Although the behavior of friction sliding bearings is well understood, the failure behavior has not been thoroughly investigated. However, predicting and understanding the failure of bearings is an important key in designing isolated structures to minimize their collapse in extreme events, and thus, this study is critical. Because of its relative simplicity and particular availability in certain markets, the failure of the double friction pendulum (DFP) bearing at its physical displacement limit is investigated. The bearing is modeled with a rigid body model including inertia for each of the bearing components. A nonlinear viscoelastic impact model is included to simulate the impact between bearing components. As isolation systems are particularly vulnerable to long-period excitations, analytical pulses are used as input excitations to investigate the influences of pulse parameters on the failure of DFP. The influences of DFP design parameters are investigated as well. To confirm that the response to the analytical pulses correctly represents the behavior under long-period ground motions, wavelet analysis to is performed on 14 pairs of pulse-type ground motion records to extract their pulses, and the failure prediction made from the extracted analytical pulse is compared with the failure from the real ground motions. It is found that using the extracted pulses provides a good estimation for the failure prediction of the ground motions.

Seismically isolated (SI) buildings are thought to be fragile when subjected to excessive input ground motions beyond design level.The authors have been proposing a new isolation bearing which has much higher seismic safety than conventional bearings.Supporting a superstructure only by the proposed bearings will enable the whole SI building to protect from any structural damage.In this paper, the development process of the proposed bearing, including the selection of the most suitable slider material, dynamic loading test of a scaled bearing, and quasi-static loading test of a full-scale bearing, is mentioned. Preliminary and detailed time history analyses of SI building models are also shown. The research results lead to the conclusion that a system applying the proposed bearings realizes an SI building with higher seismic safety than ever, if only provided a large enough isolation gap.

Base isolation of high-rise buildings has been growing in popularity in Japan, yet it is uncommon in most of the world. While tall buildings already have long periods and thus lower input accelerations, the addition of isolation can decrease inter-story drifts and greatly decrease floor acceleration, protecting building content. By protecting building content, high-rises can be kept fully operational and occupiable after earthquakes. The Japanese design code has clearly outlined procedures for designing isolated high-rises, facilitating the implementation of isolation; however, other design codes—and specifically the U.S. code—make the adoption of isolation difficult for these buildings. Using a design representative of typical isolated high-rises in Japan, it is shown that while isolation is feasible under U.S. design levels, requirements are much more stringent, and some changes from the Japanese design would be required to make the design acceptable under the U.S. code.

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In order to achieve more perfect vibration-free environment in precision manufacturing facilities such as semiconductor manufacturing factories, and apply steel frame structures to semiconductor manufacturing factories of the next generation, a smart structure was tested for active microvibration control of a 2-story steel frame building model of a 5X 3 X 4H outer size and a 2,500 kg total weight which was excited by ambient ground vibration. In the structure, piezoelectric actuators attached to the columns and the beams were used for the microvibration control by bending moment control of them. The controller was designed using the H-infinity control theory. The tests showed that the smart structure could effectively reduce the three-dimensional microvibration of the building model, and its applicability to floors and even entire buildings of semiconductor manufacturing factories having steel frame structures.

Dynamic and quasi-static loading tests for scaled and full-scale FSLRB, a new isolation bearing which consists of a conventional lead rubber bearing (LRB) and a slider bearing in series, are mentioned. The test results show that torsional behavior of LRB part in bi-directional excitation does not affect the limit state of the bearing, and both dynamic and static friction coefficients are accurately estimated by newly proposed equations utilizing effective surface pressure instead of mean surface pressure. As a conclusion, the authors think that the bearing is ready for the practical use in an isolation system with even higher seismic safety.

Summary While the performance of sliding isolators has been extensively validated under typical levels of ground motion, there have been very few experimental studies on the extreme behavior of sliding isolation bearings when the displacement limit is reached. However, to appropriately design isolated systems, from selecting the displacement capacity of the bearing to sizing the superstructure members, the behavior of the bearing as it reaches, and in some cases exceeds, the displacement limit should be well understood. A series of shake table tests to investigate the extreme behavior of double pendulum sliding bearings under strong ground motions were conducted at McMaster University. One major difference in sliding bearings around the world is how the motion of the bearing is restrained at the bearing's displacement capacity. Scaled bearings with four different types of restraining rim designs were included, representing typical sliding restraining rims found in Europe, Japan, and the United States. Experimental observation shows that the restraining rim has a significant influence on the extreme behavior of sliding isolation bearing. Key response parameters such as impact force and uplift are evaluated and compared between the different sliding bearing designs. While the bearing with no rim bearing imparts the lowest forces to the superstructure, it loses its functionality at a lower amplitude input than all the other rim types. For the other rim designs, the impact forces are significantly higher but they remained operational although damaged.