Lebenszyklusbetrachtungen als Grundlage für die Nachhaltigkeitsbewertung von Straßenbrücken

Lebenszyklusbetrachtungen spielen bei der Bewertung der Nachhaltigkeit von Bauwerken eine besondere Rolle. Sie fokussieren nicht nur auf die einmaligen Umweltwirkungen und die Investitionskosten bei der Herstellung von Bauwerken, sondern ermöglichen die ganzheitliche Beurteilung der fortlaufend anfallenden ökologischen und ökonomischen Wirkungen. Mit der Untersuchung von zwei Autobahnbrücken und zwei Überführungsbauwerken wird das Ziel verfolgt, einen einheitlichen Durchschnittswert für die ökologischen und die ökonomischen Wirkungen von Brückenbauwerken zu definieren. Der Beitrag befasst sich mit der Festlegung derartiger Referenzwerte und stellt erste Lösungsansätze zur Berücksichtigung des Recyclingpotentials von Materialien vor. Life cycle considerations as a base for assessment of the sustainability of road bridges. Life cycle considerations are important for the assessment of the sustainability of constructions. Taking the life cycle into account it is not only possible to determine single environmental impacts and investment costs arising during the construction of buildings, but also to assess the consecutive ecological and economical impacts. The aim of this study was to define a consistent average value for ecological as well as economical impacts of road bridges by evaluating two viaducts and two overcrossings. This article deals with the determination of those reference values and presents an approach how to deal with the recycling potential of materials within the life cycle assessment.     

Querschnittsgestaltung von Stahlverbundbrücken

Cross section design of composite bridges. The traffic particularly on highways has increased over the last decades. Heavily used routes need to be expended by adding more lanes. In this context the existent bridges that are already in bad condition are to be renewed. Generally the superstructure is designed with dual carriage ways. Each superstructure needs to accommodate more lanes than in the past. Due to the span length and the width of the construction possible cross sections are presented. Pros and contras are discussed.     

Instandsetzung und Verstärkung von Stahlbrücken mit Kategorie‐2‐Schäden

Refurbishment of orthotropic steel bridge decks with damages of the category 2. Many of the steel bridges built in the 1960s to 1980s, which are still located within the network of German highways and federal roads, show severe damages often induced by the considerable increase of freight traffic in the last few years. In addition, the forecasts predict a further increase of the heavy‐load traffic. Furthermore and especially in the case of many orthotropic steel bridge decks, several details were realized being no longer state of the art. This paper focuses on the so‐called category 2 damages, which comprise all damages at the longitudinal stiffeners. For this type of damage, different examples of bridges and their solutions of refurbishment are presented. Above all, one possibility of a renovation by means of mechanical fasteners, like blind‐rivets, is considered in detail. This detail is also focused by the current research project ”Refurbishment of fatigue‐stressed longitudinal stiffeners of orthotropic steel bridge decks by means of screwed solutions“ conducted at the University of Stuttgart.     

Neuartige Sandwichfahrbahnplatte für Eisenbahnbrücken

Innovative composite deck slab for railway bridges – Analysis of the fatigue behaviour of the shear connectors using the strain‐life method. At the Technischen Universität Wien (Vienna University of Technology), Institut für Tragkonstruktionen (Institute of Structural Engineering), Research Centre of Steel Structures, a new, extremely slender steel‐concrete‐steel composite (SCSC) plate is under investigation to meet the requirements of today's standards related to the geometric conditions and noise emission in the substitution of old railway bridges. The multi‐layer structure of the plate consists of two steel cover plates with an unreinforced concrete core, hence the name of sandwich plate. Perforated shear connectors, welded alternately to only one of the outer steel plates, work together to ensure the transmission of the shear flow between the outer plates, by the activation of diagonal, horizontal concrete compression struts between neighboring dowel bars. In addition to the distribution of the vertical loads in cross direction to the main girders, the SCSC deck slab also acts as main girder bottom flanges. Investigations on the static load‐bearing capacity as well as an explanation of the load‐carrying mechanism of the SCSC plate were made in ([1] [2] and [3]). Evaluation of the fatigue behaviour is presented in this work, focusing on the fatigue behavior of shear connectors of the SCSC plate. In the course of research a nonlinear, three‐dimensional finite element model served as the basis for a lifetime calculation using the local strain‐life method [4]. The aim was to investigate the relation between the range of traffic load (Load Model 71) and the bearable number of load cycles of the SCSC plate till crack initiation in the shear connectors. This paper provides an overview of the approaches used to calculate fatigue life of the shear connectors and gives a brief summary of the results.     

Ertüchtigung der genieteten Stahlbrücken am Beispiel von zwei Straßenbrücken über den Fluss Marosch in Rumänien

Genietete Stahlbrücken sind heute beinahe nur noch als Eisenbahnbrücken im Einsatz. Es gibt eine relativ geringe Anzahl an genieteten Straßenbrücken, die auf Nebenstraßen in Betrieb sind. Sie sind i. A. in schlechtem technischem Zustand. Dieser Aufsatz ist ein Plädoyer für die Ertüchtigung und Erhaltung dieser Bauwerke als Zeugen einer vergangenen technischen Kultur und Beispiel für eine ansehnliche Stahlkonstruktion. Es werden zwei Fallstudien präsentiert: eine Fachwerkbrücke mit vier Spannweiten von 40 m und ein Fachwerkgerberträger mit einer Gesamtlänge von L = 185,4 m. Maintenance of riveted steel bridges exemplary shown with two highway bridges across the river Marosch in Romania. Riveted steel structures are in present mainly railway bridges. There is a small number of existing highway bridges, generally in bad technical condition. The paper is a speech for the maintenance of these structures as technical monuments and witnesses of the past. Two case studies are presented: a truss girder bridge with fore spans of 40 m and a cantilever truss girder bridge with a total length of 185.4 m.