Fatigue assessment and strengthening measures to upgrade a steel railway bridge

The present paper deals with the experimental and analytical study of a 19th century riveted steel truss railway bridge to assess its current condition and remaining time of life. The analysis includes static and dynamic field measurements and laboratory tests. The evaluation of the capacity of the bridge for the trainloads, as well as for the seismic and wind loads, as specified by current design codes, was performed using a finite element model. Besides, after the owner's recent decision to upgrade the bridge to meet modern standards and new types of trains, the necessary strengthening was proposed, and the new estimation of the remaining fatigue life of the bridge after the suggested strengthening was also provided.     

Fatigue reliability assessment of a historic railway bridge designed by Gustave Eiffel

The evolution of the railway traffic during the last century is studied as preliminary step towards the estimation of the remaining service life of a historical bridge. The selected case study concerns the El Ourit Bridge, designed in 1889 by Gustave Eiffel and located close to the town of Tlemcen, in Algeria. A finite element model of the structure is built and the response of the bridge to train-crossing loads is numerically evaluated with the purpose of identifying the element most affected by stress variations. The Palmgren–Miner accumulation model is used to quantify the fatigue damage in this element. A limit state function based on this criterion is formulated; then, a fully probabilistic approach is adopted by assuming that the stress amplitude, the fatigue strength and the damage threshold value play the role of random variables. The obtained results are discussed in order to evaluate the residual service life of the bridge.     

钢箱梁焊接细节基于长期监测数据的疲劳可靠性评估:疲劳可靠度指标

提出基于长期监测数据的钢箱梁焊接细节疲劳可靠度的评估方法,并以润扬大桥悬索桥和斜拉桥钢箱梁顶板-U型肋焊接细节为对象开展应用研究。首先,建立疲劳损伤极限状态方程并讨论方程中各个参数的概率分布特性,在此基础上,采用最优化方法进行疲劳可靠度的求解,得到疲劳可靠度指标随服役时间增长的变化规律和日循环次数Nd的随机性对可靠度的影响。最后重点研究疲劳荷载效应增长对可靠度的影响,并据此提出对大桥日常运营管理的建议。结果表明:①将Nd作为随机变量处理是偏安全的,且Nd的随机性对斜拉桥焊接细节可靠度影响要较悬索桥更为显著;②悬索桥焊接细节的疲劳可靠度明显低于斜拉桥;③考虑疲劳荷载效应的增长会显著减小两桥焊接细节的疲劳可靠度;④为了得到钢箱梁焊接细节在服役期内的疲劳可靠度的准确评估,对其进行长期的应变监测是必要的。     

平行钢丝斜拉索疲劳性能评定I：钢丝疲劳寿命模型

平行钢丝斜拉索疲劳性能评定研究分为两部分,该文为第一部分：钢丝疲劳寿命模型。根据三参数幂函数应力-寿命模型与指定应力幅下疲劳寿命服从两参数Weibull分布,推导表征疲劳寿命的多参数Weibull模型,将疲劳寿命与应力幅统一在模型中。进一步根据疲劳截尾数据的条件概率分布建立疲劳模型参数EM估计算法,通过分析文献中钢绞线疲劳数据及研究开展的高强钢丝疲劳数据阐述多参数Weibull模型的适用性与优点。研究表明：该多参数Weibull模型能够较好地描述钢丝及钢绞线疲劳试验数据,指定应力幅时疲劳寿命简化为两参数Weibull分布,指定疲劳寿命时应力幅简化为三参数Weibull分布。文中提出的模型参数EM估计算法有效地解决了含有截尾数据的模型参数估计问题,采用全部疲劳试验数据进行模型参数估计,提高模型参数估计的准确性。     

900t高速铁路架桥机动力特性分析

运用Super SAP的动力分析模块对900t高速铁路架桥机进行整体计算,获得了各阶模态下的固有频率和振型,同时对相应模态下的主振部件进行了判别并对其刚度进行了分析,从而为其动态特性预测以及动态优化设计提供必要的依据.     

900t高速铁路架桥机动力特性分析

运用Super SAP的动力分析模块对900t高速铁路架桥机进行整体计算，获得了各阶模态下的固有频率和振型，同时对相应模态下的主振部件进行了判别并对其刚度进行了分析，从而为其动态特性预测以及动态优化设计提供必要的依据。     

Shaking table test of composite foundation reinforcement of saturated silty soil for high speed railway

Three shaking table model tests were conducted with a geometrical scale of 1:10 using a large-scale laminar shear box to investigate the reinforcement effects of compacted gravel column-net composite foundation and cement fly-ash gravel (CFG) column-net composite foundation on the saturated silty soil along the Beijing-Shanghai High Speed Railway. The research results indicate that the increase in excess pore water pressure can be restrained effectively by the compacted gravel column-net composite foundation to improve the anti-liquefaction ability of the ground, and that shear displacement of the ground can be reduced greatly by the compacted gravel column-net and CFG column-net composite foundations to improve the capability of resisting shear displacement of ground. Furthermore, the amplifying of response acceleration, induced by foundation liquefaction, and the settlement of foundation and subgrade can be reduced greatly by the compacted gravel column-net and CFG column-net composite foundations to improve the aseismatic property of the foundation and subgrade. __________ Translated from Journal of Southwest Jiaotong University (Natural Science Edition), 2006, 41(2): 190–196 [译自: 西南交通大学学报 (自然科学版)]     

Fatigue and fracture simulation of welded bridge details through a bi-linear crack growth law

This paper deals with the application of a probabilistic fracture mechanics approach to predict the fatigue life of welded steel details in the presence of cracks under bridge spectrum loading. It is based on a recently proposed bi-linear relationship to model fatigue crack growth and incorporates a failure criterion to describe the interaction between fracture and plastic collapse. The formulation leading to the expected number of cycles to failure is first outlined, followed by a simple example on a butt-welded detail. Uncertainty modelling, especially on fatigue crack growth parameters, is undertaken with the aid of recently published data in support of the bi-linear crack growth relationship. Results pertaining to fatigue reliability and fatigue crack size evolution are presented using simulation with Latin Hypercube Sampling, and emphasis is placed on a comparison between linear and bi-linear crack growth models. The latter is found to lead to higher fatigue life estimates and significantly different crack size distributions, both of which have implications on inspection schemes for steel bridge components.     

Strengthening of a steel railway bridge and its impact on the dynamic response to passing trains

Two different strengthening methods for a through-girder steel railway bridge are investigated. The studied structure is the Söderström Bridge, located in the city of Stockholm, Sweden. Due to fatigue problems, it is in need of assessment and strengthening. In one of the methods, arches are added under the bridge modifying the structural system and lowering the stress ranges for all structural members. The other method consists of prestressing the floor beams. This increases their stiffness and transforms the mean stress in the lower flanges from tension to compression. A 3D finite element model is created and verified with measurements. The different strengthening methods are tested in the model by dynamic analysis with moving train loads. The strengthening methods show some positive effect concerning the fatigue life. Changes in vertical bridge deck acceleration for high speed traffic are also presented. A comparison between the European code and the Swedish code regarding vertical bridge deck acceleration levels for high speed traffic shows large differences for the bridge.     

京沪高速铁路双线箱梁800t级架桥机方案研究

文章对京沪高速铁路架设双线整孔预制箱梁架桥机的几种典型方案进行了分析与评述，提出了800t级运架一体机的改进方案，并对其应用前景进行了展望。     

Life cycle assessment of a railway bridge: comparison of two superstructure designs

Railway bridges currently encounter the challenges of increasing the load capacity while the environmental sustainability should be achieved. However, it has been realised that the environmental assessment of railway bridges has not been integrated into the decision-making process, the standard guideline and criterion is still missing in this field. Therefore, the implementation of life cycle assessment (LCA) method is introduced into railway bridges. This article provides a systematic bridge LCA model as a guideline to quantify the environmental burdens for the railway bridge structures. A comparison case study between two alternative designs of Banafjäl Bridge is further carried out through the whole life cycle, with the consideration of several key maintenance and end-of-life scenarios. Six impact categories are investigated by using the LCA CML 2001 method and the known life cycle inventory database. Results show that the fixed-slab bridge option has a better environmental performance than the ballasted design due to the ease of maintenances. The initial material manufacture stage is responsible for the largest environmental burden, while the impacts from the construction machinery and material transportations are ignorable. Sensitivity analysis illustrates the maintenance scenario planning and steel recycling have the significant influence on the final results other than the traffic disturbances.     

Response and fatigue assessment of high speed aluminium hulls using short-term wireless hull monitoring

This paper proposes a wireless hull monitoring system that is quick to install as a short-term monitoring solution. Hull measurements have the potential to increase the accuracy of ship response predictions at a lower cost than computer simulation or towing tank models. The performance of the wireless monitoring system is validated on the all-aluminium United States Coast Guard Response Boat-Medium. The system is designed to measure ship motions and hull strain responses during high-speed operations and in harsh weather conditions. An analytical framework is developed to extract sea states from inertial measurements recorded at the ship centre-of-gravity and in a bow compartment. To assess the fatigue life of the hull during harsh weather operations, response amplitude operators (RAOs) are empirically derived to map sea states to root mean square accelerations and strain cycles measured from a high-stress hull element. A RAO that maps sea state to consumed fatigue in the hull, so termed a consumed fatigue operator (CFO), is presented which can assist in the management of an asset over its life cycle. The study reveals reliable hull monitoring during a one-week sea trial. RAO and CFO fit to hull response data are proven to provide accurate estimates.     

Fatigue behavior and statistical evaluation of the stress category for a steel-concrete composite bridge deck

The maintenance cost of bridges is rapidly increasing since many existing bridges are deteriorating or reaching their design life all over the world. Moreover, as many long-span bridges are under construction and planning in Korea, research and development on bridge decks with high load-resistance capacity as well as high fatigue strength has become a growing concern. This research gives experimental results of the fatigue behavior of a new-type of steel-concrete composite bridge deck being developed under such circumstances. The proposed composite bridge deck consists of corrugated steel plate, welded steel ribs, stud shear connectors, and reinforced concrete filler. Fatigue tests were conducted under a four-point bending test with four different stress ranges in constant amplitude. In order to determine the influence of the concrete filling, fatigue tests on partial steel specimens containing only plain corrugated steel plates were performed in advance. The partial steel specimens and the steel-concrete composite deck specimens both showed fatigue failure in the tension part concerning the fillet welding part between the corrugated steel plate and steel rib. Finally, the stress category of the fillet welding part of each specimen is evaluated based on a statistical approach of Albrecht’s probability model. The research concludes that the fatigue behavior of such steel-concrete composite decks under sagging moment can be estimated based on the classical S-N approach, focusing on steel components.     

跨海高铁施工成套信息化关键技术研究及应用

当前,信息化、智能化备受各行业关注和重视,已成为工程项目管理科学化、标准化的必然途径之一.国内高铁施工建设信息化、智能化建造应用已取得一定成效,但仍处于起步阶段.以新建福厦高铁信息化组网建设为基础,探索信息化、智能化技术在高铁施工项目管理中的应用及其建设重要意义,完善高铁桥梁建造信息化、智能化应用管理技术,提高高铁项目...     

高墩大跨度铁路桥梁悬臂浇筑施工监控

结合新建铁路贵阳至开阳南江特大桥悬臂施工监控实践,介绍了高墩大跨连续刚构桥的施工监控理论。采用有限元软件建立该桥的有限元计算模型,对该桥各施工阶段的主梁挠度及应力进行了仿真模拟分析,并在施工监控中对比分析计算数据与实测数据,以期指导施工并为同类型桥梁的施工控制提供参考。     

Impact of track irregularities and damping on the fatigue damage of a railway bridge deck slab

The structural response of reinforced concrete slabs in railway bridges is strongly influenced by local dynamic effects and, therefore, detailed calculations of internal forces have to be performed for a realistic fatigue assessment. In this context, this paper discusses the influence of track irregularities and modal damping coefficients in the dynamic response and fatigue behaviour of a railway bridge deck slab. For that purpose, track irregularities were measured (at different instants of time) and damping coefficients were determined based on acceleration records for passing trains in a real bridge. The bridge behaviour was calculated using a train–bridge interaction methodology, considering calibrated numerical models of the viaduct and the train. The fatigue damage was quantified through the linear damage accumulation method. This methodology allowed to understand the way track irregularities and damping coefficients affect the magnitude of applied bending moments and fatigue damage in the slab.     

Fatigue life prediction of heavy mining equipment. Part 1: Fatigue load assessment and crack growth rate tests

Frequent fatigue failure of heavy mining equipment has created the need for fatigue life prediction of its cracked components. As the first step, field monitoring of a cable shovel boom that had a history of chronic fatigue cracking was conducted. A set of load spectra for the boom was constructed from the collected field data. A finite element model of the boom was prepared and calibrated against the test data to predict the stress and strain histories. Eight crack growth rate coupon tests were carried out to obtain the fatigue properties of the material used. Constant amplitude equivalent stress ranges were calculated based on Palmgren-Miner’s cumulative damage rule and crack growth rate tests results.     

高速铁路隧道衬砌缺陷整治方案比选研究

为研究高速铁路隧道衬砌缺陷的整治措施,首先对衬砌缺陷的成因进行分析,同时提出两套合理的整治方案,并从经济性、安全性、适用性、有效性等方面进行对比分析,提出采用粘贴钢带加固法。该方法施工简便、施工进度快、安全度高,并可以降低成本,对隧道衬砌结构整体性影响小。     

A pilot study of the wind speed along the Rome–Naples HS/HC railway line.: Part 2—Probabilistic analyses and methodology assessment

The safety of railway operations under wind actions has recently become a topical matter due to the development of high-speed trains, which are very sensitive to crosswind conditions. For this reason, RFI (the Italian railway network) has entrusted the University of Genoa with a study of the wind hazard of the Rome–Naples High Speed (HS)/High Capacity (HC) railway line. A consistent part of such a study is focused on the probabilistic analysis of the wind speed and direction along that railway line, with the aim of developing a general procedure that can be applied to any railway line. This paper represents the logical prosecution of a companion paper where numerical simulations have been carried out of the wind fields along the line. These results are used together with a large amount of data measured by neighbouring meteorological stations in order to establish a probabilistic model of the wind speed and direction along the line. Such model provides a full representation of the wind climate and hazard of the railway line, and represents the basic step towards the development of a full risk analysis. Preliminary evaluations are also reported in order to assess the robustness and reliability of the methodology applied and the results obtained.     

Evaluation of a steel railway bridge for dynamic and seismic loads

In this study, dynamic and seismic assessment of a railway bridge system with four discrete spans giving service on a double track railway line and located in an earthquake-prone region in Turkey is presented. A three-dimensional computer model of the bridge was generated using a commercial general finite element analysis software. Field measurements such as static and dynamic tests as well as material tests were conducted on the bridge system. Validation of the finite element model was performed based on the results of these tests. The calibrated 3D model of the bridge structure was then used for necessary calculations regarding structural assessment and evaluation according to train loads as well as seismic loads. Additional members were proposed to transmit seismic loads to supports. The fourth span, which had a permanent imperfection due to truck collision was studied in detail. Results have shown that due to excessive amount of capacity loss, the only choice was to write off the fourth span.