Proposed Vehicle Loading of Long-Span Bridges

Two completely different methods have been derived for predicting the loading on a long-span bridge, given a knowledge of the average mix of traffic. Both methods are in good agreement. It is shown that the load can be represented as a uniform load and a concentrated load to give maximum moments and shears with a reasonable degree of accuracy. Unlike the findings of previous authors, the concentrated load is found to increase with the length of bridge that is loaded, whereas the uniform component decreases with length as would be expected. Examples are given for four levels of traffic ranging from very light to very heavy and comparisons show that the loading is not unduly sensitive to the percentage of trucks in the traffic stream.