Effects of Joint Stiffening on the Dynamic Response of Frames

Abstract

This paper examined the effects of joint stiffening on the dynamic response of frames subjected to lateral loads using the stiffness method. Modified Stiffness coefficients and fixed-end reactions were developed as functions of two parameters α and β representing the ratio of the length of the stiffened portion to that of the flexible portion of the left and right ends of a member respectively. In the absence of joint stiffeners (i.e. α = β  = 0) the obtained modified coefficients revert to conventional expressions. The set of equations governing the motion of the frame with stiffened joints was derived using the lumped-mass procedure. Solution of the system gave the Natural Frequencies, Joint Displacement, Bending Moment, Shear Force, and Axial Force for various values of the parameters α and β ranging from 0.00 to 0.20 respectively. An earlier work showed that stiffening of joints enhances stability. This work established that natural frequency increases with increase in joint stiffening while joint displacement decreases with increase in joint stiffening and that joint stiffening allows substantial reduction in moments which leads to economic design of framed structures.