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.

기업 재무구조의 안정성과 일반상품 무역수지 간의 관련성

신현대(Hyun-Dai Shin) 한국무역연구원 2011 무역연구 Vol.7 No.3

The purpose of the study is to investigate that the Relevance of between Stability on financial structure and the Trade balance on tangible goods. This study was used from 1999 to 2009 in data as stability on capital structure by means of independent variable that the ratio of owner’s equity, debt ratio, current ratio, quick ratio, fixed ratio, ratio of fixed assets to stockholder’s equity and long-term liabilities. At this time, the dependent variable is a trade balance on tangible goods, which was used in data 1999-2009. In condition that we have got analyzing and researching about variable’s change. Due to the research, the results of study can be summarized in the following. First, ratio, stability on provider of capital have no significant effects on the trade balance of tangible goods. In other word, ratio of stability on provider of capital, which is ratio of owner’s equity, debt ratio that have noting effect on trade balance of tangible goods. It shows us that Rata of stability on provider of capital is not importance as a variable that is controlling for the trade balance of tangible goods. Second, ratio, stability on payment capacity also have no significant effects on the trade balance of tangible goods. In other word, ratio of stability on payment capacity which is current ratio, quick ratio that have noting effect on trade balance of tangible goods. It shows us that ratio of stability on payment capacity is not importance as a variable which is controlling for the trade balance of tangible goods, too. Third, though one of ratios, stability on fund use which is a fixed ratio has significant positive effect on trade balance on tangible goods. One of ratios, stability on fund use which is ratio of fixed assets to stockholder’s equity and long-term liabilities has no significant ‘positive or negative’ effects on trade balance of tangible goods. It shows us that It n wds a managing of positive for trade balance on tangible goods whwhiwhich has aggressive angi. One ed about fixed asset. One. One ment for fixed asset has initiative about export. According to the results, it shows the necessity of the recognition about Trade balance of tangible goods and Stability on financial structure. they can be important factors as grow and development of countries. So it needs managing, coordinating, controlling.

지역시청자미디어센터의 위상 변화에 대한 평가와 정책 제언: <MBC시청자미디어센터>의 사례를 중심으로

정인숙 ( In Sook Jung ) 한국커뮤니케이션학회 2014 커뮤니케이션학연구 Vol.22 No.3

이 연구는 스마트 미디어 시대에 지역시청자미디어센터가 지속가능한 발전을 할 수 있는 물적 토대를 가지고 있는지 알아보고자 하는 문제제기에서 비롯되었으며, 조직론적 관점에서 구조적 안정성과 사업성과를 분석하여 결론을 도출하였다. 이를 위해 MBC시청자미디어센터를 사례분석하였으며, 6개 지역 센터에 대한 현지 방문을 통한 관찰, 6개 지역 센터운영자들과의 개별심층인터뷰 및 FGI를 가지는 등 다면적 방법론을 활용하였다. 연구결과 지역시청자미디어센터의 위상이 2천년대 초반에 비해 크게 약화된 것으로 평가할 수 있었으며,스마트 미디어 시대에 지역미디어 거점센터로서의 역할을 수행하기에는 적지 않은 한계가 있는 것으로 나타났다. 먼저 구조적 안정성 측면에서 지역미디어센터의 공간안정성이 일부 훼손되고 재원안정성, 장비안정성, 인력안정성이 위협받고 있는 현실이 나타났다. 구조적 안정성이 결여된 상태에서 미디어센터가 나름대로 자생력을 가지고 시청자참여프로그램 측면에서 사업성과를 보여주고 있는 것은 긍정적으로 평가할수 있는 부분이었다. 다만 이러한 사업성과가 주로 제작교육에 치우진 양적 성과라는점에서 스마트미디어시대에 필요한 미디어 능력을 배양하는 데는 근본적인 한계를 노정하고 있다. 이러한 결론을 토대로 법률적 제언을 포함한 정책 제언을 제시하였다. The purpose of this study is to explain the status change of civil media centers through analysing the structural stability and work performance. The structural stability factor consist of three subordinate concepts : space stability, finance stability, equipment stability and manpower stability. The work performance evaluated the number of public access(PA) programs and the diversity of the center activities. The on-the-spot observation and in-depth interviews intended for the chief of operation officer of the centers were conducted on six provinces ; Jeonju, Masan, Daegu, Chuncheon, Ulsan, and Mokpo. The result shows that the status of the local media education centers have been sharply undermined compared to the early 2000’s and they have limitations to perform the essential roles as a local base media center in the age of smart media environment which demand more advanced user capability and empowerment. Specially, the damage of the structural stability has considerably negative implication in respect of sustainability of local media centers. It could be possible to evaluate that the local media centers gave actual results in the area of the PA program production under even the low structural stability. Though, it has also fundamental limitation that the performance is weighted towards production side, not to diverse activities needed to cultivate the media competence. The findings suggest that the stipulation of legal condition or administrative guidance are required to support the local media center substantially.

Assessment of steel structures designed for progressive collapse under localized fires

Behrouz Behnam 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.46 No.2

Structural design against the progressive collapse has been a vital necessity for decades due to occasional tragic events. The question of whether designed structures against the progressive collapse are still robust if subjected to multi-hazard scenarios containing column removal and successive localized fires is ad-dressed in the current study. Two seven-story steel structures with an identical area but different structural configurations of 4- and 5-bays are designed against the progressive collapse; the structural components are also fireproofed for a 60 min fire resistance. The structures are then subjected to different column re-moval scenarios over different stories followed immediately by localized fires. Results indicate that the structures are not able to keep their stability under all of the considered scenarios; the 4-bay structure is more vulnerable than the 5-bay structure. It is also indicated that upper stories are more sensitive toward the considered scenarios than lower stories. To advance structural safety, two strategies are adopted: in-creasing the thickness of the insulation materials to reduce the thermal effects, or, increasing the safety fac-tor (ΩN) of the structures when designing against the progressive collapse. As for the first strategy, provid-ing a 35% and a 25% increase in the insulation thicknesses of the structural components of the 4-bay and 5-bay structures, respectively, can prevent a progressive collapse to trigger. As for the second strategy, in-creasing ΩN by 10% can enhance the structural integrity to where no collapse occurs under all of the sce-narios.

A stability factor for structure-dependent time integration methods

Shuenn-Yih Chang,Chiu-Li Huang 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.87 No.4

Since the first family of structure-dependent methods can simultaneously integrate unconditional stability and explicit formulation in addition to second order accuracy, it is very computationally efficient for solving inertial problems except for adopting auto time-stepping techniques due to no nonlinear iterations. However, an unusual stability property is first found herein since its unconditional stability interval is drastically different for zero and nonzero damping. In fact, instability might occur for solving a damped stiffness hardening system while an accurate result can be obtained for the corresponding undamped stiffness hardening system. A technique of using a stability factor is applied to overcome this difficulty. It can be applied to magnify an unconditional stability interval. After introducing this stability factor, the formulation of this family of structuredependent methods is changed accordingly and thus its numerical properties must be re-evaluated. In summary, a large stability factor can result in a large unconditional stability interval but also lead to a large relative period error. As a consequence, a stability factor must be appropriately chosen to have a desired unconditional stability interval in addition to an acceptable period distortion.

Evaluation of thermal stability of quasi-isotropic composite/polymeric cylindrical structures under extreme climatic conditions

Mohamed Gadalla,Hany El Kadi 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.32 No.3

Thermal stability of quasi-isotropic composite and polymeric structures is considered one of the most important criteria in predicting life span of building structures. The outdoor applications of these structures have raised some legitimate concerns about their durability including moisture resistance and thermal stability. Exposure of such quasi-isotropic composite/polymeric structures to various and severe climatic conditions such as heat flux and frigid climate would change the material behavior and thermal viability and may lead to the degradation of material properties and building durability. This paper presents an analytical model for the generalized problem. This model accommodates the non-linearity and the non-homogeneity of the internal heat generated within the structure and the changes, modification to the material constants, and the structural size. The paper also investigates the effect of the incorporation of the temperature and/or material constant sensitive internal heat generation with four encountered climatic conditions on thermal stability of infinite cylindrical quasi-isotropic composite/polymeric structures. This can eventually result in the failure of such structures. Detailed critical analyses for four case studies which consider the population of the internal heat generation, cylindrical size, material constants, and four different climatic conditions are carried out. For each case of the proposed boundary conditions, the critical thermal stability parameter is determined. The results of this paper indicate that the thermal stability parameter is critically dependent on the cylinder size, material constants/selection, the convective heat transfer coefficient, subjected heat flux and other constants accrued from the structure environment.

Evaluation of thermal stability of quasi-isotropic composite/polymeric cylindrical structures under extreme climatic conditions

Gadalla, Mohamed,El Kadi, Hany Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.32 No.3

Thermal stability of quasi-isotropic composite and polymeric structures is considered one of the most important criteria in predicting life span of building structures. The outdoor applications of these structures have raised some legitimate concerns about their durability including moisture resistance and thermal stability. Exposure of such quasi-isotropic composite/polymeric structures to various and severe climatic conditions such as heat flux and frigid climate would change the material behavior and thermal viability and may lead to the degradation of material properties and building durability. This paper presents an analytical model for the generalized problem. This model accommodates the non-linearity and the non-homogeneity of the internal heat generated within the structure and the changes, modification to the material constants, and the structural size. The paper also investigates the effect of the incorporation of the temperature and/or material constant sensitive internal heat generation with four encountered climatic conditions on thermal stability of infinite cylindrical quasi-isotropic composite/polymeric structures. This can eventually result in the failure of such structures. Detailed critical analyses for four case studies which consider the population of the internal heat generation, cylindrical size, material constants, and four different climatic conditions are carried out. For each case of the proposed boundary conditions, the critical thermal stability parameter is determined. The results of this paper indicate that the thermal stability parameter is critically dependent on the cylinder size, material constants/selection, the convective heat transfer coefficient, subjected heat flux and other constants accrued from the structure environment.

위성용 S대역 TCTM 디지털 송수신기 구조체 개발

차원호,이상현,서정기,오치욱 한국항공우주학회 2011 한국항공우주학회 학술발표회 논문집 Vol.2011 No.11

위성용 통신 모듈 구조체 설계시 전기 및 전자적 간섭, 무게, 구조적 안정성 등에 있어서 많은 제약을 받는다. 본 논문은 위성용 S대역 TCTM 디지털 송수신기를 개발함에 있어 아날로그 통신 시스템을 디지털 통신 시스템으로 설계함에 있어 발생된 구조적 문제점과 기능 및 성능 향상을 위한 구조 설계에 대하여 기술하였다. 개발된 통신 모듈 엔지니어링 모델 구조체는 전기 및 전자적 간섭을 피하기 위해 동일 PCB상의 부품을 구조적으로 차폐하였으며, 구조의 경량화, 구조의 안정성을 확보하도록 설계하여 제작하였다. 구조체 개발시 발생되었던 문제점을 살펴보고, 그 해결 방향을 제시한다. In design of communication module structure for spacecraft, electrical and electronic interference, mass, and structural stability have many restrictions. This paper describes the structural problems occurred replacing analogue communication system with digital and structural design for function and performance improvement in development of the S-band TCTM digital transponder for spacecraft. The EM structure of communication module developed was structurally shielded the parts on the same PCB to avoid electrical and electronic interference, designed and manufactured the structure of insuring structural weight lighting and structural stability. In this paper, we check the problems occurred in EM structure development and suggest solutions.

2차원 한계평형 및 사면안정해석을 통한 지오텍스타일 튜브 복합구조물의 안정성 분석

오영인(Oh Young-In),신은철(Shin Eun-Chul),강정구(Kang Jeong-Gu) 한국토목섬유학회 2006 한국지반신소재학회 논문집 Vol.5 No.4

지오텍스타일 튜브공법은 지오텍스타일의 필터 및 배수기능을 복합적으로 활용하는 공법으로 과거의 모래주머니, 훼브릭, 폼, 게비언 등의 개념에서 최근 수리학적 채움기법을 적용하여 해안침식방지 구조물, 슬러지의 탈수, 교량축조를 위한 가도, 여수로 공사를 위한 임시구조물 등의 신구조물 공법으로 자리매김 하고 있다. 본 연구에서는 지오텍스타일 튜브와 지반재료와의 복합구조물의 안정거동에 대하여 2차원 한계평형, 침투해석 및 사면안정해석방법을 통하여 분석하였다. 2차원 한계평형이론을 통하여 설계영향인자 및 현장여건에 따른 지오텍스타일 튜브 복합구조물의 지반공학적 안정성을 분석하였으며, 사면안정해석을 위하여 일차적으로 부정류 침투해석을 통하여 조위변동에 따른 복합구조물내의 간극수압분포를 분석하였다. 최종적으로 범용 사면안정해석 프로그램인 Slope/W를 이용한 침투분석결과와 연동하여 사면안정해석을 수행하였다. 2차원 한계평형해석 및 평면변형해석 방법을 통한 분석결과, 세가지 형태의 지오텍스타일 튜브 복합구조물 모두 안정성을 확보하고 있으며, 지오텍 스타일 튜브 구조물 자체는 수위조건 변화에 대해서는 크게 영향이 없이 안정한 것으로 도출되었다. Geotextile has been used for various types of containers, such as small hand-filled sandbags, 3-dimensional fabric forms for concrete paste, large soil and aggregate filled geotextile gabion, prefabricated hydraulically filled containers. They are hydraulically filled with dredged materials and have been applied in coastal protection and scour protection, dewatering method of slurry, temporary working platform for bridge construction, temporary embankment for spill way dam construction. Recently, geotextile tube technology is no longer alternative construction technique but suitable desired solution. The paper presents the stability behavior of geotextile tube composite structure by 2-D limit equilibrium and slope stability analysis. 2-D limit equilibrium analysis was performed to evaluate the stability of geotextile tube composite structure to the lateral earth pressure and also transient seepage and stability analysis were conducted to determine the pore pressure distribution by tide variation and slope stability. Based on the results of this paper, the three types of geotextile tube composite structure is stable and also slope stability of overall geotextile tube composite structures is stable with the variation of tidal conditions.

Quantitative Stability Analysis of an Unmanned Tethered Quadrotor

Dong Liang,Li Ding,Mingyue Lu,Rui Ma,Jie Cao 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.3

Tethered quadrotors, unmanned aerial quadrotors connected to a fixed point via tether cables, have been widely applied in numerous aerial tasks. However, their structural parameters and external disturbances give rise to dynamic stability issues, resulting in uncontrolled autonomous flight, shaking, and vibrating. Thus, this article investigates the quantitative stability of a tethered quadrotor using the Lyapunov exponent approach. First, a mathematical model of the tethered quadrotor is developed, and its dynamic stability is quantified to verify the rationality of the designed physical prototype and enhance the aerial system’s stability. Both simulation and experimental results show that the dynamic stability during the landing phase is better than that during takeoff. Finally, optimizing the structural parameters enhances the dynamic stability, which is sensitive to cable length, wind gusts, and yaw angle.