Special Section on Eurocodes and Their Implications for Bridge Design: Background, Implementation, and Comparison to North American Practice

The Eurocodes are a set of European standards providing unified rules for the design and assessment of civil engineering works and construction products. They are produced by the European Committee for Standardization (CEN) and embody national experience and research output together with the expertise of international technical and scientific organizations. The Eurocodes cover the principal construction materials, i.e., RC and prestressed concrete, steel, steel-concrete composite, and timber and other wood-based materials either singly or compositely with concrete or steel, masonry, and aluminum. The Eurocodes are part of the broader family of European standards, which include material, product, and execution standards. The Eurocodes for concrete (Eurocode No. 2), steel (Eurocode No. 3), steel-concrete composite (Eurocode No. 4), and timber (Eurocode No. 5) structures, as well as for seismic design (Eurocode No. 8), each comprise a Part 2 that explicitly covers the design of road and railway bridges. These parts are intended to be used for the design of new bridges, including piers, abutments, and foundations. The codes also permit independent jurisdictions to develop National Application Documents (NADs), which can propose modifications to the parent code (including, e.g., reduction in load intensities) to reflect national conditions.

With the publication of the Eurocodes in 2007, their implementation began extending to all European countries, and there are increasing steps toward their adoption outside Europe as reference standards for local codes and as alternatives to the traditionally used North American codes. This process has promoted training in the use of the Eurocodes and the publication of background documents as well as technical documents facilitating their implementation and use. In addition, the Eurocodes fostered applied research in structural engineering devoted to identifying gaps and possible improvements in the current edition of the provisions and provided the opportunity to incorporate the findings of new research into future code updates.

This special section of the Journal of Bridge Engineering on the Eurocodes and their implications for bridge design is intended to open a window on European research being carried out on a wide range of topics involving bridge design and assessment. The objective of the issue is to stimulate scientific discussion and exchange of results that include background, implementation, and comparisons to North American practice. The selected technical papers reflect a variety of studies (robustness; moving load models; concrete, steel, and steel–concrete composite bridges; and seismic design) from international authors (eight from Italy; three each from Ireland, Greece, Spain, and Switzerland; two each from Germany and the United States; and one from Canada) testifying to diverse interests in the analysis and advancement of the codes.

Recognition of the importance of robustness and redundancy of structural design in the face of extreme events has increased in recent years, as evidenced by the growing number of research projects and published journal and conference papers on this subject. The technical paper “Redundancy and Robustness in the Design and Evaluation of Bridges: European and North American Perspectives,” by Anitori et al., reviews current and proposed methodologies for assessing the robustness and redundancy of bridge structures, including comparisons between European and non-European codes and an overview of the latest advances in research in this area.

Accurate traffic load models are essential in bridge design and maintenance, and the technical paper “Microsimulation Evaluation of Eurocode Load Model for American Long-Span Bridges,” by Enright et al., illustrates the results of research that examines the appropriateness of current American and European load models for normal traffic on typical long-span bridges using the relatively new tools of traffic microsimulation. It is commented that the Eurocode load model has the potential for being applicable to the design and assessment of North American bridges and that the presented methodology could be used for detailed bridge assessments.

The assessment of the shear capacity of concrete slabs without shear reinforcements is based on empirical formulas obtained from the analysis of experimental results that are not always representative of the actual conditions found in RC decks. In the technical paper “Shear Design of RC Bridge Deck Slabs according to Eurocode 2,” by Rombach and Kohl, comparisons between Eurocode predictions and test results of slabs under wheel loads are discussed to highlight difficulties and unsolved questions associated with the shear design of concrete deck slabs.

Prestressed concrete bridges are the subject of two contributions. The first, a technical paper entitled “Predicting Strand Transfer Length in Pretensioned Concrete: Eurocode versus North American Practice,” by Martí-Vargas and Hale, presents a comparative study of strand transfer length provisions of European and North American codes, identifying differences and analyzing the relations between predictions and measured transfer lengths. The second, a technical paper entitled “Simplified Procedure for Evaluating the Effects of Creep and Shrinkage on Prestressed Concrete Girder Bridges and the Application of European and North American Prediction Models,” by Granata et al., illustrates a simplified approach for the linear viscoelastic structural analysis of concrete bridges with fixed or varied static schemes and uses a proposed simplified procedure to compare the results obtained through the prediction models for creep and shrinkage provided in the European and North American codes.

Structural aspects of steel bridges are also the subject of two contributions. A technical paper entitled “Comparison between Eurocodes and North American and Main International Codes for Design of Bolted Connections in Steel Bridges,” by Maiorana and Pellegrino, reviews and compares, using an illustrative example, European and non-European recommendations for bolted connections, including geometric requirements and bearing capacity predictions. The second technical paper, entitled “Simultaneous Vehicle Crossing Effects on Fatigue Damage Equivalence Factors for North American Roadway Bridges,” by Walbridge et al., reviews European and non-European fatigue design procedures applicable to metallic roadway bridges and presents a simulation-based study to investigate the effects of simultaneous vehicle crossings on the damage equivalence factors for North American road bridges. This study accounts for differences in fatigue damage due to the load model and the expected real traffic, including recommendations for amplifying the North American damage equivalence factors in cases where the effects of simultaneous vehicle crossings are expected to be significant.

Continuous steel and concrete composite bridges are a competitive structural solution for medium-span bridges, and various issues involving their behavior at service and ultimate limit states deserve specific attention. The technical paper “Slab Cracking Control in Continuous Steel-Concrete Bridge Decks,” by Gara et al., presents an analytical study of the evaluation of the effect of concrete slab casting techniques during the construction of continuous steel-concrete composite bridge decks. A simplified procedure is proposed and applied to a case study to evaluate the contributions of concrete weight and shrinkage to the slab early-age cracking as well as the calculated slab tensile stresses for different casting sequences that can be adopted to limit slab cracking.

The reduction factor method is a common approach to seismic design of structures and is included in many codes owing to its simplicity, being based on linear structural analyses, provided that response modification or behavior factors are known for the structure being considered. The technical paper “Response Modification Factors for Concrete Bridges in Europe,” by Kappos et al., presents a methodology for evaluating the response modification factors and their application to actual concrete bridges in southern Europe that have two different dissipation mechanisms—bridges with yielding piers and bridges with strong elastic piers—including comparisons with current provisions in European and North American codes.

All of the papers presented, with their reviews of the state-of-the-art, comparative examples and detailed discussions, provide an overview of recent research works being carried out in Europe and their relation to similar research in North America. Whereas issues associated with the most widespread bridge types and materials are well represented, some other materials and bridge types, such as cable-stayed, suspension, arch, movable and floating bridges, footbridges, timber, and masonry bridges, are not. The editors are cognizant of the fact that it is impossible to cover all topics in one special section, nor was this their intent. Rather, they hope that the special section will stimulate contributions in forthcoming issues of the ASCE Journal of Bridge Engineering around both the topics raised and those omitted here.

We would like to take this opportunity to thank all of the authors for their submissions and their patience during the review process. All papers for the special section were peer reviewed following the strict ASCE Journal of Bridge Engineering guidelines. In this regard we would like to thank the peer reviewers for their valuable and constructive comments, which have undoubtedly enhanced the quality of this special section. We are also grateful to Professors Vrowenvelder, Gulvanessian and Ellingwood for their interest in this special section. Throughout their professional careers, they have made significant contributions to the development of the Eurocodes and North American Standards; indeed, their names are synonymous with these documents. As such, having their perspective is invaluable. Finally, we thank the ASCE journal staff and the chief editor, Dr. Anil Agrawal, for providing the required assistance in delivering this special section.