ABSTRACT
Practically speaking, most structures should be modeled as multi-degree-of-freedom (MDOF) systems. The basic idea to deal with an MDOF system is to decouple it into several SDOF systems. When the response is linear and the damping is either absent or proportional, which roughly means that the distribution of damping forces coincides with the restoring forces, the decoupling can be conducted in an n-dimensional modal space. Although such a treatment is not always practical, the study of proportionally damped systems can provide insight on how to handle general MDOF systems. In addition, most codes use this approach for aseismic designs. Furthermore, this chapter also offers important background information for the design of damped MDOF systems.
