Large deflection and hysteric analysis of semi-rigid steel frames under cyclic loads

All connections in practice are semi-rigid in nature. They do not assume a perfectly rigid condition nor a frictionless against moment rotation. Semi-rigid connections play an important role not only in affecting the force and bending moment distribution of a steel frame, but also the damping characteristics of the complete steel structure. The additional flexibility of semi-rigid connections permits a better energy absorption than the rigid joint and at a much lower cost. Thus, it carries a high potential of wide spread use in practice. This paper describes the computational procedure for transient and vibration analysis of semi-rigid steel frames against cyclic loads, allowing for the hysteric characteristics of joints. The effect of large deflection is considered in the updated Lagrangian formulation. A numerical example on cyclic analysis of steel frame is given. It can be seen that this type of refined analysis can be carried out by a low-cost personal computer with acceptable required computer time. Consequently, it can be used in a small design office to date.