Nowadays, various types of passive control systems are being used as an effective solution to reduce the seismic responses of structures. One type of these systems, the Tuned Liquid Column Damper (TLCD), suppresses the input seismic energy by a combined action, including the movement of liquid mass in the container, a restoring force on the liquid, due to gravity loads, and the damping, due to liquid movement through the orifices. In this paper, the possible effects of seismic excitation characteristics, such as frequency content and soil condition, on the seismic performance of TLCDs, are investigated, using nonlinear time-history analyses. For this purpose, a ten-story building was modeled as an elastic MDOF structure and used for numerical analyses. For the time-history analyses, among the past strong ground motion records of Iran, 16 records with different characteristics were selected. The results of this study show that these characteristics play a substantial role in the performance of TLCDs and they should be, accordingly, considered in the designing of TLCDs. In some cases, TLCD is able to reduce structural displacement up to 50%, while, in most cases, the effectiveness of TLCD in reducing structural acceleration is not significant. However, it should be mentioned that, in real applications, de-tuning may occur, due to the inelastic behavior of structures, which can reduce effectiveness. This study also shows that the displacement reduction capacity of TLCDs is highly dependent on excitation characteristics, while the acceleration reduction capacity is not that sensitive.

The need to construct structures on soft and unstable soils due to the appropriate technical and economic conditions has led to the development of various soil remediation methods. Moreover, the experience obtained from recent earthquakes has indicated the influence of sites’ stiffness on the surface seismic ground response. One of the ways to increase the stiffness to improve the soil, especially in soft soils, is to employ inclusion piles. These types of piles can be used at the bridge's piers to reduce the seismic response of the aboveground structures. In this regard, the role of the geometry characteristics of the inclusion piles can be significant. This paper investigates the effect of changes in the geometric parameters of inclusion piles such as diameter, length, the distance between them, and surcharge on the ground seismic response based on the offshore Turkish Izmit Bridge as a case study and base model. The effective depth was obtained by comparing the ground response spectrum of the two-dimensional model with inclusion piles using FLAC2D software based on the nonlinear hysteresis model, with the depth equivalent to the acceleration response spectrum of the free-field model. The geotechnical subsurface conditions at the North Tower Izmir bay bridge consist of 10 meters of loose to medium dense sand layers with silt, underlain by 127 meters of dense sand and hard sand clay. Bedrock lies approximately 144 meters below the mudline datum. The 1D responses obtained from the FLAC 2D and DEEPSOIL 1D software have been compared using the nonlinear soil behavior to verify the numerical modeling results. Then, with the calibration of soil parameters and lateral and bottom boundaries, inclusion piles have been added to the validated free-field model in FLAC2D software. In this study, the 2D modeling process includes introducing soil layers’ characteristics and determining the lateral free-field boundaries and the quiet boundary as the bottom boundary subjected to the seven earthquake excitations is performed. The inclusion pile was modeled using the beam and cable combine elements in the FLAC2D. Besides, inclusion piles are two-dimensional elements with 3 degrees of freedom (two displacements and one rotation) at each end node. Piles interact with the FLAC grid via shear and normal coupling springs. The obtained results indicated that by increasing the ratio of distance to the diameter of inclusion piles (S/D), the effective depth decreases due to reducing the stiffness of the inclusion pile system, and after reaching a ratio of 5, it has reached a constant value. In other words, with increasing stiffness of the soil-pile system, the effect of kinematic interaction on the soil-pile system increases. Moreover, by increasing the length to diameter ratio of inclusion piles (L/D), the effective depth will first increase and then reach a constant value, in which the optimal range for the length to diameter ratio of piles is 15 to 30. Also, the effective depth increases linearly with an increasing surcharge ratio above the inclusion piles ( q ). Finally, it should be noted that the soil improvement using inclusion piles due to the kinematic interaction can apply a new foundation input motion altered from the free-field ground response. This interaction increases the effective depth of the equivalent free-field model, which can reduce responses of the aboveground structures (e. g., buildings or bridges, etc. ). Therefore, the use of this type of piles due to having more stiffness than traditional soil improvement approaches such as stone columns or deep soil mixing, etc., can be effective in order to optimally design structures located on loose or soft saturated soils.

A Markov method of analysis is presented for obtaining the seismic response of suspension bridges to nonstationary random ground motion. A uniformly modulated nonstationary model of the random ground motion is assumed which is specified by the evolutionary r.m.s ground acceleration. Both vertical and horizontal components of the ground motion are considered to act simultaneously at the bridge supports. The analysis duly takes into account the angle of incidence of earthquake, the spatial correlation of ground motion and the quasi - static excitation. A suspension bridge is analysed under a set of parametric variations in order to study the nonstationary response of the bridge. The results of the numerical study indicate that (i) frequency domain spectral analysis with peak r.m.s acceleration as input could provide more r.m.s response than the peak r.m.s response obtained by the nonstationary analysis; (ii) longitudinal component of the ground motion significantly influences the vertical vibration of the bridge; and (iii) the angle of incidence of earthquake has considerable influence on the deck response.

Introduction  A significance of seismic studies is that the correct seismic analysis of any type (seismic hazard analysis, seismic risk analysis, ground seismic response analysis, seismic site effects, and structural dynamic analysis) can offer useful economic parameters and avoid conservative design and implementation, which lead to an irrational increase in project costs and poor implementation, which in turn causes increased risk and possibility of destruction. According to the seismotectonic map of Iran (Berberian, 1976), earthquakes in Alborz are shallow. There are also some intermediate earthquakes, and overall, the eastern Alborz is more earthquake prone than the western Alborz [1].Materials and MethodsThe maximum magnitude (Mmax) is usually estimated based on the general characteristics of seismic activity and geological similarities. In applied studies, Mmax is often estimated based on correlation of seismic magnitude and different fault parameters such as rupture, fracture surface area, maximum surface displacement, and seismic moment release rate. Multiple correlations have been proposed to relate these parameters and the earthquakes magnitude. (Table 1) shows some correlations by different scholars. Correlations in (Table 1) were used to calculate the maximum empirical magnitude [3].Table 1. Correlations between the earthquake magnitude and different fault parametersCorrelationProposed byNo.Ms=5.4+LogLRMohajer and Nowroozi (1978)1Mw=3.66+0.91LnLRZare (1995)2Ms: Surface wave magnitude                                                          Lf: Fault length (km)Mw: Moment magnitude                                                                  LR: Rupture length (km) Seismicity Parameter EstimationThe K-S method was used to achieve seismicity parameters within the scope of this study [2].Discussion and ResultsThe results of probabilistic seismic hazard analysis were calculated using attenuation relationships Zare 1999 [4], Ambraseys 1995, Boore, Joyner and Fumal 1981in studying region. These results are presented in (Table 2) and (Table 3).Table 2. strong vertical ground motionReturn periodH.PGA(g)4750.2524750.44Table 3. strong Horizontal ground motionReturn periodH.PGA(g)4750.4224750.70 ConclusionThe recent Malard Earthquake with a magnitude of 5.2 on the Richter scale and multiple earthquakes with magnitudes above 4 have increased the importance of seismic studies in the region. Seismic hazard studies are among the key preliminary urban development studies for preventing seismic vulnerability. The identification of seismic source zones is closely related to development infrastructure in any region. The results of these studies are widely used in vital projects such as water, gas, oil transmission lines, dam and airport construction, and residential development, and overlooking them may cause great damages. The earthquake hazard analysis based on the accurate location of seismic zones will provide more reliable results. The investigation of the region under study, its history of seismicity, and the recent earthquakes indicate the existence of seismic activity in the region. Considering the shallow depth of earthquakes, the intensity of earthquakes occurred in the region is high. Moreover, the calculation of β and λ parameters (ranging from 6.2 to 7.6) shows the seismicity of the region, indicating the need for observing safety measures in the constructions in the region. As mentioned earlier, the recent seismic activities and earthquakes in the region have doubled the importance of seismic studies and measures for strengthening seismic stations in the region. Moreover, the review of seismic catalogs show that the study area has been inactive over the past few decades and hence its sudden activity is quite significant. Also according to the calculations, Alborz Province is located in highly active seismic zone.

Today by increasing of earthquakes and population growth and development of building industry in city or country areas, building designing against applied loads especially earthquake load have regarded by engineers. Also for supplying of life and financial safety, buildings should have appropriate performance against applied loads. In this research work, influence of scaling of near-fault and far-fault records have been treated in 4 codes 2800 Iran, 4th edition, ASCE07, IBC 2006 and UBC 97 Simultaneously. In this study 3 buildings have been used in 4,7 and 10 stories as indicators of low-rise and mid-rise buildings. The results show that in low-rise and mid-rise buildings Iranian earthquake code scaling has stricter rules to other regulations. By increasing of stories in tall­-building (10 story) every four regulations has their own performance and could be maximum according to the kind and characteristic of earthquake (PGA, Mw). In fact, regulation of 2800 Iran, 4th edition, requires separated scaling rules for low-rise and mid-rise buildings. Drift ratio in ASCE07-10 has decreased %94 to 2800 Iran. Also this value for IBC2006 %93 and for UBC %89 has decreased.

For extended structure, the seismic load has a spatiotemporal variation that simultaneously changes with time and space. The incorporation of the seismic wave spatial random variability effect is especially important when large structures such as long bridges, dams, and large buildings are analyzed. The effect of spatially varying earthquake ground motion (SVEGM) on the seismic response of earth dams is analyzed in this paper. To this end, a parametric study is conducted to investigate the effects of length to height ratio ( ) on the 3D seismic response of the studied dams. Ground motions, consistent with the three-directional lagged coherency model, are generated at different discretized cells at the base of the dam. The dams are assumed to sit on trapezoidal and V-shaped canyons and vibrate in all three directions, upstream-downstream, vertical, and longitudinal. The average coherency of different frequencies is calculated and used for the generation of SVEGM. The time histories are simulated using a spectral representation-based method. The separation distance between the cells is determined in such a way that 90% of correlation between seismic input motions can be captured. For each case of  ratio, a numerical model of the dam and its foundation is constructed using the finite difference numerical method. The 3D seismic behavior of the earth dams is evaluated under the artificially generated three-directional components of SVEGM. Generally, it is concluded that with increasing  ratio, at the midpoint of the dam crest, the difference between maximum of acceleration values obtained by applying uniform and SVEGM excitations decreases. In all cases of analyses, SVEGM has decreasing effect on the vertical displacement of dam crest.