In this paper, we introduce a semi-analytic procedure for deriving the response spectrum of the synthetic acceleration records generated using the Double-Frequency Model (DFM). DFM is a filtered white noise method for fully non-stationarity synthetic acceleration records. The proposed semi-analytic procedure is based on the theory of the first passage problem, which precludes time and computationally extensive methods such as Monte Carlo simulations. Assuming a slowly-varying envelope and evolutionary transfer functions, the procedure of estimating the elastic response of a structure is implemented in both time and frequency domains. Comparing the results of our model with previous models and approximations, we concluded that for a set of 10000 realizations of the DFM model, the semi-analytic model produces an error of less than 10% for 92% of the realizations. The accuracy of estimations is higher in the short-period compared to the long-period ranges of the response spectrum. Comparing the accuracy of approximations used to arrive at peak factors, results show that Michaelov approximation executed in the frequency domain yields the best results compared to Poisson or Vanmarcke procedures.

In this paper, the pseudo-acceleration spectra of the three accelerograms of El Centro, Naghan and Tabas, which were obtained by the linear interpolation method of stimulation (Jennings’s method) and also by using the cubic spline function, are compared with each other. Jennings' method is based on linear interpolation of excitation and is acceptable for short periods of time. In this research, three accelerograms of El Centro, Naghan and Tabas were considered, and their pseudo-acceleration response spectrum (base shear coefficient) was calculated for different damping values using linear interpolation method and interpolation with spline function. The considered damping were zero, two, five, ten and twenty percent. In order to determine the difference between the linear interpolation method and the spline function interpolation method, the time interval between the accelerometer points was divided into 2, 5, 10, 20, 50, 100, and 200 equal parts, respectively. Then, once with the linear interpolation method and again with the spline interpolation method, the internal points between the internal acceleration points were obtained and their pseudo-acceleration spectrum was calculated using the Jennings method and the interpolation method with the spline function. The calculation results showed that the pseudo-acceleration spectrum values calculated by the spline interpolation method in very short periods and low damping have a significant difference with the corresponding values of the pseudo-acceleration spectrum calculated by the linear interpolation method. It should be noted that the initial time interval between the accelerogram points of El Centro, Naghan and Tabas is 0.02 seconds.

Iran is located in a high-risk seismic region. The severe damage caused by recent major earthquakes has increased the importance of seismic evaluation methods and design procedures. To enhance seismic evaluation methods, it is necessary to provide acceleration records which are compatible with a design spectrum. In this paper, a new method is proposed to generate compatible records with a design spectrum. The method is based on dividing the response spectrum of a record into several period ranges and finding the scale factor for each range. The proposed method is used for seven real acceleration records to generate seven synthesized acceleration records, with a response spectrum compatible with the design spectrum of Standard 2800 (3rd edition) for soil type 3. Besides, seven artificial acceleration records are generated using SIMQKE I. The nonlinear dynamic behavior of two 12-story RC buildings, which were designed by a direct displacement based (DDB) method and standard-2800, are used for comparison between the two groups of records. Results state that the proposed method is suitable for analyzing and designing structures without a noticeable increase in the values of the input energy of the real records.

Summary Urban subways in the ground would change its seismic movements. Designing ground surface structure in far filed is related to the horizontal component of acceleration at the ground surface in that area. Therefore, an attempt has been made in this study to change the frequency of soil-tunnel systems and to calculate the maximum horizontal acceleration of the ground surface due to tunnel presence through changing in tunnel placement depth, its diameter and its lining thickness as well as changing the soil properties. The maximum horizontal acceleration of the ground surface has been calculated in the presence of the tunnel for soil type 4 based on code 2800. The relationship between the maximum horizontal acceleration of the ground surface and the frequency of the soil-tunnel systems will result in the production of a horizontal acceleration spectrum. In the frequency range studied, spectral accelerations in models without a tunnel have mainly higher values compared to those models that have a tunnel buried in the soil. Amplification and deamplification of the ground surface acceleration is dependent on the period of soil-tunnel systems, the properties of the model under study and the position of the point studied at the ground surface. Introduction 9 acceleration records of known influential earthquakes, 33 models (in presence of tunnel) and 7 models (in absence of tunnel) have been used in this study. Overall, about 360 nonlinear dynamic analyses have been carried out. These analyses have been made for multilayered soil while the nonlinear effects of the soil and its interaction with the surrounding structures have been considered. Methodology and Approaches This study has been conducted on a Delhi subway tunnel. ANSYS and Plaxis2D software packages have been used for the study. The ANSYS software has been used for modal analysis, obtaining the frequencies and mode shape of the soil-tunnel systems, while the Plaxis2D software has been used to analyze the time history and obtaining the acceleration values of key points of the model. Elasto-plastic Moher-Coulomb model has also been used to model the soil. Results and Conclusions In most cases (11 out of 14 cases), amplification of ground acceleration is observed at a depth of 20 m. 9 of the 14 ground acceleration amplification are related to a tunnel with a smaller radius (3. 13 m). Whatever the tunnel center image is taken away from the ground surface, we will have higher number of points in which acceleration amplification of the ground surface occurs.

This paper suggests modified proportional navigation (PN) with a weighted combination of linear acceleration and line-of-sight (LOS) acceleration feedback. For this purpose, a comprehensive miss distance analysis is carried out for PN with linear acceleration feedback and PN with LOS acceleration feedback using a fifth-order binomial guidance and control system. The miss distance (MD) due to initial heading error, target acceleration, and seeker noise are separately analyzed. A modified PN with acceleration feedback using variable gains is suggested based on MD analysis for infrared seekers as a special case. The PN strategies are compared using an equivalent effective navigation ratio, defined using the LOS rate profile solution. In addition, the first-order optimal guidance law is converted into PN with PD block with variable gains.

Integration of global positioning system (GPS) and inertial navigation system (INS) is used in airborne gravimetry to gravity field recovery. Since GPS computed position is noisy therefore the GPS acceleration which is the result of twice differentiation of GPS position will be too noisy as well. In this paper IIR low-pass filter and Kalman filter are used to smoothing the GPS acceleration and their result compared to B-spline smoother result. B-spline smoothing accuracy is reported about 1mGal in this paper data, therefore B-spline smoothing considered as a reference smoothing method. The correlation of IIR low-pass filter and Kalman filter results with B-spline smoothing result is about 97.55 and 99.83 percent, respectively. It shows that the Kalman filter result is closer to B-spline smoother. On the other hand, along with ease of design of IIR lowpass filter some other advantages such as fast computing algorithm in signal processing unlimited response hit and less memory requirement are worth mentioning. Therefore, in project with huge among of data the IIR low-pass filter could be efficient and causes the time and cost saving. Mentioned smoothing methods can also be used in INS instrumental noise reduction. Therefore, less accurate INS can be used in integration with GPS, which causes the INS cost saving and project productivity promotion.

The area of Constantine being located in a seismic zone, the management on the parameter of seismicity requires a precise micro zoning. The compilation of the historical seismic data of the area of Constantine, as those of the neighbouring areas will make it possible to determine the impact of the historical seismicity on the maximal establishment on the ground which will be an essential data for the establishment of the response spectrum for the study area.