Design criterion for fatigue strengthening of riveted beams in a 120-year-old railway metallic bridge using pre-stressed CFRP plates |
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| Affiliation: | 1. Empa, Swiss Federal Laboratories for Materials Science and Technology, Structural Engineering Research Laboratory, Dübendorf, Switzerland;2. EPFL, Swiss Federal Institute of Technology Lausanne, Steel Structure Laboratory (ICOM), Lausanne, Switzerland;3. University of Arkansas, Department of Civil Engineering, Fayetteville, AR, USA;4. ETHZ, Swiss Federal Institute of Technology Zürich, Institute of Structural Engineering (IBK), Zürich, Switzerland;5. University of Tehran, School of Civil Engineering, Tehran, Iran;1. University of Brest, Dupuy de Lôme Research Institute - IRDL CNRS FRE 3744, 6 avenue Victor Le Gorgeu, 29238 Brest, France;2. University of Porto, INEGI, Engineering Faculty, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal;3. ISISE, Department of Civil Engineering, University of Coimbra, Rue Luis Reis Santos, Pólo II, 3030-788 Coimbra, Portugal;4. University of Oviedo, Department of Construction and Manufacturing Engineering, Campus de Viesques, 33203 Gijón, Spain;5. National Society of French Railways - SNCF, Civil Engineering Department, 15 rue Jean Philippe Rameau, 93574 La Plaine Saint-Denis, France;1. Department of Civil Engineering, Monash University, Clayton, VIC 3800, Australia;2. Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, Melbourne, Australia;3. Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland;4. VicRoads – South West Victoria, 180 Fyans Street, South Geelong, VIC 3220, Australia;1. Empa, Swiss Federal Laboratories for Materials Science and Technology, Structural Engineering Research Laboratory, Dübendorf, Switzerland;2. ETHZ, Swiss Federal Institute of Technology Zürich, Institute of Structural Engineering (IBK), Zürich, Switzerland;3. School of Civil Engineering, University of Tehran, Iran;1. Structural Engineering Research Laboratory, Swiss Federal Laboratories for Materials Science and Technology (Empa), Dübendorf, Switzerland;2. Resilient Steel Structures Laboratory, Swiss Federal Institute of Technology Lausanne (EPFL), Lausanne, Switzerland;3. Department of Civil and Construction Engineering, Swinburne University of Technology, Melbourne, Australia;4. Department of Civil Engineering, Monash University, Melbourne, Australia |
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| Abstract: | This study presents a design criterion developed for fatigue strengthening of a 120-year-old metallic railway bridge in Switzerland and presents a pre-stressed un-bonded reinforcement (PUR) system developed to apply the strengthening. The PUR system uses carbon fiber reinforced polymer (CFRP) plates; however, unlike conventional pre-stressed CFRP reinforcement methods, preparation of the existing metallic bridge surface is not required. This decreases the time required for on-site strengthening procedures. The principle of the constant life diagram (CLD) and two fatigue failure criteria (Johnson and Goodman) are described. Analytical formulations are developed based on the CLD method to determine the minimum CFRP pre-stress level required to prevent fatigue crack initiation. The PUR system uses an applied pre-stress force to reduce the mean stress level (and stress ratio) to shift an existing fatigue-susceptible metallic detail from the ‘at risk’ finite life regime to the ‘safe’ infinite life regime. The applied CLD method is particularly valuable when the stress history of the detail is not known and it is difficult to assess the remaining fatigue life. Moreover, it is shown that the currently adopted approach in many structural codes which emphasizes stress range as the dominant parameter influencing fatigue life are non-conservative for tension–tension stress patterns (i.e., stress ratios of 0 < R < 1). Analyses show that the modified Johnson formula accurately reflects the combined effect of stress range, mean stress level, and material properties, and offers a relatively easy design procedure. Details of a retrofit field application on members of a riveted wrought iron railway bridge are given. A wireless sensor network (WSN) system is used for long-term monitoring of the on-site CFRP stress levels and temperature of the retrofitted details. WSN measurements indicate that increases in ambient temperature result in increased CFRP pre-stress levels. |
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| Keywords: | A Carbon fiber A Laminates B Fatigue C Finite element analysis (FEA) Retrofit |
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