关于OVM250平行钢绞线拉索体系的抗疲劳及耐久性技术研究

随着现代大跨度斜拉桥的发展,由于平行钢绞线拉索（PSC）是现场逐根组装的,在制索、输送、吊装、牵引、张紧等过程中均无需大型设备等优点,且拉索防腐蚀性能优良,因此越来越受到设计人员的青睐。作为承重部件,拉索被称为斜拉桥的生命索,其可靠性和耐久性是决定斜拉桥安全性和使用寿命的关键因素。根据国际推荐规范中的要求,对拉索疲劳、防腐和振动控制进行了深入研究,优化了OVM250 PSC系统,研究成果已成功应用于多个斜拉桥工程。     

大跨度斜拉桥拉索安全性分析方法研究

斜拉桥的斜拉索在运营期间的安全是斜拉桥结构安全的最重要条件之一,对斜拉索安全性的分析显得至关重要。考虑构成平行钢丝束斜拉索的高强钢丝本构行为的不均匀性和钢丝之间的相互影响,将Matteo的钢丝延脆性模型和MonteCarlo仿真方法相结合,建立斜拉索的强度模型,并从可靠度观点出发分析了斜拉索在桥梁运营条件下安全系数的变异和演化特性,并提出断丝率随服务期演化的线性经验公式来描述拉索的退化问题。在此基础上提出了大跨度斜拉桥拉索安全性分析的工程方法,并以招宝山大桥最长索为例,详细阐述了分析过程,该方法为斜拉桥拉索的安全评估与剩余寿命估算提供了依据。     

大跨斜拉桥拉索内外置阻尼器选型实例研究

随着斜拉桥跨径的增大,拉索逐渐变长,其内阻尼低、固有频率分布广的特点越来越突出,在外界因素的激励下拉索易发生振动,因此有必要选择合适的拉索阻尼器进行减振控制.本文研究了多座国内外具有代表性的大跨度斜拉桥的内外置阻尼器的选用情况,对拉索阻尼器的选型特点进行分析,结果表明:具有较大索力和较短长度的斜拉索通常使用内置阻尼器,...     

基于定期检测与遗传算法的大跨度斜拉桥损伤识别

为了对运营中的斜拉桥进行安全性评估,首先需要根据实桥测试结果对结构损伤进行初步识别。在斜拉桥定期索力检测与主梁关键截面的应力监测结果的基础上,提出斜拉桥损伤识别的遗传算法,并编制了复杂结构损伤识别的遗传算法程序,通过各期结构检测结果之间的变化来反演检测期间结构参数的变化,据此识别结构损伤位置与程度,保证了在结构参数化有限元模型存在识别误差的情况下也能得到正确的损伤识别结果。宁波招宝山大跨度预应力混凝土独塔斜拉桥的损伤识别仿真结果表明,本文方法和程序具有较高的识别精度,并可推广应用于其它复杂结构的损伤识别。     

大跨斜拉桥索力监测研究——以乌江二桥为例

大跨斜拉桥拉索索力状态是衡量桥梁是否处于正常运营状态的一个重要标志。本文首先对斜拉桥拉索索力监测的方法和原理进行了阐述;然后,结合乌江二桥对监测系统、索力监测的设计做了介绍;最后对乌江二桥索力监测的结果进行了分析,从而对拉索索力的状态进行了评估,为斜拉桥桥梁状态的评估提供了依据。     

Damage identification of a large-span concrete cable-stayed bridge based on genetic algorithm

The global stability of a structure, the stiffness of its main girder and concrete tower, and the variation of the forces of its stay cables are key issues to the safety assessment of an in-service cable-stayed bridge. The efficiency and rationality of local elaborate non-damage-identification could be enhanced by the primary damage identification of cable-stayed bridges on the basis of periodic detection of the cable force and strain monitor in key sections of the main girder. The genetic algorithms of damage identification for cable-stayed bridges were investigated in this paper on the basis of the monitor data of the cable force and strain in a key section of the main girder. A damage detection program for complex civil structure was generated to implement the identification of damage location and extent. The deterioration of the structure was calculated according to the variation of monitor data. It is demonstrated that the results of damage identification from the parametric finite element method are accurate. The method had been verified using a long-span concrete cable-stayed bridge in Ningbo, which has been in use for the past four years. Translated from China Civil Engineering Journal, 2006, 39(5): 85–89 [译自: 土木工程学报]     

Drag loading of circular cylinders inclined in the along-wind direction

The drag wind loading on the stay cables of long cable-stayed bridges is discussed based on two recent long-span cable-stayed bridge designs. For wind along the bridge, the available design literature on cable drag coefficients either do not cover the actual cable configurations or are too conservative. Therefore, some simple design values had to be devised. These design values for the cable drag coefficient are then compared with measured drag coefficients for various types of cable surface treatments introduced to suppress rain-wind vibrations. A modified expression depending on cable diameter and inclination is also proposed and the applicability of the expression is discussed.     

Influence of Stabilizing Cables on Seismic Response of a Multispan Cable-Stayed Bridge

Abstract:   A recent trend in the design of long-span bridges is multispan cable-stayed bridges with three or more towers. A critical problem of multispan cable-stayed bridges is the stabilization of the central tower(s), which has resulted in increasing application of stabilizing cables. The Ting Kau Bridge in Hong Kong is one of a few multispan cable-stayed bridges adopting stabilizing cables ever built. In this article, the dynamic properties of multispan cable-stayed bridges with stabilizing cables and the effect of stabilizing cables on bridge seismic response are studied by referring to the Ting Kau Bridge. Based on a validated 3D finite-element model, modal analysis is conducted which shows that the longitudinal stabilizing cables bring about a number of global modes with strong modal interaction among the deck, towers, and cables. The seismic response and internal force in the central tower are found to be much larger than those in the side towers. The longitudinal stabilizing cables are very effective in reducing the internal force in the central tower generated by longitudinal earthquake excitation, but insignificantly affect the seismic response in the bridge deck and side towers. As a whole, the stabilizing cables act favorably in the reduction of seismic response of the bridge.     

OVM250钢绞线斜拉索锚固系统可靠性研究

随着现代大跨度斜拉桥的发展,钢绞线斜拉索采用现场制索,具有无需大型制索、运输、吊装和张拉牵引设备、拉索的整体防护性能优越等优势,已越来越受到设计者的青睐。钢绞线斜拉索作为斜拉桥的承重构件,堪称斜拉桥的生命索,其可靠性是决定斜拉桥安全可靠的关键因素之一。文章主要介绍了OVM250钢绞线斜拉索体系设计改进过程中对拉索锚固系统的可靠性研究,通过有效提高拉索锚具组件的疲劳性能的设计手段,对拉索锚固单元进行优化设计,保证拉索锚具组件的安全可靠,通过OVM250-139拉索锚具组件的疲劳试验,进一步验证了OVM250钢绞线拉索体系优异的抗疲劳性能。     

非对称独塔斜拉桥施工监控斜拉索张拉方案研究

由于斜拉桥结构较为复杂,为了使桥梁实际施工状态接近于理想状态,桥梁在施工建设过程中必须进行严格的监测与控制。本文以浙江省金华市金婺大桥为研究背景,该桥为非对称独塔斜拉桥,桥塔两侧主梁跨径及材料不同,在斜拉索张拉过程中,主梁空间效应显著且易产生不平衡力矩。对斜拉索张拉方案开展研究。研究结果显示,相比于斜拉索一次张拉方案,采用二次张拉方案时,桥梁的应力状态、索力等指标较好,满足施工监控要求。     

大跨度混凝土斜拉桥模态试验技术研究

随着大跨度斜拉桥建设的迅速发展,试验模态分析对于验证设计、建立结构动力学模型以及桥梁安全运行的状态评估具有重要意义。斜拉桥是由索、梁和塔三种受力特点完全不同的构件组成的组合体系,尤其是混凝土斜拉桥由于恒载内力较钢斜拉桥大很多,且振动信号衰减更明显,其模态试验比其它桥型更加困难。本文通过研究混凝土斜拉桥的模态参数特点,发展了一种包含两种方式基于环境激励的桥梁模态试验方法(UINO法),提出了利用互功率谱法进行模态参数识别的分析技术,并以此为基础开发了桥梁模态试验专用软件系统QL-SYMT。通过多座大跨度混凝土斜拉桥的模态试验证明,该系统不仅能有效识别出桥梁的模态参数而且方便易行。     

Influence of fatigue on cable arrangement in cable-stayed bridges

Cable arrangement in cable-stayed bridges is one of the key issues in optimizing the design of this typology of bridges. Oscillating axial forces in the cables due to vehicular loading is usually the parameter on which attention of the designer is focused. The cables are particularly vulnerable to fatigue phenomena but the variation of axial forces in hangers depending on load configuration and cable arrangement was not deeply studied despite the fact that it is an important parameter in relation to the fatigue behaviour of the overall bridge. In this context, this paper mainly deals with the influence of fatigue on cable arrangement in cable-stayed bridges. The analysis is carried out by performing moving load analysis along the deck, and a parametric analysis of cable arrangement. Moreover, a lifetime assessment considering different corrosion propagation in cables is shown.     

Parametric oscillation of cables and aerodynamic effect

This paper addresses the aerodynamic effect on the nonlinear oscillation, particularly parametric vibration of cables in cable-stayed bridges. A simplified 2-DOF model, including a beam and a stayed cable, is formulated first. Response of the cable under global harmonic excitation which is associated with wind speed is obtained using the multiple scales method. Via numerical analysis, the stability condition of the cable in terms of wind speed is derived. The method is applied to a numerical example and a long-span bridge to analyze its all stay cables. It is demonstrated that very large vibration at one of the longest cables in the middle span of the bridge can be parametrically excited when the wind speed is over around 210 km/h (58.5 m/s).     

斜拉索病害及其养护维修

在国内,斜拉桥以其跨越能力和独特的美观效果在近二十年内得到长足的发展和广泛的应用。然而,由于斜拉桥结构体系本身的复杂性、材料本身的缺陷,施工技术、方法、质量问题,环境腐蚀,车辆超载及运营期养护管理不到位等因素,使得已建成的斜拉桥的拉索或多或少地出现各种病害。这不仅影响了桥梁的使用性能和正常运营,甚至会降低桥梁主体结构安全余地,给桥梁带来安全性方面的隐患和耐久性方面的缺陷。本文先对我国现有的斜拉桥拉索病害情况进行较详细的调查分析,归纳总结斜拉桥拉索的使用现状及主要病害如PE护套开裂,索丝腐蚀断裂,锚具腐蚀、疲劳开裂等,并对病害的产生原因进行分析。在此基础上,提出相应的包括设计、建设中的建议,运营和管理阶段的养护维修策略和措施。     

斜拉索的换索施工技术

斜拉桥在国内建设越来越多,随着斜拉索使用年限到来,为了延长桥梁的使用寿命,需要对斜拉索进行更换。本文着重介绍柳州壶西大桥的斜拉索更换施工技术。该桥为预应力混凝土独塔双索面斜拉桥,跨径2×120米。斜拉桥上部结构为板梁式结构,两边对称布置26对扇形拉索,共104根。换索施工过程包括:旧索放张,拆除;新索安装、张拉;新索锚固区域防腐;施工测量(索力、标高、位移)。     

应用碳纤维缆索的大跨度悬索桥抗风稳定性研究

为了探讨碳纤维复合材料缆索在大跨度悬索桥中应用的可能性,以主缆等轴向刚度为原则,拟定了一座主跨为1490m的碳纤维复合材料主缆悬索桥,并运用三维非线性计算理论进行了空气静力和动力稳定性分析。通过与同跨度钢主缆悬索桥的比较,讨论了不同主缆材料对大跨度悬索桥抗风稳定性的影响。分析结果表明:大跨度悬索桥采用碳纤维复合材料主缆后,静风作用下结构的变形增大,但其静风稳定性却与钢主缆悬索桥基本接近;由于结构自振频率特别是扭转频率有显著的提高,使得其空气动力稳定性要比钢主缆悬索桥好。因此从抗风稳定性角度而言,大跨度悬索桥采用碳纤维复合材料主缆是可行的,但是主缆截面尺寸的确定应采用等轴向刚度的准则。     

异型钢结构单塔宽幅箱梁斜拉桥设计分析

以山西省长治市神农湖大桥为例,介绍独塔斜拉桥的总体设计思路及主要构件,包括索塔、索塔锚固系统、主梁、斜拉索;并对主桥整体和索塔锚固系统进行静力分析。结果表明,主桥整体结构在成桥状态和施工阶段均满足规范要求,且索塔锚固系统设计合理。研究成果可为同类桥梁的设计、计算提供建议和参考。     

Reliability assessment of cable-stayed bridges based on structural health monitoring techniques

This paper presents the reliability analysis approach of long-span cable-stayed bridges based on structural health monitoring (SHM) technology. First, the framework of structural reliability analysis is recognised based on SHM. The modelling approach of vehicle loads and environmental actions and the extreme value of responses based on SHM are proposed, and then models of vehicle and environmental actions and the extreme value of inner force are statistically obtained using the monitored data of a cable-stayed bridge. For the components without FBG strain sensors, the effects and models (extreme values) of dead load, unit temperature load, and wind load of the bridge can be calculated by the updated finite element model and monitored load models. The bearing capacity of a deteriorated structure can be obtained by the updated finite element model or durability analysis. The reliability index of the bridge's critical components (stiffening girder in this study) can be estimated by using a reliability analysis method, e.g. first order reliability method (FORM) based on the models of extreme value of response and ultimate capacity of the structure. Finally, the proposed approach is validated by a practical long-span cable-stayed bridge with the SHM system. In the example, reliability indices of the bridge's stiffening girder at the stage after repair and replacement after 18 years of operation, and the damaged stage are evaluated.     

Risk assessments of long-span bridges considering life-cycle cost concept and near-fault ground motion effect

The influence of the near-fault ground motion on the response of long-span bridges must be considered as a critical factor for seismic design because the response indicates different aspects from existing earthquake characteristics. Also, it is important to note that the safety index for the risk assessment of long-span bridges is determined based on the minimum expected life-cycle cost E(LCC). In this study, earthquake characteristics are analyzed by creating elastic and inelastic response spectrums with actual measurement records (Chi-Chi earthquake records) and then the numerical analysis of the long-span bridge in Namhae, Korea is performed according to the increase and reduction of the member stiffness based on the standard design., the reliability evaluation of the long-span bridge considering aleatory uncertainties is performed on the basis of the combined results of static analysis and seismic response analysis. Also, the minimum LCC is estimated based on failure probabilities by the different alternative design. Because of epistemic uncertainties, the results of reliability evaluation and the LCC of optimal design are selected as random variables; the safety index, failure probability and expected minimum LCC are re-evaluated with regard to critical percentage values for a risk-averse design of the long-span bridge, and are presented graphically using cumulative percentages. It is, therefore, expected that this study will provide the basic information for the risk assessment and optimal design method in performing seismic design of the long-span bridge considering earthquake characteristics.     

漳州战备大桥斜拉索挂设

漳州战备大桥斜拉索采用OVM200型平行钢绞线拉索体系。本文介绍了该斜拉索挂设安装及斜拉索的等值张拉工艺,为部分斜拉桥的施工和评定提供经验数据。