Articles written in Sadhana
Volume 34 Issue 3 June 2009 pp 421-437
The theory for structural control has been well developed and applied to perform excellent energy dissipation using dampers. Both active and semi-active control systems may be used to decide on the optimal switch point of the damper based on the current and past structural responses to the excitation of external forces. However, numerous noises may occur when the control signals are accessed and transported thus causing a delay of the damper. Therefore, a predictive control technique that integrates an improved method of detecting the control signal based on the direction of the structural motion, and a calculator for detecting the velocity using the least-square polynomial regression is proposed in this research. Comparisons of the analytical data and experimental results show that this predictor is effective in switching the moving direction of the semi-active damper. This conclusion is further veriﬁed using the component and shaking table test with constant amplitude but various frequencies, and the El Centro earthquake test. All tests conﬁrm that this predictive control technique is effective to alleviate the time delay problem of semi-active dampers. This predictive control technique promotes about 30% to 40% reduction of the structural displacement response and about 35% to 45% reduction of the structural acceleration response.
Volume 35 Issue 5 October 2010 pp 631-647
A relief valve parallel to the throttle valve is added to a Velocity dependent hydraulic damper (VDHD) so that the oriﬁce size that regulates the oil ﬂow can be adjusted. This device adjustment will allow the damper to have an adaptive control of damping by changing its damping coefﬁcient. A mathematical model including a serial friction model and a small damper that is parallel to the friction model added to the Maxwell model for simulating the actual energy-dissipating behaviour of the VDHD was proposed in this research. To extend the useful value of VDHD, a numerical analysis model based on the SAP2000 nonlinear analysis program was applied to simulate the energy-dissipating characteristics of VDHD in this study. The analysis results obtained by using the mathematical model and the proposed SAP2000 numerical model conform to the seismic resistant test results, and conﬁrm that the SAP2000 nonlinear analysis program can accurately describe the actual energy-dissipating behaviour of the VDHD installed on structures under various energy-dissipating situations.