Analysis of frames with partially restrained connections

Abstract

Steel structures have long been widely used in different countries because of their relative economy and ease of construction. The connections of the constituent members of these types of constructions play an important role in affecting the behavior of the structure. In the conventional methods of steel frame analysis, the behavior of joints is represented by idealized models, either as a rigid joint or a pinned joint. The available design techniques are mostly based on these idealized conditions. In reality, most connections are semi-rigid and possess certain amount of rotational stiffuess. They are termed as partially restrained connections or semi-rigid connections. Experimental studies have shown that the connection moment-rotation characteristics are non-linear and the analysis procedure must follow non-linear approach. A computet program capable of analyzing frames with semi-rigid connections has been developed. The program is a non-linear type, iterative in nature and based on incremental or stepwise loading. The program is a generalized one and can be used to analyze frames with any type of known semi-rigid connections. The program can handle general types of loading implementing through a series of load increments. The connection flexibility effect has been incorporated by the matrix formulation given by Monforton and Wu. The non-linear behavior of the connections has also been incorporated by the polynomial moment-rotation relationship given by Frye and Morris polynomial model for different types of connections. With the help of the developed program several investigations have been performed to study the behavior of steel frames with semi-rigid connections. The first study describes the effect of flexible connections on the behavior of frames, its internal distribution 'of forces and lateral drift. The effect of bracing, as a sway resisting system on high rise building frames have also been studied. The effect of bracing on the internal force distribution and in controlling the sway of frame has been studied. The behavior of frame with mixed use of rigid and semi-rigid connections has also been encountered. Efforts have been directed to find the best-suited orientation of mix-mode c~a steel frame in this investigation. A comparison of the results as obtained by the non-linear analysis of frame with those of linear analysis using single stiffness of connection has also been included in this work. Finally, the effect of connection size parameters of semirigid connections on the behavior of frame has also been studied ..