Coupling Effect of Nodal Deviation and Member Imperfection on Load-Carrying Capacity of Single-Layer Reticulated Shell

Hui-jun Li,Yoshiya Taniguchi 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.3

Single-layer reticulated shell is sensitive to imperfections. To clarify the eff ect of member imperfection, nodal deviation and their couplings on load-carrying capacity of reticulated shell, the equivalent load method (ELM) is developed in the present study to establish single-layer reticulated shell with random member imperfection, and its realization procedures in FEM package are well-elaborated. The main conclusions are summarized as follows: the proposed ELM is of high effi ciency to form member imperfection in space structures. For reticulated shell only with member imperfection, the limit load is more or less infl uenced by member imperfection. With the increase of amplitude of member bow imperfection, limit load gradually decreases. Load-carrying capacity of reticulated shell with larger amplitude of bowed member is more sensitive to bending direction of bowed member than the one with smaller amplitude. Load-carrying capacity of the reticulated shell considered is extremely sensitive to nodal deviation. For reticulated shell with nodal deviation and member imperfection, the eff ect of member imperfection on load-carrying capacity is closely related to the magnitude of nodal deviation. Loadcarrying capacity of shell with smaller nodal deviation is obviously aff ected by member imperfection, while not sensitive to member imperfection for reticulated shell with larger one. Member imperfection can be neglected when nodal deviation is large enough. Load-carrying capacity of reticulated shell is also infl uenced by bending angle of bowed member. On the whole, load-carrying capacity of reticulated shell with larger amplitude of member imperfection is more sensitive to bending direction than the reticulated shell with smaller one.

제형 및 사인형 주름 강판의 초기 불완전 형상을 고려한 전단 좌굴 특성 비교

서건호,손수덕,이승재,Seo, Geonho,Shon, Sudeok,Lee, Seungjae 한국공간구조학회 2021 한국공간구조학회지 Vol.21 No.4

This paper conducted a comparative analysis of the shear buckling characteristics of trapezoidal and sinusoidal corrugated steel plates considering of their initial imperfection. Initial imperfection refers to the state where the shape of the corrugated plate is initially not perfect. As such, an initially imperfect shape was assumed using the eigen buckling mode. To calculate the buckling stress of corrugated steel plates, the linear buckling analysis used a boundary condition which was applied to the plate buckling analysis. For the comparison of trapezoidal and sinusoidal corrugation, the shape parameters were assumed using the case where the length and slope of each corrugation were the same, and the initial imperfection was considered to be from 0.1% to 5% based on the length of the steel plate. Here, for the buckling analysis, ANSYS, a commercial FEA program, was used. From the results of buckling analysis, the effect of overall initial imperfection showed that the larger the initial imperfection, the lower the buckling stress. However, in the very thin model, interaction or local buckling was dominant in the perfect shape, and in this case, the buckling stress did not decrease. Besides, the sinusoidal model showed higher buckling stress than the trapezoidal one, and the two corrugation shapes decreased in a similar way.

불완전함의 영성 ‐ 헨리 나우웬을 중심으로

오방식(OH Bang-Sik) 장로회신학대학교 기독교사상과 문화연구원 2020 장신논단 Vol.52 No.5

Geometric Imperfection Distributions of Existing Reticulated Shells: Theoretical and Experimental Analysis

Wu Jun,Luo Yongfeng,Wang Lei 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.5

Geometric imperfection is one of the most disadvantageous factors that impair mechanical behaviors of existing reticulated shell structures. However, the available consistent mode methods and statistical methods which usually applied in designing structures can hardly estimate the actual geometric imperfection distribution for existing structures, because these methods use the assumed imperfections. In this paper, a Markov Random Field (MRF) theoretical model of existing reticulated shells is established by introducing the theory of probabilistic graphical model. The unit of graphic model named node clique are proposed to deduct the geometric state function of reticulated shells, based on the local Markov property. Then the inversion function along with its iterative equation is established to predict geometric imperfection distribution of existing reticulated shells. The MRF method makes the predicted distribution of the numerical model as consistent as possible with its corresponding actual structure, and only a few measurement nodes are needed as known conditions. An experimental structure of K6 single-layer reticulated shell is built to verify the proposed theory by comparing the calculated geometric imperfection distribution results with the actual measured data. Meanwhile, the signifi cance level of the calculated results between MRF and traditional stochastic method is analyzed, which shows MRF method can eff ectively predict the geometric imperfections of single layer reticulated shells.

Probabilistic analysis of buckling loads of structures via extended Koiter law

Kiyohiro Ikeda,Makoto Ohsaki,Kentaro Sudo,Toshiyuki Kitada 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.32 No.1

Initial imperfections, such as initial deflection or remaining stress, cause deterioration of buckling strength of structures. The Koiter imperfection sensitivity law has been extended to describe the mechanism of reduction for structures. The extension is twofold: (1) a number of imperfections are considered, and (2) the second order (minor) imperfections are implemented, in addition to the first order (major) imperfections considered in the Koiter law. Yet, in reality, the variation of external loads is dominant over that of imperfection. In this research, probabilistic evaluation of buckling loads against external loads subjected to probabilistic variation is conducted by extending the concept of imperfection sensitivity. A truss arch subjected to dead and live loads is considered as a numerical example. The mechanism of probabilistic variation of buckling strength of this arch is described by the proposed method, and its reliability is evaluated.

Probabilistic analysis of buckling loads of structures via extended Koiter law

Ikeda, Kiyohiro,Ohsaki, Makoto,Sudo, Kentaro,Kitada, Toshiyuki Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.32 No.1

Initial imperfections, such as initial deflection or remaining stress, cause deterioration of buckling strength of structures. The Koiter imperfection sensitivity law has been extended to describe the mechanism of reduction for structures. The extension is twofold: (1) a number of imperfections are considered, and (2) the second order (minor) imperfections are implemented, in addition to the first order (major) imperfections considered in the Koiter law. Yet, in reality, the variation of external loads is dominant over that of imperfection. In this research, probabilistic evaluation of buckling loads against external loads subjected to probabilistic variation is conducted by extending the concept of imperfection sensitivity. A truss arch subjected to dead and live loads is considered as a numerical example. The mechanism of probabilistic variation of buckling strength of this arch is described by the proposed method, and its reliability is evaluated.

Prediction of Ultimate Behaviors in Cold-formed Steel Bolted Connection by the Introduction of Initial Geometric Imperfection in FE Modeling

Kim, Tae Soo,Kuwamura, Hitoshi,Cho, Taejun The Iron and Steel Institute of Japan 2008 ISIJ international Vol.48 No.5

<P>Experimental research and nonlinear finite element analysis for the structural behaviors of single shear test on bolted connections fabricated with cold-formed stainless steel have been conducted. Failure criteria for prediction of failure mode of bolted connections under static shear and out-of-plane deformation, <I>i.e.</I>, curling criteria were proposed based on experimental data for calibration of FE modeling. Failure mode and ultimate strength predicted by recommended FEA procedures with solid element showed a good correspondence with those of previous test results and the validation of FEA method was verified. The previous numerical analyses of bolted connection were carried out on geometrically perfect specimens. However, it has been known that geometric imperfection of thin-walled members must be considered in a FE model to simulate the actual shape of specimen. Therefore, in this paper, parametric studies were carried out based on the validity of numerical modeling of bolted connections in cold-formed stainless steel so that authors investigated the influence of initial geometric imperfection of connected plate on its structural behavior. Solid element and shell element with reduced integration were introduced as an element type and included two types of geometric imperfection. Consequently, FE modeling technique of cold-formed stainless steel bolted connection introducing initial imperfection to compensate the function of shell element and to induce the curling was proposed.</P>

Nonlinear thermal post-buckling analysis of graphene platelets reinforced metal foams plates with initial geometrical imperfection

Yin-Ping Li,Gui-Lin She,Lei-Lei Gan,Hai-Bo Liu 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.46 No.5

Although some scholars have studied the thermal post-buckling of graphene platelets strengthened metal foams (GPLRMFs) plates, they have not considered the influence of initial geometrical imperfection. Inspired by this fact, the present paper studies the thermal post-buckling characteristics of GPLRMFs plates with initial geometrical imperfection. Three kinds of graphene platelets (GPLs) distribution patterns including three patterns have been considered. The governing equations are derived according to the first-order plate theory and solved with the help of the Galerkin method. According to the comparison with published paper, the accuracy and correctness of the present research are verified. In the end, the effects of material properties and initial geometrical imperfection on the thermal post-buckling response of the GPLRMFs plates are examined. It can be found that the presence of initial geometrical imperfection reduces the thermal post-buckling strength. In addition, the present study indicates that GPL-A pattern is best way to improve thermal post-buckling strength for GPLRMFs plates, and the presence of foams can improve the thermal post-buckling strength of GPLRMFs plates, the Foam- II and Foam- I patterns have the lowest and highest thermal post-buckling strength. Our research can provide guidance for the thermal stability analysis of GPLRMFs plates.

Effects of Correction by Heating/Pressing on Mechanical Behavior of Steel Bridge Pier

Mikihito Hirohata,Takuya Morimoto,You-Chul Kim 한국강구조학회 2009 International Journal of Steel Structures Vol.9 No.1

A series of experiments was conducted in order to elucidate effects of correction by heating/pressing on mechanical behavior of steel bridge piers. Local buckling deformation of specimens due to loading considering the situation of an earthquake was corrected by heating/pressing, with or without water-cooling. Some out-of-plane deformations were inevitably left to avoid cracking in the welds. This geometric imperfection was defined as residual imperfection. After the correction, the same loading experiment was conducted. From the results, no deterioration was confirmed in mechanical properties of the steel even with water-cooling only if heating temperature was kept below A1 transformation temperature. Although it is ideal to have local buckling deformation repaired within the allowance of initial deflection in correction by heating/pressing, it was elucidated that making the residual imperfection mode opposite to local buckling mode was reasonable for guarantee of the maximum load of the corrected structure. A series of experiments was conducted in order to elucidate effects of correction by heating/pressing on mechanical behavior of steel bridge piers. Local buckling deformation of specimens due to loading considering the situation of an earthquake was corrected by heating/pressing, with or without water-cooling. Some out-of-plane deformations were inevitably left to avoid cracking in the welds. This geometric imperfection was defined as residual imperfection. After the correction, the same loading experiment was conducted. From the results, no deterioration was confirmed in mechanical properties of the steel even with water-cooling only if heating temperature was kept below A1 transformation temperature. Although it is ideal to have local buckling deformation repaired within the allowance of initial deflection in correction by heating/pressing, it was elucidated that making the residual imperfection mode opposite to local buckling mode was reasonable for guarantee of the maximum load of the corrected structure.

Computational analysis of the nonlinear vibrational behavior of perforated plates with initial imperfection using NURBS-based isogeometric approach

VeisiAra Abdollah,Mohammad-Sedighi Hamid,Reza Arash 한국CDE학회 2021 Journal of computational design and engineering Vol.8 No.5

In this article, an isogeometric analysis through NURBS basis functions is presented to study the nonlinear vibrational behavior of perforated plates with initial imperfection. In this regard, the governing equations of plate dynamics, as well as the displacement–strain relations, are derived using the Mindlin–Reissner plate theory by considering von Karman nonlinearity. The geometry of the structure is formed by selecting the order of NURBS basis functions and the number of control points according to the physics of the problem. Since similar basis functions are utilized to estimate the accurate geometry and displacement field of the domain, the order of the basic functions and the number of control points are optimized for the proper approximation of the unknown field variables. By utilizing the energy approach and Hamilton principle and discretizing the equations of motion, the vibrational response of the perforated imperfect plate is extracted through an eigenvalue problem. The results of linear vibrations, geometrically nonlinear vibrations, and nonlinear vibrations of imperfect plates are separately validated by considering the previously reported findings, which shows a satisfactory agreement. Thereafter, a coefficient of the first mode shape is considered as the initial imperfection and the vibrational analysis is reexamined. Furthermore, the nonlinear vibrations of the perforated plate with initial imperfection are analysed using an iterative approach. The effects of the perforated hole, initial imperfection, and geometric nonlinearity are also addressed and discussed.