Fatigue safety examination of a 150-year old riveted railway bridge

Built in 1859, the railway bridge over the Rhine between Koblenz (Switzerland) and Waldshut (Germany) consists of a three span continuous riveted steel truss girder and an approach viaduct in natural stone masonry. Due to ever increasing traffic demands the fatigue safety and service life of the bridge needed to be examined. Examination methods as defined in the new Swiss Codes on Existing Structures using updated load models and structural resistance are applied to investigate this structure that is for more than 150 years in service. Due to this rational approach, it could be shown that the bridge can remain in service for a long future service life. This paper describes the chosen approach and reports on the most significant results. In particular, the main principles and assumptions followed in this project are outlined. Also, scenarios for future maintenance and rehabilitation interventions are developed and compared on the basis of life cycle costing. The approach allows for more realistic examination of the fatigue life of the riveted steel structure and also includes an comprehensive approach including cultural and economic valuations

Proportionality of interventions to restore structural safety of existing bridges

The proportionality of interventions on existing structures comprises a comparison between effort (cost) and benefit of interventions with the objective of an efficient use of means. This contribution discusses the evaluation of interventions to restore sufficient structural safety of existing bridges as encountered in real case applications. The considered hazard scenarios include accidental actions and one extreme live load event. For all hazard scenarios, structural safety check could not be fulfilled. Consequently interventions to restore structural safety were developed and their efficiency was analysed by a comparison of risk reduction with respect to safety costs. In addition, safety requirements, operational availability of the structure, magnitude of damage as well as the preservation of material and cultural values were considered. In three of the four cases the safety interventions turned out to be disproportionate. This paper presents a review of the chosen approach and assumed values and numbers used to estimate risk reduction and corresponding safety costs. Finally, issues are raised regarding the decision to implement or not the intervention to restore structural safety

Das neue Schweizer Normenwerk zum Umgang mit bestehenden Tragwerken

Mit der Normenreihe SIA 269 stellt der Schweizerische Ingenieurund Architektenverein seinen Mitgliedern ein Hilfsmittel zur Verfügung, das den Umgang mit bestehenden Tragwerken wesentlich verbessern wird und dabei die Kreativität der Ingenieure herausfordert und auch ermöglicht. In diesem Aufsatz wird das neue Normenwerk vorgestellt. Nach der Erläuterung von Grundsätzen und Tätigkeiten werden wesentliche Aspekte bestehender Tragwerke behandelt und mit Beispielen von Stahlbauten von hohem kulturellem Wert illustriert, bei denen bereits in den letzten Jahren die im Normenwerk SIA 269 festgehaltenen Regeln der Baukunde angewendet wurden. The new Swiss Codes for engineering of existing structures. The Schweizerische Ingenieur- und Architektenverein (Swiss Society of Engineers and Architects) introduces the series of Codes SIA 269 as a tool that will provide guidance for their members to significantly improve engineering of existing structures. These standards will challenge the civil engineering community and allow for creativity. This paper presents the main content of the SIA 269 codes. Principles and activities are outlined. Main aspects of existing structures are discussed and illustrated by means of examples of existing steel structures of high cultural value which have been rehabilitated over the last few years already applying the state-of-the-art rules as establish now in the Codes SIA 269

“STRUCTURAL UHPFRC” TO ENHANCE BRIDGES

“Structural UHPFRC” stands for Ultra-High Performance Fiber Reinforced Cementitious Composite material that is complemented by reinforcing and prestressing steel to enhance the resistance and durability of structural elements. Properties of impermeable, tensile strain hardening UHPFRC are outlined in view of structural applications. Two fundamental concepts to enhance concrete bridges have been developed by research and validated by applications in Switzerland: 1) Rehabilitation and strengthening of existing concrete structures by adding a layer of structural UHPFRC, and 2) Construction of new structures in Structural UHPFRC, often composed of precast elements. These applications show that Structural UHPFRC has made its proof as a novel building material and technology to enhance bridges and structures in general. Structural UHPFRC is the advent of a new construction era

Wir müssen den Mut haben, die Zukunft neu zu denken

Prof. Dr. Eugen Brühwiler entwickelte mit seinem Team einen hochbelastbaren Ultrahochleistungs-Faserbeton (UHFB). Als Professor der Eidgenössischen Technischen Hochschule Lausanne (EPFL) leitet er seit 1995 den Lehrstuhl für Erhaltung und Sicherheit von Bauwerken. Sein Name ist fest mit einem der Standardwerke des Brückenbaus verbunden: „Stahlbetonbrücken“, das er gemeinsam mit Professor Menn überarbeitete

Rehabilitation and strengthening of concrete structures using Ultra-High Performance Fibre Reinforced Concrete

An original concept is presented for the durable rehabilitation and strengthening of concrete structures. The main idea is to use Ultra-High Performance Fibre Reinforced Concrete (UHPFRC) complemented with steel reinforcing bars to “harden” and strengthen those zones of the structure that are exposed to severe environmental influences and high mechanical loading. This concept combines efficiently protection and resistance properties of UHPFRC and significantly improves the structural performance of the rehabilitated concrete structure in terms of durability. The concept has been validated by means of field applications demonstrating that the technology of UHPFRC is mature for cast in-situ and prefabrication using standard equipment for concrete manufacturing. This novel technology is a step forward towards more sustainable structures

Tensile fatigue behaviour of ultra-high performance fibre reinforced concrete (UHPFRC)

The tensile fatigue behaviour of ultra-high performance fibre reinforced concrete (UHPFRC) under constant amplitude fatigue cycles is presented. Three series of uniaxial tensile fatigue tests up to a maximum of 10million cycles were conducted with the objective to determine the endurance limit of UHPFRC that was supposed to exist for this material. The fatigue tests reveal that an endurance limit exists in all three domains of UHPFRC tensile behaviour at S-ratios ranging from 0.70 to 0.45 with S being the ratio of the maximum fatigue stress to the elastic limit strength of UHPFRC. Rather large variation in local specimen deformations indicates significant stress and deformation redistribution capacity of the UHPFRC bulk material enhancing the fatigue behaviour. The fatigue fracture surface of UHPFRC shows features of the fatigue fracture surfaces of steel, i.e. fatigue crack propagation is identified by a smooth surface while final fracture leads to rather rough surface. Various fatigue damaging mechanisms due to fretting and grinding as well as tribocorrosion are identified