|M.Sc Student||Abecassis David|
|Subject||Seismic Retrofitting of Frame Structures by Energy|
Dissipation Devices Linked to Shear Walls
|Department||Department of Civil and Environmental Engineering||Supervisor||Professor Oren Lavan|
|Full Thesis text - in Hebrew|
The deflection lines of walls are different than the deflection lines of frames. Thus, wall-frame systems present an efficient seismic resisting system, in particular for tall buildings. Hence, connecting the two systems by energy dissipation devices (EDD) to result in wall-EDD-frame systems is expected to lead to an efficient energy dissipation mechanism.
The research goals are, therefore, to assess, in a rigorous manner, the seismic behavior of wall-EDD-frame structures. Emphasis is given to seismic retrofitting of existing frame structures using this system. The non-dimensional controlling parameters of such systems are first revealed. In turn, an extensive parametric study is carried out so as to lead to important insight on the behavior of such systems. Finally, important tools that can be used by practicing engineers for initial design of such systems are provided.
In the first stage of the research, the equations of motion of the structural system were formulated. As the damping matrix is non-proportional, use is made of modal spectral analysis in the complex numbers domain to assess the structural system responses. In the second stage, in order to identify the controlling parameters and to reduce their number, a dimensional analysis is carried out. In the next stage, in order to assess the effect of the non-dimensional controlling parameters on responses of interest, an extensive parametric study is carried. For that purpose a MATLAB code was developed. Furthermore, various responses of interest are presented as functions of the controlling parameters.
The analysis of the parametric study results revealed that, compared to a rigid connection between the new wall and the existing frame, a connection made by dampers leads to much smaller wall and connection responses. Much smaller frame total accelerations were also observed. On the other hand, the frame responses were somewhat higher. That is, if the reduction of frame responses by connecting with viscous dampers is sufficient, this connection is preferable. Furthermore, it was shown that adding a spring with a relatively low stiffness in parallel to the damper leads to a considerable further reduction in the frame responses while barely increases those of the new wall. The study also revealed that the wall-EDD-frame system is efficient even when the periods of the frame and the wall are similar. This is in contrast to conclusions made by others that are based on research related to coupled systems that have similar deflection lines.