• Earthquakes and Structures
• /
• 제14권1호
• /
• pp.21-32
• /
• 2018

Prefabricated structures are constructed by bolted connections of separated members. The design and analysis of these structures are generally performed by defining fully hinges for the connection of separated members at the joint of junction. In practice, these connections are not fully hinged. Therefore, the assumption of semi-rigid connections (restrained or partially fixity) instead of fully hinge connections is a more realistic approach for bolted connections used in the prefabricated elements. The aim of this study is to investigate the effects of semi-rigid connections on seismic performance of prefabricated structures. Nonlinear static analysis (pushover analysis) of a selected RC prefabricated structure is performed with SAP2000 structural analysis program by considering various partially fixity percentages for bolted connections. The target values of roof displacements obtained from the analyses according to ATC-40, FEMA-356, FEMA-440, and TEC-2007 codes are compared each other. The numerical results are given in tables and figures comparatively and discussed. The results show that the effects of semi-rigid connections should be considered in design and analysis of the prefabricated structures.

• 한국구조물진단유지관리공학회 논문집
• /
• 제13권1호통권53호
• /
• pp.115-124
• /
• 2009

본 연구에서는 구조물에 발생하는 변상 진전 특성을 수치 해석적으로 평가할 수 있는 기법을 새롭게 개발하기 위한 연구를 수행한 것이다. 이를 위해서, 변상발생 메커니즘을 토대로 하여, 인장균열 발생 후, 휨압축에 의한 압축손상까지를 해석에 반영하였다. 특히 인장균열이 발생하고나서 압축손상이 발생하기까지의 해석 단계를 위해서는, 등가소성힌지길이 개념을 새롭게 도입하여, 균열의 진전을 해석하게 된다. 등가소성힌지 길이개념을 도입함으로써, 균열발생단면에 대한 단면력, 즉, 축력과 모멘트를 균열폭과 관계지어 균열폭의 확장을 추적해 나가게 된다.

• Steel and Composite Structures
• /
• 제16권4호
• /
• pp.437-454
• /
• 2014

The influence of spacers on the behaviour and ultimate capacity of intermediate length CFS open section columns under axial compression is investigated in this paper. The focus of the research lies in the cross- section predominantly, failed by distortional buckling. This paper made an attempt to either delay or eliminate the distortional buckling mode by the introduction of transverse elements referred herein as spacers. The cross-sections investigated have been selected by performing the elastic buckling analysis using CUFSM software. The test program considered three different columns having slenderness ratios of 35, 50 & 60. The test program consisted of 14 pure axial compression tests under hinged-hinged end condition. Models have been analysed using finite element simulations and the obtained results are compared with the experimental tests. The finite element package ABAQUS has been used to carry out non-linear analyses of the columns. The finite element model incorporates material, geometric non-linearities and initial geometric imperfection of the specimens. The work involves a wide parametric study in the column with spacers of varying depth and number of spacers. The results obtained from the study shows that the depth and number of spacers have significant influence on the behaviour and strength of the columns. Based on the nonlinear regression analysis the design equation is proposed for the selected section.

• Structural Engineering and Mechanics
• /
• 제82권3호
• /
• pp.385-400
• /
• 2022

Sky-bridges between adjacent buildings can enhance lateral stiffness and limit the impact of lateral forces. This study analysed the structural capabilities and dynamic performances of sky-bridge-coupled buildings under various sets of ground motions. Finite Element (FE) analyses were carried out with the link being iteratively repositioned along the full height of the structures. Incremental dynamic analysis (IDA) and probabilistic damage distribution were also applied. The results indicated that the establishment of sky-bridges caused a slight change in the natural frequency and mode shapes. The sky-bridge system was shown to be efficient in controlling displacement and Inter-Storey Drift Ratio (%ISDR) and reducing the probability of damage in the higher floors. The most efficient location of the sky-bridge, for improving its rigidity, was found to be at 88% of the building height. Finally, the effects of two types of materials (steel and concrete) and end conditions (hinged and fixed) were studied. The outcomes showed that coupled buildings with a sky-bridge made of steel with hinged connection could withstand ground motions longer than those made of concrete with fixed connection.

• Steel and Composite Structures
• /
• 제46권4호
• /
• pp.565-575
• /
• 2023

This study represents a numerical research in vibration and buckling of functionally graded material (FGM) beam comprising edge crack by using finite element method (FEM) and multilayer perceptron (MLP). It is assumed that the material properties change only according to the exponential distributions along the beam thickness. FEM and MLP solutions of the natural frequencies and critical buckling load are obtained of the cracked FGM beam for clamped-free (C-F), hinged-hinged (H-H), and clamped-clamped (C-C) boundary conditions. Numerical results are obtained to show the effects of crack location (c/L), material properties (E₂/E₁), slenderness ratio (L/h) and end supports on the bending vibration and buckling properties of cracked FGM beam. The FEM analysis used in this paper was verified with the literature, and the fundamental frequency ratio ($\overline{P_{cr}}$) and critical buckling load ratio ($\overline{{\omega}}$) results obtained were compared with FEM and MLP. The results obtained are quite compatible with each other.

• Ocean Systems Engineering
• /
• 제11권1호
• /
• pp.17-42
• /
• 2021

Articulated loading platforms (ALPs) belongs to a class of offshore structures known as compliant. ALP motions have time periods falling in the wind excitation frequency range due to their compliant behaviour. This paper deals with the dynamic behavior of a double hinged ALP subjected to low-frequency wind forces with random waves. Nonlinear effects due to variable submergence, fluctuating buoyancy, variable added mass, and hydrodynamic forces are considered in the analysis. The random sea state is characterized by the Pierson-Moskowitz (P-M) spectrum. The wave forces on the submerged elements of the platform's shaft are calculated using Morison's Equation with Airy's linear wave theory ignoring diffraction effects. The fluctuating wind load has been estimated using Ochi and Shin wind velocity spectrum for offshore structures. The nonlinear dynamic equation of motion is solved in the time domain by the Wilson-θ method. The wind-structure interactions, along with the effect of various other parameters on the platform response, are investigated. The effect of offset of aerodynamic center (A.C.) with the center of gravity (C.G.) of platform superstructure has also been investigated. The outcome of the analyses indicates that low-frequency wind forces affect the response of ALP to a large extent, which otherwise is not enhanced in the presence of only waves. The mean wind modifies the mean position of the platform surge response to the positive side, causing an offset. Various power spectral densities (PSDs) under high and moderate sea states show that apart from the significant peak occurring at the two natural frequencies, other prominent peaks also appear at very low frequencies showing the influence of wind on the response.

• 생물환경조절학회지
• /
• 제17권3호
• /
• pp.188-196
• /
• 2008

본 연구는 소형 파이프하우스 설계시 구조계산에 필요한 지점조건을 구명하기 위하여 실물크기의 파이프 하우스에 환산된 적설하중 및 풍하중을 재하하여 온실의 붕괴양상과 변위 및 변형도를 측정하였으며, 측정값을 여러 가지 지점조건에 대해 구조해석한 값과 비교 분석하였다. 온실에 작용하는 적설 및 풍하중의 등분포 하중을 집중하중으로 환산할 때 환산된 집중하중의 개수별로 하중효과를 비교 분석한 결과, 적설하중의 경우 최소 2개 이상의 집중하중으로 환산하는 것이, 풍 하중의 경우 각각의 등분포된 수압면의 하중을 1개씩의 집중하중으로 환산하는 것이 등분포하중과 유사한 하중효과가 나타나는 것으로 분석되었다. 변형도의 변화를 분석한 결과 적설하중 작용시에는 예측된 바와 같이 처마부위에서 붕괴된 것으로 나타났으며, 풍하중 작용시에는 풍상측의 처마와 지점부위의 변형이 가장 크게 발생하였고 다음으로 풍하측의 처마와 곡부의 변형이 크게 발생하였으며, 가장 큰 변형을 나타낸 처마가 위험부위로 판단되었다. 응력과 변위에 따른 지점조건을 분석한 결과 지점조건에 따른 변위의 크기는 변위방향과 모델종류에 관계없이 모두 지면고정 <지하고정<지면힌지<지하힌지 순으로 나타났으며, 별도의 기초 없이 서까래를 땅속에 바로 매입하여 설치하는 소형 파이프 하우스의 구조설계시 지점조건을 매입깊이에서의 지하고정으로 하는 것이 바람직할 것으로 판단 되었다.

• 대한조선학회지
• /
• 제14권4호
• /
• pp.3-14
• /
• 1977

There are many Beam-Column connections in general structures and ship structures. For simplicity and convenience of analysis, the connections are mostly considered hinged when not reinforced or rigidly fixed when reinforced. This paper has intended to analyze the Beam-Column connection which is assumed two dimensional flat plate. The analysis has been preformed by Finite Element Method following the change of moment of inertia at connection. The conclusion of this investigation is as follows: By reinforcing or increasing the moment of inertia at connection part, the stress distribution of whole structure and the stress concentration at that part are relieved. Displacements of beam(when column is fixed) are almost linearly decreasing by the change of moment of inertia at connection.

• 복합신소재구조학회 논문집
• /
• 제3권2호
• /
• pp.1-10
• /
• 2012

In the present study, an Element-Based Lagrangian Formulation for the nonlinear analysis of shell structures is presented. The strains, stresses and constitutive equations based on the natural co-ordinate have been used throughout the Element-Based Lagrangian Formulation of the present shell element which offers an advantage of easy implementation compared with the traditional Lagrangian Formulation. The Element-Based Lagrangian Formulation of a 9-node resultant-stress shell element is presented for the anisotropic composite material. The element is free of both membrane and shear locking behavior by using the assumed natural strain method such that the element performs very well in thin shell problems. The arc-length control method is used to trace complex equilibrium paths in thin shell applications. Numerical examples for laminated composite curved shells presented herein clearly show the validity of the present approach and the accuracy of the developed shell element.

• Earthquakes and Structures
• /
• 제13권5호
• /
• pp.443-454
• /
• 2017

When eccentrically braced steel frames (EBFs) are in the desired failure mode, links yield at each layer and column bases appear plastically hinged. Traditional design methods cannot accurately predict the inelastic behavior of structures owing to the use of capacity-based design theory. This paper proposes the use of performance-based seismic design (PBSD) method for planning eccentrically braced frames. PBSD can predict and control inelastic deformation of structures by target drift and failure mode. In buildings designed via this process, all links dissipate energy in the rare event of an earthquake, while other members remain in elastic state, and as the story drift is uniform along the structure height, weak layers will be avoided. In this condition, eccentrically braced frames may be more easily rehabilitated after the effects of an earthquake. The effectiveness of the proposed method is illustrated through a sample case study of ten-story K-type EBFs and Y- type EBFs buildings, and is validated by pushover analysis and dynamic analysis. The ultimate state of frames designed by the proposed method will fail in the desired failure mode. That is, inelastic deformation of structure mainly occurs in links; each layer of links involved dissipates energy, and weak layers do not exist in the structure. The PBSD method can provide a reference for structural design of eccentrically braced steel frames.