Shinta Yoshitomi

Non-monotonic optimal damper placement via steepest direction search

An efficient and systematic procedure is proposed for finding the optimal damper positioning to minimize the dynamic compliance of a 3-D shear building model. The dynamic compliance is expressed in terms of the transfer function amplitudes of the local interstorey drifts evaluated at the undamped fundamental natural frequency. The dynamic compliance is minimized subject to a constraint on the sum of the damping coefficients of added dampers. Optimality criteria are derived and the optimal damper positioning is determined via an original steepest direction search algorithm. This algorithm enables one to find an optimal damper positioning sequentially for gradually increasing damper capacity levels. A non-monotonic design path with respect to the total damper capacity level often appears in the application of this algorithm. A new augmented algorithm via parameter switching is devised to find this non-monotonic design path. Copyright

Effects of support stiffnesses on optimal damper placement for a planar building frame

An efficient and systematic procedure is proposed for finding the optimal damper positioning to minimize the dynamic compliance of a planar building frame. The dynamic compliance is expressed in terms of the transfer function amplitudes of the interstory drifts evaluated at the undamped fundamental natural frequency. The dynamic compliance is minimized subject to a constraint on the sum of the damping coefficients of added dampers. Optimality criteria are derived and the optimal damper positioning is determined via an original steepest direction search algorithm. This algorithm enables one to find an optimal damper positioning sequentially for gradually increasing damper levels. The influences of support-member stiffnesses on the response suppression level and on the optimal damper positioning are also disclosed numerically. Copyright

Post-Tensioning High-Hardness Rubber Damper System for Vibration Control of Residential Houses and Building Structures

A new vibration control system including viscoelastic or viscoplastic rubber dampers is proposed for residential houses. This system consists of braces and a damper unit including a high-hardness rubber damper or a linear rubber damper. The high-hardness rubber damper possesses many unprecedented properties such as large stiffness, small temperature and frequency dependencies compared to most of usual viscoelastic dampers. Post tensioning forces are introduced into the braces to reduce small gap in joint parts and this system has high damping performance for micro-vibration. The control system can absorb sufficient energy through the high-rubber damper and post tensioning braces. A concept is introduced called an effective deformation ratio, i.e. the ratio of the actual damper deformation to the interstory drift of the frame, as a criterion to measure the damping performance and effectiveness of this system. To find out principal parameters that affect greatly the effective deformation ratio of the proposed new vibration control system, an incremental analysis method taking into account the geometrical and material nonlinearities is developed to simulate the main characteristics of this vibration control system. The accuracy of the analysis method is investigated through the comparison with the results by two simple analysis methods. The comparison with the experimental result is also conducted for further investigation.