Abstract
Walls and frames have different deflection lines and, depending on the seismic mass they support, may often poses different natural periods. In many cases, wall-frame structures present an advantageous behavior. In these structures the walls and the frames are rigidly connected. Nevertheless, if the walls and the frames were not rigidly connected, an opportunity for an efficient passive control strategy would arise: Connecting the two systems by energy dissipation devices (EDDs) to result in wall-EDD-frame systems. This, depending on the parameters of the system, is expected to lead to an efficient energy dissipation mechanism. This paper studies the seismic behavior of wall-EDD-frame systems in the context of retrofitting existing frame structures. The controlling non-dimensional parameters of such systems are first identified. This is followed by a rigorous and extensive parametric study that reveals the pros and cons of the new system versus wall-frame systems. The effect of the controlling parameters on the behavior of the new system are analyzed and discussed. Finally, tools are given for initial design of such retrofitting schemes. These enable both choosing the most appropriate retrofitting alternative and selecting initial values for its parameters.
Highlights
Many of the relatively new buildings located in seismic regions were designed according to stringent seismic codes
When a non-rigid connection is used, the constant velocity graphs will be adopted with Sa(T′) = 1.38 m/s2 that is evaluated at the fundamental period of the bare frame, 1.8 s
If such a drift could be accommodated by the frame, a large decrease could be attained in other responses compared to those of the rigid connection option: the wall over-turning moment is 19% of that of the rigid connection; The frame acceleration is 17% of that of the rigid connection and 70% of that of the bare frame, and; the connection force is 12% of that of the rigid connection. These huge differences are attributed to three factors: a viscous damper as a connection dissipates energy reduces the response; the forces in viscous dampers are out-of-phase with forces due to displacements and with inertia forces, and; the period of the damped system is much longer than that of the rigidly connected system
Summary
Many of the relatively new buildings located in seismic regions were designed according to stringent seismic codes. When a non-rigid connection is used, the constant velocity graphs will be adopted with Sa(T′) = 1.38 m/s2 that is evaluated at the fundamental period of the bare frame, 1.8 s. This is slightly conservative as the third mode has a period smaller Tc. When a rigid connection is used, the constant acceleration graphs will be adopted with Sa(T′) = 6.25 m/s2 that is evaluated at the fundamental period of the rigidly connected system, 0.4 s.
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