Due to their large displacement capability and stable energy dissipation associated with a compact shape and new highly performing materials, the use of concave sliding isolators have been continuously increasing for application in buildings and bridges. In this paper the results of dynamic tests on full scale devices are presented. Their response was studied in a wide velocity range, for bi-directional patterns under different compressive loads. In this range of loading characteristics, which is typical of design for earthquake excitation, the behavior of these isolators appears significantly affected by the multi-directionality of the motion, and more specifically by the degradation of the coefficient of friction due to heating phenomena at the sliding surface. An analytical model, applicable to the prediction of bi-directional sliding behavior of friction-based isolators has been experimentally validated. Results of this study suggest that these phenomena should be considered in the design of structures equipped with these popular anti-seismic devices.
An elementary model of soil and rock avalanches, debris run-out and fast spreads triggered by earthquakes
The model considered in this paper for analysis of fast and large ground movements is based on the equations of motion, mass and energy balances and on conventional ground parameters. The model capability is checked for the Pandemonium Creek rock avalanche in British Columbia, the Shum Wan Road debris run-out in Hong Kong and a coal mine waste fast spread at Aberfan in Wales. The analytical model can be used for first estimates of basic ground movement parameters such as the travel distance, peak velocity and acceleration. Despite its simplicity, the model still requires the use of some ground parameters and an assessment of the initial mass conditions a priori by the user.