Effect of Semi-rigid Connection on Post-buckling Behavior of Braced-Steel Frames

Practically, rigid beam-column connection has a relative flexibility which reduces their resistance to moments and this lead to partially restrained connection which is called semi-rigid connection. This research presents a numerical analysis using finite element method by ANSYS software to predict the effect of semi-rigid beam-column connections on post-buckling behavior of braced and unbraced frames and make a comparison between them. The beam and column of the frames were modeled using beam element and the semi-rigid connections were modeled as rotational springs with different rotational stiffness values in linear elastic stage. The results show that, the load-displacement curve of the braced frame is less affected by changing the beam-column connection from rigid to semi rigid with different rotational stiffness values as compared with that of the unbraced frame although this changing has slight effect on the ultimate vertical displacement. Also the results show that the semi-rigid connection should be take into account in analysis and design of braced and unbraced steel frames to obtain more realistic results.