Contribution to transient analysis of inelastic steel frames with semi-rigid connections

Dynamic behavior of multistory flexibly connected steel frames under earthquake excitations is studied in this paper. The numerical model that simultaneously includes nonlinear connection behavior, member yielding and geometrical nonlinearity of the structure is developed. Flexibility of connection is idealized by nonlinear rotational spring and dashpot in parallel. The refined-plastic hinge method is adopted to simulate member plasticity, for which it is assumed to be lumped at the ends of beam elements and base end of columns. A plastic hinge is idealized by nonlinear rotational spring, which is then combined with connection spring to form a resultant spring (spring-in-series). Transient response of the ductile seven-story steel frame under different intensities of the earthquake excitation is investigated. Characteristic results are presented and discussed.