Abstract
A local and global finite element analysis of the stringer-floor beam connection of a 19th century riveted railway bridge in Spain made of puddle iron were performed to obtain the maximum principal strains in the riveted connecting angles corresponding to bending moments from train loading on the bridge. Due to the anisotropic nature of puddle iron, the connecting angles were modelled using Hill anisotropic plasticity potential and a parametric study in the local FE model of the connection was performed. A laboratory specimen fabricated with original stringers dismantled from the railway bridge was tested to calibrate the numerical models, so the yield stress ratio that best fitted experimental results was obtained. Based on the method of constant fatigue-life diagram and modified Goodman fatigue failure criterion, it was detected that the connecting angles were prone to fatigue crack initiation, as the combination of mean stress and alternating stress amplitude at the toe of the angle fillet remained outside the infinite fatigue-life region. An innovative strengthening system based on adhesively-bonded carbon-fiber reinforced polymer (CFRP) angles was designed to prevent fatigue crack initiation in the connecting angles of the stringer-floor beam connection. Different CFRP laminate layouts were numerically evaluated and a proper configuration was obtained that reduced both the mean stress and the alternating stress amplitude in the connecting angle to shift from finite fatigue-life region to infinite fatigue-life region in the constant fatigue-life diagram. To validate the effectiveness of the proposed CFRP strengthening method, its application on a second laboratory specimen fabricated with original stringers was evaluated experimentally and compared with numerical results. The research study conducted showed that the use of adhesively-bonded CFRP angles was an effective strengthening system in reducing the stress level in the fillet region of the puddle iron connecting angles (where fatigue cracks are prone to initiate) and consequently could increase fatigue life of the stringer-floor beam connection.
Highlights
In Europe, more than 35% of railway bridges are more than 100 years old [1], so they are reaching the end of their expected service life
Based on the method of constant fatigue-life diagram and modified Goodman fatigue failure criterion, it was detected that the connecting angles were prone to fatigue crack initiation, as the combination of mean stress and alternating stress amplitude at the toe of the angle fillet remained outside the infinite fatigue-life region
An alternating stress amplitude of 134.44 modulus (GPa) Yield strength (MPa), 58.21 MPa and 101.18 MPa was computed, respectively, for these train loads (Table 8). These combinations of mean stress and alternating stress amplitude were represented in the constant fatigue-life diagrams (CLD) of Figure 20 and it is clearly observed that the connecting angle is prone to fatigue crack initiation for train load models UIC 71 and Renfe S335
Summary
In Europe, more than 35% of railway bridges are more than 100 years old [1], so they are reaching the end of their expected service life. Old riveted metallic railway bridges have been subjected to a large number of cyclic loads during their service life, so many of them could experience fatigue damage in certain construction details, limiting their residual life. A relatively large number of damage cases have been reported for stringer-floor beam connections in riveted metallic bridges [2,3]. These connections have some rotational stiffness, partially restraining the rotation of stringer ends [4]. To prevent the fatigue crack initiation of connecting angles and to extend the service life of these connections, the stresses in those fatigue-prone details could be reduced by the application of strengthening strategies
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