Loading spectrum for highway bridges and damage criteria for cumulative loading

Bridges are presently designed to withstand the bending moments and shear forces produced by a standard design truck such as AASHO H2O-S16. However, bridges are subjected to a large number of loads of different magnitude randomly ordered with respect to time. This thesis describes a literature summary to obtain a description of the magnitude of loads and number of occurrences (load spectrum) on highway bridges. Secondly, the behaviour of bridges under random fatigue load was investigated.;Literature concerning the damage criteria of bridges is very limited and no criteria has been found which satisfactorily summarizes the cumulative damage to bridge materials by random loads.;From the data obtained at weigh stations of the gross weight and.axle loads of actual trucks, a general description of the load spectrum was obtained. By applying factors to allow for regional trends and local factors a design spectrum could be obtained for any particular bridge.