Accuracy of the ISIS bridge methods for prediction of afflux at high flows

This paper presents the experimental results and findings from investigation into the accuracy, capability and suitability of the ISIS software package to model flow through bridge structures. Different types of bridge models, in terms of soffit shape, set in a two‐stage channel with various roughness conditions, were used for this study. In order to simulate natural environmental conditions, the original experimental data were scaled up using the undistorted‐scale method. One‐dimensional ISIS bridge methods, the ARCH bridge method, USBPR bridge method and the Bernoulli loss unit, were applied to both original experimental data and the scaled‐up data. The results for the ARCH bridge method and the USBPR method of ISIS are significantly different from the measured data and the Bernoulli loss unit. The Bernoulli loss unit, which uses Bernoulli's equation in ISIS, is the most accurate method to compute the afflux of bridges in waterways.     

某异型系杆拱桥吊杆张拉控制分析

刚性拱柔性系杆组成的系杆拱桥可通过张拉吊杆调整主梁成桥线形,本文以某异型拱桥主梁在恒载作用下的竖向位移为零为控制目标,利用影响矩阵法计算各吊杆同时张拉时的张拉力,计算结果符合该异型系杆拱桥的结构体系规律。考虑到实际施工中各吊杆必须分批次张拉,先期和后期张拉的吊杆会相互影响,导致不同张拉顺序各吊杆的张拉力也不同,本文利用倒装法按照四种不同的张拉方案计算各吊杆实际施工过程中需要的张拉力,以使吊杆全部张拉完成后满足设计成桥状态。最后,通过比较分析得出该异型系杆拱桥最为合理的张拉方案。     

石拱桥的有限弹簧法分析及其安全性评价

依据计算几何学的分割理论,开发了对石拱桥进行任意形状单元划分的计算机前处理系统,提出了用有限弹簧法模拟石拱桥力学性能的计算方法。其特点是能够把石拱桥的拱圈看成个别石材块体构成的不连续体,考虑拱圈随着偏心压缩而引起的石材块体间开口变形的同时,也考虑拱背填料和拱圈的相互作用及其它的荷载分散效果。数值模拟了多跨石拱桥在分布活荷载及其水平地震荷载作用下的力学性能,并进行了安全性评价。     

非贯通节理Jennings强度准则的岩桥弱化和节理面起伏角修正

 通过对具有不同粗糙程度(以节理面起伏角表示)的共面非贯通人工节理进行不同法向应力水平下的直剪试验,研究节理面起伏角对非贯通节理剪切强度的影响,分析在剪切过程中岩桥力学参数的弱化机制。现有Jennings准则将岩桥视为完整岩块,计算所得的剪切强度与直剪试验结果存在较大偏差。在试验结果的基础上,考虑剪切过程中岩桥力学参数的弱化和节理面起伏角的影响,对Jennings准则进行修正。将修正Jennings准则计算的非贯通节理剪切强度结果与直剪试验结果对比,结果表明：修正Jennings准则的计算结果与试验结果吻合较好,能较好地预测具有规则起伏角的非贯通节理剪切强度。     

超宽桥面连续梁拱组合式桥梁设计

结合工程实例,总结了连续梁拱组合式桥梁的设计体会和设计要点,并采用空间有限元法对该桥梁进行了结构受力计算,分析了拱粱分担荷载比对超宽桥面梁拱组合式桥梁结构横、纵向传力的影响.     

Dynamic analysis of a cable-stayed deck steel arch bridge

A theoretical and experimental research work in relation to the cable-stayed Barqueta bridge is described in this paper. Barqueta bridge, across Guadalquivir river, links the city of Seville with Scientific Park Cartuja 93. During rush hour cars may cover one half of the bridge lanes for more than one hour. Full-scale tests were carried out to measure the bridge dynamic response. The experimental program included the dynamic study for two different live load conditions: the bridge with one half of its lanes full of cars, and the bridge empty of cars. Modal parameter estimations were made based on the acquired data. Ten vibration modes were identified in the frequency range of 0-6 Hz by different techniques, two of these modes being very close to each other. The traffic-structure interaction is also studied. Experimental results were compared with those obtained from a three-dimensional finite element model developed in this work. Both sets of results show very good agreement. Finally, a damage identification technique has been applied to determine the integrity of the structure. Results obtained from a test developed in July 2005 have been correlated with experimental results obtained in October 2006 using the damage index method.     

Fast bridge deflection monitoring through an improved feature tracing algorithm

Completely non‐contact and fast measurements are still the focus of vision‐based monitoring in real‐bridge applications. Overall, a fast deflection measurement method, that traces the natural features of structures instead of artificial targets, was developed in this study. More specifically, due to the tiny scale change between images and the small deformation level of small and medium bridges, a simplified fast‐Hessian detector and a pre‐purification‐based RANdom Sampling Consistency (RANSAC) were proposed and verified by performing experiments under different illuminations. The non‐target deformation measurement method based on an improved algorithm was applied to field testing of an arch bridge with 100 m main girder and showed better processing speed and sub‐pixel accuracy than their originals. The optical results obtained by an industrial camera were consistent with other contact‐type sensors, such as level gauges and inclinometers.     

特大跨径钢管混凝土拱桥成桥荷载试验

为检验拱桥的受力状况和承载能力是否符合设计要求,对特大跨径钢管混凝土拱桥进行了成桥荷载试验。建立钢管混凝土拱桥的三维有限元模型,对桥梁在设计荷载作用下的结构变形和内力进行了验算。同时为考虑试验过程中温度对桥梁变形和应力的影响,对拱桥进行温度实时监测,获得温度变形和温度应力关系睦线,基于得到的温度修正曲线进行了桥梁在实际加载条件下的变形和应力修正。试验结果表明：桥梁的刚度满足设计要求。     

某双曲拱桥的动静力测试及承载能力评估

本文以某双曲拱桥的承载力评估为例,在总结几种有限元模型离散方法的基础上,结合双曲拱桥的结构形式,提出采用梁板结合的模拟方法,用大型通用有限元软件ANSYS进行了双曲拱桥的模型建立.同时,阐述了双曲拱桥的动载及静载试验的试验方法与过程,包括用等代荷载的方法确定荷载车辆、各种工况的分级加载、动载及静载试验测点的布置.依据有限元分析结果与动静力荷载结果的对比分析,对工程实例桥的承载能力进行了评估分析,得出了该桥当前的结构性能和状况.结果表明,正确的计算模型是评定双曲拱桥承载能力的关键,有限元法中的板梁法结合双曲拱桥的结构形式,是双曲拱桥结构空间分析的一种有效方法,以有限元理论分析和动静力荷载试验相结合的方法能较为全面地评定双曲拱桥的承载能力,可为同类桥梁计算分析及承载能力评定提供参考.     

单肋斜拉拱桥横向稳定性的实用计算

斜拉拱桥是一种将斜拉桥和拱桥相结合的新型桥梁结构形式,索拱共同受力使得拱的稳定性区别于一般拱桥。单肋斜拉拱是斜拉拱桥稳定性研究的基础,本文基于能量原理,在综合考虑桥面刚度、吊杆非保向力、斜拉索非保向力的前提下,推导了单肋斜拉拱横向失稳临界荷载的实用计算公式,并通过算例验证了实用计算公式的正确性,借助实用公式分析了斜拉索参数：斜拉索预张拉力、斜拉索倾角、索在拱的布置范围、主塔与拱的距离对单肋斜拉拱横向失稳临界荷载的影响。     

The nonconventional thin-walled arch rib design and its numerical verification of a long span steel arch bridge

Arch bridges have been widely constructed in China owing to their versatile structural configurations and competitive costs. The concept of using high performance prestressed steel wires to withstand the huge horizontal thrust at arch ends has greatly encouraged the engineering practices of large span arch type bridges constructed on soft soil foundations where normally arch structure is an inappropriate selection. However, many technical challenges including the design details, structural behavior and construction method still need to be carefully investigated to ensure the bridge′s safety. As a new practice of such tied arch bridge with nonconventional thin-walled steel box rib and the longest span of this type in the world, this paper presents the innovative design concept and the corresponding studies in regard to its structural behavior compared with conventional single arch design, the shear lag effect of the thin-walled arch rib and its stress distribution via numerical analysis of different finite element models are also investigated. The results show that the current design can reach a very good structural behavior under design load cases, and moreover, provides another very useful engineering practice for long span arch bridge constructed on soft soil foundations.     

考虑几何非线性的新型索拱桥拱轴线优化

鉴于新型索拱桥存在明显几何非线性的力学特点,针对已有拱轴线迭代优化方法收敛性不好的问题,提出在主拱圈为两铰拱的索拱桥有限元模型基础上,进行几何非线性的拱轴线迭代优化方法,以解决考虑几何非线性的超大跨径索拱桥拱轴线迭代的收敛性问题。以跨径600m索拱桥作为算例,验证方法的有效性及收敛性。算例结果表明,与仅考虑线性迭代相比,考虑非线性迭代后的主拱圈弯矩分布更合理,最大正弯矩小35%,最大负弯矩小17%,主拱圈应变能小23%;收敛性分析结果表明,该方法比主拱圈为无铰拱有限元模型方法收敛性能更好,不同的初始拱轴线均能收敛于稳定的结果。     

垂直提升开启式拱桥动力特性分析

首先介绍了垂直提升开启式拱桥的基本组成以及开启与闭合过程的实现,然后运用有限元软件MIDAS/Civil对一座垂直提升开启式钢管混凝土人行拱桥进行了动力特性的数值分析,研究了桥梁闭合状态和开启状态下的自振频率和振型,分析了拱肋刚度和横撑数量对该类型桥梁自振特性的影响。结果表明:桥梁开启前后的振动频率在第5阶时差别稍大,其他各阶自振频率几乎相同,振型也基本相同;开启后开启段主梁的纵向和竖向振幅较大;增大拱肋的刚度,结构自振频率增大,有利于提高拱桥的整体稳定性;横撑数量的多少对拱肋的耦合振动影响最大;所得结论可以为同类型桥梁的设计和抗震分析提供参考。     

基于开裂后双曲拱桥的加固分析

结合工程实例,探讨分析了开裂后双曲拱桥的结构分析方法,并依据结构分析成果与试验结果的对比,对双曲拱桥的结构性能进行了评价分析,得出了该桥当前的结构性能状况,进而验证该方法的可行性。     

梁拱组合体系桥施工监控

施工监控在结构新颖梁拱组合体系桥梁施工中是必要的。以北京通州北运河大桥为例,阐述了此类桥梁施工监控的目的、要点及方法。通过建立有限元模型进行施工模拟,分析了不同施工方案的优缺点。根据实测数据和理论计算结果,表明温度作用对该梁拱组合体系桥结构受力的影响较大,温度效应也应引起足够重视。     

下承式钢管混凝土系杆拱桥的冲击系数研究

以泰兴滨江大桥为例,根据下承式钢管混凝土系杆拱桥的结构特点,采用大型通用有限元软件ANSYS对该桥进行有限元离散。采用梁单元beam4模拟钢管混凝土拱肋（内部混凝土及外部钢管）、系杆及横梁等构件,用杆单元Iinks模拟吊杆,用壳单元she1163模拟桥面铺装层,用实体单元solid45模拟桥面系的预制空心板部分,建立了系杆拱桥的空间计算的有限元模型,进行模态分析,得到各阶自振频率及振型。建立四分之一车辆模型作用下的拱桥车桥耦合振动模型,并利用MATLAB语言编制程序,分析了移动车辆荷载作用下下承式钢管混凝土系杆拱桥的响应,系统地得到了该桥在不同车速,不同车道,不同阻尼,不同路况的振动响应等力学性能。本文所得出的主要结论和有关研究成果可为大跨度钢管混凝土系杆拱桥设计时的冲击系数取值,研究车辆对系杆拱桥的冲击性能和后期桥梁养护确定荷载效应分析提供参考。     

钢管混凝土拱桥动力特性的有限元分析

桥梁结构的动力特性是结构动力分析、抗震分析的重要参数,采用通用有限元软件ANSYS对朝阳市东大桥钢管混凝土拱桥的动力特性进行了分析,得到了其振型和频率,并对大桥的动力性能做了评价,有助于今后建立大桥的档案和健康诊断评估。     

中承式钢管混凝土拱桥动力特性分析

本文以某大桥为例,用MIDAS大型有限元软件计算了该大桥200 m跨钢管混凝土拱桥的自振频率和振型,用软件对中承式钢管混凝土拱桥动力特性进行了计算和分析。     

双曲拱桥加固技术应用与实践

针对接渡大桥（双曲拱桥）的病害,分析其产生原因,并对不同的病害分别采用增大截面加固法及增强横向联系加固法进行结构补强加固,以促进双曲拱桥加固技术的应用与实践。     

超大跨双线铁路简支梁桥设计与结构受力分析

介绍了目前国内最大跨度、最大梁段重量的双线铁路双箱单室截面简支梁桥的设计及基本施工步骤,并采用实体模型方法及梁格法对该桥在5道横隔梁和7道横隔梁下各荷载工况下的受力、变形特性及动力特性做了详细分析。分析结果表明:本桥型在设计荷载作用下受力性能完好,且5道横隔梁方案比选优于7道横隔梁方案。本桥型的设计将为我国建设高标准铁路桥梁具有一定的借鉴和参考价值。