Base isolation technology has been widely theoretically and experimentally investigated, and it has also been verified through many severe earthquakes. Three dimensional (3-D) isolation technology was proposed several years ago, and the 3-D isolation theory has well developed till now. However, the development of 3-D isolation technology was deeply affected by the 3-D isolator devices. Many presented 3-D isolators are generally made up of complicated components, such as rubber, springs, dampers or theirs combinations. These isolators have some problem in certain extent, such as difficult fabrication process or little energy dissipation ability along the vertical direction. This paper presents a novel 3- D isolator which is made up of martensitic shape memory alloy wires through weaving, rolling, and punching. Mechanical properties of 3-D shape memory alloy pseudo-rubber isolator (SMAPRI) are investigated including compression, shear, and compression-shear loading with different frequencies and amplitudes. The mechanical behavior of isolators with different parameters is also compared. Accordingly, the mechanism resulting in the above differences is also analyzed. Experimental results indicated that 3-D SMAPRI has good mechanical properties and energy dissipation ability along both of horizontal and vertical direction. The fabrication process of the proposed 3-D isolator is relatively easy and the mechanism of isolation is clearer than the traditional 3-D isolators. Therefore, this new kind of 3-D isolator has good potentiality in both of seismic isolation for civil infrastructures and industrial isolation for important or precision equipment.
During the past several strong earthquakes, most of the highway bridge suffered from unseating and pounding damage
due to large displacement between the adjacent frames. One traditional approach for mitigating the unseating of the
highway bridge is to use restrainers made of steel cables and rods. However, the elastic design demands of the restrainers
will induce large additional forces on the structural components of the bridges. The aim of the study is to investigate the
effects of the strong ground motions on the unseating and pounding damages of the base-isolated highway bridges, and
the performance of the shape memory alloy (SMA) restrainers for the unseating reduction of the highway bridge. An
analytical model of the highway bridge with SMA restrainers and pounding effects is established, and the performance of
the SMA restrainer for eliminating the bridge unseating and pounding of the highway bridge is also analyzed. Numerical
simulation results indicate that the pounding strongly increase the structural responses and the SMA restrainer can be
effectively used to mitigate the bridge unseating and pounding damage when subjected to the strong ground motions.
KEYWORDS: Bridges, Control systems, Earthquakes, Control systems design, Motion models, Structural engineering, Systems modeling, Electroluminescence, Motion analysis, Wave propagation
Seismic pounding between the adjacent segments of the multi-span concrete highway bridges can result significant structural damage. The aim of this paper is to explore the possibility of implementing the semi-active control technology to mitigate the pounding of the highway bridges under severe earthquake excitations. The analysis of this study is focused on the highway bridges with base isolation systems. Mechanical model of the collision between the adjacent superstructure segments and the governing equation of motion of the highway bridges with pounding effect are firstly introduced, and the analytical model of highway bridges with a semi-active control system is presented by using the instantaneous optimal control algorithm for lighting the pounding of the structures. The results show that the semi-active control system can effectively reduce the structural pounding of the highway bridges under earthquake excitations if the semi-active control system was appropriately designed.
Hybrid control platform is investigated in this paper for mitigating microvibration of a batch of high tech equipment installed in a high tech facility (building) subject to nearby road vehicle-induced horizontal and vertical ground motions. Hybrid control platform, on which high tech equipment is installed, is mounted on the building floor through a series of passive mounts and controlled by hydraulic actuators in both horizontal and vertical directions. The hybrid control platform is taken as an elastic body with significant bending modes of vibration, and a sub-optimal control algorithm is used to manipulate the hydraulic actuators with the actuator dynamics included. The governing equations of motion of the coupled platform-building system are established in the absolute coordinate to facilitate the feedback control and performance evaluation of the platform. The horizontal and vertical ground motions at the base of the building induced by nearby moving road vehicles are assumed to be random and statistically stationary processes. A typical three-story high tech building is selected as a case study. The case study shows that the ground motion and vibration of the high tech building are higher in the vertical direction than in the horizontal direction. The use of hybrid control platform can effectively reduce both horizontal and vertical microvibrations of a vast quantity of high tech equipment to the level satisfying the most stringent microscale velocity requirement specified in the BBN criteria.
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