The Dynamics of Shear-Type Frames Equipped with Chain-Based Nonlinear Braces

In recent years a number of bracing devices have been proposed, analyzed, and applied to real cases, since in engineering applications the construction of frames equipped with braces is a widespread practice. In the present contribution, a nonlinear bracing system is introduced and applied to the case of shear-type moment-resistant frames. The frame is considered here as the primary structure and is assumed to have linear elastic behavior and the bracing system is considered as a secondary, additional structure. The bracing system is made of two chains, each of them constructed as the assemblage of two axial elements (springs) undergoing axial force, only. The springs that are assumed to have linear elastic behavior are connected to each other in the chain and to the frame through hinges. The global behavior of the system is nonlinear, since the restoring force of the bracing system is a piecewise-defined function. In order to asses the performance of the whole nonlinear system, its behavior is compared with that of the linear primary structure alone, through a suitable concise descriptor.