Abstract
There is a large number of old riveted railway bridges that are still in use in the UK and around the world. Due to their considerable age, which in many cases is over 100 years, their useful life-span may be close to its end. Fatigue cracking has been observed in riveted bridge connections over the years, confirming that the connections in these bridges are susceptible to fatigue damage. Although considerable research has been conducted on the fatigue behaviour of riveted bridges, only a small percentage of this research has concentrated on riveted connections. In this thesis, a general methodology for the fatigue assessment of riveted railway bridges is presented by concentrating on the fatigue behaviour of their connections. The methodology is developed through the fatigue analysis of a finite element model of a 10 m span riveted railway bridge, typical of a very large number of old railway bridges in the UK. As a first step of such a methodology, a global finite element analysis of the bridge is performed in order to identify, on an S-N basis, the most fatigue-critical connections. Probabilistic methods are also employed in order to determine the reliability of those connections. The global analysis is then followed by a detailed investigation of a refined finite element model of this connection, which is developed with the aid of benchmark studies on simple finite element models of riveted lap joints. This second step of the methodology aims at identifying, on an S-N basis, the hot spots and potential crack initiation sites in the connection itself. In both steps, the analysis is carried out in terms of present day and historical train loading. In the context of these investigations, the most important parameters that affect fatigue damage, estimated on an S-N basis, are found to be the connection stiffness, the detail S-N classification and the rivet clamping force. By ranking the bridge connections according to their fatigue damage, the inner stringer-to-cross-girder connections are identified as the most fatigue-critical. The fatigue life of these connections is found to be governed by stress levels which are close and below the fatigue limit of the relevant detail. The rivet holes and the angle fillet are identified as the most fatigue-critical locations on the connection where fatigue cracking may initiate. Quantitative results are obtained for the critical connections under various scenarios. The results obtained in this thesis can also be used in planning effective inspection regimes for these bridges.