Journal of Seismology and Earthquake EngineeringJournal of Seismology and Earthquake Engineering
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Feed provided by Journal of Seismology and Earthquake Engineering. Click to visit.Effects of Change in the Parameters of Initial Water Displacements on Energy and Amplitude ...
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In tsunami modeling, usually, the source parameter of an earthquake or landslide is computed by geophysicists, and an initial water displacement precisely similar to the seabed dislocation created by the source is obtained. Next, the initial water displacement is propagated in a predefined mesh grid using Computational Fluid Dynamics (CFD). Here, aside from the source of an earthquake or landslide, we have proposed a formula consisting of three scaling's and one rotation parameter, for creating a 3-D Initial Water Displacement (IWD). Each time one parameter was changed, and the resulting initial water displacements were modeled in a sea like modeling area. The propagated wave was recorded by the four arbitrary tide gauges at different depths near the shore. The finite difference method was used as our numerical modeling scheme in a mesh grid consisting of 100 × 150 km with an equal grid resolution of 500 m having reflective boundaries. The ratio of maximum amplitude and energy of the signal was computed in all of the arbitrary tide gauges. The results show that if an IWD is extended in the direction of the shoreline, theimpact would be much lower than when the IWD is extended perpendicularly to the shoreline. The result of this study is beneficial in obtaining maximum amplitude and energy of IWD's with variable scaling and rotation parameters. Moreover, our method can be further extended to obtain charts with more values assigned to these parameters.Fri, 18 Sep 2020 19:30:00 +0100Seismic Performance of Deep Excavations Restrained by Anchorage System Using Quasi Static Approach
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Soft grounds amplify the earthquake motions and the peak ground acceleration increases when passing through them. Thus, the response of structures constructed on such sites would be more severe than others. The deep excavations are one of the most vulnerable geotechnical structures during earthquakes particularly when performed in soft grounds. Hence, they have to be stabilized and restrained for these circumstances. Using the anchorage system is one of the most common methods to stabilize such excavations. The influence of different factors such as soil characteristics, and anchors' geometry and properties on seismic response of so-called restrained deep excavation is an important issue that needs to be focused on. In the present paper, the results of quasi-static finite element analyses of deep excavations performed in soft and stiff grounds during earthquake loadings have been presented, compared and discussed. The results show that considering adequate values for the anchor parameters (such as; angle, length and distance between the anchors and the amount of pre-stress force in them) leads to accurateand satisfactory design safety and deformation controls of the excavationSun, 22 Nov 2020 20:30:00 +0100Experimental and Numerical Investigation of Steel Frame with Shear Panel at Mid-Span
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During the last two decades, the semi-supported steel shear wall (SSSW) has been introduced as an alternative to the traditional form of steel plate shear wall (SPSW) system. In this paper, a numerical and experimental study on the behavior of a pinned connection steel frame with a mid-span shear panel, as well as the effect of opening existence on the system behavior is investigated. In this system, shear panel consisting of infill steel plate, stiffeners perpendicular to infill plate and secondary columns are placed in the middle of the steel frame span with pinned connections and unlike conventional SPSW system and SSSW system, the buckling of the infill plate is prevented and energy dissipation is carried out by shear. Experimental studies were performed on two specimens with a scale of 1:2. The characteristics of both specimens are the same and the only difference is the presence of opening in the second specimen. The results showed that in both specimens, the hysteretic curves were spindle-shape and without pinching. Moreover, numerical results were in good agreement with the experimental ones. Numerical studies showed that the energy dissipation and shear strength were increased with decreasing the opening ratio as well as decreasing height to thickness ratio of the infill plate. For example, in models with slenderness ratio of 200, the dissipated energy and maximum strength in the model with an opening ratio of 0.4 were about 47% and 38% less than that of the model without opening, respectively.Fri, 18 Sep 2020 19:30:00 +0100Behavior of Tunnels against the Reverse Faulting Deformations Using Centrifuge Test and ...
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The permanent ground deformation during the earthquake faulting induces moderate to severe damages to the underground tunnels. The majority of the investigations on the behavior of the tunnels against fault offset were in the rock medium. There is very little available in the literature about the fault-tunnel interaction in alluvial soil. This paper has studied the interaction between a continuous tunnel and reverse faulting within a dense sandy alluvial deposit. An experimental centrifuge test, alongside the numerical modelling, has been utilized for this purpose. It has been shown that the longitudinal strains of an infinite tunnel were much higher than that of a finite length tunnel. The results have also displayed that there are critical cross-sections along the tunnel's length that maximum curvatures, moments, shears, and axial forces occur in them. The numerical parametric study on the variation of the Fault Zone Width (FZW) and reinforcement content (rs) have shown that higher rs values would be more useful in tunnel resistance against faulting. Besides, smaller FZW will make higher deformations, moments, and forces in the concrete lining. The optimum rs value has been obtained as 4%.Fri, 18 Sep 2020 19:30:00 +0100Neighbour Matrix for Optimal Seismic Design of RC Frames for Minimum Total Life-Cycle Cost
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Structures are subjected to different probable earthquake excitations in their lifetime, which have different destructive effects. Life-cycle cost analysis is an appropriate tool for assessing the structural performance to obtain the best economic scenario over its lifetime. Therefore, it is necessary to define a method for optimal seismic design with life-cycle cost objective. However, the nonlinear behaviour of structures under severe earthquakes and the need to synchronize the various constraints of the seismic code require use of innovative methods instead of optimal classical methods. In this paper, the total life-cycle cost of buildings is the optimization objective for the seismic design of reinforced concrete frames.Therefore, a simple novel optimization algorithm is introduced by defining "Neighbours Matrix". This algorithm reaches a path to minimize the objective throughout the steps, based on changing the objective function in "Neighbour RC frames". The results of optimum seismically design of RC frames including 5-, 8- and 12-story frames indicated that this algorithm reached optimum RC frame with acceptable performance and few numbers of analyses. Also the convergence rate was high because when total life-cycle cost was the objective function, after two steps with a small number of analyses, the TLCC was decreased about an average 25%. The robustness of the algorithm was confirmed by evaluation of the coefficient of variation of structures in the optimal path.Sun, 22 Nov 2020 20:30:00 +0100Reliability Analysis of Seismic Stability of Gotvand Dam, Southwest of Iran
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Seismic design of an embankment dam is a vital step in the design procedure of this important infrastructure. Deterministic approaches such as quasi-static and Newmark method have been employed to evaluate slope stability of embankmentdams. However, the variables required for a slope stability analysis, e.g. soil strength, pore pressure and loading parameters involve uncertainties which cannot be handled in the traditional deterministic methods. As an alternative, reliability analysis might be conducted to assess reliability indexes and the related failure probability of embankment dams. In this study, based on probability theories, a reliability analysis is performed to evaluate the seismic stability of an embankment dam (i.e., Gotvand dam) constructed in Iran. The probability of failure under seismic loading is considered for different sources of uncertainties involved in the problem, including uncertainty of loading, and the friction angle of core material as a strength parameter. Employing some statistical parameters, dynamic analysis is performed to determine the influence of friction angle variation on seismic slope stability. Significant pore pressure may build-up during cyclic loading, especially, when mixed clay (mixed clay and gravel) constitutes the dam core. Also, an undrained behavior of core materials has a great importance. Therefore, to estimate the effect of pore pressure build-up during seismic loading, two types of core materials (pure clay and mixed clay) are considered in this research. The results of dynamic analysis by finite element method are used to obtain the critical surface and acceleration in the embankment. Then, Newmark approach is employed to calculate the permanent displacement of the dam. Finally, reliability analysis is conducted and seismic performance of Gotvand dam during the earthquakes is investigated.Fri, 18 Sep 2020 19:30:00 +0100