Seismic Behavior and Design of Wall–EDD–Frame Systems

Abstract

Walls and frames have different deflection lines and, depending on the seismic mass they support, may often possess 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 effects 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.

Modal properties and seismic behaviour of buildings equipped with external dissipative pinned rocking braced frames

“…Eqn. ( 17 ) and ( 18 ) provide closed-form estimates of the changes of the dynamic properties of the system due to the dissipative towers and can be quite useful as very often the external towers are quite rigid. In the next section, the approximation of rigid tower behaviour is evaluated by considering different retrofit configurations.…”

Dissipative steel exoskeletons for the seismic control of reinforced concrete framed buildings

“…The use of a dissipative endoskeleton (DEN), constituted of steel supporting braces connecting adjacent storeys and equipped with devices dissipating energy by means of different mechanisms (e.g., metallic yielding, friction sliding, fluid orificing, viscoelastic deformation, and phase transformation of metals), is an effective and widely used technology for the retrofitting of buildings as it offers certain advantages (e.g., ease of inspection and replacement and low maintenance costs) in comparison to traditional solutions 1–7 . However, the insertion of dissipative braces in structures built in line with former seismic codes can induce significant changes in their collapse mechanism with a notable increase in the axial load transmitted to columns and foundations, 8 requiring local strengthening and great care and attention when connecting joints to the original frame 9 . A number of other potential downsides are worth mentioning.…”

“…One option exploits the horizontal displacement between the existing structure and external reaction structures (e.g., fixed r.c. walls and steel towers), which are connected by dissipative links at the floor levels 9–11 . The advantage of retrofitting from outside the structure is that interference with structural and nonstructural components inside the building can be avoided.…”

Seismic performance of buildings retrofitted with nonlinear viscous dampers and adjacent reaction towers

“…Lavan has used an analytical formulation with non‐dimensional quantities to assess the efficiency of linear viscus dampers in wall‐EDD‐wall systems, showing that the main effect of the additional damping is to reduce the pseudo‐accelerations in the structure. Lavan and Abecassis have studied wall‐EDD‐frame systems, showing with an extensive parametric analysis that the seismic response of an existing frame can be efficiently reduced by connecting it to new walls with linear viscous dampers.…”