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The President: This must have been a most exciting job with many problems to overcome. It was a congested site, with restrictions of allowable pressures on the ground. The factors which influence the engineering design are quite amazing; I think you said that it was imperative to obtain a uniform pressure on the ground and that that particular restriction to some extent led you to adopt the curve columns.
In this paper is presented a study on dynamic stability of thin-walled bars with open cross-section, subjected to compression by an axial force, composed from a static component and a variable one. The case of non-symmetric profiles is analysed in the first instance, to obtain general equations of vibratory motions; these are then particularized for profiles with an axis of symmetry, currently used in construction.
In his paper, the author has modelled the behaviour of compression members by assuming that they will have a buckling load given by Rankine's formula, and that they can undergo unlimited contraction at this load. It is well known, however, that compression members generally show some drop of load-carrying capacity after the critical load has been reached. On the other hand, it is quite reasonable to assume that tension members will elongate plastically under a constant yielding load (ignoring strain-hardening effects), provided that premature joint failure is prevented. Results of experimental work on compression members with varying degrees of end restraint have been plotted in Fig Cl. These values were mostly taken from a paper published by Francis and Stevens1 describing work carried out at the University of Melbourne, but also include results from Paris and van den Broek. It can be seen from Fig C1 that the critical loads of compression members are more closely related to the squash and Euler loads than to the Rankine load.