ABSTRACT
ABSTRACT: European railway bridge stock consist mainly of 4 major bridge types, with age ranging form extremely old masonry arch bridges, middle-age metallic bridges and newly built concrete and composite (steel/concrete) bridges. Small span lengths, less than 10 m, are dominating. Furthermore railways typically assess serviceability as rout bases. Traffic interruptions need to be avoided almost entirely. Many of the existing bridges are in need prolonged life considering the design life when built. In addition it is not uncommon that the owner wishes to increase the speed, weight and traffic volume on the already busy routes. If these situations occur a thoroughly structural investigation is needed. First the remaining capacity is calculated, preferable with methods that consider real material data and loads. If uncertainties regarding for example boundary conditions exist monitoring might be needed. Nevertheless, if calculations and monitoring shows that the load carrying capacity is not enough strengthening can be one alternative to replace the structure. There are numerous different methods to strengthen existing structures of concrete, metal or masonry and the strengthen method chosen is largely dependent on the environment, type of original design, existing object, estimated future use and so on. In a sustainable society, the transportation work carried out by rail ought to be larger than today. In order to enable such an increase, the capacity of existing railway bridges needs to be increased too. This is also the objective of the project “Sustainable Bridges – Assessment for Future Traffic Demands and Longer Lives”. There are three specific goals:
1. Increase the transport capacity of existing bridges by allowing higher axle loads (up to 33 tons) for freight traffic with moderate speeds or by allowing higher speeds (up to 350 km/hour) for passenger traffic with low axle loads.
