Seismic isolation systems

A conceptual study on the vertical seismic isolation system for FBR components is underway. A series of shaking table tests and analytical worics are included to assess the feasibility of the system. 

Italy The key issues and tasks in nuclear R D in Italy are focused on the following areas (1) collaboration with General Electric on ALMR (optimization of safety parameters for a fast burner oxide core, studies with the aim of reaching the best burning capability of the PRISM MOD B oxide core, satisfying the safety criteria) (2) seismic isolation systems (guidelines development, seismic isolation tests, analytical studies), and (3) SPX reactor commissioning and service activities. 

Iqbal A (2006) Soft first storey with seismic isolation system. In NZSEE conference, Napier, CDROM paperlD 36... 

A three dimensional seismic isolation system for the reactor building is adopted to achieve the standardization of design. The base size of the building is 40mx40m, and the height is 55m. Shortening the construction schedule on-site is very important to reduce the plant construction costs, thus an optimum combination of steel structure and concrete structure is being considered. 

The 4S-LMR has a standard seismic design with horizontal seismic isolation systems, acceptable for a variety of siting conditions. 

S5mians, M. D., Kelly, S. W. (1999). Fuzzy logic control of bridge structures using intelligent semi-active seismic isolation systems. Earthquake Engineering Structural Dynamics, 25(1), 37-60. doi 10.1002/(SICI) 1096-9845(199901)28 K37 AID-EQE803>3.0.CO 2-Z... 

Alhan, C., Gavin, H. (2004). A parametric study of linear and nonlinear passively damped seismic isolation system for buildings. Engineering Structures, 24, 485-497. doi 10.1016/j. engstmct.2003.11.004... 

Seismic isolation systems to reduce the quantity of structural materials and to standardize the plant design independent of site conditions,... 

Seismic design 3-dimensional seismic isolation system... 

A seismic isolation system for the reactor building is adopted to standardize the design. The base size of the building is 40x40 m, and the height is 55 m. 

For seismic design, JSFR adopts an advanced seismic isolation system for SFR that mitigates the horizontal seismic force by thicker laminated rubber bearings with a longer period and the improvement of damping performance by adopting oil dampers (Okamura, 2011). 

Commission of Japan, 2006). Hence, the demonstration reactor of JSFR must adopt an advanced seismic isolation system, which is a practicable modification of previous technologies, because the earthquake force that affects the primary components must be mitigated more than that of the previous seismic isolation system. 

The advanced seismic isolation system for SFRs adopts laminated rubber bearings, which are thicker than those of the previous design, as well as oil dampers. As a result of the examination, the specification of the advanced seismic isolation system for SFRs is that the natural frequency in the horizontal direction is 0.29 Hz and in the vertical direction it is 8.0 Hz (Okamura et al., 2011). 

Base isolation systems are passive systems, and they do not have the ability to adapt and change their properties in different external excitation (e.g., near- or far-fault excitation). With the addition of an active or semi-active control device to a base-isolated structure, a higher level of performance can be achieved without a substantial increase in the cost. This thought has led to another type of hybrid control system, referred to as hybrid seismic isolation, consisting of active or semi-active devices introduced in base-isolated structures (see Fig. 9). Although base isolation has the ability to reduce interstory drifts and structural accelerations, it increases base displacement, hence the need for an active or semi-active device. In addition, a semi-active friction-controllable fluid bearing has been employed in parallel with a seismic isolation system (Feng and Shinozuka 1992 Sriram et al. 2003). 

Other types of metallic dampers have been developed for beam-column connections, braces and base isolation systems. Early developments include the U-strip hysteretic dampers and the T-ADAS damper. Other examples include the honeycomb damper used as seismic isolation system in bridges, C-shaped and E-shaped hysteretic dampers for bridges, slit-type dampers applied to beam-column connections or brace members, yielding shear panels, cast-iron yielding fuses installed in braces and hourglass shape pins installed in beam-column connections. A complete reference list for the aforementioned metallic dampers is provided in Vasdravellis et al. (2014). 

Seismic isolation systems are ideally suited for implementation within a performance-based framework because (a) robust characterizations of their behavior can be made through experimentation, (b) the variance of observed behavior from expected is often low relative to conventional structural elements, and (c) it can be challenging or even impossible to achieve an enhanced performance objective without the use of seismic isolatirai. Compared to conventional strucmral system for seismic resistance, isolation provided a unique and reliable means of simultaneously reducing earthquake damage in both... 

The roots of seismic isolation as a means for protecting structures from earthquakes go back to the latter part of the nineteenth century. While there appeared to be significant interest in creating an innovative seismic protective system, few opportunities were available for practical application. The first documented proposal for a seismic isolation system appears to be in an 1870 US patent filed by Jules Touaillon that describes a double-concave rolling ball bearing (Eenz and Constantinou 2006). Other early proposals include a 1906 US patent by J. Bechtold and a 1909 British patent by J. A. Calantarients (Buckle... 

The concept of base isolation is quite simple. The seismic isolation system is a group of low-stiffness elements that is placed between the foundation and the structure and reduces the effects of the earthquake on the latter. Use of these elements causes a decrease of the fundamental frequency of the structure shifting it away from both its fixed-base frequency and the predominant frequencies of the grotmd motion (Kelly 20(H). 

Fig. 5 Idealized force-displacement relation of a typical seismic isolation system (Constantinou et al. 2007b)...

In short, as mentioned earlier in this entry, the presence of a seismic isolation system (with... 

The reduction of seismic demand is achieved by reducing the mass of the structure and modifying the structural system toward a favorable shift of the fundamental period of the structure [e.g., through seismic isolation systems or absorption of seismic energy see... 

The question of optimal design for stiffness and friction of seismic isolation systems has been addressed previously in the literature (e.g., Constantinou and Tadjbakhsh (1983), lemura et al. (2007), Jangid (2005)). The method of equivalent linearization in conjunction with a random process model for the earthquake excitation tuned to the El Centro record was used in Jangid (1996). Here, a full nonlinear dynamic analysis will be used as a basis for the computation of the structural response. The ground motion is modeled as a nonstationary (i.e., evolutionary) random process hence, the response should to be characterized in suitable probabilistic terms. 

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