In this special session, six papers on evaluation, assessment, repair and retrofit of fatigue and corrosion damage in steel highway and railway bridges are presented and discussed. We have a number of steel highway and railway bridge structures especially in urban area in Japan. Some of those structures suffer various types of fatigue and corrosion damage, but replace of them should be too expensive, and restriction or close of the traffic could be hardly allowed. So, rehabilitation of those structures becomes of great importance. Speakers are professors and experts on steel bridge structures who are working in universities, expressway companies and railway companies.

Efficient road infrastructure is one of the essential requirements for sustainable mobility and economic growth. The increase of freight transport during recent years has led to a situation where a significant proportion of bridges on Federal Roads in Germany and other European countries have already reached their limit capacity.

The expected strong increase in freight traffic (40% until 2030) together with the presente age and condition distribution, create serious challenges for owners and operators with regard to safety and availability of the road network.

To make sure that the future increase in freight traffic can be managed with a suficiente safety level assessments of existing bridges that will in many cases lead to measures for upgrading and/or replacement of bridges have to be carried out. Hence, a strategy for the assessment together with a rehabilitation program for upgrading and/or replacing bridges has to be defined.

The special session will deal with challenges for owners and operators. The first presentation will set the scene. Following statistics and facts the risk based top down approach for the prioritization of the bridge stock regarding the necessity for reassessments will be presented (Author: J. Krieger, Federal Highway Research Institute, Bergisch Gladbach, Germany).
The second presentation will describe the methodologies, tools and approaches that are being used for the re-assessment of existing bridges on Federal Roads in Germany (Professor B. Novák, University of Stuttgart, Germany).

The third presentation will address Non Destructive Evaluation methods that can be used for retrieving as built construction details of existing bridges. (Dr. Herbert Wiggenhauser, BAM – Federal Institute of Materials Research and Testing, Berlin, Germany).
Presentation four will focus on automated multi sensor assessment of concrete bridge deck assessment (N.N.).

Presentation five will present case studies for re-assessment including the realization of
compensation and/or upgrading measures (N.N.).

This Special Session focuses on practical state of the art guidelines for the assessment and decision-making procedures required for the life-cycle management of existing concrete bridges. The objective of this Special Session is to highlight the recent developments in the field of assessment and decision-making procedures for the life-cycle management of bridges. The Special Session covers the following topics:

. Survey and critical analysis of available evaluation / decision-making procedures;
. Practical decision making procedures for coherent assessment of existing bridges;
. Survey processes involving visual examination and utilizing various forms of sampling and localized condition testing for a meaningful assessment;
. Tools and techniques for surveys and monitoring;
. Optimizing surveys and monitoring;
. Characterization of deterioration mechanisms – benchmarks/synopsis;
. Prognosis methods;
. Threshold levels for structural performance – structural decision.

Any sort of structure is designed with a reasonable safety level. These expected performances are achieved by following code requirements, which specify the strength and the deflection levels under given combinations of dead, anthropic and environmental loads.

Despite the theoretical assumption of a suitable reliability, many types of structures don’t exhibit the expected performance levels, revealing lacks in our modelling and/or design approaches.

Among the main case of these failures, we experienced:

. some change in the boundary conditions, like excessive excursion of the bearing supports, settlement of foundations, scour effects in mobile riverbeds or pressure evolution against earth retaining structures;
. insufficient level of detailing;
. insufficient refinement in modelling techniques, due for instance to the pretension of managing together mechanical behaviours which develop at different scales;
. ingenuous assumptions of the material constitutive laws, in particular dealing with time dependant responses;
. the coupling among mechanical behaviours and environmental actions, based on too simplified modelling of the exposure effects, due for instance to wind, to fire, to corrosion or to wandering currents;
. occurrence of exceptional events, like collisions, explosions or terrorist attacks.

Many of these single items have their own specialized approaches, like multiscale, multiphysics techniques. Less frequent is the use of these tools in systemic analyses of complex structures, in complex environmental expositions.
Aim of this Special Session on “Unexpected and Sudden collapses”, is to call for contributions in the fields of design assessments, structural modelling, structural reliability and structural robustness, focussed on recurrent problems involving the bridges structures, according to a holistic view of the whole engineering process.

During the implementation of asset management strategies, maintenance actions are required to keep assets at desired performance levels. In case of roadway bridges, performance indicators, which can be obtained by inspections, non-destructive testing or monitoring systems, are established for components. These indicators allow to assess if quality control plans are accomplished. In Europe there is a large disparity regarding the way indicators are quantified and goals specified. COST Action TU1406 aims to bring together research and practicing communities in order to establish a European guideline and analyse the use of new indicators related to roadway bridges sustainable and economic performance.

Bridges for High-Speed Railways involves very specific problems where the train-track-bridge system behavior is of great relevance. The main scope of this thematic session is to present advanced knowledge in several topics on this subject, considered most relevant to the design, monitoring, maintenance, safety and management of this type of structures, and share the most innovative and interesting experiences on this field.

The session addresses modern IT and AI tools in bridge engineering. Knowledge about the existing traffic infrastructure gains more importance with increasing transport volume on one hand and ageing of bridges on the other. Engineers produce data, knowledge and resulting experience during inspections, maintenance measures, repair, field testing and in laboratory testing. Although public resources were spent in research, often, the knowledge about processing, interpretation and reuse of preexisting knowledge may be restricted to few publications or inside a consultancy. Expert systems allow transfer of inspection results into recalculation. The session calls for case studies about infrastructure knowledge management using artificial intelligence and knowledge-based expert tools.

A relatively small number of bridges (highway, railway and pedestrian bridges) has some sort of control device installed to attenuate the amplitudes of motion or stresses in order to improve serviceability and / or safety of the whole structural system or some of its main components.

In most cases the control system is designed and installed to solve a structural misbehavior or loss of structural integrity and safety margin which arise soon after the completion of the bridge or later while it is in full service. The most common structural problems are related to earthquakes, aerodynamic / aeroelastic phenomena and fatigue cracks, the latter usually caused by the dynamic interaction between heavy vehicles and the structure.

In very few cases a new bridge is designed under the concept of a controlled structure or controlled structural components. This is partly because engineers do not have yet a design code for controlled bridge structures. A counterexample of this attitude is the design of very tall buildings under action of wind forces and / or earthquakes.

The aim of this Special Session is twofold:

(I) To discuss these problems bringing forward new ideas and proposals to get reliable designs for lightweight and resistant bridge structures provided with control systems which require low maintenance;

(II) To report on long term performance of existing controlled bridge structures and also of the proper control devices, bringing to open discussion the sometimes hidden occurrences of wearing of mechanical parts, aging of materials, besides the need for frequent inspection and maintenance etc.

We hope that sound examples of successful performance of existing controlled bridge structures and the improvement of our knowledge in designing efficient and durable passive or active control systems through the exchange of ideas and true experience in overcoming operational faults shall guide engineers to design new controlled bridge structures.

Since the 1920s, and in response to the rapid growth of highway traffic volume, researchers and scientists have developed many different types of sensors to monitor the weight of vehicles traveling on the roadway. Weigh-in-motion (WIM), a technology that estimates the static weight of a vehicle by measuring the dynamic tire force while the vehicle is moving at highway speeds, provides an efficient way to monitor the truck weight spectra. Additionally, WIM sensors provide the configuration, speed information, and lane position of the vehicle. Moreover, the knowledge of live load spectra and its multiple presence statistics is essential in the development of new generation reliability-based design specifications. Also, various load rating and bridge evaluation guidelines include site-specific live load data collection to help provide a more accurate picture of the actual load and resistance performance of old and deteriorating bridges.

Considering these issues, the main goal of this special session is to highlight different aspects of WIM technologies and their success (or limitations) stories when applied to bridge structures. Various types of instrumentation and their configuration will be highlighted. Error minimization, signal processing, and temperature compensation in weighing will be also presented. Just like other types of sensors, WIM sensors also have their own strengths and limitations and the advantages and disadvantages of different types of systems will be presented. Current Standards and guidelines will be addressed in relation to site conditions and limitations of the standards for the application of highway WIM system. It is also intended to help develop guidelines for collecting live load data and its statists that will applied in the evaluation, assessment, and load rating of bridges by incorporating WIM data, structural health monitoring, probabilistic methods and prediction of long term live load effects. This Special Session will provide a platform for researchers from leading countries to discuss and compare various WIM methodologies that were adopted by their respective transportation agencies from various perspectives such as accuracy, life-cycle cost, life span, and application constraints. This Special Session will also promote and enhance future collaboration between different parties on this subject. Invited researchers and practitioners as well as vendors and owners will present results from their recently completed or ongoing research work and case studies.

The technique of Building Information Model (BIM) has been paid wide attention in recent years. Along with the development of the corresponding researches and applications, the influences of BIM on the building engineering are gradually recognized. The application of BIM in the bridge engineering is also under a rapid development. With the consideration of the specific characteristics of bridges in technique, industry level, organization and operation methods, etc., the development of BIM in bridge engineering has its own characteristics. This special session will focus on the development and applications of BIM in the bridge engineering in recent years, especially the possible influences of the development of BrIM on the safety, maintenance and management of bridges, and the trend of development as well.

If construction interventions on existing bridges are necessary, their objective must be to really improve the bridge. An original method for the durable rehabilitation and strengthening of concrete bridges is based on the casting of a thin layer of Ultra-High Performance Fiber Reinforced cement-based Composites (UHPFRC). This layer of UHPFRC significantly strengthens those zones that are exposed to severe environmental influences and high mechanical loading. This concept combines efficiently protection and resistance properties of UHPFRC and significantly improves the structural performance of the bridge. Recent research results and application cases are presented.

Accelerated Bridge Construction (ABC) methods are developed to overcome many challenges that arise due to extended periods of construction. ABC brings in many advantages, including enhanced safety and significantly reduced user cost. While a few highway agencies have integrated ABC to their regular practices, many others are implementing ABC at experimental level to broaden their experience as well as to provide opportunities for others to learn. During past several years, many innovative approaches have been developed and implemented. This session will aggregate the state-of-the-art practices, lessons learned, performance, and research.

Most decisions regarding bridge maintenance planning and interventions are taken by owners who control entire bridge stocks. For this reason, analysis of bridge safety, reliability, resilience and sustainability are particularly meaningful when performed at the transportation network level. This special session aims at bringing together different approaches for performance prediction and maintenance planning of bridge networks, including system reliability, scenario simulation, numerical optimization, Bayesian networks, and fault trees. It will be the right venue to compare the approaches and spark ideas on how to combine the benefits of each one.

The special session will describe the Operation & Maintenance strategy envisaged by MOP (bridge owner). Chacao Bridge is a double main span suspensions bridge for road traffic having a total length of 2754m to be completed by 2020. MOP has prescribed a design life of 100 years and the durability of all bridge elements has to be considered in order to meet this requirement. The presentations will introduce the project, given an overview of the O&M strategy and describe use of corrosion protection by dehumidification.