Unified analysis of static and dynamic behavior of steel frames with semi-rigid connections considering geometric nonlinearity

Abstract

Semi-rigid beam–column connections play a crucial role in governing the overall behavior of steel frames, especially in geometric and dynamic nonlinear problems, where the structural stiffness is no longer constant but depends closely on the working state of the connections. This paper proposes a unified analysis approach for steel frames with semi-rigid connections, in which static and dynamic behavior are considered within a single computational framework, accounting for both connection nonlinearity and geometric nonlinearity. Based on the connection model and a state-updating strategy, the study clarifies the relationship between the effective stiffness of the frame and the nonlinear development of the connections. The results indicate that assuming constant stiffness and natural frequency may lead to significant errors in predicting the dynamic response and fail to capture the nature of resonance shift in the nonlinear domain. The study also confirms the necessity of a unified analysis approach for evaluating resonance and controlling vibrations of steel frames under realistic working conditions.