Recently, pin supported wall systems have proved to be very useful and effective in seismically retrofitting frame structures. These systems comprise of a wall attached to the existing building and connected by a hinge to the foundation. These systems efficiently prevent soft/weak story mechanisms, while a well controlled deformation pattern can be guaranteed, with initial fundamental period similar to that of the original structure. In order to improve the energy dissipation and the seismic performance of the system, viscous dampers can be integrated in the system, reducing the displacements, forces and the accelerations in the main structure by dissipation a large portion of the input energy.
Albeit the advantages of viscous dampers in general, and the damped pin supported wall system in particular, simple design methodologies for practicing engineers are not available. It is the aim of this paper to present a new simplified methodology (hand calculation method) for the design of such systems. An approach for the estimation of the pushover curve of the existing frame, assuming a straight deformation line, is first presented. Then, an equivalent nonlinear single degree of freedom is formulated. This system is then linearized, and the required added damping is evaluated, so as to obtain a desired target displacement.
The simplified approach was implemented for the retrofitting of a nine story benchmark moment resisting steel frame. The obtained design was then subjected to nonlinear time history analyses. The comparison shows that the peak displacements experienced by the system are very similar to the target.
This simplified approach and methodology, can help structural engineers in the seismic retrofitting of frame structures using the proposed damped pin supported wall system. The approach can be easily used, and requires neither FEM analysis nor nonlinear analysis. It can be easily executed by hand calculation. Thus, with the methodology at hand, a broader use of viscous dampers, and specifically the damped pin supported wall system, is expected. This may improve the sustainability of the existing buildings' inventor.