The loads used in current codes are defined as characteristic values, notionally based on a statistical analysis of the real distribution of loads which may occur over a long time period. Silo loads do not yet have any statistical pedigree, and the data base to develop one will not be available for a long time. Moreover, it is not only the amplitude of the design load which is in question but the pattern of the loading. Unsymmetrical loads which can arise under entirely symmetrical conditions (Fig. 5) have only be properly recognised in the last few years. The 'patch' load developed in Germany (Fig. 10) and since adopted elsewhere has not been properly verified. Unsymmetrical loads caused by defined unsymmetrical conditions (e.g. eccentric discharge) have been extensively studied, but no agreed method of treating them can be found at present [36, 37, 8, 12], and recent experiments  suggest that more than one pattern of pressures will be required for a satisfactory definition.