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1.
风荷载作用下的钢管混凝土拱桥非线性稳定性分析 总被引：1，自引：1，他引：1
淳安南浦大桥为一净跨径308m中承式钢管混凝土桁式拱桥，宽跨比较小，该桥拱肋的横向稳定是桥梁安全性的关键，文章运用非线性稳定分析的基本理论，得出了该桥在不同风荷载作用下稳定性分析的结果。结果表明：风荷载对该桥稳定性的影响很小，而材料非线性对该桥的稳定性影响较大。 相似文献
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国内外针对大跨度钢管混凝土拱桥抗震方面的研究则处于相对薄弱的阶段,成桥实例很少,而国内现行公路及铁路桥梁抗震设计规范对此类桥梁结构的抗震性能也尚无具体规定.本文以四川白日坝大桥为工程背景,用ANSYS软件建立了该桥的空间有限元模型,进行了该桥的自振特性分析,讨论了拱肋、横撑等参数对其动力特性的影响.分析表明,拱肋刚度、横撑刚度及数量对钢管混凝土拱桥的动力特性具有较大的影响. 相似文献
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落叶松胶合木是我国自产加工的工程材,开展了一座落叶松胶合木人行拱桥的静力模型试验与有限元数值分析。模型比例1/3,模拟跨径38.07 m的实际木结构拱桥。模型拱肋、横撑、拱上框架及桥面板等主要构件均采用落叶松胶合木及钢板螺栓连接,连接件与支座采用Q235钢。对制作模型桥木材,进行了顺纹拉、压试验和抗弯弹性模量与泊松比试验。考虑结构配重、人群荷载及拱肋控制截面最不利受力,分9个工况加载,测试拱肋的应变与位移。采用有限元软件,针对木拱桥模型,建立有限元模型进行数值分析。试验与分析结果表明,落叶松胶合木拱桥的强度与刚度满足我国木结构设计规范要求,证明了落叶松胶合木可以用于实际工程。 相似文献
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双曲拱桥裂缝的原因及对策李延军（吉林省汪清林业局）１种类１．１水平裂缝：发生在拱肋与小拱波的联结处，先出现在拱顶，然后逐渐向１／４点拱脚处发展。拱顶部位裂缝一般较宽，拱脚处较窄，裂缝断断续续，严重的贯通全拱，使肋与波版分离，整体的拱圈变成迭合拱圈，拱... 相似文献
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碧水双曲拱大桥位于大兴安岭地区呼中区碧水镇东北角,距镇中心三公里左右.该桥建于1973年,全桥总长为329.74米,是10孔净跨30米的钢筋混凝土双曲拱桥,矢跨比为1/8,主拱为等截面悬链线装配式双曲拱.拱轴系数m=1.756,断面为两肋单波.桥面净宽:净——4.5 2×0.25米.桥的立面如图一所示.由于该桥形体单薄年久失修,加之运材汽车车型的变化,平均载量的提高等原因,使人们感到桥体现状不佳.有大修加固之必要.肉眼观察,拱肋没发现异常变化,而拱波的裂纹现象比较严重.我们邀请东北林业大学派员对该桥进行动载试验.电测应力和挠度表明,需要对立拱圈加固.加固的方法:一、在拱波底面布设钢筋网后,采用喷射钢纤维混凝土的方法加固;二、两拱肋之间.在原有横系梁的基础上,每孔桥再匀布增设六根钢筋拉杆,以加强拱圈的整体性.该工程由齐铁一处路桥工程公司承担施工. 相似文献
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以大型有限元分析软件ANSYS为平台,建立桩-冻土体相互作用的有限元模型,结合工程实例对多年冻土地区灌注桩基础在横向荷载作用下的位移和应力进行分析,并在此基础上分析桩径、冻土温度对其横向承载力的影响。 相似文献
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大跨径双曲拱桥,拱脚的恒载轴向力(N)较拱顶大,拱脚截面压应力((?))增高。从力学观点而言,总是按其受力状况,考虑主拱圈沿着拱跨设为变截面(即变拱肋,或变拱板)。显然,这样不论是浆砌料石作拱肋,还是现地浇筑,或是无支架吊装拱肋,主拱圈的施工工艺过程,都颇为复杂。同时,为使弯矩(M)不致过多的分向拱脚,拱顶与拱脚的截面高度也不宜相差过大,否则就削弱了双曲拱的作用和意义。因此,对于大跨径双曲拱桥的设计,如何合理选用主拱圈的问题,有必要研究。 相似文献
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为正确评价林区现有桥梁的技术状态，本文论述了林区钢筋混凝土及预应力混凝土简支梁桥理论计算挠度限值与实测挠度限值的不同．并在分析荷载试验资料的基础上，参照铁路部门的规定，提出了林区钢筋混凝土简支梁桥在使用荷载作用下的实测挠度限值为跨径的１／３０００、预应力混凝土简支梁桥为跨径的１／１６００，该限值可作为荷载试验评定桥梁质量时的刚度指标。 相似文献
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黄民元 《中南林业科技大学学报(自然科学版)》2011,31(2)
通过钢管混凝土刚架系杆拱桥受力性能的研究,为实践工程提供有利指导。主要从以下几个方面进行研究:考察钢管混凝土刚架系杆拱桥结构的受力性能,分析其在恒载、活载作用下的结构内力分布;对钢管混凝土刚架系杆拱桥结构参数,即,拱轴线、系杆力、拱墩刚度比等进行了分析,考察它们对结构内力的影响规律,具有较强的运用价值。 相似文献
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双曲拱桥拓宽改造后内力重分布的探讨 总被引：1，自引：0，他引：1
为了加强现有双曲拱桥的结构承栽力和交通通行能力，提出了利用刚架片双向拓宽改造的方法，对现有双曲拱桥的上部结构进行加固改造，并利用有限元分析软件基于应力重分布理论对改造前后的主拱圈（拱肋）应力变化进行分析计算，论证该方法的可行性和合理性： 相似文献
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为定量描述同向双车道中一条车道上前导车的横向偏移以及相邻车道行车状况对跟驰车的影响,建立考虑横向偏移和超车可能性的跟车模型.对不同行驶情况下超车可能性系数进行分类讨论和量化.通过线性稳定性理论分析了模型的稳定性条件,在开放性的边界条件下对不同参数下模型进行数值模拟.模拟结果显示,车流密度较小车速较大时,横向偏移系数越大超车可能性越大,对车流疏通有促进作用,反之,在车流密度较大车速较慢时,会加剧堵塞发生.模拟结果验证了模型的有效性,也能较客观反映现实中同向双车道上跟车状态. 相似文献
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Kei Sawata Tatsuya Shibusawa Kazuo Ohashi Javier Ramon Sotomayor Castellanos Yasunori Hatano 《Journal of Wood Science》2008,54(1):45-53
Nail-head pull-through, lateral nail resistance, and single shear nailed joint tests were conducted on medium density fiberboard
(MDF) with different density profiles, and the relations between the results of these tests and the density profiles of MDF
were investigated. The maximum load of nail-head pull-through and the maximum load of nailed joints were little affected by
the density profile. However, the ultimate strength of lateral nail resistance, the stiffness, and the yield strength of nailed
joints were affected by the density profile of MDF and showed high values when the surface layer of the MDF had high density.
It is known that bending performance is also influenced by density profile. Therefore, the stiffness and the yield strength
of nailed joints were compared with the bending performance of MDF. The stiffness of nailed joints was positively correlated
with the modulus of elasticity (MOE); in the case of CN65 nails, the initial stiffness of joints changed little in response
to changes in MOE. The yield strength of nailed joints had a high positive correlation with the modulus of rupture (MOR).
The stiffness and the yield strength of nailed joints showed linear relationships with MOE and MOR, respectively. 相似文献
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Estimating stem and root-anchorage flexibility in trees 总被引：2，自引：0，他引：2
This paper describes a nondestructive method for distinguishing root flexibility from stem flexibility in living trees. It is used here for Sitka spruce (Picea sitchensis (Bong.) Carrière.), but is applicable to any species where the main stem is normally straight and near-vertical. Well-known engineering equations permit the calculation of deflected shape for a vertical cantilever with arbitrary distribution of mass and bending stiffness, when infjected to a lateral force. The equations are used to calculate stem deflections of four Sitka spruce trees for which the stem and branch mass distribution and stem taper have been measured. Free parameters in the mathematical model are a nominal value of Young's Modulus E (assumed uniform and isotropic over the cross section and height of the tree stem) and a root-anchorage stiffness k. The former allows the stem to curve, whereas the latter represents the flexibility of the roots and allows the stem to tilt elastically at ground level. For each of the four trees, the calculated deflection curve is compared with actual deflections measured when the living tree is pulled by a rope at a specified point. By adjusting both E and k, iteratively, a best fit solution is obtained. This provides a simple and effective way to determine both stem stiffness and root hinge stiffness from a single experiment on a living tree. 相似文献
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研究了亚麻纤维(flaxfiber,FF)的含量和马来酸酐接枝聚丙烯(MAH-g-PP)对聚丙烯/亚麻纤维(PP/FF)复合材料各项性能的影响,通过扫描电镜研究了复合材料的界面结构.结果表明:随着FF含量增大,复合材料拉伸强度、硬度和热变形温度提高;添加MAH-g-PP提高了复合材料力学性能和热稳定性,降低了复合材料吸水性. 相似文献
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为研究空心胶合木梁柱式结构体系抗侧力性能,对纯框架及框架-人字撑两种单跨结构试件进行了单调及低周反复加载试验,考察了结构破坏模式、耗能能力、刚度等抗震性能。结果表明:纯框架与框架-人字撑结构均具有一定抗侧力性能,但纯框架结构承载能力较弱,不建议单独用于工程实践;框架-人字撑结构具较大抗侧刚度及承载力,分别为纯框架的6.3倍及2.68倍,但其延性仅为纯框架的67%。两种结构失效前强度退化小于30%,具足够剩余承载力。 相似文献
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Ivan Orosz 《Wood Science and Technology》1975,9(1):25-44
Summary Tension members with edge knots or edge knotholes deflect laterally when they are loaded by a tensile force. In order to consider this behavior for determination of tensile strength ratio (TSR), second-order theory is applied. A matrix displacement method of structural analysis developed from the slope deflection method is used to implement the second-order theory. The method reveals that in a member with a single edge knot the lowest TSR is obtained when the lateral deflection is negligible, and when the ends are hinged. For a stiffness value (EI/L) that is small, both end conditions (hinged and fixed) yield the same TSR; for large stiffness value, fixed end condition always gives a higher TSR than a hinged end condition because the moment is reduced at the defect as a result of the fixed ends. The method further reveals that the maximum moment for two edge knots on the same edge is lower than when they are on opposite edges.The findings are important because they can provide guidance in planning tensile testing methods for lumber, in interpretation of results of tests, and in design considerations. These findings help to develop better relationships between TSR, which is an index of tensile strength (T), and apparent modulus of elasticity, Ea, which are so important for the determination of the best predictor of T.Maintained at Madison, Wis., in cooperation with the University of Wisconsin. 相似文献
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为满足使用功能及美观上的需要，无推力下承式系杆拱通常被设计成少横撑和无横撑，此时就必须验算其横向稳定性。而目前有限元通用程序给出的是一个综合性的计算结果，设计青无法具体分析各项几何及材料参数的影响程度，从而不可能通过变更设计或采取有针对性的措施来提高稳定系数。因此，探讨解析解或各种近似的计算方法还是很有必要的。本文以无横撑下承式系杆拱桥侧倾稳定问题为背景，用能量变分方法导出了其侧倾临界荷载的近似解析解。 相似文献