Abstract
Abstract This paper presents the fundamentals for prediction of a more realistic behavior of planar steel frames with semi-rigid connections under dynamic loading. The majority of the research in this area concentrates on the nonlinear static analysis of frames with semi-rigid connections. Indeed, few studies have contributed to the nonlinear dynamic and vibration analyses of frames. Therefore, this article first describes the frames’ semi-rigid connection behavior under monotonic and cyclic loads, and presents the independent hardening technique adopted to simulate the joint behavior under cyclic excitation. In a finite element context, this paper presents an efficient numerical methodology that is proposed in algorithmic form to obtain the nonlinear transient response of the structural system. The paper also presents, in algorithmic form, a complete description of the adopted connection hysteretic model. Satisfying the equilibrium and compatibility conditions, and assuming only the connection’s rotational deformation due to bending as variable, this work obtains the tangent stiffness and mass matrices of the beam-column element with semi-rigid connections at the ends. The study concludes by verifying and validating the proposed numerical approach using four structural steel systems: a L-frame, a two-story frame, a six-story frame, and a four-bay five-story frame. The analyses show that the hysteresis of the semi-rigid connection has a strong effect on the frames’ responses and is an important source of damping during the structural vibration.
Highlights
In the structural design and construction of reticulated steel structures involving one or more floors, the beam‐column and column‐base connections play a significant role in their structural response
The current paper evaluates, using the CS‐ASA Program Computational System for Advanced Structural Analysis; Silva, 2009, the nonlinear dynamic response of planar steel frame, considering geometric nonlinear effects and the semi‐rigid characteristics of the connections between the structural elements
This paper brings the numerical results obtained from an alterated CS‐ASA version, which allow repre‐ sent the semi‐rigid connection hysteretic behavior, in order to allow a better modeling of the nonlinear transient response of planar steel frames with flexible joints
Summary
In the structural design and construction of reticulated steel structures involving one or more floors, the beam‐column and column‐base connections play a significant role in their structural response. This paper brings the numerical results obtained from an alterated CS‐ASA version, which allow repre‐ sent the semi‐rigid connection hysteretic behavior, in order to allow a better modeling of the nonlinear transient response of planar steel frames with flexible joints This is an extension of the CS‐ASA initial module that contemplated the static nonlinear analysis and some cases for dynamic nonlinear analysis and vibration Galvão et al, 2010; Silva, 2009. If the connection is being unloaded from A to B and the loading pro‐ cess begins before the unloading has been completed, say at F, the moment‐rotation behavior of this element will follow the FA trajectory until it reaches the last reverse moment encountered At this point, the loading process follows the original moment‐rotation curve obtained, considering the last permanent rotation fp. The inter‐ vals between the two successive time instants should be small so that these variables can be defined with ade‐ quate precision
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