Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux

Type de document

RAPPORT DE RECHERCHE

Langue

anglais

Auteur

CREMONA ; PATRON SOLARES ; JOHANSSON ; LARSSON ; EICHLER ; HOHLER ; KUHN

Résumé / Abstract

The present section of Deliverable D.4.3 is delicated to the static and fatigue assessment of old metal bridges. It forms the basis of the Chapter 7 guideline developed in work package 4 (WP4) "Guideline for load and Resistance Assessment of Existing European Railway Bridges. This section is divided into four parts related to the four research activities of the WP4 metal subgroup : analysis of material properties of existing metal railway bridges, fatigue of riveted structure, update assessment methods for riveted structures, enhanced non destructive techniques for inspecting riveted structures. The preparation of this document has been carried out by the Rheinisch-Westfälische Technische Hochschule Aachen, Germany (PSP), by the Lulea University of Technology, Sweden (LTU), and the Laboratoire Central des Ponts et Chaussées, Paris, France (LCPC). The knowledge of the material properties of existing metal bridges is essential for the resistance assessment and the determination of the remaining lifetime of old metallic bridges. Yet, especially the old bridges require more exact and efficient assessment methods that call for a precise description of the material. This is why a major part of the performed work and of this background document part has been focused on the material properties of old metal bridges. Among the problems met in metal bridges and material properties estimation, fatigue is the most common cause of failure. To be able to make accurate assessments of existing bridges, it is important to know the behaviour of bridges exposed to fatigue, and how the old materials behave due to cyclic exposure. The technique of riveting is no longer used in bridges due to more developed methods of assembling plates as welding. Due to this fact there is often missing information in codes (Eurocode for example) how to deal with and assess riveted structures. An important part of D4.3.6 consequentely deals with the evaluation of riveted structure remaining lifetime. The main question answered herein is how to make a safe estimation concerning the remaining life in service. Influencing factors are also investigated, such as corrosion, clamping force and material properties etc. to be able to perform estimations of the remaining life for a detail or a structure the detail category is essential. From tests on both full scale structures and small sizes specimens retrieved from bridges taken out of service a detail category for riveted structures has been derived. The possible traffic load on steel rail bridges is usually limited by the fatigue resistance, but for certain situations the static resistance has also to be checked. Most design rules foe steel structures, for instance those in Eurocode 3, are applicable also to riveted structures. However, some information is missing on how to deal with the special case that elements are intermittently connected in contrast welded structures that are connected continuously. One such issue is how to definie the cross section class of a riveted member. On question that is not covered in a reasonable way is the distance between rivets in the direction of stress. Another is to quantify the positive effect of restraint to local buckling provided by the connecting angles. Proposal for answers to those questions have been tasks handled by the metal subgroup and are presented in this background document. As the traditional methods for assessing the resistance of steel bridges are based on elastic analysis, a method for utilizing a limited redistribution of bending moments based on beam theory is also described. At last, this report presents a synthesis of non destructive techniques for steel bridges, with emphasis to riveted bridges. Their requirements in terms of reliability are presented and advantages and disadvantages are highlighted. A section is dedicated to acoustic emission which presents interesting features for bridge monitoring. ; RAPPORT DE CONTRAT