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A dynamic analysis of elastic–viscoplastic systems, incorporating the modal co-ordinate transformation technique, is presented. The formulation results in uncoupled incremental equations of motion with respect to the modal co-ordinates. The elastic–viscoplastic model adopted allows the analysis not to involve yielding regions and loading/unloading processes. An implicit Runge–Kutta scheme together with the Newton–Raphson method are used to solve the non-linear constitutive equations. Stability and accuracy of the numerical solution are improved by utilizing a local time step sub-incrementing procedure. Applications of the analyses to multi-storey shear buildings show that good results can be obtained for the maximum displacement response by including only a few lower modes in the computation, but the prediction of the ductility factor response tends to underestimate the peak values when too few modes are used. In addition, stable and valid results can be obtained even with a sizable time step increment. 相似文献
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The quasi-static development of the force, pore pressure and displacement is obtained in the system of a circular elastic pile partially embedded in a saturated porous elastic soil, and loaded axially on the top. The porous elastic soil is governed by Biot's theory. The problem is decomposed into two systems, namely, an extended porous elastic half-space in the absence of the pile characterized by the material constants of the medium, and a fictitious pile represented by a Young's modulus equal to the difference between the Young's moduli of the real pile and the medium. The problem is found to be governed by a Fredholm integral equation of the second kind. Laplace transforms are applied to time functions involved, and Hankel transforms to the radial coordinate of which the origin is at the centre of the pile. Numerical solutions are obtained for final and initial solutions for various practical values of the parameters involved. 相似文献
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This paper presents a method for the analysis of free field ground motions at various depths from actual seismograph records. The proposed method replaces the propagating rupture on the fault surface by a fictitious focal point and a seismograph station in the vicinity of the given soil site. A fictitious focal point and seismograph station scheme is used to calibrate the free field ground motion of the soil site. The harmonic vibration analysis of the half space, which elastodynamic infinite elements are adopted in the far field and finite elements in the near field, yields the Fourier transform of any constituent wave in terms of the amplitude of the forces applied at the focal point, thus in terms of the Fourier transforms of the accelerations in three orthogonal directions recorded at a seismograph station. If a seismograph station is in the far field (as it is usually), the recorded values there can be transformed into the values at the infinite element node by means of appropriate shape functions. The results can be more refined in case of the availability of simultaneous records at more seismograph stations. In case of N stations, we assume N fictitious focal points, and solve a set of 3N simultaneous equations of 3N forces, three orthogonal forces at each focal point. Naturally, only the results by the present method were ‘exact’ at the calibrated points, and should be accurate in-between and near those points. The accelerations at the points near seismograph stations at various depths can also be obtained. An appropriate inverse Fourier transform algorithm will properly yields all results as time functions. 相似文献
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This study endeavors to show the inadequacy of thin beam eigenfunctions commonly used to represent displacement profiles of tall buildings in the finite strip analysis. Particularly, the model fails to reflect the correct building behaviour whenever the storey-shear distortion may be significant. An attempt is made, therefore, to develop a new set of strip shape functions that is free of the above shortcoming. A polynomial series is specially constructed and shown to be effective for all building types. Several tall building examples are tested and the results clearly exhibit the versatility and surprisingly high accuracy of the proposed finite strip model, in both static and free vibration analyses. 相似文献
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