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In structural engineering, the Bouc–Wen model of hysteresis is used to describe non-linear hysteretic systems. It was introduced by Bouc and extended by Wen, who demonstrated its versatility by producing a variety of hysteretic patterns. This model is able to capture, in analytical form, a range of hysteretic cycle shapes matching the behaviour of a wide class of hysteretical systems. Due to its versatility and mathematical tractability, the Bouc–Wen model has gained popularity. It has been extended and applied to a wide variety of engineering problems, including multi-degree-of-freedom (MDOF) systems, buildings, frames, bidirectional and torsional response of hysteretic systems, two- and three-dimensional continua, soil liquefaction and base isolation systems. The Bouc–Wen model, its variants and extensions have been used in structural control—in particular, in the modeling of behaviour of magneto-rheological dampers, base-isolation devices for buildings and other kinds of damping devices. It has also been used in the modelling and analysis of structures built of reinforced concrete, steel, masonry, and timber. ==Model formulation== Consider the equation of motion of a single-degree-of-freedom (sdof) system: here, represents the mass, is the displacement, the linear viscous damping coefficient, the restoring force and the excitation force while the overdot denotes the derivative with respect to time. According to the Bouc–Wen model, the restoring force is expressed as: where is the ratio of post-yield to pre-yield (elastic) stiffness, is the yield force, the yield displacement, and a non-observable hysteretic parameter (usually called the ''hysteretic displacement'') that obeys the following nonlinear differential equation with zero initial condition (), and that has dimensions of length: or simply as: where denotes the signum function, and , , and are dimensionless quantities controlling the behaviour of the model ( retrieves the elastoplastic hysteresis). Take into account that in the original paper of Wen (1976),〔 is called , and is called . Nowadays the notation varies from paper to paper and very often the places of and are exchanged. Here the notation used by Ref.〔Song J. and Der Kiureghian A. (2006) Generalized Bouc–Wen model for highly asymmetric hysteresis. Journal of Engineering Mechanics. ASCE. Vol 132, No. 6 pp. 610-618〕 is implemented. The restoring force can be decomposed into an elastic and a hysteretic part as follows: and therefore, the restoring force can be visualized as two springs connected in parallel. For small values of the positive exponential parameter the transition from elastic to the post-elastic branch is smooth, while for large values that transition is abrupt. Parameters , and control the size and shape of the hysteretic loop. It has been found〔Ma F., Zhang H., Bockstedte A., Foliente G.C. and Paevere P. (2004). Parameter analysis of the differential model of hysteresis. Journal of applied mechanics ASME, 71, pp. 342–349〕 that the parameters of the Bouc–Wen model are functionally redundant. Removing this redundancy is best achieved by setting . Wen〔 assumed integer values for ; however, all real positive values of are admissible. The parameter is positive by assumption, while the admissible values for , that is , can be derived from a thermodynamical analysis (Baber and Wen (1981)〔Baber T.T. and Wen Y.K. (1981). Random vibrations of hysteretic degrading systems. Journal of Engineering Mechanics. ASCE. 107(EM6), pp. 1069–1089〕). 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Bouc–Wen model of hysteresis」の詳細全文を読む スポンサード リンク
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