Another Saddle Design Question

[pperlich]

I am studying up on Saddle Design using Bednar (2nd Edition) and Moss (4th Edition). Concerning longitudinal forces (wind, seismic, etc.) Moss computes an increased saddle load, and then goes through the shell stresses. To me, that seems to come short of a full analysis. First the fixed saddle will apply a moment to the shell that is not considered. Secondly, since the vertical load is increased on one saddle, then the other saddle will have a decreased vertical load. Add those two things up, and the simple overhanging simply supported beam formula doesn't accurately model the longitudinal bending moment in the shell.

What are your thoughts on this observation?

Are there any other published methods that provide a more complete analysis of longitudinal (and transverse) loads on saddle supported vessels?

 

[BJI]

I am not up to date with those books but your observations appear to be correct. The critical area in the shell is near the horn of the saddle so the basic beam equations are not sufficient. To answer you section question, the best reference for this is the paper by Zick, but probably worth referring to PD5500 Annex G for the calculation method.

 

[SnTMan]

My opinion, it (Zick w/ external loadings added) is enough of a mess already. Making it more complicated will not likely make it more accurate.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand