Sustainable bridges: assessment for future traffic demands and longer lives

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Sustainable Bridges

Assessment for Future Traffic Demands and Longer Lives

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Dolnośląskie Wydawnictwo Edukacyjne

Wrocław 2007

Sustainable Bridges

Assessment for Future Traffic Demands and Longer Lives

Edited by Jan BieÒ

Wroc≥aw University of Technology, Poland

Lennart Elfgren

Luleå University of Technology, Sweden

Jan Olofsson

Skanska Sverige AB, Sweden

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This book has been published with support from the Integrated Project “Sustainable Bridges – Assessment for Future Traffic Demands and Longer Lives” (TIP3-CT-2003-001653) within the 6^th Framework Programme of EU.

The information in the present book does not necessarily reflect either the position or views of the European Commission.

Edited and reviewed by

Jan Bień, Lennart Elfgren, Jan Olofsson

Editorial Board Jan Olofsson, Sweden Lennart Elfgren, Sweden Brian Bell, UK Björn Paulsson, Sweden Ernst Niederleithinger, Germany Jens Sandager Jensen, Denmark Glauco Feltrin, Switzerland Björn Täljsten, Sweden Christian Cremona, France Risto Kiviluoma, Finland Jan Bień, Poland

Technical editors

Dorota Rawa, Paweł Rawa Layout

Zdzisław Majewski Cover design

Sławomir Pęczek, EDITUS Cover photographs Paweł Rawa

Printed by

Wrocławska Drukarnia Naukowa PAN ul. Lelewela 4, 53-505 Wrocław, Poland

Published by

Dolnośląskie Wydawnictwo Edukacyjne ul. Ojca Beyzyma 20b, 53-204 Wrocław, Poland e-mail: biuro@dwe.wroc.pl

www.dwe.wroc.pl

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Guideline for load and resistance assessment of existing European railway bridges . . . J.S. Jensen, J.R. Casas, R. Karoumi, M. Plos, C. Cremona, C. Melbourne 221 Capacity assessment of European railway bridges. Limit states and safety formats . . . J.R. Casas, E. Brühwiler, A. Herwig, J. Cervenka, G. Holm, D. Wiśniewski 231 Updated rail traffic loads and dynamic amplification factors . . . E. Brühwiler, A. Herwig

243 Structural assessment of concrete railway bridges . . . M. Plos, K. Gylltoft, K. Lundgren, J. Cervenka, S. Thelandersson,

L. Elfgren, A. Herwig, E. Brühwiler, E. Rosell

251

Improved assessment methods for static and fatigue resistance of old metal railway bridges . . . C. Cremona, A. Patron, S. Hoehler, B. Eichler, B. Johansson, T. Larsson 261 The analysis and assessment of masonry arch bridges . . . C. Melbourne, J. Wang, A. Tomor

273 Safety assessment of railway bridges by non-linear analysis . . .

J. Cervenka, V. Cervenka, Z. Janda 283

Bayesian updating, a powerful tool for updating engineering models using results

of testing and monitoring . . . L. Neves, D. Wiśniewski, P. Cruz

293

6. Advanced technologies of railway bridge rehabilitation

Rehabilitation of railway bridges . . . B. Täljsten, A. Carolin, R. Helmerich

303 Repair and strengthening of railway bridges – guideline . . . A. Carolin, B. Täljsten, H. Pedersen

313 Quality assurance of CRFP-strengthened reinforced concrete structures using automated

thermographic investigation . . .

R. Helmerich, M. Röllig, A. Schultz, J. Vielhaber 321

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Mineral based bonding of CFRP to strengthen concrete structures . . . B. Täljsten, T. Blanksvärd, A. Carolin

331 Near Surface Mounted Reinforcement (NSMR) to strengthen concrete structures . . . B. Täljsten, A. Carolin

341 CFRP strengthening of the Örnsköldsviks bridge – field test . . . B. Täljsten, M. Bergström, O. Enochsson, L. Elfgren

355 Investigation of steel I-beams strengthened with CFRP plate . . . D. Linghoff, M. Al-Emrani

365 Durability increase of bonded CFRP-steel joints via appropriate surface preparation . . . M. Feldmann, J. Naumes

377

7. Practical implementation of the project results

Bridge monitoring demonstrations in the Sustainable Bridges Project – synthesis of results . . . R. Kiviluoma

389 Low power wireless sensor network for long term structural health monitoring . . . R. Bischoff, J. Meyer, G. Feltrin

397 Dynamic parameters of old steel railway bridge monitored by vibration tests . . . J. Zwolski, P. Rawa, M. Gładysz, A. Roszkowski

409 Field testing of old bridges . . . C. Cremona, J. Bień, L. Elfgren

423 Dynamic amplification factors for a riveted steel bridge. Assessment by monitoring

of the Keräsjokk Bridge in northern Sweden . . . O. Enochsson, T. Larsson, L. Elfgren, A. Kronborg, B. Paulsson

435 Testing to failure of a reinforced concrete railway trough bridge in Örnsköldsvik, Sweden . . . . L. Elfgren, O. Enochsson, A. Puurula, H. Thun, B. Paulsson, B. Täljsten

445 Advanced methods of testing and analysis of old masonry bridge in Oleśnica . . . T. Kamiński, C. Trela

461 Instrumentation of the Avesnes/Helpe bridge . . . C. Cremona, R. Leconte, G. Feltrin, B. Weber, J. Bień, P. Rawa, J. Zwolski, L. Dieleman

473

Author index . . . 489

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Foreword

At present we have great challenges as inhabitants of the Earth. We are living in a society with cheap fossil energy and an expanding urban population. This exerts high demands on the infrastructure in the form of railways, roads and buildings of different kinds. However, we do not know if cheap energy will be available in the same way in the future. At the same time climate seems to be changing and becoming more unstable and unreliable. This is probably to some extent due to the expanding human use of energy and release of greenhouse gases.

To help our society to be more sustainable, it is important to retain and use what we already have where possible, rather than investing in new structures. Instead of tearing down old, often beautiful, railway bridges and replacing them with new ones, we need to preserve and upgrade them by using better assessment, monitoring and strengthening methods. This was the aim of the European Integrated Research Project “Sustainable Bridges – Assessment for Future Traffic Demands and Longer Lives” when it was accepted for funding by the European Commission.

The project established the following three specific goals:

• increase the transport capacity of existing railway bridges by allowing higher axle loads (up to 33 tons) for freight traffic at moderate speeds or by allowing higher speeds (up to 350 km/hour) for passenger traffic with low axle loads,

• extend the residual service lives of existing bridges by up to 25%,

• enhance management, strengthening, and repair systems,

and has been running since December 2003. It will complete its work by the end of November 2007 and the conference being held in Wrocław, Poland on October 10–11, 2007 is its major dissemination activity.

A consortium consisting of 32 partners drawn from railway undertakings, consultants, contractors, research institutes and universities has carried out the project, which has a gross budget of more than 10 million Euros. Material for this book has been collected not only from the partners in the project, but also from other experts, in order to give a broad picture of the challenges and the available tools.

We heartily welcome everyone to Wrocław and the conference. We hope this book will provide a good overview of the work that has been done and of the main results. We have come a long way towards our goals. However, there is much work to be done to test and implement the methods presented. We therefore hope that this book will inspire the readers to utilise our guidelines and report their opinion to the authors. There will certainly be a need for development and further work in order to increase the capacity and service life of existing bridges.

Jan Olofsson Lennart Elfgren Jan Bień

Project Coordinator Scientific Leader Dissemination Leader

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Railway bridges in Europe

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The need of R&D for existing structure

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The need of R&D for existing structures

Gerard DALTON

This paper will point out the importance of R&D for existing structures. Today and tomorrow existing structures are dominating. Only a small part of the bridge stock is replaced every year. At the same time the society expects that the Infrastructure Managers shall meet new demands. These demands are for higher speeds, higher axle loads, increased availability, less disturbance and reduced maintenance costs. Also environmental and aesthetic considerations have to be considered. Therefore R&D for existing structures is of great importance for the society and the Infrastructure Managers to meet future needs.

1. BACKGROUND

There are probably in excess of a half million railway bridges in the geographical area covered by the 27 Member states in the European Union and EFTA countries (Norway and Switzerland). More than half of these bridges are of Masonry Arch construction ranging, from small culverts to large imposing structures that will remain part of the lasting heritage of the railways for some time to come.

Throughout the development of the railways since the 1830’s, railway engineers have taken advantages of new advances in material technology, changing from stone to reinforced and pre- stressed concrete and from cast iron to wrought iron and then to many improved grades of structural steel. Each railway period has also seen new forms of construction, employing different protective systems.

This rich and enduring heritage of structural forms requires Railway Bridge Engineering to be understood in its widest context, covering preservation and conservation, materials technology, prefabrication and assembly, connections and welding, protective systems, dynamic loading and impact protection and the integration of all this knowledge to achieve an optimum life cycle balance.

The particularly restrictive access limitations placed on railway engineers, both in terms of topography and operational hindrance, demands the most appropriate and timely intervention to maintain, restore, strengthen or renew structures.

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1. Railway bridges in Europe

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For all these reasons, research into the technology of railway bridges must consider both the context within which the engineers must exercise their function and the duty cycles which the structures must endure.

An understanding of these factors leads one to appreciate the need for continuing research and development into these areas, many of which are specific to the railway environment. The large value of the existing bridge inventory also demonstrates the return on investment that can be achieved from well focused research. While there are no exact figures on the overall value of the entire European bridge inventory, a rough assessment can be made.

Among the countries that participated in the investigation carried out by Work Package 1 (WP1) of the Sustainable Bridges project, the number of bridges was approximately 220,000.

Given that the cost per meter for a new built bridge may be 30.000 € for a single track bridge and approximately 50.000 € for a double track bridge and taking an average span of 20 metres long it is easy to appreciate that we are talking of a huge asset value of several billions of Euros. The situation for tunnels is similar. In 2002, the total tunnel length among the former EU 15-members, Norway and Switzerland was estimated at nearly 4000 km.

Historically R&D attention has been focused, to a large extent, on new bridges and tunnels.

There has also been a focus on road bridges and tunnels, due to the expansion in the road sector during the last thirty years. This means that R&D into existing railway bridges needs to be the subject of special attention.

2. THE NEED OF R&D FOR EXISTING STRUCTURES

Before outline some specific topics for possible future research it is worthwhile highlighting some of the different aspects of maintaining the existing railway bridge heritage.

2.1. Preservation and Conservation

Experience shows that many bridges remain in active service for longer than originally contemplated. This arises due to a number of factors, such as:

• reserve of strength, due to original conservative design assumptions,

• lower cumulative traffic load, than anticipated at time of design,

• existing traffic volumes, or other operational considerations, inhibit major intervention and favour extending the practical life of the existing structures,

• some mid-life strengthening or enhancement may have been carried out,

• budgetary consideration may necessitate a more closer scrutiny of the intrinsic life of the structures to obtain maximum life extension,

• heritage considerations may prevent the replacement of the structure.

Consequently, railway engineers must preserve the bridge asset base, in an optimum way, paying particular attention to structures that need to be conserved in a manner that will allow them to continue to serve their function, without material alteration to their appearance or architectural integrity.

2.2. Materials Technology

The contrasting age and range of construction materials in the entire stock of railway bridges places special importance on an understanding of materials and the potential application of new technology. In some case this involves the utilisation of old and new materials in a composite way in order to achieve the most economical solution. Innovative

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The need of R&D for existing structures

15 utilisation of modern materials, such as Fibre-Reinforced Polymers (FRP), reinforced earth, under sleeper pads and ballast matting will demand continuing research and development to adapt their use for specific rail applications.

2.3. Prefabrication and Assembly

The installation and repair of railways bridges in the track, with minimum restrictions to existing rail traffic, has necessitated particular forms of construction to be adopted that are not normally required in other transport fields. Site access often dictates that individual bridge elements are restricted in weight to enable them to be lifted or slid into position. The use of this form of construction means that railway engineers must obtain satisfactory strength and performance from the overall structure through the assembly of individual elements.

2.4. Connections and welding

For the reasons stated in section 2.3, many railways bridges achieve their overall strength, performance and durability through the inter-connection of prefabricated elements, such as rail bearers, cross girders and lattice structures. The oldest stock of bridges have relied on riveting and bolting to achieve structural integrity while more recent structures have incorporated welded plates, high-strength steel bar and cables in their fabrication.

2.5. Protective systems

The restricted access to many railways bridges, in terms of their isolated geographical location and the difficulty of inspection of many parts of their structures, due to coverage with ballast or other materials, places a special importance on protective systems such as waterproofing layers and metal coatings. The application of such systems, during or between intervals of rail traffic, requires constant research for new solutions to ensure satisfactory performance and durability.

2.6. Dynamic load

Railway bridges are subject to particular stresses due to dynamic loading from various configurations of rolling stock and possible out-of tolerance conditions of vehicles and track.

The transition from softer soil conditions to a more rigid structural form also presents challenges for the design and maintenance of bridge approaches.

2.7. Accidental impact

Bridges supporting tracks, over or under roads, suffer the risk of road vehicle impact and innovative ways to avoid or avert the worst effects of such damage is an important issue requiring ongoing attention.

3. NEW DEMANDS ON THE INFRASTRUCTURE MANAGERS (How UIC has responded)

The demand for increased speed on many existing lines is common in Europe. The adoption of higher speeds necessitates special considerations when it comes to the assessment of the strength of existing bridges. The UIC project, BRIDCAP, has considered how to measure and evaluate dynamic effects on bridges. UIC has also carried out studies on aerodynamics, which exert a greater influence at speeds in excess of 200 km/h.

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Figure 1. Forsmo bridge. This bridge was upgraded to 30 tonnes axle load in 2005. The upgrading was done during 21 timeslots

UIC has also produced several leaflets connected with higher axle loads such as in relation to the Testing and approval of railway vehicles from the point of view of their dynamic behaviour – Safety – Track fatigue – Ride quality, the classification of lines for axle loads up to 25 tonnes and the specifications of track components when the axle loads are more than 22, 5 tones.

Increased availability and less operational hindrance is an increasingly important question, due to a resurgence of railway traffic in Europe. Several European railways have had their all-time highest levels of traffic during 2005 and 2006. Therefore the need for more available capacity for operations is of high priority. To address this, UIC has been active in the signalling area (ERTMS) and in more durable forms of track construction (such as ballastless track) and maintenance approaches (use of Under Sleeper Pads and ballast mats) and studying capacity management.

Reduction in maintenance costs is also vital. Therefore UIC has been active in many projects during recent years. One example is the EU project INNOTRACK. Together with the industry the focus is to reduce maintenance costs.

During the last twenty years, environmental and aesthetic considerations have become more important and are designed into new projects. Sustainable development is now demanded as a natural part of everyday life. Infrastructure Managers have to fulfil these demands. Some classically constructed bridges represent an important historical heritage and have to be maintained. The UIC Masonry Arch Bridge project has considered such aspects.

4. COMMON EUROPEAN R&D IS NECESSARY

Today, most Infrastructure Managers have reduced the size of their organisations. The reduction of staff has been significant in many railways in Western Europe. At the same time, the continuing high cost of infrastructure provision is partly shaped by the maintenance of specialist technology and the varying age of the parts of the railway

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The need of R&D for existing structures

17 system. The situation can be partly addressed through increased international cooperation and shared costs with other IMs. This is the reason why more and more R&D needs to be carried out in cooperation in Europe and the Sustainable Bridges project is a good example of a collaborative approach.

UIC is today involved in approximately 25 EU-projects. This indicates that involvement in joint research in EU projects is now an integral part of UIC’s European activities. It is UIC’s opinion that international cooperation can and should be increased. In this regard, the following topics would have common appeal for future research, having been identified by our Panel of Structures Engineers:

a) Research on detailed solutions for the repair of masonry arch bridges.

b) Minimising cost and traffic interruption during maintenance and reinvestment work.

c) The use of prefabricated elements in rail bridges.

d) Noise reduction on existing steel bridges.

e) Temporary bridges and the embankments and foundations supporting temporary bridges.

f) Research for strengthening and repair methods to extend life and bearing capacity.

g) Advanced Monitoring systems (AMS) for existing railway bridges.

h) Further studies on the dynamic behaviour of existing structures.

i) Research on “Good design practice” for water proofing and anti corrosion systems of existing bridges.

Further research should be based on the results of “Sustainable Bridges” and efforts will be necessary to transform the information and results into guidelines which are easy to handle for practitioners in the railways. The important results of research should transfer into the common knowledge of railways. It is clear that innovative approaches to whole life cost optimisation are essential in the management of the inventory of bridges within the European railway network.

5. THE UTILISATION AND MAINTENANCE OF THE OUTPUT FROM EU PROJECTS

To initiate and to realise international R&D-projects there is a need of networks. In UIC there is a Panel of Structure Experts (PoSE) established for bridges and tunnels. The PoSE has been working effectively for many years and today consists of members from nearly 30 countries. The group continues to produce many valuable leaflets and other technical documents, many of which have been utilised in the new Eurocodes.

Today the PoSE group is active in four main areas concerning bridges and tunnels:

• exchange of information,

• initiation of R&D-projects,

• coordination of R&D-projects,

• input to Eurocodes.

The PoSE group played an important role when the Sustainable Bridges (SB) project was created. Personal contacts between the members of a number of interested IMs permitted the formation of a strong team, who already knew each other. This has been very positive for SB.

During the realisation of SB good coordination has been achieved with UIC projects, such as BRIDCAP and Masonry Arch bridges.

The PoSE-group has also been active through liaison partners in SB. A continuous information exchange between the PoSE and SB has taken place during recent years. The PoSE members have also continuously been invited to SB workshops.

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If the work of the SB project is to retain its applicability, in a changing technology field, the output will need to be maintained and updated. UIC is willing to support SB to maintain the results of this project.

6. CONCLUSIONS

The Sustainable Bridges project has been working in an important discipline, which has been a neglected area of common research to date.

The results will accordingly be beneficial to Infrastructure Managers and their Structures Experts but will need to be maintained and updated, over time.

The body of work created and the future research effort will help to provide inspiration to address the demands of the rail business for more available capacity and less operational hindrance during essential works.

The current work and future research and development will complement the ongoing activities of the Panel of Structures Experts in UIC.

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UIC project on assessment, inspection and maintenance of masonry arch railway bridges

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UIC project on assessment, inspection and maintenance of masonry arch railway bridges

Zoltán ORBÁN

Masonry arch bridges represent a large proportion of the railway bridge stock. Many of them belong to the civil engineering heritage of the railways, therefore their management require careful consideration. Maintenance strategies should promote solutions that are directed towards their preservation and restoration by relying on their existing structural capacity and give preference to stabilization rather than their substitution or replacement. The paper introduces the results of an international project entitled “Improving assessment, optimisation of maintenance and development of database for masonry arch railway bridges”. The project is organised by the International Union of Railways (UIC) with the participation of 14 railway administrations and many consultant institutions, spanning a period of 4 years. The principle objective of the project is to collect and develop tools that help optimising the life-cycle management of masonry arch bridges, help reducing their maintenance costs and promote an effective exchange of good practice between the railway administrations.

1. INTRODUCTION 1.1. General introduction

Masonry arch bridges form an integral part of the railway infrastructure. They are the oldest structure types in the railway bridge population with thousands still in service.

In order that the railways accommodate increased axle loads, train speeds and a greater volume of freight traffic, it is necessary to assess the load carrying capacity of existing masonry arch bridges. Assessment of masonry arch bridges is difficult as there is little knowledge or experience of design of these structures to modern standards, and much of the structure is hidden from view.

To provide confidence in the assessment result, reliable input parameters are required for their calculations. Accordingly effective inspection and measuring methods to establish the parameters are necessary. As well as the predominant use of visual inspections, and destructive investigation there is a tendency in recent years towards using non-destructive testing techniques.

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The current condition of masonry arch bridges varies from good to very bad, although statistics show that there are a relatively large number of bridges in a medium or bad condition with a tendency for accelerated deterioration. Accordingly there is a potential doubt as to the adequacy of masonry bridges to withstand increased axle loads, train speeds and a greater volume of freight traffic.

Contrary to doubts masonry arch bridges are proving durability with life-cycle costs significantly more economical than for the majority of other structure types. In addition, they belong to the civil engineering heritage of the railways, and their substitution or refurbishment requires careful consideration with maintenance strategies adopted to promote solutions that preserve and restore these structures instead of their replacement.

1.2. Project description

A study group was set up in 2002 by the International Union of Railways (UIC) in order to establish information on the ‘state-of-the-art’ of masonry arch railway bridges. The work was initiated by the Hungarian Railways and during the preparatory stage 13 more railway organisations joined the project. Currently the following railway administrations are involved in the project: MAV (Hungary, task leader) DB (Germany), SNCF (France), NR (UK), ÖBB (Austria), SBB (Switzerland), JBV (Norway), CD (Czech Republic), REFER (Portugal), RENFE (Spain), RFI (Italy), Japan Rail-RTRI (Japan), PKP (Poland), IR (India).

The work is carried out in close collaboration between the partaking railway administrations and consultant institutions from various countries such as: Obvis Ltd. (UK), University of Sheffield (UK), Ines Ingenieros Consultores (Spain), University of Genoa (Italy), Wroclaw University of Technology (Poland), Ingenieurbüro A. Pauser (Austria), Hochschule Bremen (Germany), Brno University of Technology (Czech Republic), University of Pécs and Orisoft Engineering Consulting (Hungary).

The project has been divided into two phases. The preparatory phase the masonry arch bridge stock has been reviewed and the state-of-the-art practices of their assessment, inspection and maintenance summarised. It has been concluded that there were no internationally accepted tools available for the reliable assessment of the load carrying capacity of masonry arch bridges and that a lack of guidance has retarded the widespread application of up-to-date inspection and maintenance procedures.

The objectives and tasks of the follow-up phase have been put together according to the conclusions of this preparatory phase.

The following work packages have been identified in the programme:

• WP1: development of assessment tools for masonry arch bridges,

• WP2: optimized inspection and monitoring of masonry arch bridges,

• WP3: optimized maintenance and repair of masonry arch bridges,

• WP4: development of information database for masonry arch bridges.

The project is funded over a period of 4 years starting from January 2003. Guides have been developed for the assessment, inspection and maintenance of masonry arch bridges. An Information System & Database has been developed on the Internet to be a reservoir for knowledge on masonry arch bridges and to provide a platform for the railway administrations to consult and share information.

2. INTRODUCTION OF THE MASONRY ARCH RAILWAY BRIDGE POPULATION A survey has been carried out to give an overview on the number, characteristics and condition of masonry arch railway bridges in the participating railway administrations. The statistics were compiled about the total masonry arch bridge population of the railways including culverts with a span not exceeding 2 m.

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21 Some conclusions derived from these statistics are summarised as follows:

• The railways participating in the project possess more than 200,000 masonry arch bridges and culverts on their lines which is approximately 60%, a significant proportion, of their total bridge stock (UIC Report, 2004). The highest numbers of arches inclusive of culverts have been reported from France (cca. 78,000 – 77% of total bridge stock), Italy (56,888 – 95%), Germany (cca. 35,000 – 39%), India (20,967 – 18%), UK (17,867 – 47%) and Portugal (11,746 – 90%).

• Bridges and culverts with short spans represent the majority of masonry arch structures (according to the survey approximately 60% of the bridge spans are under 2 m, approximately 80% are under 5 m and there are only 8,5% of arches exceeding 10 m span).

• The majority of masonry arch bridges are single-span structures (approx. 85%).

• The majority of masonry arch bridges (approx. 70%) are between 100 and 150 years old.

There is also a significant proportion (approx. 12%) of bridges more than 150 years old.

• The shapes of masonry arches are generally not recorded by the railway administrations.

The limited information has prevented any conclusions being drawn with regard to the shape of arches, except that semi-circular deep arches are the most common type.

• The vast majority of masonry arch bridges are in good and medium condition (approximately 85%) but there is significant proportion in a poor or very poor condition.

3. WP1: ASSESSMENT OF MASONRY ARCH BRIDGES 3.1. General

Assessment of masonry arch bridges is a difficult task as there is no widely accepted and reliable structural assessment procedure. Structural behaviour of masonry arches depends on several parameters but there is little experience of the effect of changes in such parameters and masonry arches have internal elements that are extremely difficult to investigate.

Several methods are available for the assessment of masonry arch bridges. These include simple conservative methods (such as MEXE) and recently developed computerized methods (such as adaptations of the mechanism method and FEM systems). Besides their particular limitations, conservative methods often underestimate the load carrying capacity, which may result in uneconomical or unnecessary mitigation measures being taken to maintain or replace bridges. Conversely the use of sophisticated new methods is generally hindered by the difficulty in provision of input parameters or prolonged data processing.

The use of advanced computerised techniques in the analysis of masonry arch bridges is a relatively new concept. Several computational techniques have been developed for this purpose including 1D frame or 2D and 3D non-linear finite element (FE) models, discrete element- -based (DE) models and combined finite element-discrete element models (FE/DE). These methods were developed to describe the complex nature of arch deformation, cracking processes and arch- -backfill interaction phenomena. Assessment of serviceability is becoming more and more important with increasing traffic volumes on masonry arches. There is however no suitable method for the serviceability assessment of masonry arches nor any criteria against which such an assessment could be made. Other shortcomings of existing methods are their inability to (or complicatedly) describe the effects of structural defects and strengthening intervention.

The objective of WP1 was to develop simple, reliable and user-friendly new assessment methods for masonry arches, improve existing ones and provide guidance for assessor engineers to the application of these integrated methodologies. A multi-level assessment procedure has been recommended starting from the most simple and conservative ‘rule of thumb’ approach towards high-level analysis tools.

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3.2. Revision of the MEXE method

The method is based on elastic principles where a two-pinned, parabolic arch static system is assumed to have a limited compressive strength of 13 tons per square foot (cca. 1.4 N/mm²). The load capacity is calculated using empirical formulas with the application of subjectively estimated modifying factors referring to the geometry and material condition of the bridge (UIC Code 778-3R). These modifying factors are determined principally by visual inspection of the bridge.

The equations involved in the MEXE method do not represent the behaviour of a real arch, but represent the best approximation that was achievable without computers when the method was developed. Because of its simplicity and quickness the method is still widely used for the assessment of railway and highway masonry arches.

UIC Code 778-3R gives guidelines for the use of the MEXE method. Experience and latest research show that in a large number of situations the method seriously underestimates the actual load-carrying capacity of the bridges. On the other hand in some other cases MEXE has been found to provide non-conservative results. The method is generally used as a first sieve for the initial assessment and preliminary determination of load capacity. As MEXE can provide unreliable values for the load carrying capacity of masonry arches, some railway administrations proposed modifications to the method in order to achieve better conformity with their experience.

A review therefore has been undertaken of the MEXE method (Harvey, 2007a). The review included reworking the basic analysis that underpins MEXE and comparing the MEXE results with output from other methods.

3.3. Rule of thumb method

An assessment method based on the load capacity being directly related to the geometrical properties of the span, rise, and ring thickness of an arch has been developed (Harvey, 2007b).

In comparison with the alternative empirical method (MEXE), this method should deliver realistic results at no increased costs.

The concept for this method is that the assessment is quick and may be carried out by artisan bridge examiners when on site inspecting the condition of the arch. The aim is to enable the majority of arches with sufficient load carrying capacity to be identified with minimum work, and thereby permit assessment engineers to concentrate their efforts on those bridges which are not so obviously adequate for the task.

3.4. Pauser’s method for the assessment of semi-circular arches

Pauser’s method (Ingenieurbüro A. Pauser, 2005a) is a simple analysis tool that may be used for the assessment of both single and multi-span arches with haunching, whether constructed in brick or stone. The method is best suited for the assessment of single span semi-circular arches.

The method is based on the analysis of the arch at its ultimate limit state of load-bearing capacity, considering only that part which may be realistically assumed to act as an arch.

The computed value for arch capacity is considered conservative as the method neglects tensile stresses, the contribution of the spandrel wall and a soil model amplifying load capacity is not used.

3.5. RING masonry arch analysis software

A new version of the widely used RING masonry arch bridge analysis software (Gilbert, 2007) has been developed in collaboration with UIC.

RING 2.0 uses computational limit analysis techniques to estimate the ultimate load carrying capacities of bridges. A two-dimensional analysis is performed with the constituent

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23 masonry blocks of a bridge being modelled explicitly. These blocks are assumed to be rigid but are separated by masonry joints (contact surfaces) at which rocking, crushing and/or sliding failures are permitted to take place. Backfill material, if present in a bridge, whilst not modelled explicitly, is assumed to disperse live loads and to provide passive restraint.

To facilitate the assessment of railway bridges RING 2.0 includes within the software railway loading models and distribution of railway loads through the track and ballast modelled in accordance with relevant UIC leaflets.

3.6. High-level assessment of masonry arch bridges

High-level assessment of arches are generally based on finite element or discrete element models. The high-level assessment is generally only necessary when a structure is found to have insufficient load capacity using a lower level assessment method, or the assessment includes analysis of the effects of damages on load capacity.

The Guide to High-level Assessment (Brencich and Gambarotta, 2006) is aimed to provide a guidance for assessor engineers on the procedure of high-level assessment of masonry arch bridges by the use of commercially available finite element software packages.

The proposed assessment procedures include incremental non linear step – wise analyses performed on beam – like models and analysis on simplified 2D or 3D models. Parametric and case studied are discussed showing the validity limits of the different approaches.

3.7. Guide to the assessment of masonry arch bridges

A guide has been developed for the whole process of masonry arch bridge assessment (Harvey, 2007c). The sections of the guide deal with: Construction, Behaviour, Deterioration, Loading (including load distribution), Inspection, Assessment and Reporting. The core section on assessment is further divided into: Basic Principles, Modelling approaches, Three- -dimensional effects, Levels of analytical tools and Complexities.

In order to determine the adequacy of a particular arch structure with the minimum degree of effort, the assessment should be carried out in levels of increasing refinement and complexity, with the initial level being based on the most conservative distributions of loads and analytical assumptions. If the structure is shown to be inadequate in relation to the required load carrying capacity at this level, assessment work should continue, with subsequent levels seeking to remove conservatism in the assessment where this can be justified.

4. WP2: INSPECTION AND MONITORING 4.1. General

Several inspection methods have been used to investigate the condition or to determine the structure of masonry arch bridges. The most common method is still the pure visual inspection.

Destructive testing is also used although there is a tendency in recent years towards using non- destructive testing techniques.

Most assessment procedures require the masonry strength and some other mechanical properties as the major input parameters for assessment. Destructive Testing (DT) of masonry bridges is therefore necessary in many instances, although it is noted that the results of most destructive tests are affected by significant uncertainties and they may provide only local information on some part of the structure, and cannot be directly extended to the whole bridge.

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Semi-Destructive Testing (SDT) methods are based on in-situ localised measurements and considered as surface or small penetration techniques which can provide only qualitative information on the masonry condition and be used only for preliminary investigation.

While conventional DT methods focus mainly on the mechanical characteristics of the materials, Non-Destructive Testing (NDT) methods can provide an overall qualitative view on the arch condition. NDT methods on the one hand seem to be most promising tools for the inspection of masonry arch bridges but on the other hand need a great deal of further study and research. The number of references and projects that have utilized NDT methods on masonry arches is very low and only a few calibration tests have been carried out. Consequently correlation of NDT data with the mechanical properties of the structure is considered limited at present. Nevertheless NDT usually requires an expert with sufficient skills to carry out the measurements and interpret the results so that the significance of data is recognized and that data is not used inappropriately. This ‘strong reliance’ upon the non-engineer specialist is generally not acceptable to the railway administrations. There is thus a need for close collaboration between bridge engineers and NDT specialists and to provide information for bridge engineers on the use of these specific testing methods.

Monitoring systems are occasionally installed on masonry arch railway bridges in order to follow the evolution of damage patterns such as cracks or deformations. The knowledge of this evolution can help preventing more serious damage or a total collapse of the structure.

Monitoring may also provide information that can be used to determine the root causes of the defects. These may be from visual inspection or electronic data collection.

Load tests are carried out only in special cases on masonry arch bridges. However load tests are considered to provide the ‘most reliable information’ on the real structural behaviour.

The objective of WP2 was to give an overview on the available testing methods of masonry arch bridges and to give recommendations for the use of the methods and for the utilization of measured data.

4.2. Determination of material properties by destructive tests

A procedure for the determination of masonry compressive strength has been developed (Ingenieurbüro A. Pauser, 2005b). The procedure includes tests on the composite masonry and tests on its components. The characteristic value of masonry compressive strength are determined according to the number of samples and the coefficient of variation of measured data. For mortars, a punch test has been developed where a 10-to-25 mm thick mortar sample embedded in-between two layers of gypsum is tested.

4.3. Non-destructive testing of masonry arch bridges

Masonry arch bridges rarely have accurate or sometimes any drawings of their construction or early repair details. The internal structure of arch bridges may be unknown from external appearance, and may include features such as haunching at support, vaulting, internal spandrel walls, ribs or the presence of saddle over the arch barrel. It may, therefore, be difficult to determine the physical dimensions of the main structural elements of the bridge. Moreover, materials used for the abutment, barrel, spandrel and backfill are variable, and interact. This inadequate knowledge of geometry and materials used complicates the problem of accurate modelling of behaviour. Further complication is the possibility of ring separation or the presence of other hidden defect and irregularities such as voids in the granular backfill immediately above the extrados, areas of reduced density and stiffness in the fill adjacent to the

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25 extrados, and cracking in the arch ring. Bridge repairs and strengthening require sufficient knowledge on existing defects and their causes too. Hence it is essential that some information of the internal structure and condition of a bridge is obtained before any remedial work or strengthening can be carried out. In this respect NDT methods can play an important role both in the inspection and assessment process and later when the result of the strengthening process has to be checked.

The objective of a testing programme can be to quantify the parameters that are required for the assessment procedure or to provide information for the evaluation of condition. As a large variety of methods is available the choice of the most appropriate method for a specific problem can be rather complex.

Recommendations have been worked out (The University of Pécs, 2006), based on the results of a test programme carried out and the experience of the railway administrations, on the use and optimal selection of NDT methods for specific inspection purposes of masonry arch bridges.

4.4. Catalogue of Damages

A visual examination is the first vital step in an effective maintenance regime. An incorrect diagnosis may lead to other mistakes, like the implementation of unnecessary repairs.

Sometimes, a lack of understanding of the behaviour of “masonry” materials makes diagnosis of causes of damage in arches difficult. In other cases if insufficient information is obtained in the inspection additional inspections will need to be carried out, thus increasing the inspection costs. Lastly, this lack of understanding can lead to an overestimate of the risk of collapse when the risk is negligible.

The Catalogue of Damages (Ozaeta and Martín-Caro, 2006) was developed using the experience of the railway administrations partaking in the project. The Catalogue is considered to be a tool to provide assistance with the inspection of masonry arch bridges. The scope of the Catalogue is limited to damages that could be detected by visual inspection of masonry arch bridges.

4.5. Load test of masonry arch bridges

If none of the analytical methods yields a sufficient result, consideration may be given to the use of an experimental approach to assess the load carrying capacity of masonry arch bridges. A calculated assessment presumes that together with the geometry, foundations and load, all essential material properties and status is known or estimated and that it is possible to describe the load transfer realistically in mathematical terms. An experimental approach evaluates the physical reality and should lead to a higher permissible working load as a rule.

Load tests may be used to verify serviceability, the load carrying safety factor and/or to calibrate an analytical model (e.g. FEM).

A suitable procedure is the application of loads to the structure and the simultaneous monitoring of the load-carrying behaviour, particularly deformations and strains as well as micro-crack formation.

One method for load testing utilises trains crossing the arch. Nevertheless, uncertainty may still remain if the load carrying safety factor has to be proofed by analytical extrapolation.

An alternative experimental non-destructive approach is to determine the load carrying capacity utilising a heavy counterweight and hydraulic load application. An external variable loading is used to reach a target load, including the necessary margin of safety, without infringing limit state criteria. On the basis of the measurements taken, either the structural

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safety is proofed or a critical load level is identified. This limit is characterised by the first signs of damage and is synonymous with the actual state of deterioration.

A guideline has been developed for the load tests of masonry arch bridges (Steffens and Gutermann, 2006). Measurements carried on selected masonry arches are evaluated in respect to coincidence with analysis results.

5. WP3: MAINTENANCE AND REPAIR 5.1. General

Masonry arches belong to the civil engineering heritage of the railways, therefore their substitution or refurbishment requires careful consideration. Total replacement of deteriorating masonry bridges is economically not feasible. The solution must therefore lie in optimised maintenance and repair strategies. Repairs to masonry bridges should take account of the existing structural capacity and replacement need only be carried out when it has been demonstrated that the existing load capacity is insufficient.

A fundamental requirement is that any maintenance and rehabilitation intervention should maintain the structural integrity of the arch and be physically, chemically and mechanically compatible with the existing structure. Strengthening works that do not take account of the fundamental modes of structural behaviour are unlikely to be beneficial.

The objective of WP3 was to give an overview on the available conventional repair and strengthening methods of masonry arches, demonstrate new methods of strengthening and to develop a methodology for the degradation modelling of arches to help their life-cycle management and intervention planning.

5.2. Repair and strengthening of arches

A survey was carried out to collect and evaluate the maintenance and repair solutions available for masonry arches in the participating railway administrations. These include methods for the restoration of waterproofing and drainage (such as drainpipes placed through the barrel, restoration of drainpipes; concrete saddle over the arch with bonded waterproofing; unbounded waterproofing on extrados; injection of arch barrel), methods for the restoration and strengthening of arch barrels (e.g. injection of arch barrel; RC shotcrete lining under the arch; concrete saddle over the arch; stitching of cracks and low pressure grouting; supporting barrel with steel rings), methods for the restoration and strengthening of abutments, piers and foundations (e.g. underpinning through the abutment;

scour protection, stitching and grouting of abutment cracks; installation of props or invert slab; injection of soil under foundations) and methods for the restoration of 3D integrity of arches (tying with rods and patrass plates; tying spandrel walls to new saddle on barrel;

load dispensing concrete slab over the arch).

Important aspects to be taken into account in the design of masonry arch repairs (Ozaeta, Martín-Caro, Brencich, 2007):

• the most frequent cause of damage to masonry bridges is inadequate drainage of water thus repair strategies should always include the restoration of waterproofing and drainage systems;

• most serious damage to arches arises from foundation problems and special attention should be given to their proper maintenance and repair;

• repair and strengthening techniques should provide sufficient resistance against foreseeable future loads and effects (e.g. increases in axle loads, speeds, dynamic effects, and physical- -chemical effects, etc.).

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27 5.3. Expert Tool for degradation modelling

An Expert Tool (Bień, Kamiński, Rawa, 2006) has been developed for modelling and analysis of masonry arch bridges with damages. The aim of work was to provide guideline for the numerical modelling of masonry arch damages and work out a methodology which can be applied in knowledge-based expert tools supporting evaluation of bridge condition, estimation of expected service life as well as ranking and maintenance planning of existing bridges.

A pilot version of a computerised expert tool entitled Masonry Bridge Damage Evaluator (MyBriDE) supporting evaluation of degradation level for masonry bridges has also been developed. The system is able to analyse the influence of the most common damage types, such as strength reduction, longitudinal fracture and loss of material, on the carrying capacity of typical masonry bridges.

6. NEW UIC LEAFLET ON MASONRY ARCH BRIDGES

The UIC leaflet on the assessment of masonry arch bridges is currently under revision and will be extended by utilising the deliverables of the project. The work is expected to be concluded in 2007.

The leaflet is intended to provide railway infrastructure owners, maintenance managers, bridge inspectors and consulting engineers with guidance on the inspection, assessment and maintenance of masonry arch bridges.

7. SIGNIFICANCE OF FURTHER RESEARCH

The deliverables developed in the current phase of the project are based on our current understanding of masonry arch bridges. Many significant matters have however been identified where there remains insufficient knowledge of the characteristics and structural behaviour of arch bridges to permit development of appropriate guidance.

Behaviour of masonry arch bridges under long-term service loads and the derivation of their serviceability limits are one of the important areas that require further research. There is a need for a predictive life-cycle management and maintenance planning of masonry arch bridges that is based on knowledge of the actual level of safety arising from a sufficient understanding to identify the degradation process, an appropriate system of acceptability criteria and the knowledge of the foreseeable effects and costs of intervention.

8. INFORMATION DATABASE

Further information on masonry arch railway bridges can be found on the Database of the project at: http://masonry.uic.asso.fr

The Database is intended to form a reservoir for existing knowledge of management processes and data applicable to masonry arches and to provide a platform to enable the railway administrations and other users to consult and share information.

ACKNOWLEDGEMENTS

The author wishes to thank the financial support of the railway administrations and the professional help of their representatives and other consultants participating in the project. The enormous help of Keith Ross (Network Rail) in reviewing and editing the reports is greatly acknowledged.

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REFERENCES

Bień, J., Kamiński, T., Rawa, P. (2006): Technology and pilot version of expert tool supporting the evaluation of the degradation level for masonry bridges with damages. UIC Report.

Brencich, A., Gambarotta, L. (2006): Guide to the high-level assessment of masonry arch bridges. UIC Report (draft).

Gilbert, M. (2006): Guide to use of RING 2.0 for the assessment of railway masonry arches. UIC Report.

Harvey, W.J. (2007a): Review of the MEXE method. UIC Report (draft).

Harvey, W.J. (2007b): Rule of thumb method for the assessment of arches. UIC Report (draft).

Harvey, W.J. (2007c): Guide to the assessment of masonry arch bridges. UIC Report (draft).

Ingenieurbüro A. Pauser (2005a): Guide to the high-level assessment of masonry arch bridges. UIC Report.

Ingenieurbüro A. Pauser (2005b): Guide to the destructive testing of masonry bridges. UIC Report.

Ozaeta, R.G., Martín-Caro, J.A. (2006): Catalogue of Damages for Masonry Arch Bridges. UIC Report.

Ozaeta, R.G., Martín-Caro, J.A., Brencich, A. (2007): Guide to the execution and control of masonry arch repairs. UIC Report (draft).

Steffens, K., Gutermann, M. (2006): Guide to the load test of masonry arch bridges. UIC Report.

The University of Pécs (2006): Recommendations to the non-destructive testing of masonry arch bridges (ed. Orbán, Z.). UIC Report (draft).

UIC Code 778-3R (1994): Recommendations for the assessment of the load carrying capacity of existing masonry and mass-concrete arch bridges, Paris.

UIC Report. (2004): Assessment, Reliability and Maintenance of Masonry Arch Bridges (ed. Orbán, Z., UIC Masonry Arch Bridges Study Group). State-of-the-Art Research Report of the International Union of Railways, Paris.

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Sustainable Bridges – A European Integrated Research Project. Background and overview

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Sustainable Bridges – A European Integrated Research Project.

Background and overview

Jan OLOFSSON, Lennart ELFGREN, Brian BELL, Björn PAULSSON, Ernst NIEDERLEITHINGER, Jens S. JENSEN, Glauco FELTRIN,

Björn TÄLJSTEN, Christian CREMONA, Risto KIVILUOMA & Jan BIEŃ

This paper describes the Integrated Research Project “Sustainable Bridges”. The Project aims to help European railways to meet the European Commission’s wish to see greatly increased use of the European railway network. This can only be achieved by allowing higher axle loads on freight vehicles and by increasing the maximum permissible speed of passenger trains. In turn, any necessary work on the existing bridge stock to help in meeting this challenge must be undertaken without causing unnecessary disruption to the carriage of goods and passengers, and without compromising the safety and economy of the working railway. This is the overall goal of Sustainable Bridges.

The Project has developed improved methods for computing the safe carrying capacity of bridges and better engineering solutions that can be used in upgrading bridges that are found to be in need of attention. Other results will help to increase the remaining life of existing bridges by recommending strengthening, monitoring and repair systems.

A consortium, consisting of 32 partners drawn from railway bridge owners, consultants, contractors, research institutes and universities, has carried out the Project, which has a gross budget of more than 10 million Euros. The European Commission’s 6^th Framework Programme has provided substantial funding, with the balancing funding coming from the Project partners. Skanska Sverige AB has provided the overall co-ordination of the Project, whilst Luleå Technical University has undertaken the scientific leadership; the remaining co-authors are the work package leaders within the Project.

1. INTRODUCTION

The European Commission has stated that it wishes to see a large increase in the use of the European railway network over the next thirty years. It has challenged the railway administrations to plan for a three-fold increase in freight traffic and a 30% increase in passenger traffic over this period. In order to meet this challenge it is important to ensure that existing railway bridges will behave properly under increased loads and higher speeds, and to upgrade them as necessary.

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The needs in this respect are similar throughout Europe even though the bridges themselves can be quite different. The resources available in each country are, however, too small to deal effectively with such a major challenge. Hence, co-ordinated activities are needed to ensure that widely accepted, pan European solutions are available to bridge owners. For this reason, an “Expression of Interest” was sent to the European Commission in June 2002 when the 6^th Framework Program was planned. The “Expression of Interest” was complied by a small group of people who became the core members of the final consortium. They had earlier, unsuccessfully, tried a somewhat similar proposal in the 5^th Framework Program. However, this time the call in December 2002 contained a theme specifically regarding Railway Transport Infrastructure, and work began to form a project proposal. A first meeting took place at the Airport in Copenhagen on February 18, 2003, followed by telephone meetings and a second meeting et the Airport in Brussels on March 24, 2003, two weeks before the proposal was to be submitted. The proposal was rated favourably and a hearing took place in Brussels on May 26, 2003, with five of the core members present. After negotiations during the summer the Integrated European Research Project “Sustainable Bridges” was approved by the European Commission for funding through the 6^th Framework programme and began its work in December 2003 with a first General Assembly meeting in Barcelona. The Project will be finalised in November 2007. The Project’s aim has been to provide better and more consistent guidelines for the assessment, monitoring, testing and strengthening of railway bridges across Europe.

Figure 1. A train with iron ore is passing a typical railway concrete trough bridge on Malmbanan in northern Sweden. The wish to reduce transport costs by allowing higher axle loads and heavier trains is one of the objects of the “Sustainable Bridges” Project which was inspired by Swedish investigations (Paulsson et al., 1997; Elfgren et al., 2007)

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Sustainable Bridges – A European Integrated Research Project. Background and overview

31 2. MAIN PROJECT OBJECTIVES AND ACHIEVEMENTS

The overall goal of the Project was to facilitate the delivery of improved bridge capacity without compromising the safety and economy of the working railway.

The main objectives of the Project were to:

• Increase the carrying capacity of existing bridges to permit axle loads of up to 33 tonnes for freight traffic at moderate speeds (say up to 100 km/h).

• Increase the capacity for passenger traffic with low axle loads (up to about 17 tonnes) by permitting the maximum speeds to be increased up to 350 km/h.

• Increase the residual lifetime of existing bridges by up to 25%.

• Enhance strengthening and repair systems.

The activities within the Project have focused on the functional requirements of railway bridges in order to achieve increased capacities and/or increased residual service life and to provide enhanced, strengthening and repair systems. The activities have also addressed efficient condition monitoring systems. The objectives, which are outlined below as they appeared in the Project bid for European Commission funding, are in line with ERRAC (2002).

The individual work package leaders, supported by the Project management team, have kept these objectives under constant review to ensure that they continue to meet the needs of the European railway administrations. Being an Integrated Project, it was possible for the Project team to modify the programme objectives and deliverables, and to reallocate resources within the agreed overall budget and Project duration, when this became necessary.

2.1. Increased allowable loads and speeds

There is a need for European railway bridges to carry increased loads (either heavier axles on freight trains or increased dynamic effects from faster passenger trains) and allow higher speeds, thus enhancing line capacity for both passenger and freight traffic. This demand can in many cases be met through better structural assessment, better understanding of the true behaviour of the structure, strengthening as necessary or by monitoring critical parameters.

A probabilistic approach for loads and resistance is one example of a new generation of methods that can be developed and applied.

Codes for the design of bridges have been developed gradually and consider all the uncertainties that are present during the design and construction phases 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 under construction. Nevertheless, the design uncertainty factors are often applied when assessing existing structures. Many bridges can be allowed to carry greater loads and faster trains if improved codes, more appropriate factors and methods for assessment are used.

One example is the Iron Ore Line “Malmbanan”, which is a line for the transportation of iron ore from northern Sweden to the coast of Norway. Here the axle load was increased from 25 to 30 tons after a thorough assessment procedure. Some bridges could carry the increased load in their existing states while others had to be strengthened, see (Paulson et al., 1997; Paulsson, 1998). The great potential for capacity improvement made available by better methods and procedures for assessment was recognized. In Figure 1 an example is given of a bridge that was monitored and assessed to allow higher loads (Elfgren et al., 2007).

The following achievements have been made:

New methods for the structural assessment of existing bridges have been developed in order to obtain better approximations of the real structural capacity.

Sustainable bridges: assessment for future traffic demands and longer lives

Sustainable Bridges

Dolnośląskie Wydawnictwo Edukacyjne

Sustainable Bridges

Assessment for Future Traffic Demands and Longer Lives

Edited by Jan BieÒ

Lennart Elfgren

Jan Olofsson

Table of contents

Foreword

Railway bridges in Europe

The need of R&D for existing structures

UIC project on assessment, inspection and maintenance of masonry arch railway bridges

Sustainable Bridges – A European Integrated Research Project.

Background and overview