6. LIMIT STATES CONCEPT
Most railway organisations would condemn a
sleeper when its ability to hold top of line or gauge is
lost. Those two failure conditions can be reached by
the following actions [4]:
1. abrasion at the bottom of the sleeper
causing loss of top;
2. abrasion at the rail seat location causing a
loss of top/line integrity;
3. severe cracks at the rail seat causing the
‘anchor’ of the fastening system to move
and spread the gauge;
4. severe cracks at the midspan of the sleeper
causing the sleeper to ‘flex’ and spread the
gauge;
5. severe degradation of the concrete sleeper
due to alkali aggregate reaction or some
similar degradation of the concrete material