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Vibration Analysis and Control New Trends and Developments Part 4

Tham khảo tài liệu 'vibration analysis and control new trends and developments part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Seismic Response Reduction of Eccentric Structures Using Liquid Dampers 65 33 The parameters of this function are 5 r p 0.5 so 0.01 . As mentioned before two TLCDs and one CTLCD are installed at the top of the building. The objective of the study is to design the optimum parameters of these dampers that would maximize the performance function stated earlier. The possible ranges for the design parameters are fixed as follows 1. Mass ratio Ji The mass ratio is defined as the ratio of the damper mass to the total building mass. It is assumed that each damper ratio can vary in the range of 0.1 percent to 1 percent of the building mass. Thus the maximum mass of the damper system consisting of three dampers could be as high as 3 percent of the building mass. 2. Frequency tuning ratio f The frequency ratio for each damper is defined as the ratio its own natural frequency to the fundamental frequency of the building structure. Here it is assumed that this ratio could vary between 0-1.5. 3. Damping ratio d This is a ratio of the damping coefficient to its critical value. It is assumed that this ratio can vary in the range of 0-10 percent. 4. Damper positions from the mass center lx in X axis and ly in y axis It is assumed that lx can vary between -8 and 5 meters and ly can vary between -4 and 3 meters The optimization process starts with a population of these individuals. For the problem at hand 30 individuals were selected to form the population. The probability of crossover and mutation are 0.95 and 0.05 respectively. The process of iteration is determined to be 300 steps. The final optimum parameters for the two optimum design criteria are given in Table 2. Performance Criteria i fl 0.47769 TLCD in X direction TLCD in y direction CTLCD A 0.008519 0.0095655 0.0014362 fr 1.2334 0.96607 1.1137 dr 0.053803 0.061988 0.052886 lx -7.38 0.45567 ly -6.479 -2.2431 Table 2. The optimal parameters of liquid dampers 3.4 Seismic analysis in time domain The parameters of liquid dampers