Determination of a reasonable impact factor for fatigue investigation of simple steel plate girder railway bridges

In Korea, there are approximately 1000 ballastless steel plate girder railway bridges that are short span and simply supported and have been in service for over 30 years. It is well known that one of the main factors affecting the durability of such bridges is the fatigue phenomenon. This study aimed to determine a reasonable impact factor for fatigue investigation of these bridges. The impact factor was obtained from a dynamic analysis modeling a bridge and a train as beam and moving masses, respectively. Train speed and the type, span length and stiffness of the bridge were considered as the main variables in the analysis. The validity of the presented impact factor was confirmed through comparison with measured values. The results of this work show that the present Korean code has a tendency to overestimate the fatigue impact factor, and a value only half of that used in ordinary static design can be used for fatigue investigation of simple steel plate girder railway bridges.