Ground motions records of the past higher magnitude (Mw>5) earthquakes have indicated that ground motions recorded at the closest distance of the near-fault are very different from those recorded from a higher distance from the site of the far-fault. Forward directivity and fling effect are the essential characteristics of the near-fault earthquakes; these can cause potentially high damage during earthquakes. Hence, to understand the effect of the far-fault and near-fault on the performance of the structure is vital to reduce the damage and perform an efficient response. In this paper, an attempt is made to evaluate the effects of far-fault and near-fault ground motions on the seismic performance of the concrete gravity dam incorporating the dam-reservoir-foundation interaction. An arbitrary gravity dam is considered as numerical example. In this, eight different earthquake records are considered for time history analyses. The seismic performance of the dam is evaluated using the cumulative-overstress-duration (COD) and demand-capacity ratio (CDR). The results obtained show the importance of the near-fault ground motion effect on the seismic performance of the concrete gravity dam.

Ground motions records of the past higher magnitude (Mw>5) earthquakes have indicated that ground motions recorded at the closest distance of the near-fault are very different from those recorded from a higher distance from the site of the far-fault. Forward directivity and fling effect are the essential characteristics of the near-fault earthquakes; these can cause potentially high damage during earthquakes. Hence, to understand the effect of the far-fault and near-fault on the performance of the structure is vital to reduce the damage and perform an efficient response. In this paper, an attempt is made to evaluate the effects of far-fault and near-fault ground motions on the seismic performance of the concrete gravity dam incorporating the dam-reservoir-foundation interaction. An arbitrary gravity dam is considered as numerical example. In this, eight different earthquake records are considered for time history analyses. The seismic performance of the dam is evaluated using the cumulative-overstress-duration (COD) and demand-capacity ratio (CDR). The results obtained show the importance of the near-fault ground motion effect on the seismic performance of the concrete gravity dam.

The Endurance Time (ET) method is a time-history based dynamic pushover procedure. In this method, the structures are subjected to gradually intensifying acceleration called an acceleration function. Then, their performances are assessed from linear to collapse level based on the interval time through which they can satisfy the required objectives. ET Acceleration Functions (ETAFs) are calibrated upon actual earthquake spectra compatible with the Iranian National Building Code (standard no. 2800). In this code, there is no distinction between far and near fault regions. ETAFs scale based spectrum increases uniformly at all periods as the time passes which is why this uniform increment is not desirable in near fault earthquakes. As the rupture propagation is oriented towards a site, near fault earthquakes have further spectral acceleration in the period over 0.6 sec compared to far fault earthquakes. The shape of the spectrum becomes richer over long periods as its level increases. In this research, ETAFs are presented for near fault target spectra, provided by Abrahamson-Silva attenuation relations. These relations have been modified by Somerville near fault correction coefficients. According to the results obtained in this research, while the new acceleration function can model directivity effects at higher periods, it also satisfies endurance time concepts.

Near-fault ground motions have caused very much damage in the vicinity of seismic sources during recent earthquakes. It is well known that under specific circumstances, intensive ground shakings near fault ruptures may be characterized by short-duration impulsive motions.This pulse-type motion is generally particular to the forward direction, where the fault rupture propagates towards the site at a velocity close to shear wave velocity. Ground motions affected by directivity focusing at near-field stations contain distinct pulses in acceleration, velocity and displacement histories. These ground motions can generate much higher base shears, inter-story drifts and roof displacements as compared to far-fault ground motions. Since structures under the effect of destructive earthquakes enter an inelastic phase, so the study of inelastic behavior of structures under the effect of such earthquakes seems to be important. This study examined maximum acceleration, velocity, displacement of the roof mass center, inter-story drifts and base shears of building in inelastic state at moment steel frame buildings designed on the basis of buildings design code against earthquake (2800 Standard, the third edition) under the near-fault records and the comparison of these parameters with the simulated ones. The results indicate that the maximum demand of drift of stories, acceleration, velocity, displacement of roof mass center and inelastic base shear and the way of hinge formation in non-linear state under the near-fault records is the same as simulated records in short buildings. Moreover, the more the height of structure becomes, the more different the behavior of structure becomes and the response is affected by more faults or errors.

In this paper, the behavior of a fault is studied using a constant strain joint model. A combination of slider and spring is used to simulate the shear behavior of faults in the plastic region in contrast to the previous models that have only used an elastic shear spring. Furthermore, the proposed joint element was used to study the behavior of a fault crossing a tunnel regarding the represented shear plastic and dilation behavior of this joint element, and for this purpose a Matlab based program called FEAFB (Finite element analysis of fault behavior) has been developed. The corresponding normal and shear stresses, shear strengths and the factors of safety, for different horizontal to vertical stress ratios and shear stiffness are analyzed and compared to the results of a similar modeling in UDEC program. The analysis indicates that the normal and shear stresses, and the shear strength are increased in the fault elements near the tunnel, and they are decreased in the elements becoming far from the tunnel surface. However, the safety factor can either increase or decrease as it becomes closer to the tunnel surface, depending on the horizontal to vertical stress ratio. Moreover, it is also shown that safety factor depends upon the shear stiffness, i.e., as shear stiffness increases, shear stress increases, and as a result, the safety factor decreases.