Acceleration-time history

The Seismic Safety Margins Research Program developed a computer code called SMACS (Seismic Methodology Analysis Chain with Statistics) for calculating the seismic responses of structures, systems, and components. This code links the seismic input as ensembles of acceleration time histories with the calculations of the soil-structure interactions, the responses of major structures, and the responses of subsystems. Since uses a multi-support approach to perform the time-history response calculations for piping subsystems, the correlations between component responses can be handled explicitly. SMACS is an example of the codes that are available for calculating seismic response for PSA purposes. 

Figure 5. Input acceleration time history obtainedfrom DSHA...

Figure 6. Fourier response spectrum for input acceleration time history...

Figure 7. Acceleration time history at the base obtainedfrom deconvolution analysis...

The surface acceleration time history obtained from the ground response analysis for two typical sites C class site and B class site are presented in Figures llaand 1 lb respectively. It can be noticed from Figure 11 that the surface peak ground acceleration for C class and B class site is 0.53 g and 0.3 Ig respectively. It is evident that the C class site amplifies the ground motion in comparison to the input ground motion with PGA of 0.3 g. However the B class site does not amplify the input motion due to the presence of a thick hard sandy clay deposits characterized by very high shear wave velocity. 

Figure 11. (a)Acceleration time history obtained at the surface for C class site (b)Acceleration time history obtained at the surface for B class site... 

The acceleration time history at the surface for the site considered is obtained from the recorded ground motion data considering similar magnitude, distance and frequency content of the controlling earthquake. The 1999 Chi-Chi earthquake accelerogram is adopted and is scaled to the required PGA. Deconvolution analysis was performed to obtain the acceleration time history at base (60m depth). 

Using Newmark s sliding block approach, for a given harmonic ground acceleration time history and a known value of k, the sliding displaee-ment (F) can be calculated by double integrating the relative acceleration [k ks)9 the bloek as follows ... 

Equinoxious frequency contours may be estimated from epidemiological studies of health effects, or from the response of human subjects, animals, cadavers, or biodynamic models to the stimuli of interest Human subjects cannot be subjected to injurious accelerations and forces for ethical reasons, and so little direct information is available from this source. Some information has been obtained from studies of accidents, though in most cases the input acceleration-time histories are poorly known. 

FIGURE 10.1 Frequency weightings for whole-body (W, and WJ and hand-transmitted 0V ) vibration. and Wj are for the z direction and X and y directions, respectively, and are applicable to seated and standing persons (see Fig. 10.2). IF ) is for all directions of vibration entering the hand. The filters are applied to acceleration-time histories a t). ISO 2631-I, I997 ISO 5349-1,2001.)... 

Fig. 16.3 Ground motion applied in pseudo-dynamic tests (a) acceleration time-history after Y component of Herzegnovi record in 1979 Montenegro earthquake (b) 5 %-damped elastic spectrum compared to target Type 1 spectrum in Eurocode 8 for ground type C (factor 40.75 applied on the time- and period axes to account for the specimen scale)...

In the following paragraphs the dynamic response of the soil-tunnel model is presented and discussed. To interpret the results, the data was windowed neglecting the parts of the signals before and after the main duration of the signals, while a filtering procedure was conducted in the frequency domain. More specifically, the acceleration-time histories were filtered between the frequencies of 10-400 Hz,... 

Figure 22.8 presents the peak acceleration profiles with depth along the three main arrays of accelerometers, namely the reference array (on the ESB box), the free field array and the vertical array across the tunnel (tunnel array). The peak values are computed as the average semi-amplitude of the cycles in the processed acceleration-time histories. Generally, as expected, the peak acceleration decreases with depth. Moreover, the acceleration at the mnnel roof slab is found to be reduced, with respect to the free field for the same burial depth, for all the earthquakes. This indicates an influence of the tonnel to the wave propagatiOTi field. The differences are amplified with the intensity of the input motion. 

Fig. 22.10 Vertical acceleration time histories on model roof slab...

Fig. 22.11 Racking distortions computed from displacement time histories obtained from acceleration time histories through double integration. Racking ratios for each earthquake...

Finally, the response of Configuration 2 to harmonic and earthquake excitation with PGA = 0.17g presented in Fig. 27.9, exhibits a similar behavior to both Configurations 1 and 3, resulting to simultaneous sliding and rotational failure. As seen from both the acceleration time histories (Fig. 27.9a) and the failure mechanisms (Fig. 27.9b) the sliding failure mode prevails, which is consistent to the critical accelerations estimated in Table 27.2. 

The structural response is evaluated in the time domain and the excitation is given in terms of a stochastic model of the input ground acceleration time history. In what follows, the model by (Atkinson Silva 2003) is implemented. The site seismic hazard is expressed as a function of M and R for given local soil conditions a further PDF p(Z) is introduced, to model the uncertainty in the ground motion time history for a given M and R. Therefore (0) is given by (0) = p(0s Ds, Ms) p(M)p(R)p(X) and the integral in Equation 11 can be written as ... 

Probabilistic or Deterministic Seismic Hazard at Engineering Bedrock Outcrop (PGA and Suite of Hazard Compatible Acceleration Time Histories)... 

Text files for input motions (acceleration time histories) including header lines describing the necessary format information to read acceleration values in the file. A text file that includes PGA values at engineering bedrock outcrop determined from seismic hazard analyses. 

Table 1 Hazard com Zeytinburnu. patible acceleration time histories selected for site response analyses in...

Three real acceleration time histories compatible with the regional seismic hazard were selected as input motion as summarised in Table 1. These records were scaled... 

Figure 3 Acceleration time histories scaled with respect to PGA and their respective acceleration response spectra used as input motion in the site response analysis.

In order to evaluate the spectrum compatibility, the acceleration response spectra of the selected acceleration time histories scaled to average PGA for the area were calculated and compared with the lowest and highest NEHRP spectra obtained from the earthquake hazard study conducted for the area as shown in Figure 3. 

Figure 7 Damage distribution in Zeytinburnu based on PGA scaled real acceleration time histories in accordance with probabilistic seismic hazard analyses.

Ansal, A., Durukal, E. Toniik, G. 2006a. Selection and Scaling of Real Acceleration Time Histories for Site Response Analyses. Proc. of ISSMGE ETC12 Workshop, Athens, Greece. 

Figure 2 Acceleration time-history (a), response spectrum (b), and Fourier spectrum (c) of the Ricker pulse excitation.

---