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Characteristics of bifurcation and buckling load of space truss in consideration of initial imperfection and load mode

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第3期14卷 206-218页

作者： Su-deok SHON Seung-jae LEE Kang-guk LEE School of Architectural Engineering Korea University of Technology and Education1800 ChungjeolroCheonan ChungnamRepublic of Korea Research Center for Urban Affair Kyungil UniversityGyeongsan-city GyeongbukRepublic of Korea

This study investigated characteristics of bifurcation and critical buckling load by shape imperfection of space truss,which were sensitive to initial conditions.The critical point and buckling load were computed by the analysis of the eigenvalues and determinants of the tangential stiffness matrix.The two-free-nodes example and star dome were selected for the case study in order to examine the nodal buckling and global buckling by the sensitivity to the eigen buckling mode and the analyses of the influence,and characteristics of the parameters as defined by the load ratio of the center node and surrounding node,as well as rise-span ratio were performed.The sensitivity to the imperfection of the initial shape of the two-free-nodes example,which occurs due to snapping at the critical point,resulted in bifurcation before the limit point due to the buckling mode,and the buckling load was reduced by the increase in the amount of imperfection.The two sensitive buckling patterns of the numerical model are established by investigating the displaced position of the free nodes,and the asymmetric eigenmode greatly influenced the behavior of the imperfection shape whether it was at limit point or bifurcation.Furthermore,the sensitive mode of the two-free-nodes example was similar to the in-extensional basis mechanism of a simplified model.The star dome,which was used to examine the influence among several nodes,indicated that the influence of nodal buckling was greater than that of global buckling as the rise-span ratio was higher.Besides,global buckling is occurred with reaching bifurcation point as the value of load ratio was higher,and the buckling load level was about 50%-70% of load level at limit point.

关键词： Space truss Geometric nonlinearity initial imperfection Snap-through Bifurcation Global buckling

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RELIABILITY ANALYSIS OF FRP LAMINATED PLATES WITH CONSIDERATION OF BOTH initial imperfection AND FAILURE SEQUENCE

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Acta Mechanica Solida Sinica 2002年第3期15卷 227-235页

作者： Chen, JQ Wang, XY Luo, C Huazhong Univ Sci & Technol Dept Mech Wuhan 430074 Peoples R China

A probabilistic progressive failure analyzing method is applied to estimating the reliability of a simply supported laminated composite plate with an initial imperfection under bi-axial compression load. The initial imperfection and the strength parameters are considered as random variables. Ply-level failure probability is evaluated by the first order reliability method (FORM) together with the Tsai-Wu strength criterion and Tan criterion. Current stresses in the laminated structure are calculated by the classical lamination theory with the stiffness modified based on the last step ply failure. Probabilistically dominant ply-level failure sequences leading to overall system failure are identified, based on which the system failure probability is estimated. A numerical example is presented to demonstrate the methodology proposed. Through parameter studies it is shown that the deviation of the initial imperfection and some of the strength parameters largely influence the system reliability.

关键词： failure sequences initial imperfection laminated-plates structural reliability first order reliability method (FORM) strength criterion

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Research on Strengthening Method of Concave Cone-toroid-cylinder Combined Shell with initial imperfection

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Journal of Harbin Institute of Technology(New Series) 2017年第1期24卷 65-70页

作者： Er Zhang Fan Wu Kairen Mao Chunzheng Liu Department of Naval Architecture Engineering Naval University of EngineeringWuhan 430033China

As a new joint structure,the impact of initial imperfection to stress of Concave cone-toroid-cylinder combined shell was analyzed. Firstly the location and shape of combined shell's initial imperfection caused by welding was studied. Secondly dominated stress was chosen after comparing varioustypical stress. Then it was analyzed that the influence of imperfection to dominated stress via changing the shape of frame's deflection and shell's concave-convex. At last the strengthening case for combined shell with imperfection was pointed out. The conclusions are:(1) Stress of frame 9 is more sensitive to initial imperfection than circumferential stress of toroidmidsurface,which is a new concern;(2) To strength the frames in the sides of toroid not only can decrease the stress of frame,but also can reduce the circumference stress of toroid's midsurface.

关键词： concave cone-toroid-cylinder combined shell initial imperfection stress strengthening scenario

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Numerical Study on Lateral Buckling Mode of Pipelines Laid on A Sleeper

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China Ocean Engineering 2023年第3期37卷 495-505页

作者： LIU Run HAO Xin-tong LI Cheng-feng YU Zheng LI Qing-xin State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China

Because non-buried submarine pipelines under cyclic thermal loading are prone to global buckling,sleepers are commonly laid along the pipeline route to induce a series of relatively small and controllable lateral buckling.A finite element model which can simulate the transformation of pipeline laid on a sleeper from vertical buckling to lateral buckling is established in this work.The parameters of sleeper affecting pipeline buckling modes are analysed,and a new kind of sleeper is proposed aimed at avoiding antisymmetric buckling.Results show that the lateral trigger force can avoid antisymmetric lateral buckling when acting between 1℃and 13℃before the critical buckling temperature.The range increases slightly with increasing trigger force.Compared with an ordinary sleeper,the proposed new sleeper with slider can reduce the critical buckling temperature by 25%,which significantly improves the success rate of sleepers.

关键词： submarine pipeline buckling mode initial imperfection new sleeper

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冲击作用下折板吸能器的数值分析

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Acta Mechanica Sinica 2022年第4期38卷 139-152,I0003页

作者：陈品元孙博华 School of Civil Engineering&Institute of Mechanics and Technology Xi'an University of Architecture and TechnologyXi'an 710055China Faculty of Mechanical Engineering&Mechanics Ningbo UniversityNingbo 315211China

折板因为结构简单而被广泛加工成吸能构件.输入动能恒定时,不同材料的折板在不同的动力学条件下。最终变形有明显的差异.为了更好地解释这种现象,利用Maple软件对Zhang-Yu吸能器方程编写了通用程序,并首次求得了吸能器的广义坐标(转角9... 详细信息

折板因为结构简单而被广泛加工成吸能构件.输入动能恒定时,不同材料的折板在不同的动力学条件下。最终变形有明显的差异.为了更好地解释这种现象,利用Maple软件对Zhang-Yu吸能器方程编写了通用程序,并首次求得了吸能器的广义坐标(转角9)随时间的变化规律.为了更好地了解吸能器的运动受参数变化的影响,计算了吸能器动力学的相图经过大量数值模拟,我们发现四折板吸能器应当是"质量敏感"型吸能结构.同时,本文建立了低碳钢和6061-T6铝合金两类折板的动态屈曲的有限元模型,并与Caladine-English动态实验和Zhang-Yu刚黏塑性模型进行了比较.结果表明.(1)Zhang-Yu刚黏塑性模型对低碳钢这种应变本敏感型材料更具有指导意义,而折板为6061-T6铝合金这种应变率不敏感材料时误差更大.并且随着初始折角的增大.Zhang-Yu刚黏塑性模型的预测误差进一步扩大.(2)根据有限元模型修正塑性铰的等效塑性长度λ值,可以提高Zhang-Yu刚黏塑性模型的预测伯的精度,我们的研究结果对折板吸能结构的设计与制造有一定的指导意义.

关键词： Mass sensitivity Crooked plate energy absorbing structure initial imperfection Maple ABAQUS

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Compressive failure analysis of unidirectional carbon/epoxy composite based on micro-mechanical models

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Chinese Journal of Aeronautics 2017年第6期30卷 1907-1918页

作者： Wei SUN Zhidong GUAN Zengshan LI Mi ZHANG Yongjie HUANG School of Aeronautic Science and Engineering Beihang University Beijing 100083 China

A 2D micro-mechanical model was proposed to study the compressive failure of Uni Directional（UD） carbon/epoxy composite. Considering the initial imperfection and strength distribution of the fiber, the plasticity and ductile damage of the matrix, the failure of T300/914 UD composite under longitudinal compression and in-plane combined loads was simulated by this model. Simulation results show that the longitudinal compressive failure of the UD composite is caused by the plastic yielding of the matrix in kink band, and the fiber initial imperfection is the main reason for it. Under in-plane combined loads, the stress state of the matrix in kink band is changed, which affects the longitudinal compressive failure modes and strength of UD composite.The failure envelope of r_1–s_（12） and r_1–r_2 are obtained by the micro-mechanical model. Meanwhile,the compressive failure mechanism of the UD composite is analyzed. Numerical results agree well with the experimental data, which verifies the validity of the micro-mechanical model.

关键词： Micro-mechanical model Unidirectional composite initial imperfection Matrix plasticity Ductile damage Kink band

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Analysis on column-bracing forces considering random initial imperfections

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Journal of Harbin Institute of Technology(New Series) 2011年第2期18卷 119-126页

作者：赵金友张耀春 College of Civil Engineering Northeast Forestry University Institute of Engineering Mechanics China Earthquake Administration School of Civil Engineering Harbin Institute of Technology

A large number of column-bracing systems were modeled and analyzed by second-order analysis using finite element program ANSYS,in which the random combination of the initial imperfections between columns and horizontal braces was well considered by Monte Carlo Method.According to the analysis results,four kinds of instability modes of column-bracing systems were found,the probability density function of the mid-height horizontal bracing forces was established based on probability statistics,and the design bracing forces were also obtained.The results indicated that the above design bracing forces are smaller than that proposed by the "Code for design of steel structures"(GB50017-2003) when the top axial compressions on the braced columns are equal,and much smaller than the latter when the top axial compressions on the braced columns are unequal.The results also indicated that the random combination of the initial imperfections between columns and horizontal braces leads to the randomness of the mid-height horizontal bracing forces in compression or in tension,so that the design bracing forces can be reduced.

关键词： column-bracing system bracing forces Monte Carlo Method initial imperfection random combination

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SNAP－THROUGH　OF　LAMINATED　ORTHOTROPIC　SHALLOW　SPHERICAL　IMPERFECT　SHELLS　WITH　TRANSVERSE　SHEAR

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Chinese Journal of Aeronautics 1996年第4期9卷 273-277页

作者： Yang Yiqian Ma Hezhong Wang Tsunkuei(Research Center Of Solid Mechanics, Beijing University Of Aeronautics andAstronautics, Beijing, China, 100083) Research Center of Solid Mechanics Beijing Univ. Aero. and Astronaut. Beijing 100083 China

The equations of large deformations of laminated orthotropic spherical shellsare derived. The effects of transverse shear deformation and initial imperfection are considered. on this basis. the semi-analytical solution of the axisymrnetric snap-throughbuckling of laminated orthotropic shallow spherical shells under uniform pressure is obtained using orthogonal collocation method. The effects of material parameters, structuralparameters, initial imperfection and transverse shear deformation are discussed.

关键词： laminated shallow shells spherical shells snap-through buckling transverse shear deformation initial imperfection orthogonal collocation method

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