Journal of Seismology and Earthquake Engineering
Year:2001 | Volume:3 | Issue:1|Papers Count:5

The purpose of this work is to evaluate the regional seismic hazard for Morocco, following the deterministic approach proposed by Costa et al [1], based on the computation of complete P-SV and SH synthetic seismograms. The input for the computations is represented by source and structural models. Seismic sources are parameterized using the knowledge about past seismicity and the tectonic regime. The regional structural model we adopted is the one proposed by Cherkaoui [2], modified in its shallower part to account for the effects of the uppermost sedimentary layers. Maps of peak acceleration, velocity, and displacements are used for the general representation of the hazard. Accelerations are in good agreement with the values determined by Jimenez et al [3] with the standard probabilistic approach.

Dynamic behavior of a multiple supported secondary system mounted on a torsionally coupled primary system is presented for bi-directional random ground excitation, which is idealized as a broad band stationary random process. Response behavior of the multiple supported secondary system is investigated by considering and ignoring the interaction between the primary and the secondary systems. The response quantities of interest are the standard deviation of the absolute acceleration at a specified node and the bending moment at a specified support of the multiple supported secondary system. For the no interaction case, input to the support of the secondary system is prescribed in the form of both pseudo and cross power spectral density function (PSDF), characterizing the correlation between various supports of the multiple supported secondary system. For the interaction case, the conventional ground PSDF can directly be used as input to the combined structural system. The responses are obtained by the frequency domain spectral analysis. The responses are obtained under a number of important parametric variations. Numerical results of the study show that the responses decrease with the increase in the mass ratio between the secondary and the primary system. Under the tuned condition, a definite maxima is observed for the higher mass ratio. For strong and weak torsionally coupled primary systems under the tuned and interaction conditions the normalized acceleration show a definite minima when orientation of the secondary system is 45°0 with the major axes of the primary system. For the other cases, the response quantities show a definite maxima at this orientation.

The geotechnical characteristics of the soil layers is one of the main factors influencing liquefaction potential of the ground. The standard penetration test (SPT) had been extensively used to measure the in-situ soil properties due to its simplicity and availability all over the world in the majority of the liquefaction studies. Nevertheless, it suffers from some shortcomings in comparison with another in –situ test called cone penetration test (CPT). In order to compare the liquefaction potentials based on the SPT data with those based on the CPT data, some sites in the southern parts of Iran have been selected and studied. The geotechnical characteristics of these sites have been measured both from SPT and CPT methods, and for the same seismicity condition, the liquefaction potential were estimated using the SPT and CPT based evaluation methods. At the end some correlations were derived between the obtained results and their validities were discussed and justified. Although the correlation factor was found to be very small and the results were highly scattered, it could be concluded that the liquefaction evaluation methods based on the SPT data show more conservative results compared with those based on the CPT data.

Results of seismic damage evaluation of a tall reinforced concrete building are presented. Plastic hinge formation patterns obtained by using DRAIN-2D and IDARC computer programs for dynamic analysis are compared. Damage indices given by IDARC are interpreted and their implications compared with those of drift ratios. Results of static push-over analysis are compared with those of inelastic dynamic time history analysis. Moreover, the result of collapse mechanism approach is compared with that of static push-over analysis. It is shown that simple collapse mechanism approach can predict the failure mode given by static push-over analysis for this building. It is concluded that drift limits in codes do not necessarily predict the degree of damage that this type of construction can sustain in severe earthquakes.