SUMMARYA real-time hybrid experimental method, in which output from an actuator-excited vibration experiment and response calculation are combined on-line and conducted simultaneously in real time, is being developed as a new seismic experimental method for structural systems. In real-time hybrid experiments, however, there is an inevitable actuator-response delay, which has an e!ect equivalent to negative damping. To solve this problem, a real-time hybrid experimental system (including an actuator-delay compensation method) was developed. And seismic experiments were conducted in order to demonstrate the advantages of this system. Experimental results obtained using the developed hybrid experimental system were compared with exact results obtained using shaking-table experiments, and it was found that the two experimental methods gave almost identical results. It can therefore be concluded that the structural response can be obtained precisely by using the developed hybrid experimental system. Comparison of these experiments showed the advantages of the hybrid experiments; that is, they are simple and economical. This is because the hybrid experiment requires only a small structure as the excitation model, while a shaking-table experiment must consider the whole structural system.

We developed an on-line experimental system for conducting hybrid experiments in real time. It combines a computer, which conducts vibration simulation and generates a control signal, and a hydraulic actuator, which conducts a vibration experiment driven by the control signal. This system compensates for actuator delay and thus enables experiments to be carried out in real time. We evaluated the stability of the experiments with respect to the mass of the structure under excitation, and we developed a new method for compensating actuator delay in order to increase the stability condition. In this method, the compensated control signal is generated from the simulation results by using not only displacement but also velocity and acceleration. This method provides a stability criterion (allowable ratio of mass of the structure under excitation to that of a numerical model) about three times larger than that from the current method.

Hyogo 660-0891 JapanFor the construction of ultra super critical (USC) power plant, 9Cr-3W base ferritic heat-resistant steels with relatively high B and no N have been investigated. Authors have been revealed in the previous report that the addition of i39ppm B significantly improves creep strength of the steels, whereas most of added B forms unidentified borides, which are deemed almost ineffective to creep strength. The effect of improved heat treatment on creep strength and distribution of B in precipitates is investigated to effectively utilize and decrease added B As a result of the analysis of the extracted residue and characterization of precipitates using field emission Auger eleotron spectroscopy (FE-AES), most of added B still forms borides in the 92ppm B added steel. These composites are almost dissolved and the B content in M23Ce carbides is significantly increased by normalizing at 142SK. It is also found by FE-AES analysis that B content in M23CG oarbides near prior-austenite grain boundaries is relatively higher than that inside grains. Creep strength at 923K for the 92ppm B added steel normalized at 1423K is not improved ~lt short times, but it is remarkably improved to almost the same level as the 139ppm B added steel at long times. This ex~Ilent creep strength is achieved resulting in improving microstructural stability through the effective utilization of added B by high-temperature normalizing.KEY WORDS: ferritic heat-resistant steel; creep; boron; FE-AES M23C6 oarblde mlcrostructure USC power plant.

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