Fatigue Crack Propagation Law of Corroded Steel Box Girders in Long Span Bridges

In order to investigate the fatigue performance of orthotropic anisotropic steel bridge decks,this study realizes the simulation of the welding process through elastic-plastic finite element theory,thermal-structural sequential coupling,and the birth-death element method.The simulated welding residual stresses are introduced into the multiscale finite element model of the bridge as the initial stress.Furthermore,the study explores the impact of residual stress on crack propagation in the fatigue-vulnerable components of the corroded steel box girder.The results indicate that fatigue cracks at the weld toe of the top deck,the weld root of the top deck,and the opening of the transverse diaphragm will not propagate under the action of a standard vehicle load.However,the inclusion of residual stress leads to the propagation of these cracks.When considering residual stress,the fatigue crack propagation paths at the weld toe of the transverse diaphragm and the U-rib weld toe align with those observed in actual bridges.In the absence of residual stress,the cracks at the toe of the transverse diaphragm with a 15%mass loss rate are categorized as type I cracks.Conversely,when residual stress is considered,these cracks become I-II composite cracks.Residual stress significantly alters the cumulative energy release rate of the three fracturemodes.Therefore,incorporating the influence of residual stress is essential when assessing the fatigue performance of corroded steel box girders in long-span bridges.

Estimating extreme temperature differences in steel box girder using long-term measurement data

The extreme temperature differences in fiat steel box girder of a cable-stayed bridge were studied.Firstly,by using the long-term measurement data collected by the structural health monitoring system installed on the Runyang Cable-stayed Bridge,the daily variations as well as seasonal ones of measured temperature differences in the box girder cross-section area were summarized.The probability distribution models of temperature differences were further established and the extreme temperature differences were estimated with a return period of 100 years.Finally,the temperature difference models in cross-section area were proposed for bridge thermal design.The results show that horizontal temperature differences in top plate and vertical temperature differences between top plate and bottom plate are considerable.All the positive and negative temperature differences can be described by the weighted sum of two Weibull distributions.The maximum positive and negative horizontal temperature differences in top plate are 10.30 ℃ and -13.80 ℃,respectively.And the maximum positive and negative vertical temperature differences between top plate and bottom plate are 17.30 ℃ and-3.70 ℃,respectively.For bridge thermal design,there are two vertical temperature difference models between top plate and bottom plate,and six horizontal temperature difference models in top plate.

Fatigue Performance of Orthotropic Steel Decks in Super-Wide Steel Box Girder Considering Transverse Distribution of Vehicle Load

This study presents an investigation on the fatigue analysis of four types of details on orthotropic steel decks(OSDs)for a cable-stayed super-wide steel box girder bridge based on finite-element analysis(FEA)with vehicle transverse distribution model(VTDM).A high-fidelity 3D FE model verified by the static load test is established to satisfy the fatigue analysis accuracy.The stress behavior of super-wide steel box girders under the vehicle load at different lane locations is investigated.Then,considering the effect of VTDM,the fatigue life analysis of four typical details is performed using the Miner cumulative damage rule.The results show that the vehicle transverse location has a great influence on the stress behavior of details with sharp influence surface,and the stress ranges in the outermost lane are larger than those in other lanes,indicating that the details of OSD in the outermost lane are prone to fatigue.The fatigue life analysis indicates that the diaphragm cutout is more prone to fatigue than other details,which should be carefully treated in bridge maintenance.

The study of temperature effects on steel box girder for Taizhou Bridge

Using the temperature gradient which was proposed by continuously measuring flat steel box girder of Runyang Bridge, temperature effects of flat steel box girder were studied for Taizhou Bridge. With three temperature gradient models （JTG D60--2004 specification, BS5400 specification and the temperature gradient which was proposed in this paper）, the stress of control sections was calculated by finite element program ANSYS. The calculated result indicated that the temperature gradient that was put forward in JTG D60-2004 specification and BS5400 specification for calculating the stress of fiat steel box girder was not suitable to apply to fiat steel box girder. The temperature gradient on flat steel box girder which was proposed in this paper was reasonable.

Fatigue Performance Analysis and Evaluation for Steel Box Girder Based on Structural Health Monitoring System

Taizhou Yangtze River Bridge as a long-span suspension bridge,the finite element model(FEM)of it is established using the ANSYS Software.The beam4 element is used to simulate the main beam to establish the“spine beam”model of the Taizhou Yangtze River Bridge.The calculated low-order vibration mode frequency of the FEM is in good agreement with the completion test results.The model can simulate the overall dynamic response of the bridge.Based on the vehicle load survey,the Monte Carlo method is applied to simulate the traffic load flow.Then the overall dynamic response analysis of FEM is car-ried out.Taking the bending moment of the main beam as the control index,the fatigue sensitive section in the steel box girder of FEM is analyzed.Based on the strain time history data of steel box girder recorded by the structural health mon-itoring system(SHM),the true stress response of steel box girder under vehicle load is extracted.Taking the cumulative fatigue damage increment as the evalua-tion index,the fati gue performance evaluation of the steel box girders is con-ducted based on the collected health monitoring data.The fatigue effect of the beam section near the steel tower,especially the first section of the middle tower,is the key section of the fatigue analysis by health morning system,which is con-sistent with the calculation results of FEM.

Study in the design and manufacture process of the elastic cable anchor box in steel box girder of Taizhou Bridge

Taizhou Yangtze River Highway Bridge is a large span suspension bridge with three pylons. The elastic cables are installed to connect the steel tower and the steel box girder. The constraints can increase the safety coefficient of the middle saddle, and improve the stress conditions of the middle pylon and decrease the deflection in the middle of the main girder, as well as the longitudinal displacement of the main girder caused by live loads. The anchorage boxes of the elastic cable are installed in the wind fairing outside the vertical web plate of the box girder. Two anchor boxes form a pair and are arranged parallelly. Eight anchor boxes are installed in the bridge. In this paper, the design scheme and the technical difficulties in manufacturing are briefly discussed with the precision control techniques.

GMA material design and construction quality control for asphalt pavement of steel box girder: Case study of the Hong Kong–Zhuhai–Macao Bridge

To improve the quality of the Hong Kong–Zhuhai–Macao Bridge paving project,a new paving layer material,Guss-mastic asphalt(GMA),was proposed in this paper by combining the advantages of two types of cast asphalt mixtures:mastic asphalt(MA)and Guss asphalt(GA).Based on the characteristics of GMA,to simulate its actual production process,this study developed a small-simulated cooker mixing equipment.Moreover,the flow degree,60C dynamic stability,and impact toughness were proposed to be used to evaluate the construction and ease,high temperature stability,and fatigue resistance of GMA cast asphalt mixtures,respectively.Moreover,the quality control standards for GMA paving materials by indoor tests,field trial mix GMA material performance tests,and accelerated loading tests were finalized.The study showed that the developed simulated cooker yielded consistent mixing results in the same working environment as the engineering cooker device.Increasing the coarse aggregate incorporation rate,coarsening the mastic epure(ME)gradation composition,and using a smaller oil to stone ratio can reduce the flowability of the GMA materials to varying degrees.The four-point bending fatigue life and impact toughness of the different GMA materials are correlated well.A mobility of<20 s,60C dynamic stability of 400–800 times/mm,15C impact toughness of400 N⋅mm,and cooker car mixing temperature control standard of 210C–230C form an appropriate control index system for the design and production of GMA cast asphalt mixtures.Simultaneously,accelerated loading tests verified the accuracy and reliability of the quality control index system that has been used in the GMA paving project of the Hong Kong–Zhuhai–Macao Bridge deck and has achieved good application results.

Research on overall assembling and welding process of steel box girder tuyere blocks of Taizhou Bridge

This article presents in detail the assembling and welding process technique of the steel box girder tuyere blocks of Taizhou Bridge. The application of this process technique effectively solves the problem of welding stress release in tuyere block assembling and welding without increasing the number of turns of the blocks and overhead welding, thus avoiding possible structural deformation due to excessive accumulation of internal welding stress, greatly reducing the repeated deformation and correction work during assembling and welding, and ensuring the weld seam quality and overall dimensions of tuvere blocks of Taizhou Bridze.

Stress and noises of steel box girders in Sutong Bridge

Sutong Bridge is a cable-stayed bridge with a main span of 1 088 m. 370 high-precision stress monitoring measured data show that in the process of hoisting the steel box girders,the stress of the main girders is in the fluctuant and complex state and many meteorological factors,such as sunshine radiation,temperature and wind,have important influence on the change of stress of the steel box girders. According to the real-time weather data,the stress data after the process of wavelet denoising from representative measuring points in different weather conditions is picked to establish the stress response brought by meteorological factors with Layered Separation method,thereby basically eliminating the influence of meteorological factors on the stress of main girders,so that accurate and reliable stress data can be got for steel box girders adjustment and cable-tensioned construction control.

Design of steel box girder for Taizhou Yangtze River Highway Bridge

Taizhou Yangtze River Highway Bridge is the first three-pylon two-span suspension bridge in China. The main girder adopts flat steamline steel closed box girder which has well wind-resistant capability and is technically mature besides beautiful appearance. Straight web plates of the steel box girder in longitudinal direction are proposed in order to ensure the integrity of the steel box girder, and to keep the stress of the steel box girder continuous in the middle pylon, as well as to reduce the gradient of the middle pylon columns. The cross section of the box girder has one box with three cells. Solid-web diaphragm plate with good integrity and high torsional stiffness is adopted. The lifting lugs are utilized in the anchors of suspender cable. In this paper, selection of the cross section of the steel box girder, the general structure design, local structure design and main structure calculation results of Taizhou Yangtze River Bridge are introduced emphatically.

Research on Construction Process of Steel Box Girder Bridge and Its Stress Analysis

The paper introduce the construction method of large segment hosting and its difficulty, and drawing up corresponding liner and stress monitoring plan. The paper gives the calculation method of shear area for such a big cantilever thin-walled steel box girder section, namely the shear coefficient computation theory of Professor Hu Haichang, and the use of this shear area perfect beam element model, structure model and the experiment prove that the shell model is more consistent, given a certain reference for similar section project.

Study on the Mechanical Properties of Irregular Curved Steel Box Girder for City Viaduct

This paper deeply analyses the influence of different local tectonic on stress performance of spatial curved steel box Girder Bridge, using the finite element analysis software to establish space finite element model of this bridge, calculation and analysis were made on the bridge of the strength, stiffness. It has certain reference value for guiding engineering design, have a good foundation for the mechanical properties and stability of linear and nonlinear further study of curved steel box girder.

考虑风-温耦合的钢箱梁外形对温度效应影响研究

为了准确分析钢箱梁外形对截面温度特性的影响规律,提出了一种考虑钢箱梁周围局部风场与温度场相互作用的有限元分析方法,采用折减系数k来建立钢箱梁周围热边界层高度处风速U_(a)与远处气象站实测风速U的对应关系,对比分析了是否考虑风-温耦合对钢箱梁截面温度分布的影响,探讨了不同风嘴形式、截面宽高比、不同栏杆形式以及铺装厚度对钢箱梁截面温度分布的影响规律。研究表明:钢箱梁周围热边界层厚度处的风速U_(a)呈不均匀分布,且与远处风速U呈线性正相关;不考虑风-温耦合会明显低估钢箱梁顶板表面温度;钢箱梁截面的风嘴、截面宽高比、栏杆参数以及铺装厚度均会影响钢箱梁横截面的温度分布,改变截面的温差,因此,在桥梁的设计中,钢箱梁外形对截面温度分布的影响不可忽视。

基于点云配准的钢箱梁数字化拼装方法

基于全站仪检测结果修正钢箱梁模型并生成对应三维点云模型,利用RANSAC聚类算法,实现钢箱梁的拼接控制截面点云数据提取,并通过利用边缘准则(Angle Criterion)算法实现截面点云的边缘提取。结合拼接控制点集的快速四点一致配准(4PCS)和快速全局配准(FGR)算法,完成钢箱梁拼接的配准拼装。结合实验室试验,通过拼装具有典型钢箱梁特征的钢结构试件,验证了本文提出钢箱梁智能化虚拟预拼装方法的精度和可行性。通过对比实体预拼装与虚拟预拼装在拼装效率和检测结果上的差异,分析了基于三维点云的装配式钢箱梁虚拟预拼装方法的诸多优势。

基于气象参数的钢箱梁竖向温度梯度模式

【目标】基于气象参数,利用统计分析和数值模拟相结合的方法,确定钢箱梁在日照环境下的温度梯度模式,以解决传统实桥温度试验方法工作量大、成本高的问题。【方法】以浙江省杭州江东大桥为例,根据热传导原理,借助有限元软件,建立了包含铺装层的钢箱梁二维数值模型,并将模型计算结果与实桥获取的少量温度测量数据进行对比,以验证模型的准确性和可靠性。【数据】基于杭州地区2014年至2016年夏季晴天及多云天的气象数据,借助有限元软件计算得到江东大桥带铺装层钢箱梁的日最大竖向正温差样本数据,并对样本数据进行统计分析,最终得到钢箱梁具有50 a重现期的竖向正温差标准值。【结果】温度计算值与实测值吻合较好,两者最大差值不超过1.5℃;江东大桥钢箱梁夏季晴天及多云天的日最大竖向正温差服从广义极值分布;江东大桥带铺装层钢箱梁竖向正温差标准值为16.82℃,该值小于按照相关桥梁设计规范计算得到的取值。【应用】不同地区气象条件差异使得规范统一的温度梯度模式无法完全涵盖中国所有区域,本研究方法为根据当地气象条件,得到适用于该地区钢箱梁的温度梯度模式提供了参考。

城区复杂条件下V形墩钢-混组合连续梁桥临时工程专项设计研究

本研究以双桥路道路工程施工为平台,开展城区复杂条件下V形墩钢-混组合连续梁桥支架体系研究。结合项目地形、地质特点及受限空间等多方面工况,利用三维建模及结构计算等手段综合考虑设计一套安全风险可控、经济价值高的临时工程体系,同时,结合施工工序,将下部结构V形墩、钢箱梁顶推、上部结构混凝土箱梁等主要结构的支架统筹考虑,周转利用,节约施工工期,降低施工成本。

晋江世纪大道大跨径简支钢箱梁上部结构设计

晋江世纪大道南延伸至科院路(南安段)工程奎峰大桥采用单孔跨径66m简支钢箱梁桥上跨主路左、右辅道。本文应用MIDAS对大跨径简支钢箱梁上部结构进行有限元分析,结果表明,结构验算满足规范要求,充分体现了大跨径简支钢箱梁的结构性能及受力特征。前期设计阶段对钢箱梁上部结构往往仅采用杆系模型进行匡算分析,即此阶段仅考虑第一体系受力分析结果,计算结果表明第二体系应力较大,不容忽视。本文大跨径钢箱梁顶、底、腹板、加劲板、横隔板等构造尺寸、布置等细节可为类似的钢箱梁上部结构设计提供参考。

临时索塔辅助转体的异形钢箱梁桥落架方案研究

某跨铁路转体桥为三维不对称极度异形的钢箱梁桥,桥梁两端宽度差异非常大,钢箱梁构造特殊。钢箱梁落架过程涉及到梁体、索塔、斜拉索及钢支架受力的相互协调问题。以该异形钢箱梁为研究对象,建立数值模型,对斜拉索张拉及支架拆除的各施工步骤进行数值模拟分析,确定合理的落架顺序。研究表明,采用临时索塔,设置斜拉索辅助主梁受力是转体施工时必要且合理的措施,合理的拆除顺序是先拆除中部靠近梁端的支架,再逐步向中墩处拆除跨中支架,斜拉索全部张拉完成后再拆除边墩及中墩位置处的支架,落架过程中结构受力和变形均处于合理范围。

大块件桥梁钢箱梁免吊装快速施工关键技术

市场经济环境下,我国桥梁工程建设水平不断提升,出现了较多桥梁形式。钢箱梁属于较为常见的一种。具有自重轻、强度高等优点,不过在实际施工环节由于钢箱梁块件较大,存在较大的施工难度,需要积极探究有效的技术手段,实现大块件桥梁钢箱梁施工高质量开展。基于此,本文对大块件桥梁钢箱梁免吊装快速施工技术原理进行分析,并结合实际工程,探究大块件桥梁钢箱梁免吊装快速施工关键技术。希望在本文研究下,为相关人员提供参考借鉴,促进钢箱梁免吊装快速施工技术水平持续提升。

南京仙新路长江大桥主桥结构设计

南京仙新路长江大桥主桥为跨径1760 m的单跨钢箱梁悬索桥,主缆垂跨比1/9,边跨跨径580 m,边中跨比0.33。该桥上、下游各设1根主缆,单根主缆由169股127∅5.4 mm镀锌铝高强钢丝索股组成,采用PPWS法施工,钢丝标准抗拉强度2100 MPa。吊索与索夹采用销接式结构,跨中设置柔性中央扣索,短吊索设置关节轴承。主索鞍采用宽鞍槽单纵肋铸焊结合构造,散索鞍采用底座式全铸结构。加劲梁采用扁平流线型封闭整体钢箱梁,总宽31.5 m,梁高4 m,顶板与U肋之间采用双面埋弧全熔透焊接。桥塔采用门形混凝土结构,总高277.3 m,其上横梁为预应力混凝土结构,外包N字造型钢结构;桥塔基础采用直径2.8 m钻孔灌注桩。南锚碇采用外径65 m圆形地下连续墙基础;北锚碇采用沉井基础,平面尺寸70 m×50 m,高50 m。对结构进行静力分析及抗风性能理论和试验研究,结果表明:结构强度、刚度均满足规范要求;在加劲梁上设置0.67 m高中央稳定板、两侧风嘴处设置1 m宽水平稳定板后,大桥的颤振、涡振等抗风性能均满足要求,且具备一定的阻尼储备。