Parametric investigation of the stability of classical columns under harmonic and earthquake excitations

Abstract

SUMMARYThe seismic response of free-standing classical columns is analysed numerically through implementation of the distinct element method. Typical sections of two ancient temples are modelled and studied parametrically, in order to identify the main factors a!ecting the stability and to improve our understanding of the earthquake behaviour of such structures.The models were "rst subjected to harmonic base motions. The analysis showed that, for frequencies usually encountered in earthquake motions, intact multi-drum free-standing columns can withstand large amplitude harmonic excitations without collapse. The dynamic resistance decreases rapidly as the period of the harmonic excitation increases. Imperfections, such as initial tilt of the column or loss of contact area due to edge damage, also reduce the stability of the system signi"cantly. The e!ects of such imperfections could be additive and the cumulative e!ect of many imperfections may render deteriorating abandoned monuments vulnerable to earthquakes. The response of more complete sections of the temple, such as two columns coupled with an architrave, did not deviate systematically from that of the single multi-drum column or indeed of the equivalent single block. Therefore, a much simpler single block analysis can be used to size-up the seismic threat to the monument.The model of the column of the Temple of Apollo at Bassae was also tested under recorded earthquake motions by scaling-up the acceleration amplitude progressively until collapse of the column. It was found that the columns are particularly vulnerable to long-period impulsive earthquake motions. A comparison of the instability thresholds associated with harmonic excitations and earthquake motions throws more light onto the dynamic response: it appears that around three cycles of monochromatic excitation at the predominant period of the expected earthquake motions lead to a gross prediction of the stability of a classical column during an earthquake.

Influence of boundary conditions on the out‐of‐plane response of brick masonry walls in buildings with RC slabs

“…[23,24,27,28]). The initial portion of the strong ground motion response of models was found to be rather insensitive to the damping level [27,28] while continued strong shaking and the reduction in amplitude of the free vibration can be sensitive to the damping [27]. For rocking motions, the natural rocking period is not constant [34], and therefore, it is impossible to specify a constant level of damping for a given mode.…”

Dynamic motion of a conical frustum over a rough horizontal plane

“…Consequently, the two dimensional analyses often performed [25,26,27,28] should fail to capture the response of these articulated systems, as the out-of-plane motion cannot be ignored. In parallel, the mechanism of energy dissipation at wobbling is different from rocking.…”

Experimental Investigation of the Seismic Response of a Multi-Drum Column

“…Also, the behavior becomes complex and the highly nonlinear response produces displacements and/or rotations of the blocks, either in group or individually [3]. As noted by Psycharis et al [4], even during the same excitation, a multi-drum column behaves following several different 'vibrational' modes, each of which is governed by a different set of equations of motion. As the response is strongly dependent on the peculiarities of excitations, with significant sensitivity even to small changes in their parameters [5]- [8], the numerical analysis of the behavior of multiblock columns becomes extremely complex if not even impossible to develop [9].…”