In-situ dynamic behavior of a railway bridge girder under fatigue causing traffic loading

Stresses in bridges due to traffic loading need to be determined as accurately as possible for reliable fatigue safety verification. In particular, the dynamic traffic effect due to running vehicles has to be considered in a realistic way. In-situ measurements of the dynamic behavior of a one-track railway bridge have been performed to analyze the complex elastic dynamic system consisting of running trains—railway track—bridge structure. The main causes for dynamic effects for fatigue relevant bridge elements have been identified to be the vertical track position, i.e. track irregularities. The dynamic behavior has been modeled with sufficient accuracy using simple models when fatigue relevant dynamic effects are studied. The results of this study allow for the consideration of realistic dynamic amplification factors for fatigue verification

Finite Element Analysis for Fatigue Damage Reduction in Metallic Riveted Bridges Using Pre-Stressed CFRP Plates

Many old riveted steel bridges remain operational and require retrofit to accommodate ever increasing demands. Complicating retrofit efforts, riveted steel bridges are often considered historical structures where structural modifications that affect the original construction are to be avoided. The presence of rivets along with preservation requirements often prevent the use of traditional retrofit methods, such as bonding of fiber reinforced composites, or the addition of supplementary steel elements. In this paper, an un-bonded post-tensioning retrofit method is numerically investigated using an existing railway riveted bridge geometry in Switzerland. The finite element (FE) model consists of a global dynamic model for the whole bridge and a more refined sub-model for a riveted joint. The FE model results include dynamic effects from axle loads and are compared with field measurements. Pre-stressed un-bonded carbon fiber reinforced plastic (CFRP) plates will be considered for the strengthening elements. Fatigue critical regions of the bridge are identified, and the effects of the un-bonded post-tensioning method with different prestress levels on fatigue susceptibility are explored. With an applied 40% CFRP pre-stress, fatigue damage reductions of more than 87% and 85% are achieved at the longitudinal-to-cross beam connections and cross-beam bottom flanges respectively

Fatigue strengthening of damaged metallic beams using prestressed unbonded and bonded CFRP plates

Bonded fiber reinforced polymers (FRPs) reinforcement systems have traditionally been found to be an efficient method for improving the lifespan of fatigued metallic structures and have attracted much research attention. Nevertheless, the performance of a bonded FRP reinforcement system under fatigue loading is basically dependent on the FRP-to-metal bond behavior. In this paper, a prestressed unbonded reinforcement (PUR) system was developed. The proposed PUR system can be used as an alternative to bonded FRP reinforcement, particularly when there is concern about the effects of high ambient temperatures, moisture, water and fatigue loading on the FRP-to-metal bond behavior. The performance of cracked beams strengthened by the PUR system was compared with that of cracked beams strengthened by the prestressed bonded reinforcement (PBR) system. A theoretical method was developed to estimate the level of prestressing sufficient to arrest fatigue crack growth (FCG). Furthermore, the method was used to examine different passive, semi-active and active crack modes with a loaded, strengthened beam. The mechanism by which a prestressed FRP plate forms a compressive stress field at the vicinity of the crack tip was also examined. Finite element (FE) modeling was conducted and the results were compared with experimental results

Loads and Dynamic Effects : Sustainable Bridges Background document D4.3

Based on the outcome of questionnaires to European Railway Authorities the following researchtopics were identified and chosen for detailed study in this project: - Summary of Several European Assessment Codes, - Assessment of actual traffic loads using Bridge Weigh-In-Motion (B-WIM), - Dynamic Railway Traffic Effects on Bridge Elements.EC Sixth Framework ProgramSustainable Bridges – Assessment for Future Traffic Demands and Longer LivesTIP3-CT-2003-001653</p

Loads and Dynamic Effects : Sustainable Bridges Background document D4.3

Based on the outcome of questionnaires to European Railway Authorities the following researchtopics were identified and chosen for detailed study in this project: - Summary of Several European Assessment Codes, - Assessment of actual traffic loads using Bridge Weigh-In-Motion (B-WIM), - Dynamic Railway Traffic Effects on Bridge Elements.EC Sixth Framework ProgramSustainable Bridges – Assessment for Future Traffic Demands and Longer LivesTIP3-CT-2003-001653</p

Structural assessment of concrete bridges

The paper summarizes the work on concrete bridges performed in the EU project Sustainable Bridges. The work provides enhanced assessment methods that are able to provide higher load-carrying capacities and longer fatigue lives for exixixting concrete railway bridges. The work is also presented in a Guideleine available at www.sustainablebridges.netThe paper summarizes the work on concrete bridges performed in the EU project Sustainable Bridges. The work provides enhanced assessment methods that are able to provide higher load-carrying capacities and longer fatigue lives for exixixting concrete railway bridges. The work is also presented in a Guideleine available at http://www.sustainablebridges.net/Validerad; 2008; Bibliografisk uppgift: Publication no 38. ISBN 978-82-8208-011-8; 20090517 (elfgren

Structural Assessment of concrete railway bridges

The aim of the work presented here was to provide enhanced assessment methods that are able to prove higher load carrying capacities and longer service lives for existing concrete railway bridges. One main objective was to develop methods for non-linear analysis since this provides the greatest potential to discover any additional sources for load carrying capacity, and gives an improved understanding of the structural response. Another main objective was to provide methods for assessing deteriorated concrete bridge. Recommendations are given regarding the effect of reinforcement corrosion, particularly on anchorage capacity. Furthermore, a methodology for improved assessment of the remaining fatigue life of short-span concrete bridges and secondary elements is presented. Other topics treated are evaluation of material properties, simplified methods for structural analysis and the bending-shear-torsion interaction