共查询到20条相似文献，搜索用时 31 毫秒
1.
首先对我国现行SRC-RC竖向混合结构过渡层的设计要求和相关规定提出了不同的看法,建议采用SRC-RC转换柱进行型钢混凝土柱到钢筋混凝土柱的过渡。介绍了SRC-RC转换柱的优点,并在RC柱和SRC柱截面抗弯刚度基础上根据抗弯刚度等效原则合成SRC-RC转换柱的截面抗弯刚度。最后给出了SRC-RC转换柱侧移刚度计算公式。 相似文献
2.
Aiming at exploring the excellent structural performance of the vein-stiffening membrane structure of dragonfly hind wings, we analyzed two planar computational models and three 3D computational models with cambered corrugation based on the finite element method. It is shown that the vein size in different zones is proportional to the magnitude of the vein internal force when the wing structure is subjected to uniform out-of-plane transverse loading. The membrane contributes little to the flexural stiffness of the planar wing models, while exerting an immense impact upon the stiffness of the 3D wing models with cambered corrugation. If a lumped mass of 10% of the wing is fixed on the leading edge close to the wing tip, the wing fundamental fre- quency decreases by 10.7%-13.2%; if a lumped mass is connected to the wing via multiple springs, the wing fundamental frequency decreases by 16.0%-18.0%. Such decrease in fundamental frequency explains the special function of the wing pterostigma in alleviating the wing quivering effect. These particular features of dragonfly wings can be mimicked in the design of new-style reticulately stiffening thin-walled roof systems and flapping wings in novel intelligent aerial vehicles. 相似文献
3.
交互影响距离理论以对话、结构、学习者的自主性三者之间的动态关系来分析远程教育,对远程开放教育学习支持服务具有重要的指导意义,即针对学生的需求特点,通过加强师生之间的对话交流,采用结构化媒体材料等支持服务缩短师生距离,并注意距离的适度问题,以有利于发挥学生的学习自主性。 相似文献
4.
The progressive collapse of steel frame structures under the blast load was investigated using LS-DYNA.The multi-material Eulerian and Lagrangian coupling algorithm was adopted.A fluid-structure coupling finite element model was established which consists of Lagrange element for simulating steel frame structures and concrete ground,multiple ALE element for simulating air and TNT explosive material.Numerical simulations of the blast pressure wave propagation,structural dynamic responses and deformation,and progressive collapse of a five-story steel frame structure in the event of an explosion near above ground were performed.The numerical analysis showed that the Lagrangian and Eulerian coupling algorithm gave good simulations of the shock wave propagation in the mediums and blast load effects on the structure.The columns subjected to blast load may collapse by shear yielding rather than by flexural deformation.The columns and joints of steel beam to column in the front steel frame structure generated enormous plastic deformation subjected to intensive blast waves,and columns lost carrying capacity,subsequently leading to the collapse of the whole structure.The approach coupling influence between structural deformation and fluid load well simulated the progressive collapse process of structures,and provided an effective tool for analyzing the collapse mechanism of the steel frame structure under blast load. 相似文献
5.
With the increase of capacity and size of the hydro-generator unit, the spiral case becomes a more super-giant hydraulic structure
with very high HD value, where H and D denote water head and maximum intake diameter of spiral case, respectively. Due to the induced lower stiffness by the more
giant size and adverse operation conditions, dynamic performances of the powerhouse and the supporting structure for the giant
units have become more important and attracted much attention. If the manner of steel spiral case embedded directly in concrete
is adopted, on some locations of the concrete surrounding the spiral case, distributed and concentrated cracks will emerge
due to high tensile stress. Although the concrete is reinforced well to control the maximum crack width, definitely these
cracks will reduce the local and entire stiffness of the powerhouse. Under dynamic loads such as hydraulic forces including
water pressure pulsation in flow passage acting on the structure, effect of the cracks on the dynamic characteristics of the
local members and entire structure needs to be evaluated. However, research on this subject is few in hydroelectric engineering.
In this paper, Three-Gorge Project was taken as an example to evaluate effect of such cracks on natural frequencies and the
vibration responses of the powerhouse under hydraulic and earthquake forces in detail. Results show that cracks only reduce
the local structural stiffness greatly but have little effect on the entire powerhouse especially the superstructure; vibrations
of powerhouse with cracks in concrete surrounding the spiral case are still under the design limits. Results in this paper
have been verified by practice of Three-Gorge Project.
Supported by National Natural Science Foundation of China (No.50679009) and Foundations for Young Teachers in Dalian University
of Technology(No.893219).
TIAN Ziqin, born in 1965, male, doctoral student, senior engineer. 相似文献
6.
艺术生产是一种符号形式生产。艺术媒介由口传媒介、印刷媒介、发展到电子媒介,艺术符号由物象、语像、发展到影像。艺术生产方式的嬗变是主体主体性的体现。由于主体主体性的表现是矛盾的,因此,作为主体的异质同构的艺术及其生产方式也显示出一种悖论性存在:当艺术媒介及符号趋向精神化、群体化、纯形式时,主体的精神取向却趋向欲望化、个体化、物质化。人类艺术生产方式历史型态也由象征型生产方式到古典型生产方式发展为浪漫型生产方式。艺术生产方式的变化使创作主体的价值倾向由实用价值发展为交流价值最后上升为文化结构价值,价值实现了历史的多维嬗变。 相似文献
7.
从力学角度分析了位于漳州市南靖县书洋镇下版村的裕昌楼，看起来摇摇欲坠，却经受七百年风雨侵蚀和无数次地震的考验，至今依然如故的原因.根据土楼建造程序、“龙骨”架在外墙小槽内与内圈竖直木柱上横梁的事实，提出了土楼的建筑等效结构模型；根据动力学扰动理论确定的扰动区厚度、三合土弹性模量和埋入土墙深度，计算出柔性固定端的等效转动刚度系数；从几何静力学、分析静力学和材料力学的压杆稳定3个方面，分析得出外墙斑驳、楼内“东歪西斜”的福建现存最古老土楼裕昌楼的极限承载能力比一般土楼极限承载能力高25．9%，其原因除墙体中埋入杉木或竹片，甚至放进大石块为墙骨以增强抗力外，力学静定结构是斜而不危另一重要因素. 相似文献
8.
王艳梅 《商丘职业技术学院学报》2012,(4):93-94
大众传播媒介是现代社会传递信息的主要物质载体,与现代社会生活密不可分,西方国家的社会科学家们就大众传媒对社会及其文化的各方面所产生的影响作了较为详尽的研究和阐述。目前我国有关传播媒体与社会科学的论说相对较少,流行音乐作为一种严重依赖大众传播媒介的音乐形式,其存在与发展都受到大众传播媒介功能的影响。 相似文献
9.
以组成物质原子的原子序数为矩阵元素,建立了物质的分子结构矩阵;指出了物质分子结构矩阵与其分子具有链状结构的物质间的一一对应关系,因此分子结构矩阵具有优良的结构选择性;同时以分子结构矩阵为基础,构建了分子结构矩阵指数,借助于因子分析法,将分子结构矩阵指数用于13种酯类物质色谱保留值的预测,结果令人满意. 相似文献
10.
以商用车空气悬架C型梁为研究对象,采用材料替换并结合拓扑和尺寸优化的方法进行轻量化设计。基于变密度法,以结构刚度最大化为目标进行拓扑优化,获得结构初始构型。在拓扑优化结果的基础上,综合考虑3种工况,以板件厚度为设计变量,各工况下的应力和变形为约束条件,质量最小化为目标,进一步进行尺寸优化。优化结果表明,设计方案满足结构刚强度要求,降低了结构的质量,达到了轻量化的效果。 相似文献
11.
To reduce the environmental impact of mechanical parts, an approach integrating structural design and material selection was studied. Adding the discrete variable of material, a hybrid optimization model was built with the aim of minimizing environmental impact and based on an ordinary structure optimization model. An optional material set was built by combining measures of qualitative and quantitative screening, while the lifecycle environmental impact of the materials was quantified using the method of Eco-indicator 99. Two groups of structurally optimal solutions were calculated with ideal and negative-ideal materials selected respectively, and then the hybrid model was simplified by comparing the solutions. A material environmental performance index was calculated using an analytic method. By comparing this index for every material in the optional material set, the optimal material can be found and the structural solutions calculated. This method was applied to a dowel bar design process as a case study. The results show that the environmental impact of each material has a significant effect on the optimal structural solution, and it is necessary to study the integration of structural design and material selection. 相似文献
12.
Bao-long LI Yi-fan WAN Jing-hai GONG 《浙江大学学报(A卷英文版)》2014,15(9):732-742
研究目的：基于找形分析建立的细胞骨架力学模型研究微丝束对细胞骨架刚度的影响。创新要点：目前存在的细胞模型很少考虑微丝束对细胞力学特性的重要作用。本文基于细胞找形模型模拟了同时包含微丝和微丝束的细胞骨架网络结构,并且分析了细胞中微丝束的排列方向、微丝束的含量以及微丝波动对细胞刚度的影响。研究方法：基于找形模型,随机生成由微丝、微丝束（梁单元）以及交联蛋白（索单元）形成的细胞骨架网络结构,依靠非线性有限元计算和样本统计,计算出模型的弹性模量。通过分别改变模型中微丝束的排列方向、微丝束的含量以及模型初始最大位移等参数,得出细胞骨架模型的弹性模量随这些参数的变化趋势,以此来研究微丝束对细胞刚度的影响。重要结论：细胞骨架网络中微丝的波动会导致细胞刚度降低;与拉伸方向平行排列的微丝束可以显著地提高细胞的刚度,相比之下随机分布的微丝束对细胞刚度没有贡献;在微丝材料总量固定的情况下,细胞刚度随着平行排列微丝束含量的增加呈现出先升高后降低的趋势。 相似文献
13.
INTRODUCTION Externally bonded fiber reinforced polymer (FRP) composites can be used to improve the flexural strength of structural members. To evaluate the flex-ural performance of the strengthened members, it is necessary to study the flexural stiffness of FRP- strengthened RC members at different stages, such as pre-cracking, post-cracking and post-yielding. Up to now, only very few studies were focused on the structural members strengthened under pre-loading or pre-cracking (Arduin… 相似文献
14.
As an important mooring arrangement in the na-val vessel, the lap link is used to join the tympanicring in lay day or for draught proofing,the capabilityof which is of vital importance to the safety of the ves-sel and personnel. However, existing lap link… 相似文献
15.
乔以东 《淮南职业技术学院学报》2004,4(3):89-91
论述了高层建筑上部结构对箱形基础的影响，上部结构与基础共同工作，增加了基础的刚度，可以对基础的变形起制约作用；在高层建筑的设计中忽略了基础的变形和位移，人为地把基础和上部结构开计算，既不经济，也不安全，无原则要对建筑物进行整体的综合考虑，即应当考虑上部结构与地基基础的共同作用；上部结构的刚度是水平刚度、竖向刚度和搞弯刚度的综合，不但对基础产生影响，对地基反力的影响也很大，共同作用分析将使上部结构、基础和地基地内力和位移等方面与常规法相比均有显著的变化；对该领域目前所存在的问题进行了探讨。 相似文献
16.
Extensive research has shown that externally bonded carbon fiber reinforced polymer (CFRP) laminates are particularly suitable for improving the fatigue behavior of reinforced concrete (RC) beams. This paper presents the research on flexural rigidity evolvement laws by testing 14 simple-supported RC beams strengthened with carbon fiber laminates (CFL) under cyclic load, and 2 under monotone load as a reference. The cyclic load tests revealed the peak load applied onto the surface of a supported RC beam strengthened with CFL is linear to the logarithm of its fatigue life, and the flexural rigidity evolvement undergoes three distinct phases: a rapid decrease from the start to about 5% of the fatigue life; an even development from 5% to about 99% of the fatigue life; and a succedent rapid decrease to failure. When the ratio of fatigue cycles to the fatigue life is within 0.05 to 0.99, the flexural rigidity varies linearly with the ratio. The peak load does not affect the flexural rigidity evolvement if it is not high enough to make the main reinforcements yield. The dependences of the flexural rigidity of specimens formed in the same group upon their fatigue cycles normalized by fatigue life are almost coincident. This implies the flexural rigidity may be a material parameter independent of the stress level. These relationships of flexural rigidity to fatigue cycles, and fatigue life may be able to provide some hints for fatigue design and fatigue life evaluation of RC member strengthened with CFL; nevertheless the findings still need verifying by more experiments. 相似文献
17.
根据动力学分析和边界条件推导出轴向运动梁的系统特征方程,利用微分求积法对本征方程离散,计算出梁横向振动的固有频率,并数值模拟了梁运动速度和刚度对固有频率的影响。 相似文献
18.
The structure stiffness of presses has great effects on the forming precision of workpieces, especially in near-net or net shape forming. Conventionally the stiffness specification of presses is empirically determined, resulting in poor designs with insufficient or over sufficient stiffness of press structures. In this paper, an approach for the structure design of hydraulic presses is proposed, which is forming-precision-driven and can make presses costeffective by lightweight optimization. The approach consists of five steps:(1)the determination of the press stiffness specification in terms of the forming precision requirement of workpieces;(2)the conceptual design of the press structures according to the stiffness and workspace specifications, and the structure configuration of the press;(3)the prototype design of the press structures by equivalently converting the conceptual design to prototypes;(4)the selection of key structure parameters by sensitivity analysis of the prototype design; and(5)the optimization of the prototype design. The approach is demonstrated and validated through a case study of the structure design of a 100 MN hydraulic press. 相似文献
19.
Catherine M. Hennessy Danielle F. Royer Amanda J. Meyer Claire F. Smith 《Anatomical sciences education》2020,13(4):527-539
Social Media has changed the way that individuals interact with each other - it has brought considerable benefits, yet also some challenges. Social media in anatomy has enabled anatomists all over the world to engage, interact and form new collaborations that otherwise would not have been possible. In a relatively small discipline where individuals may be working as the only anatomist in an institution, having such a virtual community can be important. Social media is also being used as a means for anatomists to communicate with the current generation of students as well as members of the public. Posting appropriate content is one of the challenges raised by social media use in anatomy. Human cadaveric material is frequently shared on social media and there is divided opinion among anatomists on whether or not such content is appropriate. This article explores the uses and challenges of social media use in the field of anatomy and outlines guidelines on how social media can be used by anatomists globally, while maintaining professional and ethical standards. Creating global guidelines has shown to be difficult due to the differences in international law for the use of human tissue and also the irregularities in acquiring informed consent for capturing and sharing cadaveric images. These nuances may explain why cadaveric images are frequently shared on social media. This article proposes that as standard practice, anatomists obtain informed consent from donors before sharing images of cadaveric material on social media and ensure posts include a statement stating the same. 相似文献
20.
胶原—磷酸钙复合物是最重要的人工骨框架材料。植入体内的材料结构对材料的生物降解、诱导新骨的生长具有重要的影响.通过透射电镜、扫描电镜、能谱分析等方法,研究了胶原—磷酸钙复合物结构随时间的变化关系,分析了复合物在静止状态和搅拌状态下结构变化的成因. 相似文献