The development of the bridge life-cycle performance and cost approach, with emphasis on analysis, prediction, optimization, and decision making under uncertainty, is briefly reviewed. 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 by using multi-objective optimization in order to balance conflicting criteria such as performance and cost. A number of significant developments are summarized, including time-dependent reliability, resilience, risk, and sustainability of bridges and bridge transportation networks, in a life-cycle perspective. Finally, some of the future challenges are identified and suggestions for further development are provided.

Cable-stayed bridges are complex structures which need to be monitored during service life. Requirements for monitoring vary between the different owners and indicate what are their main worries with respect to such bridges. On the basis of previous experiences some unified policies are being proposed to define monitoring requirements after taking into account not only the variables which may be more relevant to the structural behaviour but also those whose possible changes during service life are more significant. The structural parameters which are being considered are related to deck and cables vibrations, deck displacements, deck and pylons temperaturas.

Bridge dynamics and aerodynamics have been in many cases overlooked in the design stages and consequent low behavior performance and safety margin have been not rarely observed and detected by means of measurements soon after the bridge is brought into full service.

The above statement serves for any type of bridge structure – constructed with any conventional or non-conventional and composite material – having a considerable slenderness ratio typical of modern bridge´s structures.

Design and practical requirements for a high structural performance and safety are pointed out and discussed. Case examples of actual bridges subjected to dynamic forces produced by the traffic of heavy vehicles and by the wind action are explored to show the observed misbehavior and the faults which had their origin in one or a combination of some of the following main sources of problems:

1. Computational modeling of the structural system;
2. Mathematical modeling of the forces produced by the dynamic interaction between vehicles, pavement and the deck structure;
3. Mathematical models of the aerodynamic forces and lack of wind tunnel tests of reduced scale models for obtaining aerodynamic and aeroelastic coefficients to be taken into the mathematical models;
4. Lack of detailed numerical modeling and poor geometrical design of structural components and their connections which is needed to perform sensitivity analyses of stress concentration points;
5. Lack of proper fatigue analyses of these connections and components; etc.

Another relevant practical aspect worth to bring about for discussion is the lack of comprehensive short term dynamic monitoring of the overall structural behavior and also of the variation of forces and stresses in the main components of the bridge, as soon as it is brought into service. The analysis of the collected data is fundamental to verify if: (i) the structure and its foundations have been built according to the design drawings; (ii) or instead, the theoretical models employed in the design calculations were not appropriate, leading to the observed misbehavior and faults.

The full understanding of the detected problems is then essential to mitigate design and construction errors and to rehabilitate the structural system, in order it may fulfill the established requirements for a good structural performance and safety.

The relevance and usefulness of dynamic control systems and long term monitoring in improving structural performance and safety are also briefly discussed.

In a country with continental dimensions, heavily dependent on the road infrastructure for transportation of all goods and people, and with a deficient and yet underdeveloped culture of regular inspection and maintenance, Bridge Conservation is certainly a major challenge. To compose the problem, inadequate quality control during execution and/or the lack of attention during operation, have resulted in many structures in Brazil presenting performance and deterioration problems, frequently requiring important, complex and costly interventions before the minimum service life expectancy of 50 years.

Despite the effort of some rare but qualified engineers on public agencies and institutions responsible by the bridge stock, structural conservation was poor and Bridge Management was practically unheard of in Brazil until the 90´s. Only when parts of the road network started to be conceded to private operators bridge condition monitoring and planned conservation strategies begun to be required. Since then we have had some important yet localized advances in this area, but there is still a long way to go. The situation is critical and demands a radical change on the way that Bridge Conservation is valued and performed. The good news is that the level of awareness towards the issue has been growing. Transportation regulation agencies and other important players, recognizing the need to face inspection and conservation challenges, have started actions towards improving the situation, at various levels. For example, recently the first national standard on Bridge Inspection was published by ABNT and there is a growing interest on implementing a nationwide Bridge Management System.This is certainly a critical issue, given that maintaining the road infrastructure on a good level of service has a direct impact on competitiveness. Much of the so talked about Brazil Indirect Cost on exports is associated with the poor condition state of large parts of the road network. At the same time, there is aggravating factors for bridge conservation. Changes on climatic patters have in some cases expressed themselves on higher and quicker precipitation, with greater hydraulic loads and failures risks imposed in some bridges or embankments. At the same time, economic turn up have meant a rise on the quantity and maximum load of heavy vehicles on some key trunk highways, where small bridges designed for other conditions play an important role.

All in all, there is a vital need for better bridge conservation, and therefore an important opportunity for the spread of good Bridge Management practices in Brazil. But to ensure that this demand is attended properly, identifying best practices nationally and internationally and understanding how to adapt them to the changing Brazilian scenario is critical. This work aims to contribute in this sense, discussing the current panorama, identifying the most important lessons learned over the last 20 years and discussing the challenges that will need to be faced to ensure that best practices on Bridge Management are effectively applied in our country. The need to enlarge knowledge on technical issues such as deterioration synergy and smart monitoring techniques is also identified and highlighted. Although based in an analysis of Brazilian reality, many of the lessons and challenges are similar to the ones faced by other developing (and some developed) countries. Hopefully the discussion will contribute towards the construction of a common agenda aimed at fostering better Bridge Management on an international level, where IABMAS Brasil may play its role.

This lecture makes an overview on relevant aspects related with the dynamic identification and continuous dynamic monitoring of bridges and large span structures, stressing their potential at different stages of bridges’ life-cycle.

This involves, in a first instance, a characterization of the evolution of perspectives concerning testing techniques, instrumentation, modal identification, mitigation of environmental effects on modal variability estimates and vibration based damage detection.

Subsequently, a representative set of dynamic tests and monitoring applications developed by the Laboratory of Vibrations and Structural Monitoring (VIBEST, www.fe.up.pt/vibest) of FEUP on relevant roadway, railway and pedestrian bridges are presented, showing the efficiency of the developed tools and the usefulness of the testing and monitoring programs implemented, enabling the achievement of different objectives, such as:

. the development of finite element model correlations and updating;
. the vibration serviceability safety checking, particularly in case of lively bridges involving the inclusion of vibration control devices;
. the implementation of automated versions of the most powerful methods of Operational Modal Analysis, and their application for tracking the time evolution of modal parameters in long-term dynamic monitoring applications;
. the application of statistical methods to remove or mitigate the influence of environmental and operational factors (e.g. temperature, intensity of traffic, wind) on the modal variability, supporting the development of reliable techniques for vibration based damage detection;
. the experimental assessment of fatigue, based on the measurement of effects of real traffic loads;
. and the experimental assessment of aerodynamic problems in bridges based on in-situ measurements.

Current bridge design and assessment practices remain primarily focused on evaluating the strength and serviceability of individual structural members and components. While this traditional member oriented approach has led to the design of safe bridge infrastructure networks, it is widely recognized that the approach does not necessarily lead to an accurate evaluation of the actual structural safety levels nor to the efficient utilization of limited resources when making decisions related to the management of existing deteriorating structures, especially those that may be exposed to extreme events. For this reason, there is renewed interest in developing system-level assessment methods as a basis to modern bridge safety evaluation and design processes.

This presentation reviews recent proposals for developing and implementing system performance criteria in bridge engineering. The presentation reviews established concepts of reliability-based design along with emerging ideas of performance- and resilience-based design that are especially relevant for assessing and managing system-level risk. The presentation also addresses the establishment of structural redundancy and robustness metrics as well as network based ranking criteria. Insights from these reviews emphasize the need to transition bridge design and safety assessment processes from the traditional component-level approach to one that seeks uniform levels of risk across scales (from structural systems to infrastructure networks). Examples are provided to illustrate the implementation of these concepts in bridge engineering practice.

Infrastructure plays a key and vital role in the economic development of a country or region and in several parts of the world this means constructing crossings across wide rivers, bays and estuaries, which have been a hindrance to the movement of people and goods and related economic development. Where crossings have been in the form of a bridge instead of a tunnel, the choice on type of bridge has been based on comparison of environmental, durability, maintenance, safety, construction period and cost considerations.

The method of construction has a significant influence on bridge durability which has led to the use of large off-site pre-fabricated elements being used for construction. Safety against fire and ship impact has been another major consideration influencing the span and configuration of the bridge.

The key-note lecture will describe the author’s personal experience in the design and construction of large sea-crossing bridges to achieve quality and durable construction, ease of inspection and maintenance and safety against fire and ship impact.

Masonry arch bridges still represent a crucial element of the railway transportation network across Europe. Many of them are part of the historical heritage of the XIX century, and are under-designed for actual service conditions. Due to the intrinsic weakness of some structural components, to deterioration phenomena and to the updating of structural codes, masonry arched structures show often inadequate performance considering the static and seismic requirements of current codes.

Reliable methods are thus required for the assessment of static and seismic reliability, and to prioritize retrofit interventions.

Simplified procedures shall be used for large-scale planning: for this purpose the kinematic method, based on an adaptation of limit design for masonry structures, has proved to be a conceptually simple and robust procedure to verify the safety of masonry arches. If more detailed analyses are needed on single structures, non-linear analyses using F.E. models can be adopted for a more comprehensive characterization of the behaviour under static and seismic forces.

Standard strategies should be finally proposed for the rehabilitation of arch bridges, taking into account to this end the original design and construction system and limiting to the minimum the required retrofit interventions.

Bridges can be categorized by span lengths, such as short span, medium span, long span and super-long span. Bridges can also be categorized by type, such as girder bridges, arch bridges, cable-stayed bridges and suspension bridges. It will be interesting to study how long a span each of these four types of bridges can be.

Many innovative long-span cable-supported steel bridges have been built around the world. When these bridges are constructed in wind-prone regions, they suffer considerable buffeting-induced vibration. The frequent occurrence of such a buffeting response at relatively large amplitude may cause fatigue damage to steel members and their connections. Long-span bridges also carry highway and/or railway loadings, and these dynamic loadings affect the fatigue life of the bridge as well. The fatigue damage prognosis (FDP) of bridges under multiple fatigue loadings is therefore necessary for bridge maintenance, safety and management. However, it is a challenging task due to the complexity of structural systems, randomness in fatigue loadings and complicated mechanisms of fatigue damage.

Long-term structural health monitoring (SHM) systems have been developed in recent years to measure the dynamic loadings and structural responses of long-span bridges, and to assess their functionality and safety while tracking the symptoms of operational incidents and potential damage. SHM technology thus provides a promising means of tackling challenging FDP issues. However, current research has tended to separate the SHM and FDP of long-span bridges, even though their integration has been advocated in other fields to achieve a reliable and robust FDP.

This paper will present an SHM-based FDP framework for long-span bridges under combined traffic and wind loadings based on the work done by the author and his co-workers over the past 20 years. It involves five major tasks: (1) integrate multi-scale finite element modelling and model updating with stress analysis for predicting both the global and local structural responses of long-span bridges under combined traffic and wind loadings; (2) develop loading models based on incessant field measurement data from the SHM system so that the previous loading histories can be analysed and future loadings can be forecast; (3) determine the optimal placement of multi-type sensors for the best global and local response reconstruction of the bridge; (4) propose an FDP model for the bridge based on continuum damage mechanics and measurement data; and (5) examine the feasibility of the proposed SHM-based FDP method through case studies. It is anticipated that the proposed approach will be one of the most comprehensive and reliable FDP methods for long-span bridges.