The railway transport forms an important part of a whole transportation system of each country. Lithuania is being crossed by Trans-European Rail Corridors connect- ing Baltic countries via Warsaw to the rest of EU as well as Lithuania with Byelorussia, Ukraine and Russia be- coming a part of major Trans-Asian corridors (Vasili- auskas and Barysiene 2008). The main problem facing the railway bridges is that national and EU territory rail- way networks operate to different track and load stan- dards.
Actual traffic loads on bridges are quite complex be- cause of the randomness of traffic process. Normally, they are represented in the codes by simple load models, reflecting the worst loading that can be caused on the bridge by actual and future traffic. Bridge loadings de- scribed in codes of practice vary from country to country (e.g., O’Connor and Shaw 2000). It is evident that there has been a trend towards the increase in design loads and loading configurations over the years in most countries. Problems occur when different codes or standards are combined together.
In Lithuania many existing bridges were designed using codes SNiP (СНиП 84). Design of road bridges according to Eurocodes started from 2000. Lithuanian standards LST EN 1991-2:2005 lt and LST EN 1990/A1:2006 lt were issued which give rules and methods for establishing combinations of actions for road and railway bridges. Preliminary analysis and com- parison of traffic load effects determined according to SNiP and first pre-standards ENpr at that time showed that the Eurocode loads for existing highway bridges are heaver sometimes up to 1,5-2 times (Notkus 1998, 2005) and for railway bridges are considerably lighter (Notkus 1998, 2003; Cypinas 2003, Cypinas et al. 2005). This means, for example, that old highway bridges need repa- ration and strengthening that is not always reasonable. The same situation is observed and in other countries.