Floor response spectrum

Floor acceleration This is the time history of acceleration of a partictilar floor nr structure caused by a given ground acceleration (Figure 14.16). It may have an amplified narrow band spectrum due to structural filtration, where single frequency excitation and resonance may predominate, depending upon the dynamic characteristics of the structure. A floor response spectrum (FR.S). as shown in Figure 14.18, can be derived from this history. Consideration of GRS or FRS will depend upon the location of the object under test. 

These tests are standardized (e.g. see USNRC, 1988). These standards require that a component is placed on a vibrating table and that it is submitted to a higher vibratory load than that characterized by the floor response spectrum. In some cases, if necessary, the component is even verified for operation during the test. The components are tested together with their support structure to avoid a further uncertainty in the calculation of the dynamic load at the level where they are located. The excitation must include all three axes, unless S5unmetry conditions exist. 

For the calculation of other stresses, the bridge crane model can be simplified as a distributed mass beam resting on its extremities with an additional mass at the centre submitted to a vertical oscillation complying with the floor response spectrum. 

The floor response spectrum is the response spectrum for floor motion at a particular elevation of a building for a given input ground motion. 

The design floor response spectrum is the response spectrum for floor motion at a particular elevation of a building and is obtained by modifying one or more floor response spectra to take into account the variabUity of and uncertainty in the input ground motion and the characteristics of the building and the foundation. 

For actual buildings, response spectrums are often stated as a function of the height above ground on various floors (floor response spectrum). The... 

In order to determine these forces, the floor response spectrums for the building under review are determined in accordance with the method of modal response spectrums described in Section 7.3.4. Figure 7.64, as an example, demonstrates the horizontal response spectrums of a building at... 

Figure 7.64 Horizontal floor response spectrums for airplane crash horizontal acceleration at 2% damping.

The following strategy can be considered (a) time history analyses applied either to the whole system or to the stand-alone attachment, considering the acceleration histories recorded at the level of the attachment connection and (b) spectrum-based analyses defining an acceleration spectrum consistent with the time histories recorded at the points where the attachment is connected to the structures the generated spectrum is usually named Floor Response Spectrum (FRS) even if (as the case reported in Fig. 4) the FRS has been evaluated where the attachment is linked and not at the floor level. 

If the SE behavior can be decoupled from the principal system, the datum method for the evaluation of the peak acceleration at the SE is based on the Floor Response Spectrum (FRS) that given an SE element, with a defined structural period and damping, attached to a given part of a structure, having its mechanical properties, subjected to a given seismic event ( ), allows to define the peak acceleration to which the element will be subjected when the seismic event ( ) is transferred at the base of NS element. 

Usually the location of the attachment is not known in advance, so that the previous procedure can be applied considering p points obtaining p Response Spectra. For those points that are located at the same level (floor) of the P structure, a single spectrum can be evaluated (enveloping the Response Spectra), naming it Floor Response Spectrum. 

A minimum of two-thirds of the horizontal floor response spectrum shall be used as the vertical floor response spectrum unless justification is provided to show that another value produces negligible differences in the response of interest (e.g., displacements, loads, and stresses). 

When the output of the numerical analysis is requested in terms of floor response spectra, maximum relative displacements, relative velocities, absolute accelerations and maximum stresses during an earthquake, linear dynamic analysis (e.g. direct time integration, modal analysis, frequency integration and response spectrum) is generally adequate for most models. Alternatively, non-hnear dynamic analysis should be used where appropriate or necessary (e.g. structural hft-off, non-linear load dependent support, properties of foundation materials in soil-structure interaction problems or interactions between solid parts). 

In the time history method, the structural response of the system should be calculated as a function of time either directly or after a transformation to modal co-ordinates (for linear models only). The input motion should be represented by a set of natural or artificial time histories of acceleration at ground level or a specific floor level, suitably chosen to represent the design response spectrum and the other characteristics of seismic hazard (e.g. duration). 

Gluck et al. (1996) adapted optimal control theory (OCT) to the damper placement problem. OCT is used to minimise the performance objective by optimising the location of linear passive devices. Since passive dampers cannot provide feedback in terms of optimal control gains, three approaches (response spectrum approach, single mode approach, and truncation approach) are proposed to remove the off-diagonal state interactions within the gain matrix and allow approximation of floor damping coefficients. Combination of these methods with OCT and passive devices achieves an equivalent effect compared to active control. 

Vibratory loads induced by the impact should be evaluated by means of a specific dynamic analysis of structures and equipment, with account taken of the material properties of reinforced concrete subjected to dynamic loads (stiffness and damping). The floor response spectra should be calculated for all the main structural elements of the buildings which house safety related equipment. Appropriate transfer functions should be evaluated for the estimation of the vibratory action transferred to any safety related equipment. The numerical model should be specifically validated for the dynamic transient analysis, so as to guarantee a proper representation of the vibratory field at least in the frequency range in which the power spectrum of the load function has major contributions. 

Floor Response Spectra are functions that define the response spectrum of a given response parameter (e.g., acceleration, velocity, displacement) as a function of period and damping of a given structure (attachment) localized at a given point of the construction. 

Ground + buildings Ground response spectrum and corresponding time histories Floor response spectra (secondary spectra) and corresponding time histories... 

For the targeted HCLPF capacity (e.g., the Review Level Earthquake in an SMA), the floor responses (demand) are computed using the 84 % fractile (i.e., an 84 % probability of non-exceedance) of the ground response spectrum. Damping is to be assumed conservatively. 

The 1 percent damping Housner free field response spectrum anchored at 0 2g and amplified by 10 percent shall be used as the FRS only for equipment on which a dynamic analysis of record has already been performed. Use the FRS developed, for the restart program (RP) (URS/JAB 6193, 06, "Floor Acceleration Response Spectra for Updated DBF and Reg. Guide 1.60 Seismic Input, Building 105K, Savannah River Plant," August 1989) for new analyses conducted after February 1989. Justify other FRS used. 

The received signal spectrum for a single transmit/receive pair is shown in figure 13. For this pair the five target responses are clearly visible. The noise floor is approximately 10 dB, providing a signal to... 

Human brains show symmetrical necrotic lesions most consistently in the mammillary bodies but also in the periaqueductal midbrain, thalamus, and along the floor of the fourth ventricle. These are the lesions of the acute disease, not necessarily associated with disordered memory. The changes in patients from the Korsakoff end of the spectrum differ by virtue of consistent involvement of the diencephalon, particularly the medial dorsal nucleus of the thalamus. This structural lesion, rather than a reversible biochemical process, appears to be responsible for the memory loss. Thus, patients with third ventricular tumors, resection of inferomed-ial portions of the temporal lobes, or sequelae of herpes encephalitis may demonstrate classical signs of Korsakoff s psychosis (Victor et al., 1971). 

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