Extending the Fatigue Life of Steel Truss Bridges with Tuned Mass Damper Systems

Alessio Pipinato

doi:10.1155/2019/5409013

Abstract

The increasing traffic demand is continuously growing worldwide. Therefore, the life of a large stock of bridges that still exist throughout the world must be extended, ensuring at the same time that safety is not compromised for economic reason. This paper introduces the possibility to control the fatigue life of existing bridges by using a vibration control system. Based on a dynamic optimization analysis, the stresses from traffic on the bridge are obtained. Subsequently, a plate finite element (FE) model of the whole bridge is developed. The equation of motion is presented for a case study bridge, equipped with different tuned mass damper system, and the combination of external loads and train/track interaction with or without the TMD system is developed through own-developed routines and FEM software. The procedure is showcased for a case study bridge. After gaining the stress states at the critical hotspot, the fatigue crack life is evaluated by using the linear cumulative damage theory. The different TMD solution presented is demonstrated to be able to diminish the stress level in critical hotspots, improving the overall fatigue life of the bridge over an established lifetime.

Highlights

Fatigue failure of steel bridges is a well-known event that is frequently reported across the world [1,2,3]
Examining different interaction analyses and different train models with varying interaction systems, Liu et al [49] found that the results are very similar if the natural frequency of the train is much smaller than the natural frequency of the bridge, the mass of the train is smaller than the mass of the bridge, and the train is not moving at the critical speed. is should be considered for the purpose of this study, which Eurocode [50] suggests neglecting train/structure interaction
It should be noticed that not remarkable variation in the remaining fatigue life could be achieved by the use of Tuned mass damper (TMD) in existing steel railway trusses: in detail, for a yearly traffic increment of 2%, a maximum extension of the fatigue life is approximately 5 years adopting the TMD-7 solution (Figures 12 and 13)

Summary

Introduction

Fatigue failure of steel bridges is a well-known event that is frequently reported across the world [1,2,3]. E main problems recognized by the managing agencies are related to difficulties in maintenance, high noise emissions and vibrations, fatigue, and understrength capacities mainly found in transverse, main girders, and their riveted or bolted connections, while the main load-bearing elements (trusses) still have some residual capacity [17]. It should be mentioned that no design life was ever defined for the large majority of existing bridges, which means that implicitly they are supposed to last as long as the utilization (e.g., for road traffic) is given For this reason, it is crucial to implement solutions to strengthen bridges, or to control peak stresses in order to avoid fatigue failures. 3. Train-Structure Interaction e simplest interaction was studied by Saller [48]; in this formulation, the train-bridge moving load model is adopted, where the equation of motion is given by z2w zw z2. Examining different interaction analyses (multistatic or dynamic) and different train models with varying interaction systems, Liu et al [49] found that the results are very similar if the natural frequency of the train (fv) is much smaller than the natural frequency of the bridge (fn), the mass of the train is smaller than the mass of the bridge, and the train is not moving at the critical speed. is should be considered for the purpose of this study, which Eurocode [50] suggests neglecting train/structure interaction (par. 6.4.6.4)

Soil-Structure Interaction

Damping Ratios

C Bologna

A Figure 5

Conclusions