New algorithm of shape-finding of suspension bridge with spatial cables

A new algorithm is proposed to solve the problems of shape-finding of suspension bridge with spatial cables what include tedious iteration,slow convergence speed and even no convergent under some circumstances.In this paper,the stress analysis of the main cable is carried out,and the relationship between the slope change and the coordinate change is found.This paper also discussed how to find the minimum slope point of symmetrical or asymmetric main cable,and the deformation compatibility equation is established and solved to obtain the shape of main cable.The algorithm in this paper can ensure the convergence of the solution for the suspension bridge with spatial cables.The calculation accuracy is high through the demonstration of the calculation examples.

Dynamic performance of cable-stayed bridge tower with multi-stage pendulum mass damper under wind excitations——I:Theory

In this paper, wind-induced vibration control of a single column tower of a cable-stayed bridge with a multi- stage pendulum mass damper （MSPMD） is investigated. Special attention is given to overcoming space limitations for installing the control device in the tower and the effect of varying natural frequency of the towers during construction. First, the finite element model of the bridge during its construction and the basic equation of motion of the MSPMD are introduced. The equation of motion of the bridge with the MSPMD under along-wind excitation is then established. Finally, a numerical simulation and parametric study are conducted to assess the effectiveness of the control system for reducing the wind-induced vibration of the bridge towers during construction. The numerical simulation results show that the MSPMD is practical and effective for reducing the along-wind response of the single column tower, can be installed in a small area of the tower, and complies with the time-variant characteristics of the bridge during its entire construction stage.

Dynamic performance of cable-stayed bridge tower with multi-stage pendulum mass damper under wind excitations—Ⅱ: Experiment

The possibility of using a multi-stage pendulum mass damper （MSPMD） to control wind-induced vibration of a single column tower of a cable-stayed bridge during construction was studied theoretically in part I of this work. In this paper, the performance of the MSPMD for reducing bridge tower vibration is studied experimentally. A MSPMD model and a tower model of the bridge with geometry scaling of 1：100 were designed and manufactured. Calibration of the MSPMD model with different wire lengths is conducted to verify the analytical model of the damper. A series of tests for the uncontrolled freestanding tower, tower with cables, and tower with MSPMD model are then performed under harmonic and white noise excitations. The experimental results show that the responses of the tower model significantly decrease with the installation of the MSPMD model, which demonstrates the effectiveness of the M SPMD to mitigate the vibration of the bridge tower.

Study for reasonable value of friction coefficient between main cable and saddle

The value of friction coefficient between the main cable and saddle, relates to not only the anti-slippage stability of three-tower suspension bridge, but also the reasonable stiffness of the middle tower and the magnitude of rigidity of the whole bridge. First, the paper does some comparative studies about the relevant provisions of international norms, and then, summarizes the relevant load test results both at home and abroad. Finally, the paper draws the appropriate anti-slippage safety factor for the most unfavorable load in accordance with international load standards, and discusses the rationality and feasibility of the friction coefficient of 0.2 between main cable and saddle.

The Coupling Effect of Spatial Reticulated Shell Structure with Cables

The spatial reticulated shell structure with cables (RSC) is a kind of coupling working system, which consists of flexible cables, reticulated shell structure (RS) and tower columns. The dynamic analysis of RSC based on the coupling model was carried out. Three kinds of elements such as the spatial bar element, cable element and beam element were introduced to analyze the reticulated shell, cable and tower column respectively. Furthermore, such parameter influences as structural boundary conditions, grid configuration, the span-to-depth ratio and the arrangement of cable system upon structural dynamics were analyzed. The structural vibration modes can be divided into four groups based on some numerical examples. And the frequencies in the same group are very close while the frequencies in different groups are different from each other obviously. It is clear that the sequence of the appearance of the each mode group heavily depends on the comparative stiffness of the tower column system, RS and cables.

六塔单索面矮塔斜拉桥拉索设计研究

六塔单索面矮塔斜拉桥是目前我国比较少见的斜拉桥。从斜拉索选型、斜拉索构造、斜拉索锚固和斜拉索减振等角度对六塔单索面矮塔斜拉桥的斜拉索进行了设计与研究。该桥采用抗拉强度标准值为1 860 MPa的钢绞线斜拉索,每根钢绞线的理论直径为15.2 mm。梁端斜拉索通过锚具锚固在预应力混凝土箱梁的隔板齿块上,而在塔端,采用索鞍分丝管形式将斜拉索锚固在桥塔锚固区。斜拉索在梁端采用粘性剪切型阻尼器进行减振,在塔端采用减振圈减振。为了提高斜拉索的使用寿命和耐久性,在钢绞线斜拉索外表面包裹环氧涂层、防腐油脂和高密度聚乙烯(HDPE)保护套。最后结合未知荷载系数法,对斜拉索索力进行了优化设计,优化后的部分索力虽略有增加,但主梁截面弯矩和应力更加趋于平稳,有利于结构受力。

长阳天池口清江特大桥主拱圈悬臂浇筑斜拉扣挂系统设计

长阳天池口清江特大桥主桥为净跨径242 m的非对称上承式钢筋混凝土拱桥,主拱圈采用单箱单室截面,宽9.5 m、高4.0 m。资丘岸和五峰岸半跨主拱圈各分为24个和21个节段,第1个节段采用支架现浇,其余节段采用斜拉扣挂悬臂浇筑法施工。扣索采用星式和扇形组合方式布置,位于墩顶和扣塔的扣索为星式布置,位于交界墩墩身的扣索为扇形布置,并将墩身上的扣锚索设计成连续索以避免在墩身上搭设张拉平台;扣塔由8根∅800 mm×16 mm钢管组成,两岸扣塔分别高52.68 m和60.12 m;根据锚索最大索力,设计了能承受800 kN张拉力的岩锚索。建立主拱圈悬臂浇筑施工阶段MIDAS Civil有限元模型,对斜拉扣挂系统扣锚索索力进行计算,通过拆除部分扣索和调整扣锚索索力,施工期间主拱圈截面最大拉应力、扣塔最大偏位、主拱圈成拱后线形均满足要求。

桥墩倾斜方向对自浮式防撞装置防护效果影响研究

随着航道上大跨度桥梁的建设愈加广泛,其桥墩在水面附近往往具有一定的倾斜角度。为研究桥墩倾斜方向对自浮式防撞装置防护效果的影响,文章基于装备自浮式防撞装置的2种倾斜方向的桥墩与6000DWT级散货船为研究对象进行非线性有限元仿真碰撞计算,分析桥墩倾斜方向对不同航速船舶撞击下桥墩撞击力、系统能量转换、船艏结构破坏的影响。结果表明:外倾式桥墩受到撞击力更小,其防撞装置通过变形吸收能量更多、防护效果更好。研究成果可为大跨度桥墩设计与防撞装置的开发提供重要的参考价值。

风机柔性塔筒阻尼索减振研究

针对风机柔性塔筒多阶模态振动,设计了一种自锚式阻尼索,将塔筒弯曲振动的转角位移转换为线位移,驱动阻尼器耗能减振。建立了塔筒-阻尼索振动方程,得到了阻尼索为风机塔筒前两阶弯曲振动所提供的附加阻尼比解析解,通过模型试验研究了阻尼器黏性阻尼系数与风机塔筒前两阶模态振动时阻尼索提供的附加阻尼比的关系。研究结果表明:对于塔筒前两阶弯曲振动,阻尼索都能提供较大的附加阻尼比,并且附加阻尼比解析解与试验结果相吻合。基于附加阻尼比理论计算公式,对阻尼索减振性能进行了参数影响分析。

斜拉扣挂悬臂浇筑拱桥扣索力与锚索力确定方法研究

为解决钢筋混凝土拱桥拱圈悬臂浇筑施工过程中,由悬浇节段自重和挂篮重引起的部分拱圈截面拉应力与塔架偏位过大的问题,提出扣索力与锚索力确定方法。该方法基于应力叠加原理和影响矩阵确定扣索力,给出当拱圈截面拉应力不满足要求时的扣索拆除判定方法;提出通过锚索力修正系数主动调控扣索力与锚索力,使塔架产生与拱圈悬浇阶段数值接近、方向相反的偏位,给出能同时满足拱圈应力、塔架偏位和成拱线形要求的扣索力与锚索力的计算流程。以净跨径180 m的混凝土拱桥——毕节白甫河管桥为背景,开展扣索力、锚索力以及锚索力修正系数的计算,对扣索力、锚索力、拱圈应力、成拱线形和两岸塔架偏位的计算值和实测值进行对比验证。结果表明:利用所提方法得到的扣索力、锚索力与实际张拉力最大相差6.02%,该桥施工时,依次拆除5组扣索,使拱圈截面拉应力均满足设计要求;塔架偏位实测最大值为3.3 cm,满足小于最大容许偏位4.0 cm的要求;拱圈截面实测最大拉应力为1.74 MPa,满足小于1.8 MPa的拉应力设计要求,成拱线形与裸拱线形最大偏差为0.5 cm,拱圈线形良好,验证了所提方法的可行性。

常泰长江大桥主航道桥纵向约束索CFRP筋材及成品索试制试验研究

常泰长江大桥主航道桥为主跨1208 m的公铁两用双塔钢桁梁斜拉桥,采用温度自适应塔梁约束体系实现对温度的完全自适应,该体系采用CFRP索作为纵向约束索。CFRP索采用127-∅7 mm扭绞型热挤聚乙烯平行CFRP筋材成品索。为保证CFRP索的质量,首先在工业化生产线上进行CFRP筋材试制及静载拉伸试验,然后在CFRP筋材试制基础上,进行CFRP成品索的试制及静载拉伸试验研究。结果表明:CFRP筋材试拉伸的强度为3099~3886 MPa,拉伸弹性模量为181~201 GPa;CFRP成品索加载至大于100%公称破断索力时,索体内的CFRP筋材未出现开裂、损伤、断丝等现象,锚固体(锚具及铸体)未见异常,拉伸弹性模量大于160 GPa,试验结果均满足相关要求。

大跨度斜拉桥索塔侧壁锚固区受力性能分析

以大跨度斜拉桥主塔索塔锚固区为研究对象,采用Midas FEA NX软件建立索塔锚固区实体有限元模型,并对索塔锚固区空间应力进行分析。结果表明:1)主塔在挂索前后、运营阶段及断索工况下,塔壁横桥向、纵桥向应力均为压应力,预应力配束较为安全合理;2)长索锚固齿块的正上方区域锚后牵拉效应较为突出,设计过程中应加强该区域的配筋,限制其开裂。

G3铜陵长江公铁大桥桥塔基础设计

G3铜陵长江公铁大桥主桥为主跨988 m的斜拉-悬索协作体系桥,桥塔采用钢筋混凝土门形结构。3号桥塔基础比选了钻孔桩基础与沉井基础方案,4号桥塔基础比选了钻孔桩基础与地下连续墙基础方案,综合考虑基础受力性能、经济性、施工风险等,均推荐采用钻孔桩基础方案。3号、4号桥塔塔座高4.5 m,承台分别为厚7 m的圆形-哑铃形和矩形-哑铃形结构,基础分别采用68根和64根φ3.0 m钻孔桩,桩长分别为95 m和79 m,按摩擦桩设计。承台系梁采用ANSYS软件进行实体有限元分析,系梁横向受力主筋、竖向抗剪箍筋采用优化分区配置,满足受力要求。

环境因素影响下钢筋混凝土索塔爬模施工仿真分析方法

为探究爬模施工进程中索塔空间温度场和应力场分布,掌握塔柱线形特性,提出一种索塔爬模施工仿真分析方法.利用Fortran编程语言开发相应子程序,对结构施加复杂温度边界,实现不同节段混凝土水化放热、收缩徐变.利用Abaqus软件对索塔爬模施工过程进行分析.结果表明:施工过程中索塔空间温度分布不均匀,塔柱表里最大温差达25.9℃,向阳面与背阴面温差最大为9℃;考虑温度效应后,塔柱所受拉应力更大,且空间应力分布具有很强的时变性,索塔线形特征与变化规律也发生改变;施工塔顶累积竖向位移先增大后减小,在爬模第16节段达到最大值20.5 mm;施工过程塔顶累计顺桥向和横桥向位移更大,最大值分别为6.5和22.3 mm.

机动中波天线技术研究

本文提出了利用机动升降塔作为支撑,搭载轻型导电缆绳作为中波天线发射体,解决了传统中波单塔天线受高度、重量、对地绝缘等因素制约难以实现机动的问题。该机动天线可采用拖车进行运输,方便架设,可实现大功率、高效率的本地覆盖或天波覆盖,是中波天线解决机动、高效问题的创新技术,在中波应急广播领域具有一定的推广应用价值。

钢拱塔斜拉桥的温度耦合效应和索力预测

钢拱塔斜拉桥的受力体系与传统斜拉桥有所不同,为研究环境温度变化对这种异形桥塔斜拉桥主要受力部件的影响,以某钢拱塔斜拉桥为工程背景,首先基于在线监测获取的环境和部件温度数据,分析斜拉索索力、拱塔倾角和主梁应变的温度时变效应;然后以斜拉索为研究对象,通过该桥的有限元模型升降温模拟,分析各部件温差引起的温度耦合效应对拉索索力的影响;最后以环境温度、主梁温度、桥塔温度为输入,索力为输出,利用长短期记忆神经网络对实测索力-温度数据进行映射,实现数据压缩和特征提取,建立温度-索力预测模型,再对网络模型输入新的温度监测数据,以预测索力。研究结果表明:主梁和钢拱塔温度变化具有周期性,且滞后于环境温度;主梁应变与环境温度的变化趋势基本一致但具有一定的滞后性,环境温度变化对拱塔倾角的影响很小且没有周期性规律;索力与环境温度呈线性负相关,且需要考虑斜拉桥各部件的温差所引起的温度耦合效应;长短期记忆神经网络对带有时序特性的数据训练效果好,建立的温度-索力关系模型准确度高,可用于该桥索力的实时预测。

桥梁刚度变化对高速铁路独塔斜拉桥车⁃桥耦合振动的影响分析

以高速铁路独塔斜拉桥为研究对象,建立车-轨-桥耦合系统的空间多体动力学分析模型,开展高速铁路斜拉桥的车-轨-桥耦合振动的仿真分析。通过改变材料弹性模量的方式调整桥塔和主梁刚度,研究桥梁刚度变化对桥梁车-桥-耦合振动的影响规律。研究结果表明,随着桥塔刚度的增大,主梁跨中竖向和塔顶纵向位移响应逐渐减小,其峰值减幅分别为7.57%和10%;随着主梁刚度的减小,主梁跨中竖向位移和塔顶纵向位移峰值呈逐渐递增趋势,主梁刚度变化对车体竖向加速度和Sperling竖向舒适度指标影响相对较大;相比于桥塔刚度的变化,主梁刚度变化对车-桥振动响应的影响更大;整体上,列车运行的安全性和平稳性指标满足规范要求。

鲜花湖特大桥主桥设计研究

鲜花湖特大桥是G4222和县至襄阳高速公路舒城(千人桥)至金寨(皖豫界)段的主要控制性工程之一。主桥采用(118+220+118)m预应力混凝土部分斜拉桥,塔梁墩固结体系;上部结构采用单箱三室大悬臂斜腹板宽幅箱形主梁,人字形主塔,单索面扇形、横向双排布置斜拉索;下部结构结合现场环境,采用X形双肢薄壁墩、群桩基础。鲜花湖特大桥主桥构造新颖美观,融合了结构设计与景观需求。通过系统介绍该桥设计方案、结构和主要计算结果,以供同类项目参考。

斜拉桥V形钢塔-混凝土基座结合构造方式比选

某人行景观桥为空间异型钢塔斜拉桥,主塔中2根箱型钢柱在四棱台混凝土基座上方交汇呈非对称V形,钢柱轴线与其底端钢-混连接面不垂直,基座尺寸严格受制于河道防洪要求,使塔根-基座结合部构造方式设计具有挑战性。按照造价相当的标准初步拟定3种结合方案,采用ABAQUS软件分别建立相应的有限元模型,选取塔底支座反力中平面内外弯矩绝对值相加最大的组合进行模拟计算及其结果比较和对标检验。研究结果表明:承压-传剪组合式结合部可以大幅度减小桥塔根部、基座及其中锚箱的应力,使其合理满足相关规范要求。就塔根最大位移和应力幅而言,均为传剪式最大、组合式最小。组合式方案中承压板厚度较承压式减小1/3,应力虽有上升却未超限,材料利用率提高。承压式、特别是传剪式构造方案中,混凝土基座最大主拉应力远超规范限值,无法满足抗裂要求。传剪式方案中锚箱钢板Mises应力也超限22%,且与其竖向压应力和混凝土主拉应力的最大值处于同一位置。传剪式方案不适用的原因是,锚箱中侧面竖板间距太小,矩形板与柱壁连接屈从于不利构造特点,形成大转折。无论应力大小还是变形控制,组合式方案都值得优先选择。研究成果直接服务于本工程,对类似工程也有一定的参考价值。

基于调研数据的部分斜拉桥设计关键参数研究

针对部分斜拉桥设计关键参数缺少足够规范指导的问题,通过对国内外的部分斜拉桥进行设计主要参数调研统计,并与现有相关规范、科研成果进行对比研究,讨论了部分斜拉桥各型结构体系适用性、拉索布置形式,总结给出拉索倾角和间距、边主跨比、塔跨比、索梁刚度比和无索区长度等重要设计参数取值范围。结果表明,拉索倾角一般为11°~35°,主梁上拉索间距一般采用3.5 m~8 m,塔上的拉索间距一般采用0.5 m~1.2 m;3跨布置时,边主跨比一般集中在0.41~0.70,塔跨比宜采用1/3~1/13,索梁刚度比宜小于30;主跨跨中无索区长度与跨径之比宜取0.06~0.21。