120m跨钢管拱桁架结构设计

针对某仓库大跨度拱桁架结构的设计工程,采用sap2000通用有限元软件进行静力分析和构件验算。通过验算表明:该120 m跨,矢跨比为0.25的五心圆钢管拱桁架结构各杆件应力比均小于1.0,承载力满足规范要求;节点最大竖向位移为-196.1 mm,是跨度的1/612,刚度满足规范要求。此钢管拱桁架结构竖向刚度大,受力合理,造型美观,能够满足各种大跨空间结构建筑的要求。     

某空旷大跨度体育场馆的建模分析

针对体育场馆类空旷大跨度结构的设计特点,运用有限元程序,对某公司文化体育中心结构的整体受力性能、薄弱部位及大跨度网架屋盖对主体结构受力性能的影响与协同工作等问题进行了模拟分析.计算表明,此类结构具有扭转不规则性,薄弱部位常出现在空旷结构部位和弱连接部位;空旷框架部分存在相对变形大的现象.由于框架柱缺乏有效约束,其计算长度较大,P-△效应明显;网架屋盖在水平力及地震作用下对主体结构有不可忽视的作用,应考虑网架屋盖与下部框架结构的协同工作.实际设计中可考虑将网架部分按照一定的规则等代为钢梁,来近似考虑网架的刚度进行整体设计.     

新型铝电解槽摇篮架的分析与研究

文章引入了一种新型铝电解槽摇篮架的结构形式,通过运用有限元软件对该种新型摇篮架结构和传统摇篮架结构同时进行应力分析,并且将分析结果进行详细的比较,从而找出新型摇篮架结构所具有的优点,为今后电解槽摇篮架技术的发展提供了参考。     

大跨度封闭料场空间桁架拱骨架膜结构的设计与施工

本文以南方某钢厂综合料场封闭项目为例,简要介绍大跨度封闭料场空间桁架拱骨架膜结构的设计思路及施工方案,重点从结构选型、分析、设计及施工方面对大跨度空间桁架拱骨架膜结构的性能及特点进行阐述,体现出空间桁架拱骨架膜结构在料场封闭项目的优势。     

在役风电塔结构的最不利风——震组合作用响应分析

因风电塔整体结构不沿轴向对称,为明确该结构的受力特性和保证结构安全,采用国外及国内两种数值计算方法对塔筒结构进行了研究,分析风荷载作用下、地震动作用下和风–地震组合作用下的塔体结构的受力差异.在此基础上对塔筒结构进行风–地震组合作用下的不同地震动输入方向的动力响应分析进行研究.结果指出了该状态下对塔筒结构最不利的地震动输入方向以及该作用条件下塔筒结构的薄弱位置为塔筒开口位置.      

框支网格式轻质墙板结构受力性能及抗震设计

基于框支网格式轻质墙板结构抗震性能试验,量化分析结构受力性能,并提出抗震设计建议.洞口侧构造柱的设置弥补了开洞造成的强度衰减,有利于提升墙体的安全储备能力,但加重了墙体后期破坏程度,同时降低其修复能力.斜交肋格的构造形式改变传力途径,使得墙体强度退化趋于均匀,结构具有更好的变形恢复能力,且明显减小墙体的破坏程度,但是整体安全储备能力改善不大.在工程设计方面,建议转换层初始刚度比取值范围大致在1.3~1.6,由于受力过程中结构转换层刚度比衰减较明显,在设计时初始刚度比可适当高些.结构在各个受力阶段的层间位移和层间转角值均在安全界限值以内,进一步说明结构具有较高的抗倒塌能力,耗能减震性能良好.      

现浇混凝土空心楼板施工技术

文章介绍了现浇混凝土薄壁筒体空心楼板的特点、施工方法与施工质量控制,现浇混凝薄壁筒体空心楼板是一种新开发的现浇结构体系,将受力性能良好的工字梁与蜂窝状结构特性运用到楼板结构中去的一种优化体系.此结构受力合理、技术先进、性能优异、简单易行、效益显著,是建筑结构上技术性、科学性和经济性有机结合的典范,具有巨大的社会经济价值.     

大跨度钢桁拱施工阶段空间受力特性分析

根据大跨度钢桁拱的施工特点和施工工艺,对朝天门大桥进行施工阶段静动力分析,探讨了大跨度钢桁架拱桥施工阶段的空间静动力特性,验证了拱上吊机悬臂拼装法施工的可行性.     

正交胶合木填充墙-钢框架体系受力性能

采用开源地震工程模拟系统（OpenSees）对以正交胶合木作填充墙的钢框架结构进行探索性数值研究,主要研究该填充墙钢框架单元在单调和循环加载作用下的受力性能,墙体与钢框架之间的协同工作性能以及连接个数对整体结构受力性能的影响.结果表明:正交胶合木填充墙能够提高钢框架的抗侧刚度和水平承载力;柔性连接的设置使整体结构耗能性能良好;工作缝的设置减缓墙体的开裂,更大程度上发挥连接件的耗能和变形能力;连接个数对构件的抗侧能力影响较大,可以通过调整连接数量和连接间距设计出具有多种刚度和耗能能力的框架单元.      

设防烈度对框架—核心筒结构受力性能和材料用量的影响

为了考察设防烈度对钢筋混凝土框筒结构受力性能、材料用量的影响,在充分调研了目前我国100 m以上已建或在建超高层建筑的基础上,选择150~300 m范围内钢筋混凝土框架-核心筒办公类超高层作为代表性研究对象,建立了12个不同烈度、不同高度下的计算模型,详细分析了其结构的周期比、剪重比、刚重比、地震作用和风荷载影响等结构受力性能以及结构的用钢量、混凝土用量随设防烈度的变化情况.研究结果表明,对于济南恒大国际金融中心工程,随着设防烈度的提高,结构自振周期减小,扭转周期滞后于平动周期,扭转效应减小,而结构剪重比明显增加;低烈度地区结构受重力二阶效应的影响较大,整体稳定性成主要安全控制因素;地震作用的影响随设防烈度的增加而增大;6度区建筑超过200 m后,用钢量明显增加,而8度区用钢量随建筑高度呈线性增长;6度和7度区单位面积混凝土用量接近,而8度区混凝土用量增幅约为19%左右,所以设防烈度对结构工程材料用量影响显著.      

Analytical Load Rating of an Open-Spandrel Arch Bridge: Case Study

The live load structural capacity of open-spandrel arch bridge structures is difficult to quantify. In addition to live and dead loads, geometric nonlinear effects, temperature effects, and material behavior play key roles in the design and load rating of such a structure. This paper is a case study that illustrates the effect these variables have on load rating a two-span shallow concrete arch bridge. Presented are load ratings of the structure’s arch ribs using a three-dimensional finite-element model with American Association of State Highway and Transportation Officials publications. As a result of this study, a refined analysis is recommended for load rating arch bridges.     

Translational pauses during the synthesis of proteins and mRNA structure

Translational pauses are observed during a spider fibroin synthesis (1,2). The spider major ampullate (dragline) silk of the spider Nephila clavipes is composed of multiple proteins. The amino acid sequences of the partial cDNA clones for the two major dragline silk fibroin components (Spidroin 1 and 2) exhibit repetitive motifs (3,4). Our detailed inspection of the nucleotide sequences of the repetitive motifs revealed highly selective site-specific codon usage patterns within a motif, suggesting that the secondary structure of the spider fibroin mRNA is optimized by the nucleotide sequence of the fibroin gene. The results, combined with our preceding results on silk fibroin from Bombyx mori (5) suggest that translational pauses of spider silk are interpreted in terms of the mRNA secondary structure.     

ZY240型自卸车举升拉筋的改制

利用国产铲斗拉筋替代日野 ZY2 40型自卸车举升拉筋 ,可降低成本 43 6元 /根并可提高运行效率 ,而且操作方便可靠、易于更换     

Load Rating of Masonry Arch Bridges

A masonry arch bridge can be analyzed by frame analysis methods by considering a unit width of the arch ring and the overlying fill. The arch ring is divided into at least 10 segments, each of which is given cross-sectional properties corresponding to the properties of the material in the arch ring. The dead load of the arch ring and the overlying fill are considered as nodal loads, and the axle loads are applied to the frame as linearly varying pressures, based on a simplified distribution of pressures through the fill. The supports are considered to be rigid in the vertical direction and elastic springs in the horizontal direction. The elastic spring constant varies depending on the type of foundation and the condition of the springings. Based on this application of dead and live loads to the structure, the axial thrust and moment can be found throughout the arch ring, and compared to an estimate of the capacity of the arch ring. This procedure can be used to find an appropriate load rating for the structure service level. An example rating of a bridge in Adams County, Pa., is provided, along with the results of a validation field test of the structure.     

壁式采场上覆岩层力学结构分析

根据实验和现场预测结果，提出了壁式采场上覆岩层中存在抛物线形拱结构，建立了该结构力学模型，并进行了内力分析，同时提出了工作面支架受载的计算方法。     

New therapeutic prospects for the glycosphingolipid lysosomal storage diseases

The Differential Straight Arch technique, more commonly known as "Tip-Edge" (TP Orthodontics Inc.), uses a modified edgewise type bracket to allow differential tooth movement. As bracketed teeth incline toward their finishing positions, the geometry of the arch wire slot causes the vertical slot dimension available to the arch wire to increase. Advantage has been taken of this facility, to evolve an entirely new torquing system for final finishing, during the root correction phase. Instead of increasing rectangular arch wire size to fit the arch wire slot, as with conventional edgewise brackets, the Tip-Edge method reduces the vertical arch wire slot dimension to achieve a precise, three-dimensional relationship to a full-sized rectangular arch wire. The active component is provided by auxiliary springs. The method, which awaits mathematical analysis, is described and illustrated with two case reports.     

Effects of Environmental Action on Thermal Stress Analysis of Karaj Concrete Arch Dam

A three-dimensional finite element analysis is carried out to determine the thermal stresses of a concrete arch dam. Appropriate heat transfer boundary conditions in the dam body are used for air and reservoir temperature as well as solar radiation variations. A finite element model is used to determine annual variation of temperature and thermal stress in the body of Karaj arch dam in Iran as a case study. The rate of convergence of the numerical solution is examined. The temperatures predicted by the model are satisfactorily compared with the instrumentation records at Karaj Dam. Results of the finite element analysis show that probable cracks occur in a very narrow region of the downstream face. Thermal loads have the most significant effects for causing downstream cracks in comparison with self-weight and hydrostatic loads. The cracked areas of the downstream face conform to the regions that have the highest temperature in the downstream face. This can be associated with the solar radiation, which shows that two-dimensional analysis of an arch dam cannot yield accurate results and three-dimensional analysis is necessary.     

Dynamic and Impact Behavior of Half-Through Arch Bridges

The objective of this paper is to present the results of an investigation of the dynamic and impact characteristics of half-through arch bridges with rough decks caused by vehicles moving across them. Seven arch bridges modeled as three-dimensional structures with overall span lengths ranging from 20?to?200?m (65.5?to?656.2?ft) are analyzed. The American Association of State Highway and Transportation Officials Specifications HS20-44 truck is the applied vehicle loading used in the analysis and is simulated as a three-dimensional, nonlinear vehicle model with 11 degrees of freedom. Truck components include the body, suspension, and tires. The bridge deck surface is assumed to have a “good” surface roughness and is simulated using a stochastic process (power spectral density function). The effect on impact factors of span length, rise-to-span ratio, and vehicle speed is discussed. The results of the analyses show that the impact factors of bending moment and axial force will not exceed 0.4 and 0.25, respectively. The proposed impact equations are simple and conservative and can be used in the design of half-through arch bridges.     

Model structure of decorin and implications for collagen fibrillogenesis

The three-dimensional structure of human decorin, a secreted proteoglycan involved in the regulation of collagen fibrillogenesis and cellular growth, has been modeled based on the crystal structure of the porcine ribonuclease inhibitor. Both proteins contain leucine-rich repeats and share 18% identical residues. This model structure of decorin has an arch shape with the single glycosaminoglycan chain and the three N-linked oligosaccharides located on the same side of the molecule. Decorin was modeled as binding to a polar sequence of collagen type I found in the d band. The inner concave surface is the appropriate size and shape to accommodate only one collagen triple helix of approximately 3 nm in length. The binding of one collagen triple helix to decorin is proposed to play a major role in the formation of the staggered arrangement of collagen molecules within the microfibrils by preventing lateral fusion of collagen molecules.     

Cine magnetic resonance imaging study of blood flow and wall motion of the aortic arch

The aortic arch has 3D distortions in the transverse arch in the axial view, and we previously reported that this distortion is a risk factor in the pathogenesis of arch aneurysms. In this study, we evaluated blood flow and movement of the aortic arch. In 10 healthy young volunteers, ECG-gated cine magnetic resonance imaging was carried out in the axial plane of the transverse arch, the coronal plane of the ascending arch, and the long axial plane along the entire arch. 1. Left anterolateral movements around the midpoint of the transverse arch in the systolic phase were observed in all of the men (6.3 +/- 1.59 mm) and women (4.8 +/- 0.73 mm). 2. A jet flow was detected in the systolic phase along the right side of the aortic wall. At the top of the plane, this jet flow turned to the left in a clockwise rotation in the anterior view. 3. In the long axial plane, a turbulent flow in the systolic phase was observed distal to the left subclavian arterial orifice in 6 of the 7 cases. In conclusion, this turbulent flow and left anterolateral wall motion of the transverse arch are due to anatomical three-dimensional distortion of the transverse arch. We propose that these phenomena may be important risk factors in the pathogenesis of arch aneurysms.