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Performance Evaluation of Viscoelastic and Friction Passive Damping System in Steel Structures Mohammad Taghi Kazemia; Hosein Hoseini Additional dampers are employed in order to decrease the dynamic response of structure against the earthquake and wind loading recently. In this study, two types of systems related to waste of inactive energy, i.e. frictional damper which is categorized in dampers dependent on movement and viscoelastic damper which is categorized in dampers dependent on velocity, in making steel structures resistant are investigated and evaluated. Results of structures with dampers (viscoelastic damper, friction damper and combination of both dampers) were compared with the results of structures without damper. Increasing trend in dissipating energy was observed. Then, the behavior of these dampers in frames of 4, 8 and 12 stories was studied by modeling the damper directly. The analyses were conducted via nonlinear time history technique and by using earthquake records (near fault and far fault) scaled with peak acceleration and SAP 2000 14.2.2 software. The results indicate the appropriate function of the selected dampers in controlling and decreasing the seismic responses of the structure. Given that in frictional dampers the maximum force created in the damper is specified, the use of this damper in resistance building of structures is very effective especially by considering the limitation of structure capacity. منبع دانلود JSEG391435606200.pdf

Optimum parameters of tuned liquid column–gas damper for mitigation of seismic-induced vibrations of offshore jacket platforms Seyed Amin Mousavi*,†, Khosrow Bargi and Seyed Mehdi Zahrai University of Tehran, School of Civil Engineering, Tehran, Iran, Islamic Republic of Iran SUMMARY The effectiveness of tuned liquid column–gas damper, TLCGD, on the suppression of seismic-induced vibrations of steel jacket platforms is evaluated in this study. TLCGD is an interesting choice in the case of jacket platforms because it is possible to use the structural elements as the horizontal column of the TLCGD. In this study, optimum parameters of the TLCGD are obtained, considering nonlinear damping of the TLCGD and water–structure interaction between jacket platform and sea water. Equation of motions and other related formulas are derived, and using a SIMULINK model, the frequency and the head loss coefficient of the TLCGD are optimized. Results are in general agreement with those obtained in earlier studies for typical building structures. However, effects of period of the structure and ground motion characteristics on the optimum parameters are also evaluated in this study. Results show that until a particular threshold for the mass ratio, the higher the mass ratio, the higher the efficiency of the damper. After that, by increasing the mass ratio, there is no improvement on the damper efficiency. It is also found that PGA and frequency content of a ground motion have no important effect on the optimum frequency ratio, but they have a noticeable effect on the optimum head loss coefficient. Besides, frequency content has some effect on the TLCGD efficiency. It is shown that the optimum frequency of a TLCGD is uncoupled with the area ratio and the head loss coefficient, and they have no effect on the optimum frequency ratio. Copyright © 2011 John Wiley & Sons, Ltd. Received 23 November 2010; Revised 6 July 2011; Accepted 14 October 2011 KEY WORDS: passive control; tuned liquid column–gas damper; TLCD; offshore platform; seismic excitation; optimization STRUCTURAL CONTROL AND HEALTH MONITORING Struct. Control Health Monit. 2013; 20:422–444 Published online 19 December 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/stc.505 منبع: [Hidden Content] دانلود: [Hidden Content] iQ5EJ2eG.pdf