Displacement controlled rocking behaviour of rigid objects

Abstract

The capacity of a gravity structure to counter seismically induced overturning can only be estimated with good accuracy using a dynamic analysis of the rotational (rocking) motion involving large displacement theory. Seismic assessment employing quasi-static analysis can be overly conservative if the reserve capacity of this type of rocking structure to displace without overturning is not taken into account. It was revealed through dynamic testing on a shaking table that the overturning hazards of ground shaking are best represented by the peak displacement demand (PDD) parameter and that the vulnerability to overturning instability decreases with the increasing size of the object when the aspect ratio is held constant. This finding has important implications on the engineering of structures for countering moderate ground shaking in regions of low and moderate seismicity. Experimental data were validated and supplemented by computer simulations that involved generating artificial accelerograms of designated earthquake scenarios and non-linear time-history analyses of the overturning motions. Based on these simulations, fragility curves were constructed for estimating the probability of overturning for given levels of PDD and for different specimen dimensions. An expression was developed for estimating the level of PDD required to overturn rectangular objects of given dimensions for 5% probability of exceedance.

Displacement-Controlled Behavior of Asymmetrical Single-Story Building Models

“…Consequently, the risks of overturning is controlled simply by the value of RSD max of the base excitation in comparison with the depth of the object in the direction of the applied excitation. This anomaly was re-affirmed by results from shaker table experimentations as reported in a more recent publication [Kafle et al, 2011].…”

Rocking and Kinematic Approaches for Rigid Block Analysis of Masonry Walls: State of the Art and Recent Developments

“…However, while in the case of free-vibration or harmonic input forces, the response is more controllable, in the case of random motions, such as earthquakes, very large variations are found in the response of similar blocks, both in experimental and in numerical tests [21,24,[52][53][54]. This is due to the combination of different frequency contents, duration and seismic actions parameters.…”

Probabilistic Validation of the Housner Rocking Model

“…the input to the shaking table) and of the measured shaking table motion are shown. The mean of the displacement spectra of the 100 motions is also plot, as several researchers report that the maximum of the Elastic Displacement Spectrum is a good measure of the overturning potential of a ground motion [57][58][59].…”