Research on reasonable value of target reliability index for steel main girder of cable-stayed bridge considering durability

Abstract

This article studies the relationship between the target reliability index and the design life of the main girder of a long-span cable-stayed bridge to provide a theoretical basis for the design of steel girders for such an application. The changes of the bending section modulus under atmospheric corrosion and the residual ultimate stress of the section of a steel box girder under alternating loads are discussed. A resistance attenuation function for a steel girder of a cable-stayed bridge to predict the resistance change of a steel box girder over the service period is proposed, and the change characteristics of the time-varying reliability index of a steel box girder of a cable-stayed bridge are studied. By analysing the relationship between the time-varying reliability index and the evaluating benchmark value of the reliability index, the time point of maintenance and reinforcement is predicted. Based on the change over time of the difference between the time-varying reliability index and the evaluating benchmark value of the reliability index, the relation function between the target reliability index and the service lifetime of a bridge considering resistance attenuation are provided.     

基于应力指标的PC连续梁桥配束优化方法

传统的PC连续梁桥配束设计方法是比较繁琐的以试算为主获得可行解的方法,且现有可获得最优解的优化研究方法在结构受力方面存在欠缺。文章结合同济大学桥梁工程系混凝土桥梁研究室近年来在桥梁精细化设计方面的研究,针对配束问题提出了基于应力指标的PC连续梁桥配束优化方法。文章首先总结并选择合理布束形式,然后建立配束问题的数学优化模型,在满足规范和施工可行性条件下,利用遗传算法进行优化求解。既实现了配束的正向设计,又可以得到较优的方案。最后利用该方法实现了一座三跨PC连续梁桥的配束优化,验证了方法的合理性。     

Ultimate strength reliability analysis of corroded steel-box girder bridges

Structural reliability theory is a useful tool for estimating the risks associated with deteriorating structures. The aim of this study is to develop and demonstrate a procedure for the assessment of box girder bridge ultimate strength reliability with the degradation of plate members due to general corrosion taken into account. A probabilistic model for ultimate steel-box girder strength is established on the basis of an analytic formula that considers corrosion-related, time-dependent strength degradation. The study involves the selection of representative structures, formulation of limit state functions, development of resistance models for corroded steel-box girders, development of load models, development of a reliability analysis method, reliability analysis of the selected bridges and development of the time-dependant reliability profiles, including deterioration due to corrosion. The results of this study can be used for the better prediction of the service life of deteriorating steel-box girder bridges and the development of optimal reliability-based maintenance strategies.     

我国桥梁钢结构的应用现状与展望

随着公路、铁路的大规模发展,我国已成为桥梁大国.列举了世界前5名已建成的大跨度斜拉桥、拱桥、梁式桥和悬索桥.我国是钢铁大国,但钢桥建设发展缓慢,应该顺应我国钢铁产业的发展,适时发展钢、钢-混凝土结构桥梁.波形钢腹板PC箱梁桥与传统PC箱梁桥和混凝土钢板箱梁桥相比,具有更好的力学性能,因此它是钢-混凝土组合梁桥应用的首选.     

锈蚀钢箱梁桥的极限强度分析

结构可靠性理论可有效地评估结构老化的程度。通过研究给出一个程序,用于评估存在部分腐蚀板构件的钢箱梁桥的极限强度的可靠性。基于腐蚀和强度衰减的解析式,提出一种确定钢箱梁极限强度的概率模型。研究内容包括典型结构选型、极限状态方程、腐蚀钢箱梁抵抗模型的发展、可靠性分析法的发展、选定桥梁的可靠性分析和可靠性时程曲线的发展,以及腐蚀引起的结构退化。研究结果较好地预测退化钢箱型梁桥的使用年限和可靠性设计优化方案的发展。     

预应力混凝土连续箱梁桥设计改进的要点

分析了预应力混凝土连续箱梁桥混凝土结构开裂产生的规律及形成机理,从预应力混凝土连续箱梁桥的设计着手,分析结构裂缝产生的原因,提出了改进预应力混凝土连续箱梁桥的设计建议。     

四跨非对称PC连续箱梁桥预应力钢束优化设计

以广州永和大道跨线桥为工程背景,对4种预应力钢束布置方案的正截面拉应力及斜截面主拉应力进行了计算比较分析,得出了几点关于四跨非对称预应力混凝土连续箱梁桥的钢束优化思路。     

Ultrasonic C-Scan Imaging of Post-Tensioned Concrete Bridge Structures for Detection of Corrosion and Voids

Abstract:   Corrosion of the nation's transportation infrastructure is a widespread and costly problem. Efficiency, durability, safety, and environmental concerns have made the inspection and structural assessment of these structures a vital issue. The current state of the art in concrete bridge condition evaluation relies on visual inspection. However, deterioration in pre-stressing/post-tensioned strand or tendon condition is not always reflected by distress visible on the concrete surface. Further, the effect of deterioration of pre-stressing/post-tensioned steel is more disruptive than that of mild reinforcement. Strand, due to its high mechanical strength and metallurgical characteristics, is smaller in cross section than conventional reinforcing steel and is proportionally more impaired by loss of section. Methodology for pre-stressed concrete bridge condition evaluation, therefore, could be revolutionized through the development of accurate, quantitative nondestructive test methods for strand in pre-tensioned and post-tensioned structures. This article presents a new sensing method using ultrasound C-scan imaging for structural health monitoring of post-tensioned bridges. Preliminary results from tests are presented that show promising potential for the detection of corrosion and voids in concrete post-tensioned bridges.     

波折钢腹板组合箱梁桥承载能力试验研究

为研究波折钢腹板组合箱梁桥在承载能力极限状态下的受力性能,以某路桥建设总公司研发的一种装配式波折钢腹板简支箱梁为研究对象,进行波折钢腹板组合箱梁承载力试验。通过在组合箱梁桥跨中及距跨中3.33m的位置非同步分级加载,测量不同截面在各级荷载工况下的应变,进而分析鉴定箱梁实际的极限承载能力,为类似桥梁的极限承载能力试验提供参考。     

后张法箱梁预制施工技术

结合箱梁预制是桥梁施工中的重要工程,对其主要工序包括模板支设、钢筋绑扎等施工进行了分析探讨,并针对其特性指出应加强施工管理,严格控制各工序施工,从而保证后张法箱梁预制施工的质量。     

Time-variant reliability profiles for steel girder bridges

Evaluation of existing steel bridges becomes more important due to natural aging, increasing load spectra, deterioration caused by corrosion, and other problems. In the result, bridge structures exposed to aggressive environmental conditions are subjected to time-variant changes of resistance. Therefore, there is a need for evaluation procedures for an accurate prediction of the load carrying capacity and reliability of bridge structures, in order to make rational decisions about repair, rehabilitation, and expected life-cycle costs. The objective of this paper is to develop time-variant reliability models for steel girder bridges. Traditional methods based on deterministic analysis do not reveal the actual load carrying capacity of the structure. The proposed approach is based on reliability analysis of components and structural systems. The study involves the selection of representative structures, formulation of limit state functions, development of load models, development of resistance models for corroded steel girders, development of the reliability analysis method, reliability analysis of selected bridges, and development of the time-dependant reliability profiles including deterioration due to corrosion. The results of the study can be used for a better prediction of the service life of deteriorating steel girder bridges, and development of optimal reliability-based maintenance strategies.     

Bridge design with reserve and residual reliability constraints

System reliability is evolving as an important design method for selecting components and topology. It should be used to investigate the original intact structure behavior as well as providing sufficient reserve capacity under likely accident and damage scenarios. Highway bridges are an area of special concern since effort to optimize the cost of construction may not provide adequate redundant capacity. The paper describes an example in which a typical girder bridge structure is optimized (both size and girder spacing) to achieve target system performance. System reliability constraints are imposed on the behavior of the intact structure under highway loads. Also, residual system reliability constraints are imposed to control safety under specified accident scenarios corresponding to damage and “lost” members due to corrosion, fatigue, fire or accidental collisions. An optimal design framework for controlling safety under all these life cycle situations is thus provided.     

大跨连续刚构预应力混凝土箱梁温度效应分析

介绍了大跨连续刚构预应力混凝土箱梁在两种温度场下温度效应,重点分析非线性温度梯度下混凝土箱梁的温度效应,通过对比实测和JTG D60-2004公路桥涵设计通用规范的温度梯度模式,指出规范的温度梯度模式不足,提出了预防连续刚构箱梁温度效应的措施。     

专用移动支架式造桥机建造PC箱形简支梁

结合神延铁路秃尾河特大桥利用移动支架式造桥机建造32／64mPC箱形简支梁的施工实例，介绍了利用移动支架式造桥机制梁的施工方法，成功地完成了同类桥梁中最大跨度桥梁的施工。     

某无粘结预应力混凝土箱型梁的承载力分析

为正确评价某立交桥的承载能力,对其中的一跨无粘结预应力混凝土箱型梁进行了现场静载试验。建立了梁的有限元计算模型并基于静载试验结果验证了模型的正确性,论证了利用该模型对梁进行弹塑性全过程分析的可行性。然后模拟了构件在不同荷载作用下加载直到破坏的全过程。得到了梁的荷载-挠度曲线、荷载-预应力增量曲线以及开裂荷载、极限荷载等,为立交桥承载能力的评定提供了参考依据。     

波形钢腹板预应力混凝土组合箱梁扭转与畸变研究进展

有别于传统的混凝土箱梁,波形钢腹板预应力混凝土组合箱梁是一种较为新颖的桥梁上部结构形式,这种箱梁结构在偏心荷载作用下产生的扭转与畸变效应相对显著。为阐明这种箱梁的扭转与畸变特性及其研究现状,通过对大量文献的调研与实桥调查,系统介绍了箱梁扭转与畸变效应的计算理论（包括抗扭刚度）、扭转承载力、内力增大系数、横隔板的设置等方面的研究进展情况。研究表明,采用Umanski第二理论和弹性地基梁比拟法分别计算这种箱梁的扭转与畸变效应在理论上是可行的,但其工程适用性还需进行进一步检验。另外,我国在扭转承载力研究方面还较为欠缺,而在内力增大系数、横隔板的设置等方面尽管已经取得了一些成果,但还缺乏较为一致的结论。在充分考虑箱梁自身受力特性的基础上,加强波形钢腹板预应力混凝土组合箱梁扭转与畸变的研究,可为完善其设计方法奠定理论基础与提供更有力依据。     

基于ANSYS的桥梁施工健康监测研究

桥梁监测可以为控制大型桥梁的施工提供决策依据,为验证结构分析模型、计算假设和设计方案提供反馈信息。文中结合跨度为170.2m的某高速钢箱梁进行了结构健康监测技术研究。根据施工控制的理论和方法,以通用有限元软件ANSYS为平台,建立连续钢箱梁的空间有限元模型,模拟分析连续梁的顶推施工过程,计算梁在各个危险截面的变形和应力,以确保成桥状态符合设计要求。     

基于可靠度的组合桥梁设计及维护策略(英文)

Currently,the design practice of highway bridges around the world are moving towards limit states design,a reliability-based design procedure.Canadian Highway Bridge Design Code(CHBDC)is the first design code entirely developed based on limit states design philosophy,including foundations and FRP components.However,reliability of a structure decreases in service due to environmental attacks and material deterioration such as fatigue,corrosion and many other reasons.Therefore,the structure should be inspected periodically,and the reliability of the structure should be evaluated according to its age and field data.If its reliability is reduced to a certain level,a repair should be scheduled as well as some preventive maintenance measures should be implemented to prevent further deterioration.Recently,many research works have been conducted to investigate reliability-deterioration mechanisms for each type of infrastructure and its components,optimize the inspection and maintenance strategy,predict remaining service life,estimate its life cycle cost.This paper is focused on the study of reliability-deterioration mechanisms of slab on steel girder bridges due to fatigue and corrosion of steel girders as well as corrosion of reinforcement in the deck slab.Examples will also be given to illustrate the proposed life cycle management strategy for composite slab on steel girder bridges.     

某人行索桥方案研究

通过对钢箱梁斜拉桥及钢箱梁吊桥两个方案的综合比选,确定采用钢筋吊桥方案,并对桥梁的总体布置要求进行了介绍,主要阐述了钢梁、主缆及吊索等结构设计要点,为同类桥梁设计选型提供了参考。     

Nagisa桥的施工及实桥荷载试验——PC斜拉桥与钢悬索桥的混合构造

Nagisa桥是世界上首次应用预应力混凝上斜拉桥与钢筋箱梁悬索桥组合结构的混合式PC斜拉桥，本文介绍其施工方法及完桥荷载实验情况。