平面钢管桁架拱平面外稳定承载力的参数分析

介绍了桁架拱的分类和失稳特点,对平面桁架拱的有限元模型进行了讨论.采用有限元软件ANSYS分析,对影响平面钢管桁架拱的稳定性的各项几何参数进行研究,几何参数包括结构的高跨比、矢跨比、腹杆与弦杆的比值以及侧向支撑.分别进行了特征屈曲分析和考虑初始缺陷的双重非线性分析,得到各几何参数对平面钢管桁架拱的面外稳定承载力的影响程度.找出对平面钢管桁架拱平面外稳定性起控制作用的参数,从而为一般荷载作用下的平面钢管桁架拱的稳定承载力的设计提供参考.     

平面钢管桁架拱平面内稳定承载力的参数分析

对平面钢管桁架拱采用有限元软件ANSYS进行分析,对影响平面钢管桁架拱平面内稳定性的高跨比、矢跨比、腹杆与弦杆外径的比值等几何参数进行研究,考虑了全跨、半跨竖向均布荷载的荷载效应。分别进行了特征屈曲分析、非线性分析,得到各项几何参数对平面钢管桁架拱的面内稳定承载力的影响程度,找出对平面钢管桁架拱平面内稳定性起控制作用的参数,并通过考虑用钢量得到最经济的参数取值范围。     

拉索预应力折线型立体桁架拱布索方案研究

针对折线型立体桁架拱结构,提出了4种拱平面内的布索方案,研究了4种方案下预应力拱结构的静力及稳定性能,分别从结构位移的减小、索初始预拉力值的高低、水平支反力的降幅、杆件内力分布的均匀性及结构稳定性的提高5个方面与未布索立体桁架拱作了综合对比.结果表明,按照桁架拱在极限荷载作用下的屈曲形态布置撑杆拉索能够最有效地改善拱的...     

拉索预应力巨型网格结构布索形式研究

针对由预应力和巨型网壳结构组合而成的一种超大跨度拉索预应力空间结构体系,总结了该结构体系已提出的两种预应力布置形式的索杆布置原则、受力机理、具体形式与几何拓扑关系;并在此基础上提出两种改进型拉索预应力布索形式.通过与已提出的两种布索形式及未布索桁架拱进行对比分析,初步研究了改进型布索形式下立体桁架拱的静力及稳定性能.对比指标包括结构最大位移、支座水平反力、杆件内力峰值、结构稳定极限承载力及失稳模态等5个方面.分析结果表明,两种改进型布索形式的引入均可有效地提高桁架拱的结构刚度,改善结构的静力性能,并能较大地提高其稳定承载力,同时还能改善已有布索形式的缺陷,是较合理的索杆布置;其中第2种改进型布索形式的综合性能更好,是一种更有效的布索形式.     

张弦桁架结构拉索设计预应力影响因素研究

提出预应力态张弦桁架结构计算模型,采用有限元分析技术建立了拉索设计预应力计算公式,以哈尔滨国际体育会展中心屋盖张弦桁架结构型式为背景建立算例结构模型,研究了拱桁架上下弦杆截面积比对拉索设计预应力、结构特征杆件内力和结构变形的影响,以及张弦桁架结构矢跨比所产生的影响．文章的研究方法和成果可为今后此类大型张弦桁架结构的设计...     

平面钢管桁架整体稳定实用设计方法

平面钢管桁架的整体稳定性主要由其受压弦杆的平面外稳定性决定.本文针对上弦简支、承受均布荷载的平面钢管桁架,采用势能原理确定了考虑受压弦杆不均匀轴力影响的计算长度系数和考虑桁架附加扭转效应的承载力折减系数,结合轴心受压构件整体稳定相关设计规定,建立了平面钢管桁架整体稳定承载力实用设计方法.采用有限单元法,对24例不同几何参数的平面钢管桁架进行了线性屈曲分析和考虑初始几何缺陷的非线性稳定分析.由本文实用设计方法计算得到的平面钢管桁架整体稳定承载力与有限元分析结果吻合良好,验证了实用设计方法的合理性和可靠性.最后,通过非线性有限元分析讨论了较大初始几何缺陷(跨度/300)对平面钢管桁架整体稳定性的影响.     

单层索网点支式玻璃幕墙自由振动

阐述了单层索网点支式玻璃幕墙自由振动特性分析的特点,编写了相应的有限元程序,对索网结构的自振频率进行了计算分析,并讨论了节点质量、拉索截面积、拉索预应力等因素对其自振频率的影响。研究结果表明,单层平面索网幕墙结构自振频率密集,具有较强的非线性。     

点支式玻璃建筑单层索网体系的动力特性

点支式玻璃建筑单层索网体系是一种新型的柔性支承结构体系,其受力特性在很大程度上依赖于所施加的预应力。该文对新保利大厦二期幕墙工程的单层索网结构模型的动力特性进行试验研究,提取了索网在分级预应力下的前三阶频率,并与加玻璃后的情况进行了对比分析。试验结果表明,结构的低阶频率与预应力的关系基本为近似线性关系,而高阶的非线性程度更明显,玻璃对结构的刚度有较大提高,试验与有限元计算结果比较吻合。     

空腹扁网壳结构稳定分析研究

为更加深入研究空腹网壳结构的稳定性,取单种空腹扁网壳结构,在矢跨比、结构厚度、截面尺寸等不同参数变化下进行稳定分析研究。利用ANSYS有限元在先对单榀的空腹平面拱进行计算分析的基础上,进一步开展对空腹扁网壳结构的屈曲模态分析及非线性参数化屈曲分析,得出平面空腹拱和空腹扁网壳两种结构在不同参数的变化下对结构极限承载力的影...     

节点刚度对管桁架拱稳定性的影响

为研究节点刚度对管桁架拱稳定性的影响,在节点弹簧单元和壳单元滞回性能一致性得到验证的基础上,采用往复荷载下的变刚度弹簧模型代替壳单元考虑节点的半刚性。弹簧模型的节点刚度方程由节点域壳单元模型在往复荷载加载作用下的骨架曲线确定。以矢跨比为0.29,跨度为50m的管桁架拱为算例,采用材料与几何非线性有限元法对节点域弹簧模型和普通模型进行稳定性分析。结果表明：“静力失稳模态”为空间管桁架拱的最不利初始缺陷形式;节点刚度对管桁架拱的承载力影响程度与考虑初始缺陷的大小、分布形式和荷载作用范围有关。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

Quantitative trait loci （QTLs） for quality traits related to protein and starch in wheat

Quality traits in wheat （Triticum aestirum L.） were studied by quantitative trait locus （QTL） analysis in a recombinant inbred line （RIL） population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross （ChSh）. Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.