Simplified method for optimal design of friction damper slip loads by considering near-field and far-field ground motions

A simplified method is proposed for optimum design of friction dampers by considering the characteristics of design earthquakes. Optimum slip loads for 3, 5, 10, 15 and 20-storey RC frames with friction wall-dampers are obtained for a set of 20 near- and far-field earthquakes as well as artificial spectrum-compatible records scaled to different acceleration levels. Optimum solutions are shown to be more sensitive to Peak Ground Velocity (PGV) than Peak Ground Acceleration (PGA), especially for near-field earthquakes with high-velocity pulses. For identical PGA levels, far-field earthquakes on average result in 1.5 times lower optimum slip loads compared to near-field records, while they lead to 118% higher energy dissipation and 24% lower maximum inter-storey drifts. Empirical equations are proposed to predict optimum slip loads (as a function of number of storeys and PGA/PGV of design earthquakes) and their efficiency is demonstrated through selected examples.