汶川大地震公路桥梁震害分析及对策

 对5.12汶川大地震四川重灾区国(省)干线公路1 657座桥梁震害的调查检测结果加以归纳,总结出7种公路桥梁的宏观震害;归纳了梁式桥及拱桥的几种典型震害——移位、落梁、桥墩剪断、压溃和开裂、桥台墙体开裂、桥台肋板和背墙开裂、桥台填料垮塌、拱圈开裂、拱上结构开裂等,并对其进行了初步分析。根据震害,提出了桥位及桥型选择应注意的有关因素,以及针对梁体移位、桥墩破坏等震害的相关抗震对策。     

Remaining fatigue life of steel railway bridges under enhanced axle loads

In this study, various fatigue damage models proposed by researchers have been briefly discussed and found that the models are problem specific and their efficacy needs to be checked for high cyclic fatigue cases such as in railway bridges. Towards this, field studies were conducted to obtain the strain responses from a steel bridge during the passage of scheduled trains and test train formation with enhanced axle loading. Instrumentation was carried out at critical locations to obtain the responses from the girder. Three different scenarios have been considered to avoid the influence of noise. Further, numerical simulation of the bridge subjected to train loading at different speeds was carried out using ANSYS to obtain synthetic data of strain response from the validated finite element model. Analysis was carried out for normal as well as for futuristic speed of the trains. Responses obtained from field measurements as well as from numerical investigations were used to calculate the damage indices. Based on the damage indices, remaining fatigue life of the bridge was evaluated. The present study can be helpful in assessing the health condition of the railway bridges and to check the suitability of further increase in axle load or speed of trains.     

Structural health monitoring of a steel stringer bridge with area sensing

The Federal Highway Administration Long-term Bridge Performance Programme initiated an International Bridge Study by selecting a steel stringer bridge as a benchmark structure for structural health monitoring. As a part of this programme, the authors studied the application of the Long-Gauge Fibre Bragg Grating (LG-FBG) sensors on this bridge. This paper aims at illustrating the LG-FBG-related state-of-the-art technologies by taking the bridge as the test bed. (1) The concept of the LG-FBG sensor for area sensing is presented. Most fibre optic sensors measure point strains for local monitoring. In contrast, the developed LG-FBG area sensor has a long gauge (e.g. 1–2 m), and it can be connected to each other to make a sensor array for distributed strain measuring; (2) spectral analyses of the macro-strain time histories are performed to identify structural frequencies, and the results are compared with those estimated from acceleration measurements; (3) the neutral axis position of the girder of the investigated bridge is estimated from the recorded macro-strain time histories, and the results are compared with those from static truck tests and (4) a modal macro-strain-based damage index is applied for damage detection of the steel stringer bridge.     

Deployment of a dense hybrid wireless sensing system for bridge assessment

Discussed in this paper is the deployment of a dense wireless sensor system on a short span integral abutment bridge superstructure located in St. Lawrence County, New York. The Wireless Sensor Solution (WSS) is designed specifically for diagnostic bridge monitoring providing independent conditioning for accelerometers and strain transducers. During deployment, strain measurements are obtained in real-time under ambient environmental and traffic loading. Strain transducers are placed at various locations along the girders, including the top and bottom flanges of a heavily instrumented interior girder at the mid-span and the abutment ends where the neutral axis location, section modulus, and girder moments are obtained. Results from the strain data analysis aid in quantifying the bridge response; notably, detection of end fixity, load distribution, and composite action between the girders and bridge deck. The measured responses are illustrated to propose a deterioration profile based on the level of capacity and demand.     

钢筋混凝土斜拉桥寿命期内整体极限承载力分析

提出基于定期检测和健康监测技术的斜拉桥结构服役期内主梁整体失效模式及其极限承载力演化规律的分析方法,为结构的全寿命设计以及结构安全预警的分级提供理论依据。首先,利用结构的检测/监测数据,建立与实际结构状态相符的有限元模型,并分析构件的耐久性损伤,在此基础上计算考虑抗力退化的构件的极限承载力;然后,在有限元模型上施加逐级渐进的车辆荷载,分析各构件的内力状态;最后,将荷载效应超过抗力的主梁截面设置为塑性铰,改变结构体系,继续施加车辆荷载,直至结构承受的车辆荷载达到最大值,对应的变结构体系和车辆荷载分别为最终主梁整体失效模式和极限承载力。利用上述方法对我国北方某座干线斜拉桥在运营期内的4个典型状态进行计算分析,研究该桥在运营期内的失效模式及其极限承载力的演化规律。结果表明,所提出的方法可以获得在车辆荷载作用下斜拉桥主梁整体失效模式和相应的极限承载力;斜拉桥在服役过程中主梁开裂、钢筋锈蚀、边界条件变化等导致桥梁结构损伤、甚至结构体系及其相应的力学模型发生较大的变化,使结构失效模式及其极限承载力发生较大的变化。     

无伸缩缝桥梁动力特性与抗震性能研究

以福建某简支梁桥为研究背景(该桥在实际工程中已被改造为半刚性整体桥),采用MIDAS/Civil软件将原简支梁桥改造为整体桥、半整体桥与延伸桥面板桥,分别建立了5座桥的全桥有限元模型,分析了它们在地震荷载下的受力差异。结果表明:简支梁桥在地震荷载作用下易引起主梁在桥台处的落梁现象,而无缝桥可有效防止该现象的发生,其中的整体桥表现出更优的抗震性能,更适用于强震区; 在地震荷载作用下,无缝桥与简支梁桥的桩基有效作用长度均在0～10D(D为桩径)埋深范围; 整体桥桩基在大震作用下的受力性能较好,可更好地保护桩基不被破坏; 延伸桥面板桥与传统简支梁桥台底桩身受力相近,其设计可参考现行有缝桥设计规范; 无缝桥与传统简支梁桥的墩底弯矩均最大,在该处易形成塑性铰; 纵桥向地震荷载作用下,简支梁桥与延伸桥面板桥的主梁受力最不利位置分别出现在跨中与墩顶处,而整体桥、半刚性整体桥与半整体桥出现在台顶处,其受力不利部位在设计中应引起重视; 该研究结果可为无缝桥的设计计算与相关规范的制定提供参考。     

A filtering-based bridge weigh-in-motion system on a continuous multi-girder bridge considering the influence lines of different lanes

A real-time vehicle monitoring is crucial for effective bridge maintenance and traffic management because overloaded vehicles can cause damage to bridges, and in some extreme cases, it will directly lead to a bridge failure. Bridge weigh-in-motion (BWIM) system as a high performance and cost-effective technology has been extensively used to monitor vehicle speed and weight on highways. However, the dynamic effect and data noise may have an adverse impact on the bridge responses during and immediately following the vehicles pass the bridge. The fast Fourier transform (FFT) method, which can significantly purify the collected structural responses (dynamic strains) received from sensors or transducers, was used in axle counting, detection, and axle weighing technology in this study. To further improve the accuracy of the BWIM system, the field-calibrated influence lines (ILs) of a continuous multi-girder bridge were regarded as a reference to identify the vehicle weight based on the modified Moses algorithm and the least squares method. In situ experimental results indicated that the signals treated with FFT filter were far better than the original ones, the efficiency and the accuracy of axle detection were significantly improved by introducing the FFT method to the BWIM system. Moreover, the lateral load distribution effect on bridges should be considered by using the calculated average ILs of the specific lane individually for vehicle weight calculation of this lane.     

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.     

钢管混凝土拱桥地震破坏模糊评估方法

为了掌握钢管混凝土拱桥在地震后损伤和破坏情况,根据钢管混凝土拱桥各部件结构构造和受力特征,建立各个部件的杆件的基于变形或强度和能量的双重破坏评估模型,利用有限元法计算钢管混凝土拱桥非线性地震反应,研究基于模糊理论和层次分析法的地震破坏模糊评估方法。通过一座大跨钢管混凝土拱桥工程应用,由钢管混凝土拱桥的地震破坏模糊评估可知,在加速度峰值为0.1、0.2、0.4和0.8 g的地震作用下,整桥的破坏指数分别为0.150、0.152、0.172和0.318,说明在峰值为0.4 g的地震作用下桥梁为轻微破坏,在0.8 g的地震作用下,为中等破坏。     

强震区大跨高墩连续梁桥抗震性能研究

大跨度高墩连续梁桥的抗震设计,特别是在高强度地震作用下的抗震设计,目前尚无规范可遵循.以国外某大桥为例,建立了全桥的动力分析模型,计算了结构的动力特性和地震响应,针对大桥在强震作用下主梁位移反应过大以及对支座抗剪要求过高的特点,讨论了采用粘滞阻尼器和双曲面球型减隔震支座的减隔震效果,研究结果表明这些措施是有效的,可为同类大跨高墩连续梁桥的抗震设计提供参考.     

汶川地震梁式桥主梁易损性研究

为研究梁式桥主梁的地震易损性,根据汶川地区桥梁震害调查数据,统计了梁式桥主梁的破坏等级,采用数据补充的方法对原始数据进行了优化,基于补充后的主梁震害数据,采用极大似然估计法得到了梁式桥主梁的经验易损性曲线,并对结果进行了检验分析。     

桥梁损伤识别的实用模型修正方法研究

对面向损伤识别的桥梁结构模型修正实用方法进行了研究。提出了基于振动特性测量的三步模型修正策略和综合利用通用有限元程序ANSYS的优化功能进行模型修正的方法。为了缩减待修正的参数,根据计算目标函数对每个单元参数的敏感性,进行子结构划分,通过对子结构参数的修正进行结构损伤的大致定位,然后对确定为损伤的子结构的每个单元进行参数修正,进行结构的损伤定量识别和状态评估。修正算法的优化方法采用ANSYS一阶优化方法和随机搜索方法,敏感性分析和模型修正完全基于ANSYS软件进行,较适合于实际工程的应用。为了说明方法的可行性,以某一实际三跨预应力钢筋混凝土连续箱梁桥为仿真算例,以结构模型的单元刚度衰减来模拟损伤,进行损伤识别,达到了较好的效果。     

Design of Rupture Strength of Side Blocks in Elevated Steel Girder Bridges with Elastomeric Bearings

Elastomeric rubber bearings with side blocks have been extensively used as a seismic response-control device in steel girder bridges in Japan. In real scenarios, the behavior of the girder bridges with elastomeric bearings are usually complex because of the complex mechanism by which the seismically induced inertia forces at concrete deck transmits to the girder bearings. Therefore, it is important to carry out seismic response analysis of a whole bridge system considering the interaction between different structural components in order to check the performance of the side blocks during an event of severe earthquakes. The objectives of the present study are to develop a detailed three-dimensional finite element (FE) model of an elevated girder bridge system and to propose a design rupture strength for the side blocks. The FE-model is constructed based on an existing plate girder bridge considering the effect of concrete slab, girders, stiffeners, rubber bearing, pier and the damage control by the side blocks. A sequence of seismic response analysis is then performed using four different rupture forces of the side blocks by considering the Level-2 design earthquake, the 1995 Kobe earthquake and the 2016 Kumamoto earthquake. The analytical investigation reveals that the side blocks should be designed to withstand a horizontal force of at least 1200 kN in order to prevent the rupture of the side blocks and to mitigate damage of bridge piers. Moreover, the damage to the critical parts of bridge superstructure can be mitigated by strengthening the side blocks. Based on the analysis results, a retrofit plan to strengthen the side blocks of existing girder bridges is proposed.

     

openLAB – Eine Forschungsbrücke zur Entwicklung eines digitalen Brückenzwillings

openLAB – A research bridge for developing a digital twin of bridges Within the IDA-KI project, a research bridge (openLAB) is being built and loaded up to the level of severe damage. This will be accompanied by extensive measurements and investigations, thus creating a unique database for the validation of damage detection and evaluation methods under real environmental conditions using a large-scale model. This article presents the project idea, the research bridge currently under construction, and the monitoring system installed at the bridge. The methods implemented for automated data analysis and fault detection in the monitoring data are presented and validated through load tests in the openLAB. First measurements recorded during the production process of the precast girders of the research bridge underline the potential of distributed fiber optic sensors for a monitoring from day one. The information gained from the construction and operation of the bridge is provided in a digital model. The conceptualization of the so-called “as maintained“ model and the data management will be presented.     

Development of a Bridge Bumper to Protect Bridge Girders from Overheight Vehicle Impacts

Abstract:   Bridges with low clearance are vulnerable to collision with overheight vehicles. Collisions of overheight vehicles can cause fatalities and injuries to the drivers and passengers of the overheight vehicles, and damage to bridge girders. The repair of the damaged bridges can be costly and time consuming. This article investigates the feasibility of developing a bridge bumper that minimizes the physical injuries and the likelihood of fatalities and protects the structural elements of bridges by absorbing the impact energy. The article presents the results of small-scale impact experiments using the proposed bridge bumper with several options of energy-absorbing materials to protect a reinforced concrete beam. Finite element analyses are carried out to simulate the small-scale impact experiments. Optimization of the finite element model is conducted for the response quantities of interest with respect to the geometrical parameters and the material properties of the proposed bridge bumper. Such analysis can guide the design of an optimal bridge bumper that maximizes the energy dissipation and minimizes the damage to the bridge girder and the likelihood of fatalities and injuries. A possible full-scale implementation of the proposed bridge bumper is also described.     

中小跨径板式橡胶支座梁桥横向抗震设计研究

为提高中小跨径板式橡胶支座梁桥在强震作用下的横向抗震性能,在总结汶川震区该类梁桥震害特点和国内外桥梁抗震设计规范中相关抗震设计策略规定的基础上,归纳当前我国板式橡胶支座梁桥横向抗震体系存在的问题,提出适合我国中小跨径板式橡胶支座梁桥的横向抗震设计方法,即允许上、下部结构连接构件牺牲的准隔震设计方法,介绍该抗震设计方法设计思想,给出在两设防水准下结构各部件的性能目标要求。选择一座典型板式橡胶支座简支梁桥为研究对象,基于文中抗震设计方法的设计思想,提出采用新型隔震系统对计算桥例进行准隔震设计。结果表明：通过对横向限位装置力学性能参数的合理设计,通过桥梁结构在强震作用下板式橡胶支座的滑移、横向限位装置的损伤或牺牲,控制上、下部结构间传递的梁体惯性力,保护墩柱和基础等下部结构免遭严重损害,同时能有效控制墩梁相对位移,防止过大的梁体移位导致的交通阻断、甚至落梁。     

Lateral vibration of footbridges by synchronous walking

On the T-bridge (a cable-stayed footbridge) the girder vibrated laterally with a frequency of 0.93 Hz, the natural frequency of the first lateral mode, when a large number of people crossed the bridge. Some pedestrians felt uncomfortable and unsafe. The girder was excited by the lateral dynamic force which was produced by the zigzag movement of pedestrians. Once the bridge started to vibrate, some of the pedestrians synchronized with the girder vibration, which further increased the girder response. The same vibration occurred on the London Millennium Bridge and the M-bridge (a suspension footbridge), where field measurements were conducted. A dynamic model was then proposed to evaluate the pedestrians’ synchronized dynamic forces. Overall behavior of the girder response calculated by this dynamic model agreed with the measured values on the bridges. It was found by parametric studies that smaller bridge damping and smaller bridge mass produced larger girder response. Higher pedestrian density also increased the girder response unless they were too crowded to walk normally.     

预应力混凝土梁式桥安全运营监测系统研究

以一座三跨预应力混凝土连续箱梁桥作为监测研究对象,对预应力混凝土梁式桥结构安全运营监测系统进行设计,阐述监测系统的监测对象、监测内容及设计原则,并对传感器的布置进行优化设计。提出基于动态称重(WIM)技术对桥梁实施安全运营监测的方法,编制桥梁实时动力分析程序BDANS(Bridge Dynamic Analysis System)梁式桥动力分析功能模块,分析桥梁在随机车流作用下的结构动力特性,建立车辆超载超限分级预警管理系统与桥梁结构承载力安全状况分级预警管理系统。该监测系统可实时连续地监测桥梁,并对桥梁的安全运营状况进行评估。     

基于静载试验的某预应力混凝土简支板桥状态评估

我国目前阶段以及未来都有大量的桥梁需要进行检测和承载力评估.论文以国内某座预应力混凝土简支空心板梁桥为背景,介绍了基于静载试验的桥梁检测内容、过程和方法.在桥梁结构的试验测试数据和理论计算结果比较分析的基础上,对桥梁的横桥向连接性能、各板的弹性工作状况以及受力状态等方面进行了评价.同时该桥的测定和分析方法也可作为同类桥型设计和施工的参考.     

Development of an Environmental Load Estimation Model in the Planning Stage of Steel Box Girder Bridges

Currently, there is increased concern regarding environmental pollution, and research has been conducted to assess the life cycle of environmental pollutants to determine environmental compatibility. In particular, an SOC facility is expected to severely affect the environment since various materials are used through complex processes. However, countermeasures and research regarding environmental pollution in SOC facilities are insufficient. This study built design data about the steel box girder bridges of 120 that have been designed since 2000, and life cycle assessments were carried out in the planning stage. First, a standard classification of steel bridges was established, and a detailed statement of the design for basic design data and input materials for each target bridge was analyzed, and the environmental load amounts for each material that is used was estimated by applying LCI DB, presented as a characteristic value and weighted value. A correlation analysis was conducted to select the influence during the planning stage. We developed an environmental load amounts calculation model using casebased reasoning. The environmental load amounts and the estimation of the environmental load models was derived from this study and considered to be useful to produce basic data in life cycle assessment when designing steel bridges.