Analysis plane steel frame with semi-rigid connections and rigid-zones with consideration of the second order effect

Abstract

This chapter presents a practical and accurate method for analysis of plane steel frames with semirigid connections considering the second order effects. To incorporate the connection rigidity into the member stiffness, it is a common practice to model the semirigid connection as massless and zero length rotational spring. Although semirigid connections exhibit nonlinear response characteristics throughout their whole loading history, it is generally accepted that under service loading conditions the semirigid connections can be assumed to behave linearly. The first and second-order stiffness matrices of beam column of double symmetrical cross section with semirigid connections rigid zones are derived in classical manner. The derived matrices can be used in the stability, first and second-order elastic analysis of steel frames with semi-rigid connections and rigid zones. Connection flexibility and geometric nonlinearity influence the distribution of forces in the structure. Both effects contribute to a significant increase in the drift of the frame. The semirigid connections cause a shift in moments from the beam ends to the span, and as a result, the overall maximum moments decrease in beams. The connections may be used to balance positive and negative moments in beams to effect economic designs.