The assembly weights shown on the specifications I have for an External Combustion Hammer are different than those shown in the GRLWEAP database (or the sum of the assembly weights is different than the total hammer weight minus ram weight). Should the assembly weights be corrected, and if so how should I do it?

The difference may be because, on certain hammer models, the assembly weights are configured differently for the same hammer due to ballast or other considerations. The assembly weights may or may not need to be corrected. While, in general, the results of the analyses are not very sensitive to changes in the assembly weights, very large assembly weights may produce higher pile stresses and lower blow counts, the latter due the preloading effect of the soil by the higher total hammer weight. GRLWEAP provides an option (accessible by clicking on the Options/Hammer Parameters menu item) which will cause a proportional change of assembly weights. Alternatively, you can modify the hammer data file and save the modified model in the user area (ID>2000) of the hammer data file. Modifying the data file is preferable for large changes of assembly weights for which a proportional change of assembly stiffness values also may be reasonable.

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