Damping enhancement principle of inerter system

Development of a novel deformation-amplified shape memory alloy-friction damper for mitigating seismic responses of RC frame buildings

Studies on application of scissor-jack braced viscous damper system in wind turbines under seismic and wind loads

Summary

Passive control is a known method for vibrations damping in civil structures. The simplicity and reliability of passive damping devices makes them a worthy candidate in many practical applications. However, despite of its practical simplicity, the optimal design of passive controller is quite a hard computational problem. In this work, an enhanced optimal viscous passive dampers design method is proposed for seismically excited structures. The optimization is carried out with relation to performance index that consists of an H2 norm of the system and a quadratic gains norm. An algorithm is suggested for the look after a candidate optimum. It is based on Newton's optimization method with recently developed effective calculation method for the Hessian matrix. Numerical evaluation of the suggested method demonstrates a very fast convergence rate of the design algorithm and proves a performance effective dampers distribution. Copyright © 2015 John Wiley & Sons, Ltd.

Optimal viscous dampers gains for structures subjected to earthquakes

SUMMARY

In the proposed work, numerical simulations are conducted to investigate scissor-jack dampers for controlling vibrations in a seismically excited flexible truss tower. For the scissor-jack damper, new equations are developed to model the amplification factor that account for large deformations of the damper assembly. The equations are validated using computer-aided design and are used to investigate the influence of vertical deformations on scissor-jack damper amplification. Then, seismic analysis is carried out for scissor-jack dampers installed on a 3D flexible truss tower. To reduce the computational effort, a bi-model method is employed to represent the 3D truss tower as a dynamically equivalent 2D model. To describe the interaction between the structure and scissor-jack dampers, the displacement-dependent amplification factors of the scissor-jack devices and the corresponding damper forces are calculated at each time step. The response of the tower with scissor-jack damper systems is simulated for a range of damping and four major earthquakes and time histories of the displacement and absolute acceleration at each level of the tower are obtained. Results indicate that the system is effective in reducing both the displacement and absolute acceleration response of the tower without exceeding damper stroke capacity in most cases, but that damping level and earthquake intensity are important factors in the consideration of scissor-jack dampers for flexible structures subject to seismic loads. Copyright © 2011 John Wiley & Sons, Ltd.

Dynamic analysis of seismically excited flexible truss tower with scissor‐jack dampers

In the present work, numerical simulations are carried out to investigate a passive amplified structural damping
system, the scissor-jack damper, for controlling vibrations in a seismically-excited truss tower. To reduce computational
effort, a bi-model method is employed to represent the 3D truss tower as a dynamically equivalent 2D lumped-mass
model. For the scissor-jack damper, a new formulation for the amplification factor equation of the device is presented,
and then validated using CAD. The new formulation accounts for the large deformations experienced by the device as a
result of the large displacements present in the flexible tower during seismic loading. In order to capture the interaction
between the structure and control device, the displacement-dependent amplification factors of the scissor-jack devices,
and velocity-dependent forces of the dampers, are calculated at each time step. The resulting amplified damper force is
then applied back to the structure to determine its response at the next time step. The response of the tower with scissor-jack
damper systems is simulated for the El Centro and Northridge earthquakes, and time-histories of the displacement
and absolute acceleration at each level of the tower are obtained. These results indicate that the system is effective in reducing overall response of the tower without exceeding practical limits on the stroke capacity of the scissor-jack dampers.

Kyle J. Cronin

Papers

Dynamic analysis of seismically excited flexible truss tower with scissor‐jack dampers

Modeling and simulation of an amplified structural damping system in a seismically-excited truss tower