Earthquake dampers

Table 4.4-4 provides performance criteria needed to demonstrate that the functional requirements for the Zone 1 and Zone 2A ventilation exhaust systems are met No operational events can affect the ability of the HEPA and charcoal filters to perform their safety functions, since these functions ahe only required when the HCF ventilation system is operating. Furthermore, failure of filter bank inlet or outlet dampers to remain open during ventilation system operation will essentially stop the flow of Zone 1/Zone 2A exhaust air to the HCF stack. The only events that could affect the ability of the charcoal filters to perform their safety function are a fire in the MER or an external event such as an earthquake or aircraft crash that would destroy the MER. The only events that could affect the ability of the HEPA filters to perform their safety function are similar events. 

Paolacci F., Giannini R., (2008), "Study of the effectiveness of steel cable dampers for the seismic protection of electrical equipment", 14 World Congress on Earthquake Engineering, Beijin, China... 

An upper controller is designed to switch between the 625 feedback control gains during earthquake simulations. At each time step, the optimal control force is calculated based on the feedback gain for the system with damping constants that are calculated in the previous step. The force that is required for the i th device is divided by the i th dampers velocity to obtain the optimum damping constant (see Eq. 18.1). Then the closest damping constant within [5,000-25,000 Ns/m at increments of 5,000] is selected for the next time step. 

The simulations are carried out for the first 20 s of the first three, and the first 100 s of the last three earthquakes. The major response is seen in this time frame, and it also allows for more detail in the illustrations. A direct integration method for the solution of the equation of motion in Eq. 18.2 is used. Superposition of modal responses is not possible for systems with non-proportional damping, as is the case with the current structure with added dampers. The Newmark p method (by using the unconditionally stable average acceleration method) is used as the solver for aU simulations in this study. The function that implements this ordinary differential equation (ODE) solver makes sure that the simulation time step is 20 times smaller than the smallest period of the structure. If this is not the case, it interpolates the excitation data for a smaller time step, and later outputs the response at a 0.01 s. In this work, the building type structure has a minimum period of 0.108 s. Thus, the simulation takes place at 0.108/20 = 0.0054 s. 

A damper with a fixed damping coefficient will not be able to achieve a similar performance as the presented control method. The best response in far field type earthquakes is established by minimum damping with an extra control force at some time instances near field type earthquakes, on the other hand, appear to be best handled with a fixed base. Therefore, in either case a fixed valued damper will not suffice to produce a desirable structural response. At last, a smartly controlled semiactive damper is able to protect a seismically isolated building from both near and far field type earthquakes. 

Without a tuned mass damper, the top floors of very tall buildings can sway back-and-forth 30 centimeters or more in a strong wind, let alone an earthquake. 

Miyamoto International is a global earthquake and structural engineering firm that specializes in designing earthquake engineering solutions. It has offices throughout Gahfomia, and in Portland-Van-couver and Tokyo, and specializes in viscous and liic-tion cross-bracing dampers. 

Lin, W.H. Chopra, A.K. 2003. Asymmetric one-storey elastic system with non-linear viscous and viscoelastic dampers Earthquake response. Earthquake Engineering and Structural Dynamics 32 555-577. 

Goel, R.K. 2005. Seismic response of linear and non-linear asymmetric systems with non-linear fluid viscous dampers. Earthquake Engineering Structural Dynamics 34(7) 825-846. 

The dynamic response of civil engineering structures subjected to earthquake excitation can be reduced by using passive control systems such as energy dissipation devices (e.g. viscous dampers, etc.). The advantage of these systems with respect to active and semi-active control systems consist in the fact that they don t require any power supply, therefore are quite reliable and they require least maintenance. 

For large civil engineering structures it is necessary to install a sufficient number of dampers to achieve a reduction of the stmctural response due to earthquake and the performance of these dampers depends on their location in the structures. The selection of few locations out of a large number of locations for the placement of passive dampers is typically a nonlinear constrained optimization problem. This problem can be solved either by simple heuristic search approaches or through integral optimization. The first ones are simple and they yield a solution which may be close to the optimal solution, but computationally expensive, instead the second ones are fast but solution is complex. 

For both indices instead different damper distributions can be obtained using different earthquake records that can be caused by the different frequency content of each earthquake (Figure 4). Hence it has been found that the optimal distributions obtained with J3 and J4 as objective functions strongly depend on the nature of the earthquake record at the site. Hence, the optimal damper distribution for seismic excited buildings can be obtained by minimizing J4 using the design earthquake of the particular site. 

The base shear coefficient normalized with respect to the total weight ofthe building is shown in Figure 13, comparing the uncontrolled structure with the uniformly distributed dampers and the two optimal distributions obtained using the maximum interstory drift (J4) and the maximum absolute acceleration (J3) performance indices. A reduction of the base shear is observed for all the earthquake records that is slightly improved when also the optimal damper distributions are considered. 

Passive energy dissipation systems (e g. viscous dampers, metallic dampers, friction dampers etc) have been used extensively for the protection of civil engineering structures against strong earthquakes, therefore in this chapter are shown and compared three practical search methods for the optimal placement and design of dampers. They are called ... 

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Dargush, G., Soong, T. T. (1995). Behavior of metallic plate dampers in seismic passive energy dissipation systems. Earthquake Spectra, 77(4), 545-568. doi 10.1193/l.1585827... 

Lavan, 0., Levy, R. (2006). Optimal design of supplemental viscous dampers for linear framed stmctures. Earthquake Engineering Structural Dynamics, 55(3), 337-356. doi 10.1002/eqe.524... 

Lopez-Garcia, D. (2001). A simple method for the design of optimal damper configurations in MDOF stmctures. Earthquake Spectra, 17(3), 387-398. doi 10.1193/l.1586180... 

Roh, H. S., Cimellaro, G. P. (2010). (in review). Fragility evaluation of stmctures with controlled rocking columns and viscous dampers. Journal of Earthquake Engineering. 

Singh, M. P., Moreschi, L. M. (2001). Optimal seismic response control with dampers. Earthquake Engineering Structural Dynamics, 30(4), 533-572. doi 10.1002/eqe.23... 

Trombetti, T., Silvestri, S. (2004). Added viscous dampers in shear-type structures The effectiveness ofmassproportional damping. Journal of Earthquake Engineering, 8 2), 275-313. doi 10.1080/13632460409350490... 

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