Train loading on bridges since Stephenson's Rocket

Railway locomotives increased in weight from less than 10 tons in 1825 to more than 100 tons by the 1930s. Originally loading on bridges was assumed as an average weight per unit length ignoring axle concentration and generous factors of safety were used to compensate for the absence of any dynamic allowance. After the Dee Bridge collapse of 1847 Board of Trade rules were imposed. The comparatively few bridge failures under train loading are summarised. After several failures of flawed cast-iron girders these were gradually replaced after 1891. There was no rigorous consideration of dynamic effects until the 1900s. Civil engineers had been rejecting heavier new locomotives without comparing hammer blow characteristics. Dynamic effects were eventually investigated for the Bridge Stress Committee Report of 1928. With the elimination of steam traction, loading as developed for Europe was introduced and is now adopted in the Eurocodes. Comparisons are made between early and modern loadings taking account of the effect of increasing speeds.