonly assumed, since the energy dissipation characteristics are different. The flexibility of PR connections alters the fundamental frequency of the frame. Depending on the situation, it may bring the frame closer to or further from the resonance condition. If the frame approaches the resonance condition, the effect of damping is expected to be very important. However, if the frame moves away from the resonance condition, the energy dissipation at the PR connections is expected to be significant with an increase in the deformation of the frame, particularly for low damping values. For low damping values, the dissipation of energy at plastic hinges is comparable to that due to viscous damping, and increases as the frame approaches failure. For the range of parameters considered in this study, the energy dissipations at the PR connections and at the plastic hinges are of the same order of magnitude. The study quantitatively confirms the general observations made in experimental investigations for steel frames with PR connections; however, proper consideration of the stiffness of PR connections and other dynamic properties is essential in predicting the dynamic behavior.

• Steel and Composite Structures
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• 제1권4호
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• pp.427-440
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• 2001

The growing use of unprotected or partially protected steelwork in buildings has caused a lively debate regarding the safety of this form of construction. A good deal of recent research has indicated that steel members have a substantial inherent ability to resist fire so that additional fire protection can be either reduced or eliminated completely. A performance based philosophy also extends the study into the effect of structural continuity and the performance of the whole structural totality. As part of the structural system, thermal expansion during the heating phase or contraction during the cooling phase in most beams is likely to be restrained by adjacent parts of the whole system or sub-frame assembly due to compartmentation. This has not been properly addressed before. This paper describes an experimental programme in which unprotected steel beams were tested under load while it is restrained between two columns and additional horizontal restraints with particular concern on the effect of catenary action in the beams when subjected to large deflection at very high temperature. This paper also presents a three-dimensional mathematical modelling, based on the finite element method, of the series of fire tests on the part-frame. The complete analysis starts with an evaluation of temperature distribution in the structure at various time levels. It is followed by a detail 3-D finite element analysis on its structural response as a result of the changing temperature distribution. The principal part of the analysis makes use of an existing finite element package FEAST. The effect of columns being fire-protected and the beam being axially restrained has been modelled adequately in terms of their thermal and structural responses. The consequence of the beam being restrained is that the axial force in the restrained beam starts as a compression, which increases gradually up to a point when the material has deteriorated to such a level that the beam deflects excessively. The axial compression force drops rapidly and changes into a tension force leading to a catenary action, which slows down the beam deflection from running away. Design engineers will be benefited with the consideration of the catenary action.

• 한국구조물진단유지관리공학회 논문집
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• 제10권3호
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• pp.106-114
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• 2006

본 논문에서는 역강성법을 비좌굴 가새골조시스템의 내진설계에 적용하여 목표 변위를 만족시키는 비좌굴 가새의 단면적을 산정하였으며, 기존 연구와 비교하여 타당성을 검토하였다. 본 설계 방법은 개념이 직관적이고 적용이 간편하며, 고차모드 고려가 가능하고 각 층의 연성도를 개별적으로 조절할 수 있는 장점이 있다. 각 모델에 본 설계법을 적용한 결과, 전반적으로 목표변위 증가에 따라 가새 단면적이 감소하지만 층수와 연성도의 증가에 따라 일부층에서 오히려 가새 단면적이 증가하는 것을 확인하였다. 또한 항복 후 강성비의 변화가 단면적에 끼치는 영향은 가새의 항복 후 강성비가 작은 경우 더 민감한 차이를 보이는 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제4권1호
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• pp.37-47
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• 1996

The paper considers the elastic distortional buckling of overhanging beams, which consist of an internal segment with a cantilevered segment continuous over an internal support. The beams were considered loaded by a concentrated load at the cantilever tip, and the beams were either partially restrained or laterally restrained over the internal support. An efficient line-type finite element developed previously by the author was modified to incorporate loading remote from the shear centre, as well as to allow for lateral buckling without distortion. Buckling loads were obtained for a range of geometry when the load was placed on the top flange, at the shear centre or on the bottom flange. Buckling mode shapes were also obtained, and conclusions drawn regarding the influence of distortion on the overall buckling load.