Impact of Near-Fault Ground Motions on the Responses of Building Equipped with Viscous Damping Systems

Passive control systems have been widely used to minimize responses of structures subjected to ground shaking. Among others, fluid viscous dampers (FVDs), including linear and nonlinear types, are one of the most popular passive control systems. The design of FVD system for structures often involves damping reduction factor (a.k.a. B factor), which is the ratio of structural response (acceleration, velocity, or displacement) for a damping ratio of 5% to that of a damping ratio other than 5%. The B factors provided in current building codes were developed based on results of research using far-fault ground motions. The applicability of those factors for near-fault ground motions requires more research. The research presented in this thesis includes two parts. In the first part, a series of response-history analysis were conducted using single degree of freedom (SDOF) systems and 200+ pulse-like near-fault ground-motion records identified from NGA-West 2 strong-motion database. The B factors appropriate for the design of FVD systems subjected to near-fault ground motions are proposed. In the second part, the application of the proposed B factors on multiple degree of freedom (MDOF) systems was evaluated using 3-, 9-, and 20-story buildings. The results show that the ratio of pulse period of near-fault ground motion to the natural period of a structure is an important parameter for the B values. When the ratio is close to 1, FVD system is more effective in reducing displacement and acceleration responses. The peak responses of MDOF systems equipped with linear FVD system can be well-predicted using typical response spectrum analysis and the B values proposed in the first part of this thesis. However, the procedures (i.e., response spectrum analysis together with the proposed B values) need to be modified to predict the peak responses of structures equipped with nonlinear FVD systems.