Curling of concrete slabs on grade: experimental versus theoretical analysis

Bridge structures are very critical elements within a complex transportation system, and movable bridges are especially important because they provide an effective way for traffic to cross an active waterway granting passage to ships that would otherwise be blocked by the infrastructure. As a consequence, reliability assessment as well as health monitoring of movable bridge structures are challenging issues that deserve significant attention because structural failures or temporary out-of-service may have a tremendous socio-economic impact. In this perspective, the structural monitoring of movable bridge structures can support more reliable numerical simulations, thus increasing the consistency of the whole assessment process. Moving from these considerations, the present paper addresses the optimal sensor placement (OSP) for monitoring a historic swing bridge in Taranto (Italy) by means of dynamic measurements. First, the bridge structure and the structural model are briefly illustrated. Subsequently, the considered strategies for sensor positioning are presented. Comparative analyses are finally performed to support the experimental design for this special infrastructure.     

Bewegliche Brücken für den Straßenverkehr in Deutschland

Movable bridges for road traffic in Germany. In Germany there are about 120000 fixed bridges for road traffic, on the other hand there are only 130 movable bridges for road traffic in practical application. In the following paper this bridge category is presented with partly very interested technical solutions. Flap bridges with scale beam, flap bridges with deep‐seated counterbalance, lifted bridges and swing‐bridges are treated. Some notable, built bridges are presented for every category. Finally special technical dates from nearly all built bridges are summarized in tables, which give a survey for the respective movable bridges in Germany.     

Seismic analysis incorporating detailed structure–abutment–foundation interaction for quasi-isolated highway bridges

The Illinois Department of Transportation has adopted an economical and pragmatic methodology for designing earthquake-resistant highway bridges in the Midwestern United States. These so-called quasi-isolated bridges employ low-cost non-seismically designed bearing components as sacrificial structural fuses. During seismic events, fusing actions of these components and subsequent sliding of superstructures on substructures are intended to achieve response characteristics similar to those of conventionally isolated bridges that employ specially designed isolators. This study explores seismic structure-abutment-foundation interaction for quasi-isolated bridges in Illinois, employing a detailed yet efficient non-linear finite-element model for seat-type bridge abutments. The abutment model incorporates many structural components and geotechnical mechanisms that are critical to seismic response of the structure-abutment-foundation (SAF) system. Through non-linear static analyses performed on a complete bridge model, the force-transfer mechanisms, component fusing performance, and potential failure modes of the SAF system were explored. Using earthquake ground motions, non-linear dynamic analyses were conducted to evaluate seismic characteristics of the quasi-isolated bridge, sequences of critical limit state occurrences, and effects of abutment attributes on bridge seismic performance. The influence of abutment model sophistication on simulated bridge response was also highlighted by direct comparison of simulation results obtained from different models.     

Frontier of continuous structural health monitoring system for short & medium span bridges and condition assessment

It is becoming an important social problem to make maintenance and rehabilitation of existing short and medium span(10-20 m) bridges because there are a huge amount of short and medium span bridges in service in the world. The kernel of such bridge management is to develop a method of safety(condition) assessment on items which include remaining life and load carrying capacity. Bridge health monitoring using information technology and sensors is capable of providing more accurate knowledge of bridge performance than traditional strategies. The aim of this paper is to introduce a state-of-the-art on not only a rational bridge health monitoring system incorporating with the information and communication technologies for lifetime management of existing short and medium span bridges but also a continuous data collecting system designed for bridge health monitoring of mainly short and medium span bridges. In this paper, although there are some useful monitoring methods for short and medium span bridges based on the qualitative or quantitative information, mainly two advanced structural health monitoring systems are described to review and analyse the potential of utilizing the long term health monitoring in safety assessment and management issues for short and medium span bridge. The first is a special designed mobile in-situ loading device(vehicle) for short and medium span road bridges to assess the structural safety(performance) and derive optimal strategies for maintenance using reliability based method. The second is a long term health monitoring method by using the public buses as part of a public transit system (called bus monitoring system) to be applied mainly to short and medium span bridges, along with safety indices, namely, “characteristic deflection” which is relatively free from the influence of dynamic disturbances due to such factors as the roughness of the road surface, and a structural anomaly parameter.     

天津开启桥钢箱梁半支架悬拼施工技术

天津海河开启桥为双叶立转式开启桥,其跨径、开启角度、桥面宽度较大,根据结构力学特点和现场通航环境,提出半支架悬拼装方法,将架设机、临时钢管支撑、悬臂拼装等传统桥梁施工方法结合,以适应开启桥施工的现场通航条件及施工过程的受力特征,钢箱梁吊运设备利用率高,可缩短施工周期,节约施工成本,取得了良好的社会经济效益。     

Development of a bridge maintenance system for prestressed concrete bridges using 3D digital twin model

Abstract

Preventive maintenance is increasingly becoming an essential strategy in the bridge industry owing to its proactive advantage of maintaining the structural sustainability during its entire service life. Several in-use bridges lack an appropriate regular maintenance solution, leading to extra cost during the operation stage. This paper proposes a new generation of the bridge maintenance system by using a digital twin model concept for more reliable decision-making. A detailed solution is proposed in this work to enhance the bridge maintenance process using a parallel solution: a maintenance information management system based on a 3D information model in conjunction with a digital inspection system using image processing. Three-dimensional digital models are required to utilise information from the entire lifecycle of a project, including design and construction, operation, and maintenance, by continuously exchanging and updating data from each stakeholder. For the maintenance of prestressed concrete bridges, the twin models are defined and their uses are presented.     

Characterising the effect of external factors on deterioration rates of bridge components using multivariate proportional hazards regression

Within asset management of infrastructure systems, increases in maintenance needs subject to budgetary constraints have motivated the development of tools to forecast deterioration to optimise maintenance intervention. Current bridge deterioration modelling approaches, including the evolving duration-based methods, routinely rely on a priori categorisation of bridges based on design, functional, and geographic factors to account for their effects on deterioration rates. However, such preclassification is often based on engineering judgement and may not reflect the true influence of these explanatory factors. In the current study, a proportional hazards regression-based methodology was developed to identify the most critical factors affecting deterioration using the entire unsegmented bridge database. The framework designed to perform this duration-based regression on large bridge databases is presented in this paper and results from implementation on a state inventory of over 17,000 bridges are discussed. The results provide insight into the extent that explanatory factors influence deterioration rates of different bridge components. A novel aspect of the developed framework is its ability to analyse the time-dependent effects of explanatory factors on deterioration rates over the lifecycle of the structural components. This analysis can be used to develop multivariate deterioration models and inform decision-making and prioritisation strategies.     

Reinforced concrete and masonry arch bridges in seismic areas: typical deficiencies and retrofitting strategies

In recent years, appraisal of the condition and rehabilitation of existing bridges has become an ongoing problem for bridge owners and administrators in all developed countries. Reliable methodologies are therefore needed in the assessment and retrofit design phases, to identify the vulnerability of each bridge class. The specific problems of common arch bridge types are discussed herein, for both reinforced concrete and masonry structures, proper interventions for their static and seismic retrofitting are illustrated and several examples of applications are provided. Retrofitting is usually coupled with functional refurbishment, according to a methodological approach that takes into account bridge characteristics, state of maintenance and functional requirements, and environmental aspects connected with repair and strengthening systems.     

Bridge condition modelling and prediction using dynamic Bayesian belief networks

The development of a condition-based deterioration modelling methodology at bridge group level using Bayesian belief network (BBN) is presented in this paper. BBN is an efficient tool to handle complex interdependencies within elements of engineering systems, by means of conditional probabilities specified on a fixed model structure. The advantages and limitations of the BBN for such applications are reviewed by analysing a sample group of masonry bridges on the UK railway infrastructure network. The proposed methodology is then extended to develop a time dependent deterioration model using a dynamic Bayesian network. The condition of elements within the selected sample of bridges and a set of conditional probabilities for static and time dependent variables, based on inspection experience, are used as input to the models to yield, in probabilistic terms, overall condition-based deterioration profiles for bridge groups. Sensitivity towards various input parameters, as well as underlying assumptions, on the point-in-time performance and the deterioration profile of the group are investigated. Together with results from ‘what if’ scenarios, the potential of the developed methodology is demonstrated in relation to the specification of structural health monitoring requirements and the prioritisation of maintenance intervention activities.     

自行式移动模架在50m连续梁上的应用

结合某8×50m连续梁工程实例,总结了MSS自行式移动模架的组成、构造、工作原理,简述了其施工技术,为类似工程提供参考价值。     

Design and construction of two integral bridges for the runway of Milan Malpensa Airport

In this study, two bridges recently completed at the Malpensa Airport are presented. The bridges overpass the trench where the railway track from Malpensa Airport runs to the city of Milan. They are part of a U-shaped path, called the hotel (H) ring, which connects the southern ends of the two existing taxiways. Such a crossing had to: (a) intersect the railway track twice with a high skew angle, (b) carry the maximum aeronautical loads, corresponding to the gears of an AIRBUS 380 aircraft and (c) host a 60-m wide taxiway strip, plus a lateral safety lane and a service road, for a total width of 96 m. For a bridge operating in such an environment, it was imperative to reduce inspections and maintenance activities to a minimum. Therefore, the designers excluded any detail arrangements or auxiliary devices having life-cycle performances much shorter than that of the main structure. In particular, expansion joints and movable or deformable bearing supports were excluded. Such constraints led to design two structures having the peculiar features that characterise them as integral bridges. This paper will firstly recall the aeronautical and railway specifications and the other operating constraints that characterised the design. In the second part, the criteria followed in designing the foundations, the abutments and the deck are presented. The structural analyses were set out in accordance to the sequence of the construction stages. For the bridge in its service configuration, self-weight and permanent loads give rise to a set of internal forces typical of a portal frame, while the localised loads, due to the aircraft gears, induce bubble deformed shapes characterised by particular transversal load distribution mechanisms. Details of completions and finishing works are finally given.     

连续刚构桥梁养护技术研究

针对连续刚构桥梁的自身结构特点，探讨了连续刚构各关键部位的检查和养护方法，提出和总结了一些对策，可为该类桥梁的日常管理与养护维修工作提供参考。     

既有混凝土桥梁病害特征及病因浅析

根据重庆市某高速公路上21座既有混凝土桥梁的检测,既有混凝土桥梁存在梁体混凝土外观较差、梁底混凝土出现多处裂缝、曲线桥梁体滑移、预应力筋锚头及钢绞线外露、墩柱和盖梁产生裂缝、支座发生剪切变形等病害特征,并对这些病害产生的原因进行了细致的分析。对完善混凝土桥梁设计理论、施工技术、桥梁运营期间的监测及养护工作有一定的指导意义。     

钢管混凝土在桥梁工程中的应用与前景

钢管混凝土(CFST)具有承载力高、施工方便和抗震能力好等优良性能,在国内外桥梁工程中得到较为广泛的应用。全面地总结了钢管混凝土结构在梁式桥、拱桥、斜拉桥等多种桥型中的应用情况,并着重探讨了钢管混凝土桥墩的研究和应用现状。介绍了"部分钢管混凝土"桥墩的试验结果。探讨了钢管混凝土结构应用于桥梁工程中还有待解决的主要问题。最后对钢管混凝土在桥梁工程中的应用前景作了展望。     

Bridge life-cycle performance and cost: analysis,prediction, optimisation and decision-making

The development of a generalised framework for assessing bridge life-cycle performance and cost, with emphasis on analysis, prediction, optimisation and decision-making under uncertainty, is briefly addressed. The central issue underlying the importance of the life-cycle approach to bridge engineering is the need for a rational basis for making informed decisions regarding design, construction, inspection, monitoring, maintenance, repair, rehabilitation, replacement and management of bridges under uncertainty which is carried out by using multi-objective optimisation procedures that balance conflicting criteria such as performance and cost. A number of significant developments are summarised, including time-variant reliability, risk, resilience, and sustainability of bridges, bridge transportation networks and interdependent infrastructure systems. Furthermore, the effects of climate change on the probabilistic life-cycle performance assessment of highway bridges are addressed. Moreover, integration of SHM and updating in bridge management and probabilistic life-cycle optimisation considering multi-attribute utility and risk attitudes are presented.     

基于CFRP吊杆的下承式系杆拱桥结构性能研究

为解决系杆拱桥吊杆锈蚀及抗疲劳性能差的问题，提出了将CFRP材料应用于系杆拱桥吊杆的方法，通过对不同替换原则作用下系杆拱结构及吊杆构件的力学性能对比，确定了等面积原则作为材料替换的方法；利用有限元软件对比分析了不同荷载作用下CFRP吊杆与钢绞线材料间结构的静力响应，二者受力变化相差较小，CFRP材料可有效替代钢绞线作为系杆拱桥吊杆材料；并基于短吊杆效应对比分析了吊杆受力，与全桥结构替换相比，单吊杆替换对于实桥应用更为有效可行，推广了CFRP材料应用于吊杆拱桥的实际工程案例，为系杆拱桥的发展提供了新的思路。     

新材料在移动桥梁中的初步应用

介绍了FRP的研究与发展历程及分类,分析了FRP材料的特点以及与钢材相比的突出优点,分析了适合应用于桥梁工程的CFRP材料特性,介绍了国外CFRP在移动桥梁方面的研究与应用,最后指出了FRP还有待深入研究的方面。     

Dynamical identification and modelling of steel–concrete composite high-speed railway bridges

In the last few years, the construction of new high-speed (HS) railways across Europe, as well as in many other countries, has required many different bridges and viaducts. Together with classical concrete solutions, new steel–concrete composite typologies have been developed, giving light and cheap structures. Despite these studies and applications, some concerns still remain about the definition of reliable models for the evaluation of their actual dynamical behaviour under HS train passage. In particular, the influence of many structural and non-structural components, such as cross-girders and ballast, are still not well recognised. In this paper, open problems related to the dynamical assessment and modelling of new steel–concrete four-parallel-girder and box-girder solutions are exposed and analysed. A suitable procedure, based on operational modal analysis, model updating and train–bridge interaction analysis is applied to two bridges, recently built in the new Italian HS network, in order to assess and verify their dynamic behaviour under operative conditions.     

桥型象限图在构建协作体系桥梁中的研究

为推动协作体系桥梁的发展,本研究利用桥型象限图对多座现有协作体系实桥进行了构建验证,并通过桥型象限图构建出多种新的不同结构类型的协作体系桥梁。研究表明协作体系桥梁是以五类基本桥型为基础的复杂桥梁,基于桥型象限图能排列、组合出各种不同结构类型的协作体系桥梁。根据协作体系桥梁的特点,提出一类针对大跨度梁式桥跨中下挠病害的加固专用协作体系桥型方案。桥型象限图可为今后协作体系桥梁的设计与研究,提供一种简单快捷方法。     

大跨度预应力混凝土桥智能拆除技术现状与展望

为实现大跨度预应力混凝土桥拆除的安全可控,通过分析桥梁拆除的特点及存在的技术问题,明确了基于数字孪生体技术的桥梁智能拆除的概念,厘清了桥梁智能拆除技术的发展阶段,展望了基于数字孪生体技术的桥梁智能拆除应用前景,综述了数字孪生体技术在桥梁工程中的研究现状; 结合某大桥拆除工程案例,对数字孪生体技术进行探索应用,不断提高桥梁拆除过程内力状态预测和控制精度,避免再利用构件二次损伤。研究结果表明:大跨度预应力混凝土桥拆除具有恒载内力状态不确定和施工状态不可控的特点,拆除时的结构力学行为是一个瞬间释放的过程,当主梁恒载负弯矩无法匹配预应力提供的正弯矩时,墩梁结合处梁段存在底板拉裂和顶板压溃的风险; 服役桥梁在荷载和环境长期耦合作用下结构性能不断劣化,由于养护不到位导致桥梁过早进入病害高发期,迫切需要通过养护加固提升结构性能,但是“过度医疗”的桥梁结构在经过长期运营后结构性能劣化速率会不断加快,将大大缩短桥梁的使用寿命,因此在最佳的养护时机采取合适的养护措施可以有效延长桥梁使用寿命; 然而,一系列维修加固措施又会使得桥梁结构状态精准评估和预测愈发困难; 桥梁智能拆除是借助新一代信息技术,实时掌握桥梁拆除全过程的真实受力状态,通过数据驱动虚拟桥梁在拆除过程中进行自感知、自演化、自学习、自评估、自决策和自执行,逐步实现人机协同拆除、自动化智能拆除的施工创新模式; 借助三维激光扫描仪和全站仪对桥梁结构进行数字重构,精准掌握桥梁恒载分布状况及拆除梁段吊重,通过状态反演的方法对拆除前外观病害和拆除中结构响应进行状态验证和模型修正,明确病害成因及演化规律,掌握结构恒载内力状态,动态调整监控阈值逐步逼近桥梁真实应力状态,从而预先识别风险工况并采取积极高效的安全控制措施,实现桥梁拆除过程的精准预测和控制; 对桥梁拆除后再利用构件进行精确测量、有损检测、耐久性试验和长期性能实时监测,有助于提高数字化检测技术的测量精度和效率,推动桥梁结构长期性能演化规律研究; 基于数字孪生体技术的桥梁智能拆除研究方向应重点关注桥梁损伤构件无损检测技术及定量分析方法、桥梁结构病害和长期性能演化规律、既有损伤的桥梁结构精细化模拟仿真技术、基于物联网技术的桥梁智能监测系统、基于数据驱动的智能拆除机器人自动化施工技术和桥梁全生命周期内数字模型构建、使用、维护、管理体系。