Defect Inspection Technology for Steel Truss Suspension Bridges

Steel truss suspension bridges are prone to developing defects after prolonged use.These defects may include corrosion of the main cable or the steel truss.To ensure the normal and safe functioning of the suspension bridge,it is necessary to inspect for defects promptly,understand the cause of the defect,and locate it through the use of inspection technology.By promptly addressing defects,the suspension bridge’s safety can be ensured.The author has analyzed the common defects and causes of steel truss suspension bridges and proposed specific inspection technologies.This research is intended to aid in the timely discovery of steel truss suspension bridge defects.

Process Monitoring and Terminal Verification of Cable-Stayed Bridges with Corrugated Steel Webs under Contruction

In this paper,the construction process of a cable-stayed bridge with corrugated steel webs was monitored.Moreover,the end performance of the bridge was verified by load test.Owing to the consideration of the bridge structure safety,it is necessary to monitor the main girder deflection,stress,construction error and safety state during construction.Furthermore,to verify whether the bridge can meet the design requirements,the static and dynamic load tests are carried out after the completion of the bridge.The results of construction monitoring show that the stress state of the structure during construction is basically consistent with the theoretical calculation and design requirements,and both meet the design and specification requirements.The final measured stress state of the structure is within the allowable range of the cable-stayed bridge,and the stress state of the structure is normal and meets the specification requirements.The results of load tests show that the measured deflection values of the mid-span section of the main girder are less than the theoretical calculation values.The maximum deflection of the girder is−20.90 mm,which is less than−22.00 mm of the theoretical value,indicating that the girder has sufficient structural stiffness.The maximum impact coefficient under dynamic load test is 1.08,which is greater than 1.05 of theoretical value,indicating that the impact effect of heavy-duty truck on this type of bridge is larger.This study can provide important reference value for construction and maintenance of similar corrugated steel web cable-stayed bridges.

Analysis on Deflection Characteristics of Steel Cable-Stayed Bridge

Various kinds of deflection characteristics on the steel cable-stayed bridge(Nanjing No.3 Yangtze River Bridge)are investigated by different mathematical statistical methods.Firstly,via Pearson correlation coefficient calculation,it shows good consistency between the adjacent measuring point of side span or middle span.Secondly,taking mid-span deflection as an example,the correlation analysis of deflection and temperature is conducted.They are synchronous via cross correlation coefficient calculation but not completely linear and a"hysteresis loop"phenomenon of three stages is formed.The fitting result on the monitoring data at day time is consistent with the numerical value through the application of unit temperature difference between the cable and girder and the positive temperature gradient of girder in the finite element model.And the temperature effect is considerable.Vehicle loads effect is obtained from wavelet analysis.The extracted curve can indirectly reflect the change of traffic loads.Finally,the structural damage is analyzed through the trend fusion on the deflection,cable force and visual inspection from 2006 to 2015.Relevant conclusions can provide a basis for management departments to carry out special detection.

Health Monitoring-Based Assessment of Reinforcement with Prestressed Steel Strand for Cable-Stayed Bridge

This paper presents the method of reinforcing main girder of reinforced concrete cable-stayed bridge with prestressed steel strands.To verify the effectiveness of external prestressed strand reinforcement method.Static load tests and health monitoring-based assessment were carried out before and after reinforcement.Field load test shows that the deflection and stress values of the main girder are reduced by 10%~20%after reinforcement,and the flexural strength and stiffness of the strengthened beam are improved.The deflection and strain data of health monitoring of the specified section are collected.The deflection of the second span is 4 mm~10 mm,the strain range of the upper edge of the second span is-10με~-40με,and the strain range of the lower edge is 30με~75με.These values show the deflection and strain values fluctuate within a prescribed range,verifying the safety of the bridge.The reinforcement method of prestressed steel strand is feasible and effective.It can provide reference basis for the application of external prestressed strand reinforcement technology in similar projects.

Discussion on Construction Technology of Subway Tunnel Expansion under Bridge Foundation

As the urban populations grow,the number and size of subway construction projects are increasing while also meeting higher construction standards.So,subway construction projects must have a better understanding of construction technology.This article focuses on the construction technology of the subway tunnel expansion under the bridge foundation.By analyzing the engineering characteristics of the bridge foundation and using a project as an example,this article provides a detailed discussion of the construction process of tunnel expansion under a bridge foundation.This article aims to serve as a reference for subway tunnel construction in China to ensure the key points of construction technology are understood,thus improving construction quality and laying a solid technical foundation for the sustainable development of urban rail engineering.

Analysis on the Structural Type of Large-span Steel Truss Bridge Spe­cially Designed for Cables

When the installation of cables and pipelines needs to go across rivers,bridges are usually adopted to support the cables and pipelines for crossing the rivers.The measure can make full use of the space resources and have no effect on the flow pattern of rivers.For this reason,analysis on the structural-type design of a large-span steel truss bridge specially used for cables has been performed.The numerical results indicate that the stayed-cable bridge with steel truss beam and concrete main tower has better performance and improved structural type caparisoned with that of the beam and arch bridges,and the construction of the major beam can be without the temporary support.

Seismic response of the long-span steel truss arch bridge with the thrust under multidimensional excitation

Purpose–Under different ground motion excitation modes,the spatial coupling effect of seismic response for the arch bridge with thrust,seismic weak parts and the internal force components of the control section of main arch ribs are analyzed.Design/methodology/approach–Taking a 490 m deck type railway steel truss arch bridge as the background,the dynamic calculation model of the whole bridge was established by SAP2000 software.The seismic response analyses under one-,two-and three-dimension(1D,2D and 3D)uniform ground motion excitations were carried out.Findings–For the steel truss arch bridge composed of multiple arch ribs,any single direction ground motion excitation will cause large axial force in the chord of arch rib.The axial force caused by transverse and vertical ground motion excitation in the chord of arch crown area is 1.4–3.6 times of the corresponding axial force under longitudinal seismic excitation.The in-plane bending moment caused by the lower chord at the vault is 4.2–5.5 times of the corresponding bending moment under the longitudinal seismic excitation.For the bottom chord of arch rib,the arch foot is the weak part of earthquake resistance,but for the upper chord of arch rib,the arch foot,arch crown and the intersection of column and upper chord can all be the potential earthquake-resistant weak parts.The normal stress of the bottom chord of the arch rib under multidimensional excitation is mainly caused by the axial force,but the normal stress of the upper chord of the arch rib is caused by the axial force,in-plane and out of plane bending moment.Originality/value–The research provides specific suggestions for ground motion excitation mode and also provides reference information for the earthquake-resistant weak part and seismic design of long-span deck type railway steel truss arch bridges.

Application of Wireless Monitoring System to Structural Health Monitoring of Long-Spanned Cable-Stayed Bridge

The remote monitoring system applied to the construction control and health monitoring of the Nanjing Third Yangtze River Bridge is introduced. The System makes it possible to get the structure capabilities and environmental parameters of the bridge at the predetermined moment. It sends the collected data over a long distance to an assigned position for display and analysis. The related methods and working condition of the wireless monitoring system are discussed. The measured data during 48 h are employed to determine the feasibility for the closure of the bridge.

某在役铆接钢桁梁桥关键构件疲劳性能研究

精准评估现役钢桥的疲劳寿命对于桥梁结构的安全运营至关重要。该文以某在役铆接钢桁梁桥为研究对象,在对桥梁结构进行计算分析明确各构件的受力特点的基础上,针对原桥典型构件以及关键节点开展系列疲劳性能研究。数值计算结果表明,城B荷载作用下原桥典型构件以及关键节点均具有良好抗疲劳性能,疲劳寿命循环次数均大于200万次。

大跨度钢桁梁桥智能建造技术应用的可行性研究

大跨度钢桁梁桥的构件制造及拼装复杂,采用场内预制组装仍需消耗大量的人力、财力及工期。因此,本文采用BIM桥梁建模、三维激光扫描和虚拟预拼装技术,进行了基于BIM技术的施工方案模拟的可行性研究和基于BIM技术与三维激光扫描方法结合的构件加工质量检测研究,并在此基础上进行了基于BIM技术与三维激光扫描方法结合的虚拟拼装技术研究,探索了大跨度钢桁梁桥智能建造技术应用于指导工程实施的可行性。

钢桁梁断面形式对公铁两用桥上列车气动特性影响

钢桁梁断面形式的不同可能会改变桥上列车的气动力,进而影响桥上列车运行安全性和舒适性。为此,以某千米级公铁两用悬索桥为工程为背景,通过风洞试验对三种常用钢桁梁断面形式的桥上列车进行测力、测压试验。研究结果表明,当单列车位于三种钢桁梁断面形式上的上游时,列车的阻力、升力系数无明显差异,而单列车位于下游时,列车的阻力、升力系数有较大的区别;在双车状态下,由于迎风侧列车的遮挡作用,改变了不同钢桁梁断面形式下列车的流场,使得钢桁梁断面形式对背风侧列车影响较小。无论列车位于上游、下游,其三种钢桁梁断面形式下列车的阻力系数、升力系数随风攻角的变化趋势一致。当列车位于上游时,其三种钢桁梁断面形式上列车顶部和底部圆弧过渡段都出现不同程度的流动分离,使得其列车平均风压系数不同;当列车位于下游时,三种钢桁梁断面形式上列车平均风压系数变化趋势一致,说明钢桁梁断面形式对下游列车的平均风压影响较小。列车位于上、下游时,其脉动风压系数会有显著的差异,其脉动风压系数的大小受腹杆布置形式的影响要比梁高的不同更为显著。本文研究结果可为大跨钢桁梁桥的断面形式选取提供参考和依据。

公铁合建斜拉桥钢桁-混凝土板组合梁受力特性

以某主跨808 m的公铁合建新型钢桁-混凝土板组合梁斜拉桥为背景,采用ANSYS软件建立局部组合梁细化的全桥多尺度有限元模型,分析其在不同工况下双层组合梁的受力传力特性和混凝土桥面板荷载分配比,并讨论混凝土桥面板厚度t_(b)、横梁刚度变化系数λ_(K)和钢与混凝土弹性模量比λ_(E)对组合梁受力传力的影响规律。结果表明:最不利组合工况下,钢桁架最不利Von Mises应力为183.6 MPa,混凝土桥面板最大拉应力为5.3 MPa,均满足结构受力要求;沿纵向路径,钢桁架和混凝土桥面应力在节间横梁间均呈“波形”分布;上下层混凝土桥面板顶、底面应力沿横向近似呈“W”和“M”状分布,表明桥面板承受一定沿横向不均匀分布弯矩;公路及铁路混凝土桥面最大剪力滞系数分别为1.45、1.36,更宽的公路混凝土桥面剪力滞效应更显著;公路及铁路混凝土桥面分别承担上、下层结构57.46%~79.99%和33.21%~62.81%的轴向荷载,为组合梁的主要传力构件;混凝土桥面板的应力随t_(b)及λ_(K)的增大而增大,随λ_(E)的增大而逐渐减小;混凝土桥面每层平均荷载分配比ξ与t_(b)成正比,与λ_(K)及λ_(E)成反比;当t_(b)、λ_(K)和λ_(E)参数的取值范围分别为0.8~1.4、0.4~1.6以及4~10时,组合梁混凝土桥面应力及荷载分配比ξ较为合理。

基于点云切片算法的铁路钢桁拱桥线形分析

铁路桥梁线形测量对于桥梁健康检测与确保铁路安全运营具有重要作用。为提高运营铁路钢桁拱桥线形测量效率,以某3跨钢桁拱桥为例,运用地面激光扫描(TLS)技术对桥梁杆件进行整体化扫描,从桥梁线形测量精度、扫描完整性、点云个数等3方面,分析出最佳的桥梁扫描测站数为10个。运用3DNDT点云配准算法将各测站一一配准,桥梁点云配准精度为2 mm,将桥梁点云投影至xoy平面,用半径滤波器进行噪声点的去除,得到完整“纯净”的桥梁点云模型。提出点云等距切片与点云平面切片算法提取桥梁线形,并将线形点云数据导出在AutoCAD中拾取坐标。将点云切片法提取的TLS测量值、全站仪法测量结果与原始成桥线形做比较分析,结果表明:在桥面线形分析中,两方法均在跨中处A5点测量出最大变形,分别为12.69 mm、10.29 mm,两方法的最大相互较差R为2.4 mm,相关系数优于99.93%;在拱轴线线形分析中,点云切片法与全站仪法在主桁上弦跨中B4点位测量的最大变形为6.2 mm、3.9 mm,在主桁下弦跨中B10点位测量的最大变形为5.9 mm、3.5 mm,两方法的最大互相较差R为3.2 mm,相关系数优于99.87%,验证了点云切片算法的有效性与TLS测量的高精度性。拱轴线横向线形未出现明显侧移,点云等距切片得到的19个吊杆垂直度保持良好,未发生扭转与偏移。该成果对于运营铁路钢桁拱桥的线形分析与点云处理方法可提供相应的思路和参考,具有重要的实用价值。

导风栏杆参数对钢桁梁桥风车桥耦合振动影响研究

为探究导风栏杆参数对钢桁梁桥风车桥耦合振动的影响,以某典型超高墩钢桁梁桥为背景,对设置了新型导风栏杆的节段模型进行风洞试验及CFD数值模拟,得到不同导风栏杆参数及风攻角下车、桥三分力系数。在此基础上,建立风-车-桥系统空间耦合振动仿真分析模型,分析不同风速情况下不同导风栏杆间距、挡风面角度以及风攻角对车-桥系统动力响应的影响,得到最优导风栏杆参数。结果表明:随着导风栏杆间距增大,桥梁阻力系数缓慢减小,列车阻力系数呈增大趋势;随着挡风面角度的增大,桥梁三分力系数变化较小,列车阻力系数呈增大趋势;导风栏杆对桥梁三分力系数随风攻角变化的变化趋势影响较小,对列车阻力系数随风攻角变化的变化趋势影响较大;对于此类桥梁而言,导风栏杆间距为60~75 cm时挡风效果较为显著,60 cm间距导风栏杆可最大程度降低列车响应,且不显著增大桥梁响应;挡风面角度为10°~20°时挡风效果较为显著,10°挡风角的导风栏杆可以在充分发挥挡风效果的同时将列车响应控制在较低水平,且不会显著增大桥梁响应;挡风面角度相较于导风栏杆间距对车-桥系统振动影响小;导风栏杆可以有效减小3种风攻角条件下的列车脱轨系数以及-7°攻角条件下的轮重减载率,但同时也增大了-7°攻角和0°攻角条件下的轮重减载率以及桥梁中跨跨中横向位移。研究结果为进一步优化导风栏杆参数和保证列车在超高墩钢桁梁桥上安全营运提供参考。

大跨径刚性悬链桁架桥不带加劲弦顶推施工技术

针对悬链形上加劲连续钢桁梁桥建造,提出不带加劲弦多点同步顶推施工技术,在边跨设置拼装平台,在中跨设置临时墩,分段拼装,顶推钢桁梁,最后吊装合龙加劲弦。在施工中,设置大临结构,以减小钢桁梁的悬臂长度,适应了钢桁梁拼装及顶推装置布置的要求;采用同步控制系统与纠偏装置,解决了多点同步顶推与钢桁梁线性控制的难题;通过有限元仿真分析,验证了顶推过程的可行性;采用落梁法,解决了钢桁主梁合龙及加劲弦合龙的难题。

基于改进DEMATEL-ISM的钢桁梁桥施工风险影响因素研究

为提高钢桁梁桥施工过程中的安全管理,对钢桁梁桥施工中的风险因素进行分析,提出了一种基于改进DEMATEL-ISM的评价方法,首先引入三角模糊数对DEMATEL法中的直接影响矩阵进行改进,从而去模糊化以减少专家评价的主观性,再通过DEMATEL法分析各影响因素的影响度、被影响度、中心度与原因度并加以排序,对得到的主要影响因素进行初步分析,利用ISM法对筛选出的影响因素进行层次划分,得到直接层影响因素、过渡层影响因素与本质影响因素,并针对分析得到的5个本质影响因素提出深入的预防预警措施,可为钢桁梁桥施工方向的安全管理提供针对性措施,为事故预防提供一定的参考依据。

铁路钢桁梁桥明桥面复合轨枕宏-细观力学行为研究

复合轨枕是明桥面结构提质改造的重要举施,但复合成型工艺及材料特性对轨枕服役性能有直接影响。针对复合轨枕明桥面结构的特性,基于ABAQUS等仿真平台,分别建立复合轨枕的宏、细观有限元模型,从多尺度仿真角度研究列车轮载下复合材料密度,纤维束直径、取向和分布等因素对轨枕承载能力及变形影响。结果表明:增大纤维束直径、使纤维束充分分散,能够减少10%~30%的轨枕受力;改变纤维取向对提高轨枕承载力的效果较为显著,优化纤维分布取向能够使轨枕表面受力减小20%~30%;在此基础上提出“45°/0°/45°”的纤维束铺层结构,采用这种结构能在相同变形量控制水平下获得更高的承载能力,较全断面纵向铺层方案提升30%~50%。研究表明:利用复合轨枕的材料特性,优化生产制造工艺可提高其承载能力。

山区钢桁梁斜拉桥设计和工程应用研究

随着交通强国和乡村振兴等国家战略的实施,我国山区桥梁建设的数量和规模与日俱增。文章调研世界范围内2113座山区桥梁(含中国1521座),分析山区桥梁的建设难点和应用现状,阐明山区斜拉桥的关键设计技术,研究山区钢桁梁斜拉桥主梁、主塔及斜拉索的方案选型及构造设计,探讨适用于山区条件的新型斜拉桥施工方法。结果表明:我国是世界上山区桥梁建设最多的国家,贵州省又居我国首位(34.4%)。山区斜拉桥通常具有大跨径、高塔墩、小边主跨比和结构不对称等特点,运输施工易、装配程度高、抗风性能好、抗震性能优和景观造型美的结构设计成为山区桥梁的主流趋势。钢桁梁比钢箱梁斜拉桥更适应于山区的建设条件,公路钢桁梁斜拉桥一般采用两片主桁,N形桁式,主桁高度为6~9m,节间长度为6~12m,梁上标准索距为12~16m。主桁横向联系采用华伦式,桥面系常用板桁组合体系,斜拉索则主要采用钢绞线斜拉索。新开发的缆索吊机法和节段纵移悬拼法解决了山区斜拉桥主梁整节段起吊、运输和拼装的难题,可供类似桥梁借鉴和参考。

公铁混合布置大跨度斜拉桥主梁断面形式研究--以赣江公铁大桥西支主桥设计为例

以赣江公铁两用大桥西支主桥设计为例,研究一种适应上层8车道公路、下层对称双线铁路+4车道公路混合布置的主梁断面形式。提出带挑臂双索面箱桁组合断面、带挑臂单索面箱桁组合断面、矩形箱桁组合断面、矩形钢桁梁断面4种主梁断面方案,采用有限元软件分析各方案静动力性能及受力特点,综合考虑方案构造特点、技术指标、工程数量、公铁运营安全、景观效果等,确定该桥选用带挑臂双索面箱桁组合断面。该桥斜拉索最大索力16000 kN,锚固在下层钢箱梁两侧,通过有限元实体分析对锚拉板和钢锚箱式两种索梁锚固形式进行比选研究,钢锚箱形式受力合理、应力水平低、经济性好,设计采用钢锚箱形式。带挑臂双索面箱桁组合断面桥面空间布置合理、下层公铁行车干扰小、梁端竖向变形最小、经济性好,是一种适应公铁混合布置大跨度斜拉桥主梁断面形式。