Spherical Foundation Structural Seismic Isolation System: Development of the New Type Earthquake Resistant Structures

Transcription

1 Spherical Foundation Structural Seismic Isolation System: Development of the New Type Earthquake Resistant Structures AZER A. KASIMZADE, Department of Civil Engineering, Ondokuz Mayis University Samsun, TURKEY, EIZABURO TACHIBANA Department of Architectural Engineering, Osaka University 2-1 Yamada-Oka, Suita, Osaka , JAPAN, YOICHI MUKAI Department of Architecture, Graduate School of Engineering, Kobe University Kobe, JAPAN, SERTAC TUHTA Department of Civil Engineering, Ondokuz Mayis University Samsun, TURKEY, GENCAY ATMACA Provincial Directorate of Disaster and Emergency, Samsun, TURKEY Abstract: - New spherical foundation structural seismic isolation -SFSSI system has been discovered and first prototype on 23 story building with height 92 m example was presented. The SFSSI system consists of spherical foundation on surface of which rubber bearing is installed to great inverse pendulum isolation mechanism. It is allow to spherical foundation s turning around gyration centre through rubber bearing contact surface as absolute rigid body with one degree of freedom and keeps same behaviour to superstructure. Free and forced vibration of the SFSSI system was investigated. SFSSI system possible keep natural period of structure between 9 sec and 22 sec interval, which is much more than of predominant period ground motion of majority existing earthquakes including near fault zones also. Forced vibration response in time domain of the structure with SFSSI system under the strong Duzce (Turkey) Earthquake also exhibit that system s performance satisfied target aim. Keywords: spherical foundation structural seismic isolation-sfssi system; earthquake resistant structures; earthquake response control; rubber bearings; fluid dumper; durable isolation system; tall buildings ISBN:

2 1. Iintroduction Seismic isolation separates the structure from the harmful motions of the ground by providing the flexibility and energy dissipation capability through the insertion of the isolated device, called isolators, between the foundation and the building structure. The simplest sliding system is the pure friction (P-F) system well known in references, which does not have any restoring force and a period and it is very effective for a wide range of frequency inputs. In order to prevent and control large sliding and residual displacement in the P-F base isolator system, base isolation systems with a restoring force have been developed and investigated. These systems include; the resilient friction system, the Electricite de France, the friction pendulum, the sliding resilient friction, the elliptical rolling and others period-dependent base isolator systems well known in appropriate references. However, seismologists have reported on the vulnerable state of buildings isolated using a perioddependent base isolator against the near-fault pulse ground motions of intra-plate earthquakes or long-period ground motions of inter-plate earthquakes. The results of the recent studies also show that an excessively great displacement occurs in the isolation layers of these buildings. In presented work was aimed to create structural seismic isolation system, which deprived above mentioned deficiency. 2. Problem Identification In presented work was aimed to create structura l seismic isolation system, which period must b e more than of predominant period ground moti on of majority existing earthquakes including n ear fault zones also. In direction mention aim, t ried to create structure with invers pendulum sy stem s behaviour. For which, structure foot bas e and foundation contact surface made spherica l and there are separated by rubber bearing isol ators is installed through spherical contact surfa ces. It is allow to spherical foundation s turning around gyration centre through rubber bearing c ontact surface as absolute rigid body with one d egree of freedom and keeps same behaviour to t he superstructure. Obtained model was named spherical foundation structural seismic isolation -SFSSI system. Under excitation the structure with SFSSI system is wobbles around gyratio n centre through rubber bearing spherical conta ct surface (Fig. 1). Below was presented format ion, modelling and performance of the SFSSI s ystem on example 23 story steel building with h eight 92 m. 3. Problem Modelling 3.1 Free Vibration Equation of motion system around of gyration center (g.c.) presented as following: (Mρ I φ )φ + (Kρ 2 2 ± Mgρ 1 )φ = 0 (1) Where, φ is the rotation angle of the absolute rigit structure around of the gyration center; M is the total mass of the superstructure with upper part of the base;i φ is the rotational inertia of the superstructure; ρ 1 ρ 2 are distances from gyration centre to the structure mass centre and isolation application places appropriately; M is structure total mass; K is total rubber bearing isolator stiffness; φ is gayretin angle. Here possible two cases - A) gyration canter upper of the centre of mass superstructure with upper part of the base (Fig. 1a,b and Fig. 2); B) gyration centre under of the centre of mass superstructure with upper part of the base (Fig. 4c,d) ; in Eq.-s (1,2) there are separated by sign ± approprietly. The system natural period is defined as T = 2 π Mρ I φ Mgρ 1 ± Kρ 2 (2) Numerical verifications are presented on the example 23 story steel framed structure with height H=92m; the floor load including selfweight of the steel members is set at 7.84 kn/m 2.The structure is designed so that the maximum story angle is less than 1/200 under the A i distribution. The material of steel members is SN490, so that the yield strength is 357MPa. The columns have box-section, beam have H- shape section and all members are designed to satisfy FA rank building design grade. Building section plane radius is R=27m; Building total mass M=4.3x10 7 kg, total area A=52648 m 2 for case A and M=5.07x10 7 kg, total area A=A upper_under=52648 m m 2 =64665 m 2 for case B appropriately ; total rubber bearing isolator stiffness K=4.22 x10 7 N/m and K=4.98 x10 7 N/m for cases (A) and (B) appropriately. For cases (A, B) system natural period ISBN:

3 Recent Researches in Mechanical and Transportation Systems sensitivity from parameters presented by Eq. (2) was evaluated and presented in Figures 5, 6. As seen from results for structure with spherical foundation structural seismic isolation -SFSSI system possible keep natural period of structure between 9 sec and 22 sec interval, which is much more than of predominant period ground motion of majority existing earthquakes including near fault zones also. 3.2 Forced Vibration Equation of motion SFSSI system under earthquake excitation for cases (A) and (B) by the equations (3) and (4) respectively as: We are grateful for the financial support provided by the Scientific and Technological Research Council of Turkey (TUBITAK). References: [1] A.A. Kasimzade, E. Tachibana, Y. Mukai, S. Tuhta, G. Atmaca, Seismic isolation system on base ancient architecture s inherence, International Symposium on Disaster Simulation & Structural Safety in the Next Generation (DS 15), 2015, Osaka, Japan (Mρ I φ )φ (z, t) + Cb 2 φ (z, t) + (Kρ Mgρ 1 )φ(z, t) = Mu g(t)ρ 1 (3) (Mρ I φ )φ (z, t) + Cρ 2 2 φ (z, t) + (Kρ 2 2 Mgρ 1 )φ(z, t) = Mu g(t)ρ 1 (4) Were u g is ground acceleration (m/s 2 ); C = c =2.41*10 5 Ns/m total damping. Dampers(c) in Figs signed by number 4 and its arrangement presented in Fig.3. Forced vibration response in time domain of the structure with SFSSI system under the strong Duzce (Turkey) Earthquake (for Case B) was presented in Figures 7, 8. As seen from presented figures, related dependents exhibit that Structure with SFSSI system s performance satisfied target aim. 4. Conclusions Presented new spherical foundation structural seismic isolation -SFSSI system possible keep natural period of structure between 9 sec and 22 sec interval, which is much more than of predominant period ground motion of majority existing earthquakes including near fault zones also. Forced vibration response in time domain of the structure with SFSSI system under the strong Duzce (Turkey) Earthquake exhibit that system s performance satisfied target aim.sfssi system deprived from known deficiency period depended isolation systems and it is the progress of the new type earthquake resistant structures. 5. ACKNOWLEDGMENTS Fig.1 Illustration of the spherical foundation structural seismic isolation -SFSSI system: a study case ( A); b arrangement of the bearing isolators on the surface of spherical foundation; ISBN:

4 Fig.2 Illustration of the spherical foundation structural seismic isolation -SFSSI system: arrangement of the forces for study case ( A) Fig.3 Illustration of the spherical foundation structural seismic isolation -SFSSI system: arrangement of the dumpers for study case Fig.4 Illustration of the spherical foundation structural seismic isolation -SFSSI system: c study case ( B); d arrangement of the forces for study case ( B) ISBN:

5 Fig.5 SFSSI system natural period sensitivity evaluation for study case A. Fig.6 SFSSI system natural period sensitivity evaluation for study case B. ISBN:

6 Fig. 7 Forced vibration response in time domain of the dumped structure with SFSSI system under the strong Duzce (TURKEY) Earthquake: top of the structure Fig. 8 Forced vibration response in time domain of the dumped structure with SFSSI system under the strong Duzce (TURKEY) Earthquake: base plate of the structure ISBN: