Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Seismic base isolation by nonlinear mode localization
The seismic base-isolation concept examined herein consists of a linear main structure, to be isolated, which is weakly coupled to a nonlinearly sprung subfoundation. A hardening stiffness, here represented both as a continuous cubic (smooth) and as a bilinear (non-smooth) element, is used to provide the nonlinearity in the system. An internal resonance is induced in the main structure-subfoundation-ground system by tuning the subfoundation to the first deformational mode of the linear main structure. This introduces a 1:1 internal resonance between the first deformational mode of the primary structure and the subfoundation. Under the condition of third-order smooth stiffness nonlinearity, an analysis of the unforced vibration system reveals that a localized nonlinear normal mode (NNM) is induced in the system, which confines energy to the subfoundation, thus preventing any energy transfer to the main structure at frequencies outside the resonant frequency range. A numerical analysis is carried out wherein the smooth nonlinearity is replaced by non-smooth nonlinearity, and the system is excited by ground motions representing near-field seismic events. The non-smooth nonlinearity is generated by two linear springs in parallel, one including the gap or clearance which determines the onset of nonlinear behavior. The results show that, with proper tuning, any deformational mode of the primary structure can be suppressed, with resulting reductions in response. When compared with a nearly identical system without the additional clearance spring (thus making the system linear) the nonlinear system performs well. The response of the first deformational mode of the structure is almost fully suppressed, and system response to the full-sine velocity pulse, historic Erzincan earthquake, and the He model of the Erzincan earthquake showed peak reductions in the inter-storey displacements of up to 61%, and in the absolute accelerations of up to 65%.
Seismic base isolation by nonlinear mode localization
The seismic base-isolation concept examined herein consists of a linear main structure, to be isolated, which is weakly coupled to a nonlinearly sprung subfoundation. A hardening stiffness, here represented both as a continuous cubic (smooth) and as a bilinear (non-smooth) element, is used to provide the nonlinearity in the system. An internal resonance is induced in the main structure-subfoundation-ground system by tuning the subfoundation to the first deformational mode of the linear main structure. This introduces a 1:1 internal resonance between the first deformational mode of the primary structure and the subfoundation. Under the condition of third-order smooth stiffness nonlinearity, an analysis of the unforced vibration system reveals that a localized nonlinear normal mode (NNM) is induced in the system, which confines energy to the subfoundation, thus preventing any energy transfer to the main structure at frequencies outside the resonant frequency range. A numerical analysis is carried out wherein the smooth nonlinearity is replaced by non-smooth nonlinearity, and the system is excited by ground motions representing near-field seismic events. The non-smooth nonlinearity is generated by two linear springs in parallel, one including the gap or clearance which determines the onset of nonlinear behavior. The results show that, with proper tuning, any deformational mode of the primary structure can be suppressed, with resulting reductions in response. When compared with a nearly identical system without the additional clearance spring (thus making the system linear) the nonlinear system performs well. The response of the first deformational mode of the structure is almost fully suppressed, and system response to the full-sine velocity pulse, historic Erzincan earthquake, and the He model of the Erzincan earthquake showed peak reductions in the inter-storey displacements of up to 61%, and in the absolute accelerations of up to 65%.
Seismic base isolation by nonlinear mode localization
Seismische Isolierung von Gebäudefundamenten durch lokale Eingrenzung nichtlinearer Schwingungsmoden
Wang, Y. (Autor:in) / McFarland, D.M. (Autor:in) / Vakakis, A.F. (Autor:in) / Bergman, L.A. (Autor:in)
Archive of Applied Mechanics (Ingenieur Archiv) (online) ; 74 ; 387-414
2005
28 Seiten, 28 Bilder, 26 Quellen
Aufsatz (Zeitschrift)
Englisch