Design Of Moment Resisting Frame And Its Connections

Abstract

Conventional analysis and design of steel frames are usually carried out under the assumption that the beams to column connections are either fully rigid or ideally pinned. Although the adoption of such idealized joint behavior greatly simpli es the analysis and design processes, the predicted response of the idealized structure may be quite unrealistic compared to the response of the actual structure. Any structural connections deform to some extent and will resist a certain amount of bending mo- ment. The relationship between beam end moment, M, and the relative change in angle, r, can be described by means of a typical moment-rotation diagram. Moment-resisting steel frames are used frequently in low-rise and mid-rise buildings located in high seismic areas due to their high ductility and economic solutions. In these type of structures, strong column weak-beam design requirements result in larger column sections and over design in low-rise long-span buildings. To mitigate this problem, moment-resisting steel frames with energy-dissipative semi-rigid/partial strength connections can be used as an alternative to perimeter frames. By using energy-dissipative semi-rigid connections, the strong-column weak-beam requirement is eliminated and more economical column sections are used. In this study, a three- span three-bay frame with 5m ,7m and 9m span lengths is designed with Eight types of semi-rigid connections. Load combinations are taken as per the IS 800 -2007. The design with reduced connection capacity resulted in an increase in the beam weights, a decrease in the column weights and an overall decrease in the structural weight. Analysis of the frames is carried out in staad pro software ,Moment rotation curve is found out using Frye and Morris model and sti ness of the connections is found then these connections are modelled as as rotational spring element. The overdesign problem in low-rise long span-buildings is eliminated to some extent without using the perimeter frame approach. Furthermore, the top displacements in semi-rigid frames becomes lower than those of their rigid counterparts