Journal of Seismology and Earthquake Engineering
Volume:16 Issue: 2, Summer 2014

The 7.8 M earthquake occurred in south east Iran on 16 April 2013 at 10:44:20 UTC. This earthquake was the most massive earthquake in last 50 years, with tremors felt across Pakistan, Oman and UAE. According to BHRC (Iranian Building and Housing Research Center) report, this event was recorded by 33 digital accelerographs in Iran Strong Ground Motion Network. The peak acceleration was recorded in Sabz Gazz seismic station. This study presents simulation of near-field ground motions of the 2013 Iran earthquake. For this purpose, five seismic stations are selected to simulate ground motions using semi-empirical approach. Hamzehloo and Mahood (2012) attenuation relationship for south east Iran is used to obtain acceleration waveformenvelope function. Acomparison is done on characteristics of observed and simulated ground motions. The simulated results are satisfactory at many of the seismic stations. It is concluded that higher frequencies (2-10 Hz) of simulated ground motions match with observed ground motions.

In this paper, cylindrical cavities under pressure located in full space and half space are separately analyzed. Boundary element method formulated in frequency domain is used to discretize the boundary of the problems. Infinite boundary included in the problems is modeled by a special boundary named enclosing boundary. The response in the time-domain is then obtained from the frequency domain solution using Fast Fourier Transform (FFT) technique. The proposed approach is applied to Selberg problem, which consists of a cylindrical cavity in a full space loaded normal to its wall as well as the one in a half space with the same loading condition. Comparison of the obtained results with the closed form and existing numerical solutions shows that the enclosing boundary of any shape can effectively be used to model radiation of the outgoing waves into infinity. It has also been shown that the Poisson's ratio of the medium is a predominant parameter, which can influence the response of the underground cavities.

The applied loads on structures caused by fault rupture can be divided into vertical and lateral loads. There is a common agreement between researchers that diagonal piles would performbetter than vertical piles under lateral loads. However, an area of uncertainty still remains: Would the diagonal piles still perform better under various load combinations? The 1999 Kocaeli earthquake was an appropriate case for monitoring the performance of vertical piles. In this paper, based on the evidence provided byKocaeli earthquake, a study has been done to compare the vertical and diagonal piles behavior. This study is conducted in two analysis steps. First, surface fault rupture is propagated through soil in the free-field. Second, the models of the piles group is subjected to a differential displacement the same as Step 1. Totally, it can be concluded that the acceptable performance of diagonal piles group occurs only when the fault emerges near the left center of cap. Otherwise, the vertical piles group would perform better.

Due to the spatial variations of the strong ground motions and Near-Field (N-F) effects, significant and unexpected damages have been observed in long-span bridges during past earthquakes. One of the outstanding characteristics of N-F motions is the forward directivity effect seen as a single, intense, long period pulse at the beginning of velocity records in the fault-normal direction. To better understand the effect of this pulse and the wave passage effect of spatially correlated motions on the seismic response of long-span bridges in comparison with these bridge's response to the far-field earthquakes, a comprehensive case study has been done in three parts on the finite element model of a long-span bridge: 1) Uniform excitations of the model bridge with forward directivity pulses and the original records; 2) Asynchronous excitations with different shear wave velocities for impulsive part of the inputs; and 3) Comparison of the wave passage effect of two sets of near-field and far-field strong ground motions (SGMs) on the seismic response of the model bridge. The results showthat the wave passage effect of forward directivityN-F pulses can have significant influence on the bridge nonlinear response, and it becomes more evident in the soft soils causing severe seismic demands. Even in the case of rock sites, ignoring this effect can result in under-designed piers. Besides, comparison of the near-field and far-field SGMexcitations effect on the bridge response indicates that although in uniform excitations both sets cause approximately the same displacement response values, in the case of asynchronous inputs, the N-F records can produce larger ductility demands.

Dynamic behavior of Tanks under seismic loads is generally nonlinear and has been widely studied by numerous researchers. This was first introduced by Jacobsen and after that, the new method was introduced by Housner for the rigid cylindrical tanks. Fluid vibration induces hydrodynamic pressure on the wall and hence, Housner assumed and classified the seismic response of the rigid tanks into two impulsive and convective components. The Impulsive pressure is caused by the coordinated motions of a fluid part in the tank with the rigid wall of the tank, and the convective pressure is caused by the motion of the other part of the fluid on the tank's free surface. In this paper, a cylindrical steel tankmodel with a diameter of 120 cm, wall height of 125 cmand fluid depths of 60, 80, 100 and 120 cmhas been tested under Tabas, El Centro and Irpinia Earthquakes on the shaking table in the International Institute of Earthquake Engineering and Seismology. The purpose of the experiments was to determine the damping of the impulsive and convective modes of the mentioned tank and to compare the experimental results with the proposed values by API650 Code.

This work presents a study on the seismic assessment of steel frames with Friction Damper Devices (FDDs). The devices were used to dissipate seismic input energy and protect buildings from structural and nonstructural damage during moderate and severe earthquakes. In the Endurance Time (ET) method, structures are subjected to a specially designed intensifying ground acceleration function and their performance is judged based on their response at various excitation levels. In this paper, steel moment frames equipped with FDDs is investigated under Nonlinear Time History (NTH) and ET analyses. According to the NTH and ET results, it is concluded that by adding FDDs, the reduction percentage of roof displacement of frames will be decreased by increasing the number of stories. ET results show that FDDs have a vital role in energy dissipation because their hysteresis loop is rectangular.