Fatigue loading tests of concrete railway sleepers

Abstract

In fatigue loading tests, unused Finnish concrete railway sleepers of type B97 and BP99 were loaded. The purpose of the loading tests was to analyse the fatigue properties of the sleepers and the effect of fatigue on their stiffness. The significance of cracks was also estimated. The load levels were chosen so that it was possible to estimate the significance of fatigue in actual use. A total of 11 fatigue loading tests were run. Eight targeted the rail seat section and three the centre. One sleeper was also loaded only statically to serve as a reference. In fatigue loading tests sleeper specimens were subjected to 200,000 loading cycles with standard load, after which they were loaded statically to failure. Sleepers in rail seat section tests failed at under 200,000 cycles when the loading level was 195 kN or higher. A fatigue model depicting the relationship between the stress level of the sleeper and the number of loading cycles it is subjected to was developed based on the results of the fatigue loading tests. The fatigue limit determined based on the loading tests and the calculated limit state of crack formation were clearly higher than the bending moments measured in field tests. Consequently, deterioration of the railway sleepers under a traffic load and due to fatigue is highly unlikely.