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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 50
Edited by: B.H.V. Topping and M.B. Leeming
Paper IV.2

Post-Buckling of Portal Frames - Reduced Number of DOF Models

P. Providencia and E. Costa

Department of Civil Engineering, University of Coimbra, Coimbra, Portugal

Full Bibliographic Reference for this paper
P. Providencia, E. Costa, "Post-Buckling of Portal Frames - Reduced Number of DOF Models", in B.H.V. Topping, M.B. Leeming, (Editors), "Innovation in Computer Methods for Civil and Structural Engineering", Civil-Comp Press, Edinburgh, UK, pp 59-64, 1997. doi:10.4203/ccp.50.4.2
The present article exposes the incipient post-buckling behaviour of discrete elastic portal frames with a minimum number of degrees of freedom. It demonstrates that these simple models are sufficient to describe a qualitative behaviour which although generally known is also frequently forgotten or neglected because the continuous problem analysis is quite complex. In particular, the sign of the incipient curvature of the symmetric bifurcation path associated with the sway mode is shown to depend on the ratio between the beam and columns lengths (whose inverse represents a ratio between the corresponding bending stiffnesses). On the other hand, the nonsway mode appears from an asymmetric point of bifurcation.

The substitution of rigid connections by semi-rigid is also shown not to produce any drastic change to the qualitative behaviour in the post-buckling range.

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