采用近似法估算钢斜拉桥极限荷载

给出新的估算钢斜拉桥极限荷载的简便方法。采用新的用于迭代特征值计算的收敛准则来考虑斜拉桥系统中的梁-柱效应。采用新方法分别估算中等跨度和大跨度模型的极限荷载,并与非线性非弹性分析方法进行比较。结果显示,新方法能很方便的替代复杂的非线性非弹性分析而近似评估钢斜拉桥的极限荷载和失效模式。     

Nonlinear Analysis of Steel Cable-Stayed Bridges

Abstract:   In this study, a nonlinear inelastic analysis model using a softening plastic-hinge approach is proposed for predicting the ultimate load-carrying capacity of steel cable-stayed bridges. The ultimate load-carrying capacity analysis is done starting from the initial shape determination due to bridge dead load. The proposed model can consider both geometric and material nonlinearities in the nonlinear inelastic analysis for the example bridges. The load–displacement curves of the example bridges predicted by both the proposed model and the commercial code ABAQUS are compared with each other to verify the accuracy of solutions. Identical solutions between them are found. A parametric study on the example bridges is presented and their ultimate behavior is discussed.     

Static analysis of cable-stayed bridge with CFT arch ribs

A new type of cable supported bridge, cable-stayed CFT arch bridge, was proposed and its static strength was studied in this paper. Arch ribs consist of concrete filled steel tubes (CFT). CFTs have high resistance against bending moments and compressive axial forces and are ideal as arch ribs. A cable-stayed CFT arch bridge with a main-span of 300 m was designed and the safety of its structural members was checked by the limit state design method. Large deformation analysis was used to obtain sectional forces. The CFT arch ribs and the steel box girders and towers of the designed bridge satisfied the required safety criteria for ultimate design loads. The applied loads were further increased until the bridge collapsed when the arch ribs buckled. The amount of steel required for the cable-stayed CFT arch bridge was significantly lower than that for the cable-stayed bridge. It has been found that the proposed cable-stayed CFT arch bridge is feasible and potentially economical.     

Static and seismic studies on steel/concrete hybrid towers for multi-span cable-stayed bridges

A new type of hybrid high tower is proposed and applied to a multi-span cable-stayed bridge. This is basically a sandwich type structure and consists of a steel double box section filled with concrete. The filled concrete increases its strength due to the confined effect and the steel plates increase the resistance against local buckling because the deformation is restricted by the filled concrete. Therefore, this hybrid tower is expected to have high bending and compressive strength, and also a good ductile property. First, static analysis is conducted for different live load intensity and distribution because the multi-span cable-stayed bridge is a new structure and its static behavior is not fully understood. The live loads distributed in alternate spans give larger bending moment of the towers than the live loads distributed in full spans. Towers with three different heights are also studied, showing that the higher tower produces smaller displacements and bending moments. Safety of the tower is checked by the limit states design method. Serviceability is not a major problem for the hybrid tower. Second, seismic analysis is carried out for a multi-span cable-stayed bridge subjected to the medium and ultra-strong seismic waves specified in Japanese Seismic Code for Highway Bridges. Three support conditions of the girder at the tower cross beams are compared: movable, connection with linear springs and bi-linear springs. Bi-linear springs are very effective in reducing the dynamic displacements and bending moments of the towers. Restorability of the composite tower is checked when an ultra-strong seismic wave hits the model bridge. This study shows that a new steel/concrete hybrid tower is feasible for multi-span cable-stayed bridges and most effective for seismic forces when the girder is connected with bi-linear springs.     

Stability evaluation of steel girder members in long-span cable-stayed bridges by member-based stability concept

The member-based design concept utilizing the buckling length of each structural member has been widely used to assess the buckling instability of steel structures. Since steel girder members in conventional cable-stayed bridges are generally exposed to large axial forces, the buckling instability of these members should be carefully investigated in the design stage. However, analytical approaches for obtaining the buckling lengths of steel members, such as the alignment chart, story-buckling and story-stiffness methods, may not be adopted to cable-stayed bridges because these approaches imply some theoretical assumptions that are adequate only for steel framed-structures. Furthermore, the boundary conditions of steel girder members supporting by cables are obscure to be prescribed in general terms. Numerical eigenvalue analysis may be one of the most excellent candidates for determining the buckling lengths of steel girder members in that this method can handle the interactions among members implicitly without any irrelevant assumptions for cable-stayed bridges. This paper discusses detailed procedures for obtaining buckling lengths of steel girder members in cable-stayed bridges by numerical eigenvalue analysis. In order to avoid the problem of generating excessively large buckling lengths in some girder members having small axial forces, a modified eigenvalue analysis is proposed by introducing the concept of a fictitious axial force. Practical application example for a real cable-stayed bridge is illustrated with some discussions on the effect of the proposed modification and stability evaluation by member-based stability concept.     

混合式桥型对超长跨桥梁的适应性

本文对中跨为2500m的混合型斜拉悬索桥的进行了初步设计,构想了三种斜拉悬索桥和一种悬索桥桥式。从初步设计结果中比较它们上部结构钢材的重量发现,考虑到下部结构尺寸,斜拉悬索桥相对悬索桥具有优越性。另外,对这几种型式的桥梁进行了抗弯稳定性分析以及耦合颤振分析。分析结果表明,斜拉悬索桥抗弯稳定性是足够的,而且其临界风速高于悬索桥的临界风速。所以,作者认为针对超长跨度桥梁混合型斜拉悬索桥赛过悬索桥     

武汉三官汉江公路大桥技术创新

本项目系统研究并设计了大跨度预应力混凝土部分斜拉桥宽幅主梁的合理截面形式,总结了大悬臂加劲隔板箱形截面主梁的受力性能,针对性地提出了宽幅主梁耐久性防裂措施;研发了部分斜拉桥新型单侧双向抗滑锚固系统,模拟实桥进行了单根钢绞线抽换试验,可以使部分斜拉桥的斜拉索真正做到可更换、可检测     

Structural stability of cable-stayed bridges during construction

This paper presents an investigation of the stability characteristics of steel cable-stayed bridges during construction. In general, cable-stayed bridges are subjected to quite large compressive forces induced by stayed cables, and may become unstable during their construction stage, due to the excessive compressive forces induced by added construction loads. To solve the structural instability problems of the bridges under construction, a nonlinear analysis program was developed based on the theory of nonlinear finite element analysis. The complex stability characteristics of cable-stayed bridges during construction were investigated through a series of rigorous geometric nonlinear analyses, including various structural nonlinearities such as cable-sag effect, beam-column effect of girder and mast, large displacement effect, and girder-mast-cable interaction. To consider the construction characteristics of the cable-stayed bridges, a three-step analysis method is proposed, and used in the present study. In addition, the effects of various cable-arrangement types and girder-mast stiffness ratios on the stability characteristics were extensively investigated. Typical buckling modes can be classified into two categories, depending on the location of critical member or members.     

Study of super long span cable-stayed bridges with CFRP components

This paper introduces new types of cable-stayed bridges with carbon fiber reinforced polymers (CFRP) stay cables and/or a CFRP bridge deck. For each of the two CFRP components, namely, CFRP stay cables and CFRP bridge deck, the key design parameters and design strategies were determined and the appropriate value of each key design parameter was suggested. Using the suggested parameter values, six types of cable-stayed bridges with a main span length of 1400 m were selected and modeled with the finite element method, through which the procedures of designing composite cable-stayed bridges with CFRP components were presented in details. From a mechanical-behavior viewpoint (static and dynamic) a comparative study of composite cable-stayed bridges with different CFRP components was performed through numerical simulations. The economical behavior of each type of cable-stayed bridges was also comparatively studied considering the varying material price. With the high strength-to-weight ratio and other advantages of CFRP materials, it was proven in this study that the use of CFRP stay cables and CFRP bridge decks in super long span cable-stayed bridges is feasible and these types of composite cable-stayed bridges could become an excellent alternative to steel cable-stayed bridges where super long spans are desired.     

钢管混凝土主梁斜拉桥构造与设计研究

提出了一种基于钢管混凝土主纵肋的斜拉桥主梁结构,通过计算分析,验证了该结构的合理性,并和同级别跨径的其他类型主梁结构的斜拉桥进行了经济性对比分析。结果显示该结构合理、造价经济、抗震性能优越,特别适用于我国西部高烈度复杂山区地形。     

Computer-Based Bridge Management System for Permit Vehicle Routing

The traffic of special overloaded trucks (special permits) over bridges may create structural problems not only in the time of crossing but also in the service life of the bridge (cracking in concrete bridges affecting their durability, fatigue in steel bridges, etc.). Therefore, the owner agency responsible for a bridge network should look carefully at the maximum loads acting on the bridges and the problems they may cause according to their actual condition. This article presents the work carried out by the authors concerning the possibility of passage permission of overload permits in the main highway network of Spain. Most of the bridges are quite new and very well documented, but also older bridges are present whose documentation is not available. The work is summarized in a bridge management system (BMS) installed on a PC. The computational model performs the structural analysis of the bridges crossed by a defined special vehicle in a quick and automatic way and compares the results with the maximum allowable actions over the bridge, the result being authorization or not of the passage. The computational models are developed for most common bridge types in the network and are of limited value for very complex structures such as cable-stayed or suspension bridges. The BMS is now in use in the complete trunk road system in Spain. The software developed has shown its usefulness in assisting bridge engineers in the decision-making process of permit passage.     

Performance of cable-stayed bridge pylons subjected to blast loading

Since the terrorist attacks of 2001, concern about potential car bomb attacks on buildings and infrastructure such as bridges and tunnels has increased tremendously. Design for better performance of these structures subjected to blast load is important to prevent progressive collapse of the structure and catastrophic loss of lives. The objective of this research was to study the performance of hollow steel box and concrete-filled composite pylons of a cable-stayed bridge subjected to blast loads. Car bomb detonation on the deck is assumed to be the most likely scenario to occur. A coupled numerical approach with combined Lagrangian and Eulerian models was used to consider the interaction of the deck and pylon with the air that transfers the explosion effect to the bridge. The non-linear explicit finite element analysis program, MD Nastran SOL700 was used to simulate the spatial and time variation of the blast load as well as blast shock wave-bridge interaction response. The blast resistance of two different types of pylons was investigated in a comparative study. The study established damage patterns of the pylon and showed superior performance of the concrete-filled composite pylon over the hollow steel box pylon. For the hollow steel box pylon, the P-Δ effect on the instability of the pylon subjected to blast load was significant.     

System reliability evaluation of in-service cable-stayed bridges subjected to cable degradation

Abstract

The cables in a cable-stayed bridge are critical components supporting the long-span girders and ensuring their functionality. However, cables are prone to fatigue damage and atmospheric corrosion, which directly affect the bridge safety. This study presents a framework for system reliability evaluation of in-service cable-stayed bridges subjected to cable degradation. The effect of cable strength degradation on the system reliability is demonstrated through simulation on a parallel-series system representation. Learning machines are utilised to approximate the non-linear and dynamic response functions of critical components due to cable rupture, and the system reliability is finally evaluated from the event tree established by the β-unzipping method. Both short-span and long-span cable-stayed bridges are selected as prototypes to investigate the influence of cable degradation on the system reliability. On this basis it is revealed that cable degradation can significantly influence the collapse mechanism of a cable-stayed bridge and thereby lead to a significant reduction in the system reliability. This phenomenon is associated with cable spacing, where a spare cable system seems more sensitive to cable gradation. It is demonstrated that the consideration of cable corrosion and correlation is essential for lifetime safety evaluation of in-service cable-stayed bridges.     

基于斜拉式人行天桥荷载试验的有限元分析

以某斜拉式钢结构人行天桥结构为研究对象,对其进行了静载试验和有限元分析,得出以下结论:墩柱位置出现压应力,而梁中部则出现拉应力;在最不利形式试验荷载工况下,实测桥墩处箱梁两端压应变最大,在试验荷载作用下主梁、墩塔和索塔的截面应力实测值均小于理论计算值,应力校验系数小于1.0,说明结构强度满足设计要求,在试验荷载下有一定安全储备,结构安全可靠;有限元分析能有效运用于斜拉式钢结构天桥的整体结构安全评价中。     

Multi-scale fatigue damage prognosis for long-span steel bridges under vehicle loading

Fatigue damage prognosis for long-span steel bridges is of the utmost importance in bridge maintenance and management. In this study, a multi-scale fatigue damage prognosis algorithm is developed to calculate the trans-scale fatigue damage accumulation of newly-built long-span steel bridges under vehicle loading. The necessity and procedure of establishing a multi-scale finite element (FE) model of a newly-built long-span bridge for fatigue damage prognosis are first introduced. The future vehicle loading on the bridge is forecasted using the recorded weigh-in-motion (WIM) data and the agent-based traffic flow micro-simulation method. Then, the multi-scale fatigue damage prognosis algorithm is developed based on the multi-scale FE model and using the future vehicle loading. Finally, the proposed algorithm is applied to a newly-built long-span cable-stayed bridge for the time period from 2010 to 2020. The results show that the macro-scale fatigue damage accumulation and micro-scale short crack evolution of the critical components of the bridge can be simultaneously predicted and visualized. The proposed algorithm can be used as a numerical tool for fatigue damage prognosis of steel bridges where (or near where) WIM station is installed.     

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。     

邕江大型斜拉桥变形观测方法与精度分析

随着经济的高速发展,跨江大桥、跨海大桥越来越多,与此同时,国内外桥梁坍塌事故时有发生,因此,各省市有关部门加强了对桥梁安全性能的监测力度,2007年开始南宁市在市政府的部署下,由市政工程管理处负责,对横跨邕江上的几座大桥进行全面的健康检查,本文主要介绍白沙大桥的变形观测方法及精度分析。     

钢塔斜拉桥地震反应特性分析

针对一个实际钢塔斜拉桥工程,采用有限元软件SAP2000进行了动力特性和地震反应分析,并以主塔为混凝土塔的苏通大桥作为参照,对斜拉桥的动力特性、主塔地震反应和抗震性能等进行了比较分析。结果表明:相对于混凝土塔,钢桥塔的刚度和质量较小,轴压比略大,斜拉桥纵飘和主塔侧弯振型周期较长,主塔重力几何刚度对桥梁动力特性的影响较大,从而显著增大了塔顶及主梁的纵向地震位移,但对主塔及其基础的地震内力影响较小。钢塔斜拉桥的抗震性能较好,在7度地震区,地震作用不会控制钢塔及其基础的结构设计。     

斜拉桥索鞍的抗滑键基于超张负摩阻锁紧的作用原理及施工工艺研究

斜拉桥中采用塔上鞍座锚固的钢绞线拉索在金属分丝管道内受到摩阻效应的影响而具有抗滑锚固性能。分析斜拉索钢绞线单侧布置抗滑键进行锁定、抗滑键双向交叉布置的型式实现拉索整体抗滑锚固构造的传力机理,同时提出斜拉索基于超张负摩阻锁紧抗滑键的作用原理及施工工艺。且考虑到有个别分丝管在施工中难免会变形或堵塞,造成钢绞线不能穿孔而形成质量事故,有必要采取措施防止。在原有的分丝管中增加备用管道是比较简单的有效方法,也可作为今后桥梁加固所需的备用管道。