Modelling aspects of structures isolated with the frictional pendulum system

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SUMMARYThis experimental investigation deals with the earthquake behaviour of a nominally symmetric and a mass-asymmetric three-storey structural model isolated with the frictional pendulum system (FPS). Both accidental and natural torsion are evaluated in the structure by using recorded accelerations in all building oors and measured deformations at the isolation level. A 3D-shaking table was used to subject the model to ÿve di erent ground motions, including impulsive as well as far-ÿeld subductionzone type earthquakes. Results show that the analytical predictions of the earthquake behaviour of the isolated structure, as obtained from a physical model of the FPS, are in close agreement with the true complex inelastic measured behaviour of the FPS. Besides, experimental results also validate previous observations about the importance of accounting for the variability of the normal loads in modelling the earthquake behaviour of FPS isolators. Measured torsional deformation ampliÿcations at the base of the building vary, in the mean, from 2.5% to 6% for the symmetric and asymmetric structural conÿgurations, respectively. In relation to the ÿxed base structure, the reduction factors for the base shear of the isolated structure are, in the mean, about 3.9 for both conÿgurations. Finally, it is concluded that the FPS is capable of controlling the lateral-torsional motions of mass-asymmetric structures quite e ectively by aligning the centre of mass of the superstructure with the centre of pendular and frictional resistance of the isolation system.

Section: Introductionmentioning

confidence: 56%

Section: Responses Consideredmentioning

confidence: 99%

An experimental study of nominally symmetric and asymmetric structures isolated with the FPS

Llera

Almazán

2003

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“…For additional information about friction pendulum systems, the reader is referred to the literature (e.g., ). More detailed examination of this topic would lead beyond the scope of this paper, which should focus more on the methodical extension of the new MOR strategy as well as the application on a complex realistic system.…”

Section: Practical Application Of the New Approachmentioning

confidence: 99%

A new model order reduction strategy adapted to nonlinear problems in earthquake engineering

Bamer

Amiri

Bucher

2016

SUMMARYEarthquake dynamic response analysis of large complex structures, especially in the presence of nonlinearities, usually turns out to be computationally expensive. In this paper, the methodical developments of a new model order reduction strategy (MOR) based on the proper orthogonal decomposition (POD) method as well as its practical applicability to a realistic building structure are presented. The seismic performance of the building structure, a medical complex, is to be improved by means of base isolation realized by frictional pendulum bearings. According to the new introduced MOR strategy, a set of deterministic POD modes (transformation matrix) is assembled, which is derived based on the information of parts of the response history, so-called snapshots, of the structure under a representative earthquake excitation. Subsequently, this transformation matrix is utilized to create reduced-order models of the structure subjected to different earthquake excitations. These sets of nonlinear low-order representations are now solved in a fractional amount of time in comparison with the computations of the full (non-reduced) systems. The results demonstrate accurate approximations of the physical (full) responses by means of this new MOR strategy if the probable behavior of the structure has already been captured in the POD snapshots.

“…Furthermore, during the most recent seismic events (Turkey, Taiwan), the seismic performance of short=medium-span bridges has shown that the displacements induced by strong ground motions can far exceed the capacity of such multi-supported structures, even if base isolation devices were placed at the bearings. In fact, all the bearings under a given structure are commonly designed to have the same period and to be subjected to the same lateral displacement, but in practice, the dynamic responses of the bearings are not the same [1]. In particular, the e ects of an initial base displacement caused by small di erential settlements on the response quantities induce an additional spatial variation in the input acting on the bridge superstructure [2].…”

Section: Introductionmentioning

confidence: 99%

Seismic response of multi‐span simply supported bridges to a spatially varying earthquake ground motion

Zanardo

Hao

Modena

2002

139

SUMMARYThis paper carries out a parametrical study of the pounding phenomenon associated with the seismic response of multi-span simply supported bridges with base isolation devices. In particular, the analyses focus on the causal relationship between pounding and the properties of a spatially varying earthquake ground motion. In order to include the e ect of the torsional component of pounding forces on the seismic response of the whole structure, a three-dimensional (3D) ÿnite element model has been deÿned and 3D non-linear time-history analyses have been performed. A parametrical study on the size of the gaps between adjacent bridge decks has highlighted that the pounding e ects are ampliÿed when the spatially varying ground motion time histories at each support are considered. Because of a spatially varying input, the pounding forces can assume values 3-4 times larger than those derived by a conventional seismic analysis with uniform input or with spatial input but considering ground motion wave passage e ect only. The numerical results show that in order to achieve an acceptably safe structural performance during seismic events, a correct design of the isolation devices should take into account the relative displacements calculated by means of a non-linear time-history analysis with multi-support excitation.