Stability Analysis of Prestressed Space Truss Structures Based on the Imperfect Truss Element

Zhen Zhou,Shao-ping Meng,Jing Wu 한국강구조학회 2009 International Journal of Steel Structures Vol.9 No.3

Prestressed space truss structures have been widely used in various public buildings in recent years. However, because of its large span, the length of its members also increases. Therefore the member initial curvature will probably affect the stability of the structure. This paper focuses on the truss element with initial geometrical imperfection under high axial load. The relation between axial force and deformation, the expression of axial tangent stiffness, and the concept of initial curvature coefficient for truss element are established. With the example of prestressed cable-stayed arch-truss structure, the influence of member initial curvature on nonlinear stability performance of the structure under various prestress values is studied. The result indicates that member initial curvature has little influence on global stiffness of the structure before buckling, but has great influence on the performance of the structure after buckling and on limit load of the structure. Under different prestress values, the limit load–member initial curvature curves are parallel and almost linear. The proposed method in this paper can be widely applied into nonlinear stability analysis of various prestressed space truss structures with large span, so that the influence of member initial curvature on structural stability can be estimated. Prestressed space truss structures have been widely used in various public buildings in recent years. However, because of its large span, the length of its members also increases. Therefore the member initial curvature will probably affect the stability of the structure. This paper focuses on the truss element with initial geometrical imperfection under high axial load. The relation between axial force and deformation, the expression of axial tangent stiffness, and the concept of initial curvature coefficient for truss element are established. With the example of prestressed cable-stayed arch-truss structure, the influence of member initial curvature on nonlinear stability performance of the structure under various prestress values is studied. The result indicates that member initial curvature has little influence on global stiffness of the structure before buckling, but has great influence on the performance of the structure after buckling and on limit load of the structure. Under different prestress values, the limit load–member initial curvature curves are parallel and almost linear. The proposed method in this paper can be widely applied into nonlinear stability analysis of various prestressed space truss structures with large span, so that the influence of member initial curvature on structural stability can be estimated.

Dynamically Adaptive Finite Element Mesh Generation Schemes

Yoon, Chong-Yul,Park, Joon-Seok Computational Structural Engineering Institute of 2010 한국전산구조공학회논문집 Vol.23 No.6

The finite element method(FEM) is proven to be an effective approximate method of structural analysis if proper element types and meshes are chosen, and recently, the method is often applied to solve complex dynamic and nonlinear problems. A properly chosen element type and mesh yields reliable results for dynamic finite element structural analysis. However, dynamic behavior of a structure may include unpredictably large strains in some parts of the structure, and using the initial mesh throughout the duration of a dynamic analysis may include some elements to go through strains beyond the elements' reliable limits. Thus, the finite element mesh for a dynamic analysis must be dynamically adaptive, and considering the rapid process of analysis in real time, the dynamically adaptive finite element mesh generating schemes must be computationally efficient. In this paper, a computationally efficient dynamically adaptive finite element mesh generation scheme for dynamic analyses of structures is described. The concept of representative strain value is used for error estimates and the refinements of meshes use combinations of the h-method(node movement) and the r-method(element division). The shape coefficient for element mesh is used to correct overly distorted elements. The validity of the scheme is shown through a cantilever beam example under a concentrated load with varying values. The example shows reasonable accuracy and efficient computing time. Furthermore, the study shows the potential for the scheme's effective use in complex structural dynamic problems such as those under seismic or erratic wind loads.

유한요소/경계요소 연성해석을 통한 수중 구조기인소음 해석

이두호(Dooho Lee),김현실(Hyun-Sil Kim),김봉기(Bong-Ki Kim),이성현(Seong-Hyun Lee) (사)한국CDE학회 2012 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2012 No.2

Radiated noise analysis from ship structure is a challenging topic due to difficulties in accurate calculation of fluid-structure interaction as well as massive degree of freedoms of the problem. To reduce the severity of the problem, a new fluid-structure interaction formulation is proposed in this paper. The complex frequency-dependent added mass and damping matrices are calculated using the high-order Burton-Miller boundary integral equation formulation in order to obtain accurate values over all frequency bands. The calculated fluid-structure interaction effects are added to the structural matrices calculated by commercial finite element software, MSC/NASTRAN. Then, the impedance and underwater radiation noise due to an excitation of structure are calculated. The accuracy of the present formulation is compared with those from the conventional finite element/boundary element formulation. The present formulation enables us to sequentially perform the fluid-structure coupled analysis in fluid and structure parts, which makes the method be implemented in commercial finite element software.

역사계 참사 전시의 서사구조 분석 및 연출특성에 관한 연구 -시모어 채트먼의 서사구조 분석론을 중심으로-

번소계,맹지윤,최익서 한국공간디자인학회 2024 한국공간디자인학회논문집 Vol.19 No.3

(연구배경 및 목적) 역사계 참사를 중심으로 한 전시는 인류에게 교훈을 주는 역할을 중심으로 현대인의 사고를 자극하고 잠재적인 갈등에 관한 사회적 관심을 촉구한다. 아직 다수의 전시공간은 역사계 참사의 연출에 있어 유물 중심의 일방적인 전달 방식을 갖고 있는데, 이는 공간의 의도와 목적은 명확하게 전달될 수 있어도 제한된 정보를 전달하여 역사적 사건에 대한 폭넓은 이해와 개인의 경험에 따른 다양한 상호작용에 한계를 갖게 한다. 따라서 본 연구는 전시에서 서사적 공간연출의 배경을 시모어 채트먼(Seymour Chatman)의 서사구조의 개념을 중심으로 전시의 서사 구조와 연출 요소를 분석하여 연구하였다. 역사계 참사 전시를 중심으로 한 전시 사례의 서사 구조를 확인하고 효과적인 연출 요소의 작용을 분석하고 결과를 도출하여 연구의 가치와 전시공간의 방향성을 확인하는 것을 목표로 한다. (연구방법) 연구 방법으로 첫째, 문헌을 통해 역사계 참사 전시의 개념과 역할을 분석하였다. 두 번째로 시모어 채트먼의 서사 구조 개념에 따라 전시공간에서의 서사 구조를 도출하였다. 세 번째 서사 구조 중 전시공간 플롯의 구조형식과 주요한 연출 요소의 특성을 도출하였다. 마지막으로 도출한 서사적 전시연출에 관한 특성을 중심으로 2000년 이후 완성된 대표적 전시공간을 사례 대상으로 분석하여, 서사 구조의 형식과 연출 요소의 특성을 결론으로 도출하였다. (결과) 역사계 참사 전시의 서사구조는 직선적, 단속적, 피카레스크의 3개 플롯 형식이 있으며, 연출 요소는 형태, 구조, 재료, 빛, 텍스트 요소로 다섯 가지 유형으로 분류할 수 있다. 연구 결과, 오늘날 역사계 참사 전시는 주제에 대한 다양한 접근이 가능한 서사 구조를 가지고, 이를 연출 요소의 활용을 통해 전시공간의 전통적인 기능에 국한되지 않고, 개인적 이해와 체험을 유도하고 있었다. 나아가, 전시의 성격이 참사에 관한 기억과 반성을 촉진할 수 있는 장소로 중심성을 갖고 있어 효과적 연출 요소를 통한 서사구조를 강조하고 있었다. (결론) 본 연구를 통해 역사계 참사를 중심으로 한 전시주제를 최대한 살리기 위해서는 공간의 서사구조 설계와 공간연출 요소의 다층적 결합이 중요하다. 전시와 관람객의 상호소통이 가능한 전시공간을 조성한다면 과거의 참사를 통해 긍정적인 새로운 가치를 만들어 나갈 수 있을 것이다. (Background and Purpose) Exhibitions focusing on historical disasters stimulate modern thinking and call for social attention to potential conflicts, focusing on their role in teaching humanity. Several exhibition spaces have a one-sided method of conveying historical disasters centered on relics. Although the intention and purpose of the space can be conveyed, limited historical information is conveyed, preventing a broad understanding of historical events. This places limits on various interactions depending on individual experiences. Therefore, this study explored the background of the narrative space production in the exhibition by analyzing the narrative structure and production elements of the exhibition, focusing on Seymour Chatman’s concept of “narrative structure.” The goal is to confirm the narrative structure of exhibition cases centered on historical disaster exhibitions, analyze the operation of effective production elements, and derive results to confirm the research value and the direction of the exhibition space. (Method) As a research method, the concept and role of historical disaster exhibitions are analyzed through literature. The narrative structure in the exhibition space is derived according to Seymour Chatman’s concept of “narrative structure.” Within the narrative structures, the structural form of the exhibition space plot and the characteristics of major production elements are derived. Focusing on the characteristics of narrative exhibition production, representative exhibition spaces completed after 2000 are analyzed, and the form of narrative structure and characteristics of production elements are highlighted as a conclusion. (Results) The narrative structure of historical disaster exhibitions has three plot types – linear, intermittent, and picaresque. The production elements can be classified into five types – form, structure, material, light, and text. As a result of the study, today’s historical disaster exhibitions have a narrative structure that allows various approaches to the topic. Through the use of production elements, they are not limited to the traditional function of the exhibition space and induce personal understanding and experience. Furthermore, as the nature of the exhibition is central to a place that can promote the memory of and reflection on the disaster, the narrative structure, through effective production elements, is emphasized. (Conclusions) To maximize the exhibition theme centered on historical disasters, a multi-layered combination of space narrative structure design and space production elements is important. If we create an exhibition space where exhibitions and visitors can interact, we will be able to create new positive values ​​through past disasters.

원통형 복합재 격자구조체의 구조안전성 평가 기법 연구

임재문,강승구,신광복,이상우 한국복합재료학회 2017 Composites research Vol.30 No.6

In this paper, evaluation method of structural integrity of cylindrical composite lattice structures was conducted. A finite element analysis was used to evaluate the structural integrity of composite lattice structures. In order to verify the optimal finite element in the evaluation of the structural integrity, finite element models for cylindrical composite lattice structure were generated using beam, shell and solid elements. The results of the finite element analyses with the shell and solid element models showed a good agreement. However, considerable differences were found between the beam element model and the shell and solid models. This occurred because the beam element does not take into account the degradation of the mechanical properties of the non-intersection parts of cylindrical composite lattice structures. It was found that the finite element analysis of evaluation of structural integrity for cylindrical composite lattice structures have to use solid element. 본 논문에서는 원통형 복합재 격자구조체의 구조안전성 평가 기법에 대해 연구를 수행하였다. 구조안전성 평가는 유한요소해석을 통해 수행하였다. 구조안전성 평가를 위한 최적의 유한요소를 확인하기 위해 원통형복합재 격자구조체 유한요소모델은 빔, 쉘 그리고 솔리드 요소를 사용해 생성하였다. 쉘과 솔리드 모델의 유한요소 해석결과는 서로 유사하게 발생되었다. 그러나 빔 모델의 경우, 쉘과 솔리드 모델의 결과와 큰 차이가 발생하였다. 이것은 빔 요소가 원통형 복합재 격자구조체 섬유 비교차부의 기계적 물성저하를 고려하지 못하기 때문이다. 원통형 복합재 격자구조체의 구조안전성 평가를 위한 유한요소해석은 쉘 또는 솔리드 요소를 사용해야 하는 것을 확인하였다.

구조 동적 해석을 위한 적응적 유한 요소망 형성

윤종열 한국방재학회 2010 한국방재학회논문집 Vol.10 No.1

구조물의 방재를 위해서 구조물의 효율적인 유지관리는 필수적이며, 여기서 신뢰 있는 구조물의 동적해석은 중요한 역할을 한다. 유한요소법은 구조해석법으로 가장 많이 사용되는 방법으로 자리 잡고 있으며, 요소와 요소망이 제대로 선택되면 신뢰 있는 해석 결과를 출력한다. 시간 영역 동적해석에 유한요소법을 사용하려면 각 시간 단계에서 요소망을 재형성할 필요가 생길 수 있는데, 여기에 연산 시간 측면에서 효율적인 적응적 요소망 전략을 사용하면 편리하다. 본 연구는 시간영역 동적해석에서 전 단계 해석 결과를 사용하여 계산된 대표 변형률 값을 오차 평가하는데 사용하고, 요소 세분화는 절점 이동인 r-법과 요소 분할인 h-법의 조합으로 효율적으로 계산하는 적응적 요소망 형성 전략을 제시한다. 적용한 캔틸레버보의 예제를 통하여 정확성과 연산 효율성을 검증하였고 나아가 방법의 간단함이 지진 하중, 풍하중 등에 의한 복잡한 구조 동적 해석에도 효율적으로 사용될 수 있는 것을 보여 준다. Reliable dynamic analysis is essential in order to properly maintain structures so that structural hazards may be minimized. The finite element method (FEM) is proven to be an affective approximate method of structural analysis if proper element types and meshes are chosen. When the method is applied to dynamics analyzed in time domain, the meshes may need to be modified at each time step. As many meshes need to be generated, adaptive mesh generation schemes have become an important part in complex time domain dynamic finite element analyses of structures. In this paper, an adaptive mesh generation scheme for dynamic finite element analyses of structures is described. The concept of representative strain value is used for error estimates and the refinements of meshes use combinations of the h-method (node movement) and the r-method (element division). The validity of the scheme is shown through a cantilever beam example under a concentrated load with varying values. The example shows reasonable accuracy and efficient computing time. Furthermore, the study shows the potential for the scheme's effective use in complex structural dynamic problems such as those under seismic or erratic wind loads.

Simulation and Analysis of the Temperature Field and the Thermal Stress of an Inverted-Siphon Concrete Structure Based on the Contact Friction Element

Zheng Si,Yanlong Li,Lifeng Wen,Xiaoqi Du 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.8

Mass concrete structures are prone to suffer temperature destruction during construction and operation because of their own mechanical properties and the role of cement hydration; therefore, the law of temperature field and temperature stress changes is crucial. This paper is based on the heat conduction theory and contact friction element theory under general external load. The heat conduction matrix, node thermal load vector, equivalent stiffness-constraint matrix and equivalent load vector of the contact friction element are each added to the whole heat conduction matrix, thermal load vector and total stiffness matrix, and the total load vector according to the finite element integration rule to establish the thermal-stress calculation model of the contact friction element. Combined with the Qi River inverted siphon project, this paper analyzed the temperature field and temperature stress using the three-dimensional finite element method, considering the changes of concrete thermodynamic parameters with age and the outside air temperature and other conditions, and obtained the distribution and variation in temperature field and temperature stress during the construction of an inverted siphon. The research results are of great significance for temperature control and crack prevention of inverted siphon structures. The thermal-stress calculation model of the contact friction element overcomes the limitations that it is difficult to use the current contact surface model to perform the temperature field simulation and further improves the application of the contact friction element model in the simulation of the temperature field and the temperature stress of mass concrete.

Elastodynamic infinite elements based on modified Bessel shape functions, applicable in the finite element method

K.S. Kazakov 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.42 No.3

In this paper decay and mapped elastodynamic infinite elements, based on modified Bessel shape functions and appropriate for Soil-Structure Interaction problems are described and discussed. These elements can be treated as a new form of the recently proposed Elastodynamic Infinite Elements with United Shape Functions (EIEUSF) infinite elements. The formulation of 2D horizontal type infinite elements (HIE) is demonstrated, but by similar techniques 2D vertical (VIE) and 2D corner (CIE) infinite elements can also be formulated. It is demonstrated that the application of the elastodynamical infinite elements is the easier and appropriate way to achieve an adequate simulation including basic aspects of Soil-Structure Interaction. Continuity along the artificial boundary (the line between finite and infinite elements) is discussed as well and the application of the proposed elastodynamical infinite elements in the Finite Element Method is explained in brief. Finally, a numerical example shows the computational efficiency of the proposed infinite elements.

A new finite element procedure for fatigue life prediction of AL6061 plates under multiaxial loadings

Tarar, Wasim,Herman Shen, M.H.,George, Tommy,Cross, Charles Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.5

An energy-based fatigue life prediction framework was previously developed by the authors for prediction of axial, bending and shear fatigue life at various stress ratios. The framework for the prediction of fatigue life via energy analysis was based on a new constitutive law, which states the following: the amount of energy required to fracture a material is constant. In the first part of this study, energy expressions that construct the constitutive law are equated in the form of total strain energy and the distortion energy dissipated in a fatigue cycle. The resulting equation is further evaluated to acquire the equivalent stress per cycle using energy based methodologies. The equivalent stress expressions are developed both for biaxial and multiaxial fatigue loads and are used to predict the number of cycles to failure based on previously developed prediction criterion. The equivalent stress expressions developed in this study are further used in a new finite element procedure to predict the fatigue life for two and three dimensional structures. In the second part of this study, a new Quadrilateral fatigue finite element is developed through integration of constitutive law into minimum potential energy formulation. This new QUAD-4 element is capable of simulating biaxial fatigue problems. The final output of this finite element analysis both using equivalent stress approach and using the new QUAD-4 fatigue element, is in the form of number of cycles to failure for each element on a scale in ascending or descending order. Therefore, the new finite element framework can provide the number of cycles to failure at each location in gas turbine engine structural components. In order to obtain experimental data for comparison, an Al6061-T6 plate is tested using a previously developed vibration based testing framework. The finite element analysis is performed for Al6061-T6 aluminum and the results are compared with experimental results.

A new finite element procedure for fatigue life prediction of AL6061 plates under multiaxial loadings

Wasim Tarar,M.-H. Herman Shen,Tommy George,Charles Cross 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.5

An energy-based fatigue life prediction framework was previously developed by the authors for prediction of axial, bending and shear fatigue life at various stress ratios. The framework for the prediction of fatigue life via energy analysis was based on a new constitutive law, which states the following: the amount of energy required to fracture a material is constant. In the first part of this study, energy expressions that construct the constitutive law are equated in the form of total strain energy and the distortion energy dissipated in a fatigue cycle. The resulting equation is further evaluated to acquire the equivalent stress per cycle using energy based methodologies. The equivalent stress expressions are developed both for biaxial and multiaxial fatigue loads and are used to predict the number of cycles to failure based on previously developed prediction criterion. The equivalent stress expressions developed in this study are further used in a new finite element procedure to predict the fatigue life for two and three dimensional structures. In the second part of this study, a new Quadrilateral fatigue finite element is developed through integration of constitutive law into minimum potential energy formulation. This new QUAD-4 element is capable of simulating biaxial fatigue problems. The final output of this finite element analysis both using equivalent stress approach and using the new QUAD-4 fatigue element, is in the form of number of cycles to failure for each element on a scale in ascending or descending order. Therefore, the new finite element framework can provide the number of cycles to failure at each location in gas turbine engine structural components. In order to obtain experimental data for comparison, an Al6061-T6 plate is tested using a previously developed vibration based testing framework. The finite element analysis is performed for Al6061-T6 aluminum and the results are compared with experimental results.