Development of semi-active mass damper with impulsive reaction

A new semi-active mass damper, included active joint to control Lock/Unlock between the mass of damper and structure, is proposed to avoid “de-tuning effect” in this study. A ten-floor shear building with Tuned Mass Damper (TMD) and Semi-Active Mass Damper (SAMD) under excitation of 26 earthquake records is simulated by numerical analysis to compare the shock absorption effects. Analysis results show that: (1) Shock absorption of roof displacement and root mean square (RMS) roof displacement is 9.9%, 15.8% and 67.9%, 70.9% for structure with TMD and SAMD under excitation of Kobe 1995 earthquake respectively. Shock absorption of roof displacement and RMS roof displacement 52.7%, 62.1% and 55.7%, 66.3% for structure with TMD and SAMD under excitation of Sumatra 2007 earthquake respectively. (2) Structural response of building with SAMD controlled is very low sensitivity to frequency ratio. SAMD control effect is better than that of TMD on near fault earthquakes and suitable for far-field earthquakes. Otherwise, SAMD is almost without “de-tuning effect”. (3) Shock absorption ratio of the roof displacement responses and RMS displacement responses for structure with SAMD under excitation of far-field earthquake is above 38% and 62%, respectively. The frequency ratio of SAMD controlled should be limited to less than 4.0 to avoid enlarging the maximum acceleration responses. The practicability of this proposed SAMD has been verified by numerical analysis.