In Reference 60 Horn presents experimental data from tests of struc- 

 tural models which have been purposely fabricated imperfectly circular in 

 specified out-of- roundness patterns. He also presents a comprehensive 

 comparison and discussion of theory vis-a-vis experiment. 

 PLASTIC GENERAL INSTABILITY OF SHELL AND RING FRAMES 



Although it is true that prior to reaching its ultimate load-carrying 

 capacity, a ring- stiffened cylindrical shell first undergoes elastic de- 

 formations, optimum design of such a structure must eventually be based 

 on considerations of inelastic behavior. The elastic general-instability 

 mode and the theories developed to predict this behavior have already been 

 discussed in a previous section. It remains for us to give due consider- 

 ation to the inelastic general-instability mode as was done for both the 

 axisymmetric and asymmetric inelastic panel-instability modes. 



Taking advantage of what has already been discussed in connection 

 with the asymmetric inelastic buckling of a stiffened cylindrical shell 

 between adjacent ring frames, and coupling this to the "split-rigidities" 

 concept underlying the Tokugawa-Bryant formula for elastic general insta- 

 bility, it becomes rather obvious to the reader what a possible approach 

 to the inelastic general-instability problem might be. 



Lunchick followed this avenue of thinking, and by introducing the 

 Shanley tangent-modulus concept for the buckling of a column in the in- 

 elastic range, he was able to derive a formula for plastic general insta- 



lls 



