Earthquake ground motions are affected by the earthquake magnitude, topographic features, and the geological structure of the ground, as well as the distance of the area under the earthquake to fault. The ground motions close to the fault are quite different from ground motions away from the seismic source. The ground motions, which are at about 20 km from the rupture are generally named as near-fault (NF) ground motions [1][2][3][4]. Some recent earthquakes like as Northridge 1994, Kobe 1995, 1999 Chi-Chi etc. are known as a short-duration impulsive motion that exposes the structure to high input energy at the beginning of the motions [5]. These motions have velocity pulse amplitude. This specialty cannot be seen in records obtained far-field (FF) regions [6]. The velocity pulse duration must be larger than 1.00 second and also the ratio of the peak ground velocity (PGV) to the peak ground acceleration (PGA) must be larger than 0.10 second [7].Two main categories of the NF ground motions are fling-step and forward-directivity, respectively. The fling-step motions cause permanent static displacement in ground, whereas directivity effects do not create permanent displacement. Comparison to the FF ground motions, directivity-effects having the long-period and high-density and the fling-step effect causing permanent static ground displacements, are destructive for structures [8].
Minarets are one of the specific structure types used commonly in Islamic Countries. Many minarets were damaged or collapsed during catastrophic events like earthquake. During an earthquake to understand the minarets' behavior are so important since dynamic response of these structures depends on a detailed understanding of their structural characteristics, such as geometrical shape, supporting system, mode shapes, natural frequencies and modal damping ratio etc. This paper examines in detail a Turkish style reinforced concrete (RC) minaret, its finite element modeling, modal analysis and earthquake analysis. A reinforced concrete minaret which is generally built in Turkey is selected as an application. Three-dimensional (3D) model of the minaret and its modal analysis are performed to obtain analytical frequencies and mode shapes using ANSYS finite element program. The minaret's linear transient analysis is carried out using the 1992 Erzincan earthquake ground motion record to obtain the earthquake behavior of the minaret. At the end of the study, the calculated displacement responses and maximum-minimum principal stresses concentrations for the minaret are briefly discussed and illustrated.
In this study, a coupled model based on the boundary element and the finite element methods is used to analyze the dynamic responses of two-dimensional model resting on layered soil medium under spatially varying ground motion effects. The dynamic response of the soil-structure systems is obtained in the frequency domain. The results of the finite element and the coupling finite-boundary element models are compared with each local soil conditions. In the seismic analysis of the system, the substructure method is employed. In the standard finite element model, both the structure and semi-infinitive soil medium are modeled by the finite elements, however, in the coupling finite-boundary element model, the structure and the soil medium are modeled respectively by the finite and boundary elements, both. In the last method, the special features and advantages of two methodologies are considered. In the coupling of finite-boundary element method, the equivalent finite element approach is used in which the boundary element region is transformed as an equivalent finite element and the final system is solved as a stiffness problem. Results of the study show that the coupling finite-boundary element method can provide realistic and effective modeling of soil-structure interaction problems as compared with standard finite element method results.
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