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Velocity Response (velocity + response)
Selected AbstractsThree-dimensional vibration control of high-tech facilities against earthquakes and microvibration using hybrid platformEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2010Xiao-Jian Hong Abstract High-tech equipments engaged in the production of ultra-precision products have very stringent vibration criteria for their functionality in normal operation conditions and their safety during an earthquake. Most previous investigations were based on simplified planar models of building structures, despite the fact that real ground motions and structures are always three-dimensional. This paper hence presents a three-dimensional analytical study of a hybrid platform on which high-tech equipments are mounted for their vibration mitigation. The design methodology of the hybrid platform proposed in this study is based on dual-level performance objectives for high-tech equipments: safety against seismic hazard and functionality against traffic-induced microvibration. The passive devices (represented by springs and viscous dampers) and the active actuators are designed, respectively, to meet vibration criteria corresponding to safety level and functionality level. A prototype three-story building with high-tech equipments installed on the second floor is selected in the case study to evaluate the effectiveness of the hybrid platform. The optimal location of the platform on the second building floor is determined during the design procedure in terms of the minimal H2 cost function of absolute velocity response. The simulation of the coupled actuator-platform-building system subjected to three-dimensional ground motions indicates that the optimally designed hybrid platform can well achieve the dual target performance and effectively mitigate vibration at both ground motion levels. Copyright © 2009 John Wiley & Sons, Ltd. [source] Hybrid platform for high-tech equipment protection against earthquake and microvibrationEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2006Y. L. Xu Abstract To ensure the high quality of ultra-precision products such as semiconductors and optical microscopes, high-tech equipment used to make these products requires a normal working environment with extremely limited vibration. Some of high-tech industry centres are also located in seismic zones: the safety of high-tech equipment during an earthquake event becomes a critical issue. It is thus imperative to find an effective way to ensure the functionality of high-tech equipment against microvibration and to protect high-tech equipment from damage when earthquake events occur. This paper explores the possibility of using a hybrid platform to mitigate two types of vibration. The hybrid platform, on which high-tech equipment is installed, is designed to work as a passive isolation platform to abate mainly acceleration response of high-tech equipment during an earthquake and to function as an actively controlled platform to reduce mainly velocity response of high-tech equipment under normal working condition. To examine the performance of the hybrid platform, the analytical model of a coupled hybrid platform and building system incorporating with magnetostrictive actuators is established. The simulation results obtained by applying the analytical model to a high-tech facility indicate that the proposed hybrid platform is feasible and effective. Copyright © 2006 John Wiley & Sons, Ltd. [source] Hybrid platform for vibration control of high-tech equipment in buildings subject to ground motion.EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2003Part 1: experiment Abstract This paper presents an experimental study, while a companion paper addresses an analytical study, to explore the possibility of using a hybrid platform to mitigate vibration of a batch of high-tech equipment installed in a building subject to nearby traffic-induced ground motion. A three-storey building model and a hybrid platform model are designed and manufactured. The hybrid platform is mounted on the building floor through passive mounts composed of leaf springs and oil dampers and controlled actively by an electromagnetic actuator with velocity feedback control strategy. The passive mounts are designed in such a way that the stiffness and damping ratio of the platform can be changed. A series of shaking table tests are then performed on the building model without the platform, with the passive platform of different parameters, and with the hybrid platform. The experimental results demonstrate that the hybrid platform is very effective in reducing the velocity response of a batch of high-tech equipment in the building subject to nearby traffic-induced ground motion if dynamic properties of the platform and control feedback gain are selected appropriately. Copyright © 2003 John Wiley & Sons, Ltd. [source] Hybrid platform for vibration control of high-tech equipment in buildings subject to ground motion.EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2003Part 2: analysis Abstract The experimental results of using a hybrid platform to mitigate vibration of a batch of high-tech equipment installed in a building subject to nearby traffic-induced ground motion have been presented and discussed in the companion paper. Based on the identified dynamic properties of both the building and the platform, this paper first establishes an analytical model for hybrid control of the building-platform system subject to ground motion in terms of the absolute co-ordinate to facilitate the absolute velocity feedback control strategy used in the experiment. The traffic-induced ground motion used in the experiment is then employed as input to the analytical model to compute the dynamic response of the building-platform system. The computed results are compared with the measured results, and the comparison is found to be satisfactory. Based on the verified analytical model, coupling effects between the building and platform are then investigated. A parametric study is finally conducted to further assess the performance of both passive and hybrid platforms at microvibration level. The analytical study shows that the dynamic interaction between the building and platform should be taken into consideration. The hybrid control is effective in reducing both velocity response and drift of the platform/high-tech equipment at microvibration level with reasonable control force. Copyright © 2003 John Wiley & Sons, Ltd. [source] An adaptive spacetime discontinuous Galerkin method for cohesive models of elastodynamic fractureINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2010Reza Abedi Abstract This paper describes an adaptive numerical framework for cohesive fracture models based on a spacetime discontinuous Galerkin (SDG) method for elastodynamics with elementwise momentum balance. Discontinuous basis functions and jump conditions written with respect to target traction values simplify the implementation of cohesive traction,separation laws in the SDG framework; no special cohesive elements or other algorithmic devices are required. We use unstructured spacetime grids in a h -adaptive implementation to adjust simultaneously the spatial and temporal resolutions. Two independent error indicators drive the adaptive refinement. One is a dissipation-based indicator that controls the accuracy of the solution in the bulk material; the second ensures the accuracy of the discrete rendering of the cohesive law. Applications of the SDG cohesive model to elastodynamic fracture demonstrate the effectiveness of the proposed method and reveal a new solution feature: an unexpected quasi-singular structure in the velocity response. Numerical examples demonstrate the use of adaptive analysis methods in resolving this structure, as well as its importance in reliable predictions of fracture kinetics. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||