A review of experimental investigations and assessment methods for masonry arch bridges

Masonry arch bridges constitute a significant proportion of European road and rail infrastructures. Most of them are well over 100 years old and are supporting traffic loads many times above those originally envisaged. The inherent variation in their constituent materials, the traditional design criteria and methods used for their construction, their deterioration over time caused by weathering processes and the development of other defects, significantly influence the mechanical response of these historic structures. A deep understanding on the numerous factors that affect the structural behaviour of masonry arch bridges and on the analysis methods to assess the life expectancy of such bridges and inform maintenance and strengthening strategies is essential. This paper provides a critical review of the experimental studies that have been carried out and of the assessment approaches that have been developed in the last three decades to these aims. The current knowledge is established and areas of possible future research work are identified, with the aim of providing students and researchers, asset managers and bridge owners, and practitioners with a guidance for research activities and maintenace strategies.     

Bauwerks‐Management‐System (BMS) – Werkzeug zur Substanzerhaltung für Verkehrsbauwerke

Bridge Management System (BMS) – a tool for maintenance of highway structures. The federal road network of Germany contains a large number of highway structures like bridges, tunnels, retaining walls and others. The maintenance programs to be prepared for this purpose not only require a high budget, but also influence the economy and society as a whole. Due to growing volumes of traffic and higher weights of trucks, bridges are subjected to increasing loads which implies that maintenance costs will be rising in the future. Considering the fact that financial resources become continuously tighter, the maintenance costs have to be spent in a way to obtain the greatest possible benefits. This task will in the future be supported by the application of individual computer programs in the frame of a comprehensive Management System (Bridge Management System, BMS). Firstly, the BMS is to provide the Federal Ministry with an overview of the current situation at the overall network level, and allow it to come to financial requirements as well as strategies for realising long‐term objectives. Secondly, the states and authorities are to be supplied with recommendations for performing improvements at the object level and the state network level in compliance with given strategies and budgetary restrictions. The paper describes the existing regulations as well as procedures for the support of maintenance planning which are currently being developed for computer application. Important topics are information technology, development of maintenance strategies and assessment procedures on object and network level.     

Computational platform for the integrated life-cycle management of highway bridges

Throughout their service life, highway bridges are subject to progressive deterioration in performance; an issue that may render the use of these facilities unsafe at some point in time. Over the last few decades, there has been successful research towards developing procedures for establishing the various vital elements required in the life-cycle management of civil infrastructure. It is noted, however, that frameworks for integrating these elements together are lacking. The objective of this paper is to present an integrated framework for the life-cycle management of highway bridges in the form of a detailed computational platform. The elements integrated into the framework include the advanced assessment of life-cycle performance, analysis of system and component performance interaction, advanced maintenance optimization, and updating the life-cycle performance by information obtained from structural health monitoring and controlled testing.     

Iterative Equation Solver for Bridge Analysis Using Neural Networks

A technique for enhancing finite-element analysis equation solvers for particular problem domains, i.e., particular classes of structures such as highway bridges, is presented. The technique involves merging artificial neural networks, used as a domain knowledge-encoding mechanism, together with a preconditioned conjugate gradient iterative equation-solving algorithm. In the algorithm, neural networks are used to seed the initial solution vector and to precondition the matrix system using customizable and trainable neural networks. A case study is presented in which the technique is applied to the particular domain of flat-slab highway bridge analysis. In the case study, neural networks are trained to encode the load-displacement relationships for concrete flat-slab highway bridges. Analytical load-displacement data are generated using finite-element analyses and subsequently used to train neural networks. Acting collectively, the neural networks predict approximate displacement patterns for flat-slab bridges under arbitrary loading conditions.     

Seismic life-cycle cost analysis of ageing highway bridges under chloride exposure conditions: modelling and recommendations

Chloride-induced corrosion of highway bridges constitutes a critical form of environmental deterioration and may result in significant escalation of seismic life-cycle costs due to increased fragility during earthquake events. Most of existing literature tends to adopt simplistic uniform area loss assumptions in lieu of potentially complex, yet realistic and more detrimental, pitting corrosion models for seismic vulnerability analysis. Since the degree of deterioration depends on the severity and duration of exposure, there exists a need to investigate the influence of uniform vs. pitting corrosion assumption on seismic life-cycle costs for varied chloride exposure conditions. A case-study example of a highway bridge in Central and Southeastern US reveals consideration of pitting corrosion as critical for extreme exposures compared to relatively minor settings. Subsequently this study provides recommendations to aid bridge engineers and stakeholders to balance between computational cost and accuracy of results to aid prompt decisions on rehabilitation of ageing bridges in different exposure conditions. A framework is also included to compute seismic life-cycle costs from generic measures of corrosion, independent of assumed exposure scenario. This framework is particularly helpful for seismic loss assessment of highway bridges in chloride exposure zones with periodic field measurements to estimate the extent of structural deterioration.     

Seismic fragility assessment of highway bridges: a state-of-the-art review

Safety and serviceability of highway bridges, during and after an earthquake, is a prerequisite to ensure continuous transport facilities, emergency and evacuation routes. Recently, fragility curves have emerged as important decision support tools to identify the potential seismic risk and consequences during and after an earthquake. There has been a substantial increase in interest among researchers in the topic of seismic fragility assessment of highway bridges as evidenced by the growing number of published literature. Advanced computational techniques and available resources have led to the development of different methodologies for fragility assessment. This study presents a review of the different methodologies developed for seismic fragility assessment of highway bridges along with their features, limitations and applications. This study presents a review of available methodologies and identifies opportunities for future development. This study mainly focuses on the key features of different methods and applications rather than penetrating down to a critique of the associated analysis procedure or mathematical framework. It synthesises the existing information on fragility analysis, presents it in concise and useful tables, and explains different applications for different purposes, which would motivate decision-makers and stake holders to extend the application of fragility curves for more informed decision-making.     

浅析公路旧桥改造管理

结合海南省目前公路旧桥的现状,研究了公路旧桥常出现的主要病害,分析了公路旧桥养护管理存在的问题,提出了公路旧桥改造措施,指出了解国内外公路旧桥改造的方法和发展方向是搞好旧桥改造工作的关键。     

过街天桥冬季防滑设计研究

对北方多雪地区的过街天桥在冬季容易使行人滑倒的问题进行了分析,通过对不同过街天桥的调研,总结出通过改变建筑构造和材料的方法来解决多雪地区过街天桥上冬季防滑的问题,以期指导实践。     

Bridge retrofit prioritisation for ageing transportation networks subject to seismic hazards

The deteriorating state of highway bridges is traditionally ignored in estimating the seismic reliability of transportation networks. In this study, the present day seismic reliability of ageing bridges in highway networks is evaluated through a time-dependent seismic fragility analysis of typical bridge classes. An efficient algorithm based on finite-state Markov Chain Monte Carlo simulations is also presented to assess the reliability of large ageing highway bridge networks without the need to simplify the network topology. The criticality of ageing bridges is then assessed through different proposed ranking strategies to arrive at an optimised seismic retrofit prioritisation. A case study on an existing bridge network with 515 bridges in the state of South Carolina, USA reveals striking differences between results of the proposed ranking strategies and those from state-of-the-practice methods. Such differences emphasise the significance of accounting for network-level importance in seismic retrofit programs of ageing transportation networks.     

A condition assessment method for roadside assets

Infrastructure condition assessments provide key information for monitoring the quality of infrastructure, planning and budgeting of maintenance and rehabilitation activities and establishing performance goals. Although the literature is rich in condition assessment methods for roadway pavement and bridges (and to some extent for traffic signs), it is lacking such methods for roadside assets. This paper describes the development and validation of a condition assessment method for 12 roadside asset types and maintenance activities that are related to roadway safety, drainage, cleanliness and vegetation. These assets and maintenance activities are located in the area between the outside edges of the outside shoulders and the right-of-way boundaries. On divided highways, the median is also included. The developed condition assessment method consists of a set of performance standards, a visual inspection procedure to assess compliance with these standards and a statistical analysis procedure to determine the roadside level of service. To test and validate the developed method, it was applied to five highway corridors in Texas, USA, representing different climatic conditions, topography, traffic volume and population density (urban vs. rural). These field trials provided insights into the developed method, including practicality, reproducibility and probability distribution function which best represents the sample unit score.     

关于公路桥梁设计中的耐久性分析

较好的质量安全性、耐久性是公路桥梁设计中最关键的控制点。设计师们要在进行公路桥梁设计的过程中,对出现的安全性问题和耐久性问题进行仔细的分析。有侧重性地提出设计方法,保证公路桥梁在投入使用后满足交通车辆对安全和稳定的需要。本文对公路桥梁设计中的一些问题及原因进行了分析,希望能为公路桥梁工程提供一些参考意见。     

The use of nested sampling for prediction of infrastructure degradation under uncertainty

Because of the competing demands for scarce resources (funds, manpower, etc) national road owners are required to monitor the condition and performance of infrastructure elements through an effective inspection and assessment regime as part of an overall asset management strategy, the primary aim being to keep the asset in service at minimum cost. A considerable amount of information is then already available through existing databases and other information sources. Various analyses have been carried out to identify the different forms of deterioration affecting infrastructures, to investigate the parameters controlling their susceptibility to, and rate of, deterioration. This paper proposes such an approach by building a transition matrix directly from the condition scores. The Markov assumption is used stating that the condition of a facility at one inspection only depends on the condition at the previous inspection. With this assumption, the present score is the only one which is taken into account to determine the future of the facility. The objective is then to combine nested sampling with a Markov-based estimation of the condition rating of infrastructure elements to put some confidence bounds on Markov transition matrices, and ultimately on corresponding maintenance costs.     

Bridge performance indicators based on traffic load monitoring

The assessment of the existing road bridges as a part of bridge management networks has been a subject of several European research projects and actions in the last few decades. Bridge management includes a series of activities, interconnected in order to achieve optimal balancing of required costs, potential risks and overall bridge performance. This paper discusses a valuable link between a specific indicator (traffic load information calculated using Bridge Weigh-in-Motion measurement data) and the corresponding structural performance (reliability of existing bridge). It is shown that implementation of weigh-in-motion measurements in the probabilistic assessment of existing road bridges can reveal hidden bridge reserves and predict bridge reliability development over the required lifetime. Consequently, such approach can yield an unrestricted use of the bridge over a much longer remaining service life. Broader advantages lie in an improved road network management, road bridges in particular, and in a more sustainable development of infrastructure network and greater satisfaction of road users and owners.     

Reliability analysis for highway bridge deck assessment

An assessment procedure based on structural system reliability principles, has been developed for highway bridges with concrete or composite decks. It concentrates on the ultimate flexural limit state of slabs and takes account of the fact that the failure of the structure is dependent on the combination of the applied loads, their variability, both spatial and in amplitude, and on the variability of geometric and material properties. Recognising that each of a number of topologically distinct collapse mechanisms may contribute to the overall probability of system failure, an optimisation technique is used in conjunction with structural reliability analysis in order to establish for each mechanism the critical geometry and the associated probability of occurrence.The procedure can be implemented in the assessment of existing bridge structures, where the use of plastic analysis may reveal strength reserves not utilised in design and, hence, alleviate the need for strengthening. By modelling the bridge as a virtual series system and analysing a finite number of collapse mechanisms, bounds on system failure probability in flexure can be estimated. An example of its intended use is presented for a solid slab concrete bridge deck.     

Direct displacement-based assessment with nonlinear soil–structure interaction for multi-span reinforced concrete bridges

A practical and readily implementable seismic assessment procedure for multi-span reinforced concrete bridges is introduced in this paper. The procedure is based on an existing direct displacement-based assessment (DDBA) approach, and accounts for nonlinear dynamic soil–structure interaction (NLSSI) effects. Several simplified bridge structures lying on shallow foundations have been used as application examples. The validation has been done by comparing DDBA+NLSSI with the results of finite-element nonlinear time-history simulations by means of incremental dynamic analysis. Moreover, the influence of NLSSI on the assessment procedure has been evaluated by considering the same bridges with fixed base and with NLSSI effects. In spite of its simplicity that presently prevents its use for complex bridge structures, the proposed procedure is found to provide fast and reliable results, useful to give a first-level screening on a large set of bridges for highlighting the most critical situations, as well as to carry out fast parametric analyses to produce fragility curves in the framework of performance-based vulnerability/risk assessment.     

Optimization of bridge maintenance strategies based on structural health monitoring information

Highway bridges are subjected to strength degradation processes. Under budget constraints, it is important to determine the best maintenance strategies. Optimized strategies, based on prediction models, are already considered for the maintenance and operation of highway bridges. Prediction models are updated both in space and time by using non-destructive testing methods. Nevertheless, there is an urgent need for the efficient inclusion of structural health monitoring (SHM) data in structural assessment and prediction models. Indeed, SHM allows keeping strength degradation processes under control and should be included in life-cycle cost models. The lifetime reliability of structures is characterized by survivor functions. The SHM data enable to update the probability density function of time to failure through a Bayesian process. The aim of this paper is threefold: (a) to include SHM data in a bridge life-cycle cost analysis, (b) to determine optimal maintenance strategies based on monitoring information, and (c) to show the benefits of SHM. Optimal strategies are determined considering the cases without and with including monitoring results; the benefit of monitoring is then highlighted. The proposed concepts are applied to the I-39 Northbound Bridge over the Wisconsin River in Wisconsin, USA. A monitoring program of that bridge was performed by the ATLSS Engineering Research Center at Lehigh University.     

Acoustic emission to assess and monitor the integrity of bridges

Increased axle loads and traffic density necessitate strengthening and widening of traditional masonry arch bridges. The question remains as to how to evaluate the condition of a bridge and assess the effect of modern traffic on its serviceability? The focus of this paper has been the evaluation of the potential for the acoustic emission technique to provide cost effective in-situ long term monitoring of bridge condition. The work was performed on a bridge chosen to be representative of both masonry and reinforced concrete construction methods. The results demonstrate that acoustic emission technique can be applied to condition assessment of bridges. These results confirm that strong acoustic emission signals are obtained from reinforced concrete structures and demonstrate that acoustic emissions can be detected in masonry structures but at lower energy levels. The experimental programme has shown that AE is useful in detecting crack growth and determining the position of the crack tips at a much earlier stage in their development, before they are noticed during visual inspection     

Fatigue analysis of long-span suspension bridges under multiple loading: Case study

Long-span suspension bridges are often subject to multiple types of dynamic loads, especially those located in wind-prone regions and carrying both trains and road vehicles. Fatigue assessment shall be performed to ensure the safety and functionality of the bridges. This paper proposes a framework for fatigue analysis of a long-span suspension bridge under multiple loading by integrating computer simulation with structural health monitoring system. By taking the Tsing Ma Bridge in Hong Kong as an example, a computationally efficient engineering approach is first proposed for dynamic stress analysis of the bridge under railway, highway and wind loading. The fatigue-critical locations are then determined for key bridge components, and databases of the dynamic stress responses at the critical locations are established. The time histories of dynamic stresses induced by individual loading during the design life of the bridge are generated based on the databases. The corresponding stress time histories due to the combined action of multiple loading are also compiled. Finally, fatigue analysis is performed to compute the cumulative fatigue damage over the design life of 120 years. The results indicate that it is necessary to consider the combined effect of multiple loading in the fatigue analysis of long-span suspension bridges.     

Real-Time Quality Monitoring and Control of Highway Compaction

Compaction quality affects the long-term performance of highways, and thus is important in the highway construction. The current practice for compaction quality control primarily relies on the monitoring of rolling parameters such as rolling passes, speed and vibration of rollers, and lift thickness. Soil samples are randomly collected to evaluate the compactness. This practice is subject to two main limitations. First, the compaction monitoring and measurement are not always comprehensive since limited samples are manually collected. Second, compaction information cannot be disseminated to owners, supervisors, contractors, and operators in timely fashion. In this study, intelligent compaction (IC) technology is leveraged to monitor and control highway compaction quality. A new measure of compaction quality, compaction power per unit volume (E), is created and used with other IC measurement values such as compaction meter value (CMV) to achieve more reliable monitoring and assessment. Field experiments were conducted. The results demonstrated that the integration of CMV and E in the regression model leads to a higher coefficient of determination than that of using only CMV or E. A real-time monitoring system is developed, which not only evaluates the compaction quality of the entire area, but also synchronizes the compaction information among owners, supervisors, contractors, and operators in real-time. As such, this system cultivates an integrated “operator–contractor–supervisor–owner” quality control mechanism, which can improve the current highway compaction practice.     

城市与公路桥梁技术状况评定方法对比分析

为研究中国城市与公路桥梁技术状况评定方法的差异和适用性,科学选择评定方法,针对《城市桥梁养护技术规范》(CJJ 99—2003)、《公路桥涵养护规范》(JTG H11—2004)、《公路桥梁技术状况评定标准》(JTG/T H21—2011)和《城市桥梁养护技术标准》（CJJ 99—2017）的理论基础和实际应用进行了对比分析。首先详细阐述规范中不同桥梁技术状况评定方法的基本理论和实施方法,然后从标准类型、评定方法、评定过程、病害分级、评定层次和等级、适用性和优缺点等方面对几种评定方法进行对比分析,并在多座病害程度不同的各种类型桥梁上开展应用对比研究,最后结合应用情况提出针对不同状况评定方法的改进建议。结果表明:现有公路、城市桥梁状况评定方法大都采用综合评定方法,在本行业的桥梁状况评定和养护管理中都起到了重要作用,但在理论结构、计算模型、评定方法、评分标准、等级划分和实际评定应用方面存在一定差异,每种评定方法均有其适用性,各有优缺点,在使用过程中需要互相借鉴、取长补短;针对不同评定方法在实践应用中出现的问题,需要从桥梁病害源头、评定具体实施细则和信息化、智能化评定等方面进行完善和改进。