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Sustainable Bridges
Assessment for future traffic demands and longer lives

In order to double (or even treble) the transportation by rail over the next 20 years, the load capacity and the mean residual service life of railway bridges needs to be increased. the project determines methods by which this could be achieved.

Tags: Rail

Background

There is a great demand for European railway bridges to carry increased loads and allow higher speeds increasing infrastructure capacity for passenger and freight traffic. In many cases these demands can be met through proper structural assessment, determination of the true behaviour of the structure, strengthening of certain sections or by monitoring critical properties. Research has shown that there is a great potential for a big step forward in all these areas. Using a probabilistic approach for loads and resistance is one example of a new generation of methods that can be developed and applied.

Codes for bridge design has been developed gradually and have been designed to consider all the uncertainties that are present in the construction phase of a structure. These codes are also often used for the evaluation of existing bridges. However, far better information on material and structural properties is available for an existing structure than for one not yet built. Nevertheless the same factors of safety are often applied to existing structures as to the ones being constructed. Many bridges can be allowed to carry greater loads and faster trains if better codes and methods for assessment are used.

The project will save about €1 000 million (2% of the capital value of the bridges) by allowing increased loads and extending residual service life.

Objectives

The project objectives are:

- to increase the transport capacity of existing bridges by allowing axle loads of up to 33 tons for freight traffic with moderate speeds or for speeds of up to 350 km/hour for passenger traffic with low axle loads

- to increase the residual service lives of existing bridges by up to 25%

- to enhance management, strengthening and repair systems.

The objectives are achieved by different measures, for example:

- developing new methods for structural assessment of existing bridges in order to obtain better approximations of the real structural capacity

- giving guidance and using background material for a new code and guidelines for structural assessment

- determining models for the progressive development of reinforcement corrosion

- developing a scanning application and a combination of echo methods for condition assessment

- developing, implementing and testing monitoring systems based on optical fibres, micro-electro-mechanical-systems (MEMS), a local area communication infrastructure and smart data processing tools

- preparing guidelines for monitoring

- developing easy-to-handle systems and a guideline for quality assurance of repair and strengthening

- applying the developed methods on demonstration bridges

- disseminating the new results by publications, a website, training courses/workshops, seminars and a conference.

Test to failure of a reinforced concrete bridge in order to evaluate strengthening and assessment methods
Test to failure of a reinforced concrete bridge in order to evaluate strengthening and assessment methods
Lennart Elfgren

Description of work

Much research has been carried out in relation to this field of research but there is a need for integration, innovative development and testing in order to establish procedures for the safe and effective management and upgrading of railway bridges.

The work is carried out in nine work packages (WP):

WP1: Map existing bridge types to find critical points

WP2: Internal review and guidance. Investigate present and future loads and load distributions. Check demands for traffic interoperability between countries

WP3: Develop new methods for inspection and condition assessment

WP4: Develop improved methods to determine the capacity of structures

WP5: Develop monitoring methods based on new IT

WP6: Develop new repair and strengthening methods using e.g. carbon fibres

WP7-8: Demonstrate the new methods by field testing and monitoring on bridges

WP9: Training bridge owners, consultants and contractors in the use of these new methods.

The project is carried out by a consortium of bridge owners, consultants, contractors and research institutes from all over Europe. Jan Olofsson, Skanska, Sweden, is Manager and Prof. Lennart Elfgren, Luleå University of Technology, Sweden, is Scientific Leader. They are assisted by a team of work package leaders and report to an executive board appointed by a general assembly consisting of all members of the consortium.

Results

More than 40 deliverables are planned; most of them are already available in preliminary versions.

- A group of railway owners has mapped the existing stock of over 220 000 railway bridges. Over 35% of the bridges are more than 100 years old, while only 11% are less than 10 years old. Small span bridges dominate, with 62% of the bridges spanning less than 10 metres, while only 5% have spans larger than 40 metres.

- Measurement methods available for quantifying the present situation have been collected in a toolbox making information accessible to bridge engineers. Proposals for use in new condition assessment systems and connections to a unified damage classification scheme are made.

- Monitoring techniques (sensors, data communication and data processing) are being developed.

- A guide for assessment of loads, capacity and resistance has been drawn up.

- Repair and strengthening methods are developed.

- The developed methods are tested on five existing bridges. One of them has been loaded to failure after being strengthened with near-surface mounted carbon fibre reinforced polymer bars.

- Training courses are planned.

- A conference on Sustainable Bridges is planned for October 2007 in Wroclaw, Poland.

- A website has been set up at www.sustainablebridges.net

The project, in the summer of 2006, is more than half way through and the overall progress is very good.

Suggested Structural Health Diagnostic System for Bridges including examples on sensor, acquisition, communication and diagnostic systems
Suggested Structural Health Diagnostic System for Bridges including examples on sensor, acquisition, communication and diagnostic systems
Björn Täljsten

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