A smart structure was tested for active vibration control of frame structures in which the bending moment of the columns was controlled by stack-type piezoelectric actuators integrated into the columns. Excitation tests were carried out for a model of a four-storey building 3.7 m in height and 2000 kg in total weight in which thirty-two piezoelectric actuators 25 mm × 25 mm × 36 mm H were used for bending moment control. The actuators were installed in two ways: in one case eight actuators were attached to each column of the first storey, and in the other case four actuators were attached to each column of the first and second storeys. Two control strategies, a model-matching method and the H ∞ control theory, were examined for the smart structure. The tests showed that the smart structure could effectively reduce the responses of the building model, and all combinations of actuator installation method and the control strategy yielded almost the same performance.
In this paper, three case studies intending to apply smart materials to civil structures are presented. The first one is a study of response control using piezoelectric actuators. Actuators are inserted into the bottom of a column to produce a bending moment force. A control algorithm using the model matching method is introduced, and this algorithm is checked in shaking table tests of a four story frame. The second one is damage sensing of a structural member, using electric resistance characteristics of shape memory alloys. The relationship between electrical resistance and strain of shape memory alloy wire is studied and the maximum strain of the specimen which is regarded as a structural member is estimated. The third one is an energy dissipation device using super-elastic characteristics of a shape memory alloy. A basic energy dissipation device model using nitinol wire is proposed. The energy dissipation capacity is investigated by device tests, and an analytical model is constructed based on the test results.
SUMMARYThe application of active mass damper (AMD) systems into buildings has been studied analytically and experimentally during the 1980s. The main purpose of these systems is to reduce the vibrations of buildings during strong winds or small earthquakes in order to improve the comfort of the building occupants. The authors have worked on the study and development of an AMD system using an electroservo-type hydraulic actuator.First, the control technique of AMD with hydraulic actuator is formulated. Hydraulic actuators have an advantage of high durability and high cost performance, however, they also have non-linear dynamics, which makes their control di cult.Second, the applications of this system in the buildings are shown. The authors have applied this AMD system to four buildings in Japan. The outlines of these AMDs and buildings are described individually. To verify the control performance of the AMD in these buildings, free vibration tests were carried out just before their completion. Free vibration test results of each building demonstrated good control performance. After the completion, wind and earthquake observations were conducted. The records have shown a good performance of energy absorption of the vibration during wind excitation and small level earthquakes.
To apply smart structures to buildings, a new vibration control strategy is proposed for flexural-shear type frame structures with smart structures using piezoelectric actuators. Actuators are incorporated in columns, and the response of the entire structure is reduced by control of the bending moment and axial force of the columns. Combined application of these two controls is performed by arrangement of actuators. Two control strategies were tested: one involves the use of a model matching method and the other is based on H ∞ control theory. Excitation tests were conducted with a four-storey frame structure with a total weight of 2000 kg and a height of 3.7 m, having H-section steel beams incorporating actuators as columns. The effectiveness of combined use of bending moment control and axial force control of columns with smart structures was confirmed.
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