The Experts below are selected from a list of 23541 Experts worldwide ranked by ideXlab platform

Nam Hoang - One of the best experts on this subject based on the ideXlab platform.

  • design formulas for damping of a stay cable with a damper
    Journal of Structural Engineering-asce, 2008
    Co-Authors: Yozo Fujino, Nam Hoang
    Abstract:

    The performance of a damper in controlling large-amplitude vibrations of a stay cable in a bridge is influenced by essential parameters such as the amount of sag and flexural rigidity of the cable, and the Stiffness of the damper Support. In this paper, accurate asymptotic formulas are analytically derived for the modal damping ratio of a general cable. The formulation includes the parameters mentioned above and is appropriate for a damper having a finite Support Stiffness. For a viscous damper, the influential parameters are explicitly incorporated as reduction and modification factors in the modal damping formula, which significantly simplifies the design procedure for stay cables. The analytical results are also extended to high-damping rubber dampers which have recently been encountered in practice. Finally, important formulas relevant to the design of both types of dampers are tabulated.

Jiyan Wang - One of the best experts on this subject based on the ideXlab platform.

  • Effects of flexible Support Stiffness on the nonlinear dynamic characteristics and stability of a turbopump rotor system
    Nonlinear Dynamics, 2010
    Co-Authors: Changqing Bai, Jiyan Wang
    Abstract:

    Using a flexible Support is an efficient approach to solving the subsynchronous problems in a turbopump. In this paper, nonlinear rotordynamic analysis of a liquid fuel turbopump with a flexible Support is presented using a dynamic modeling including two key destabilizing factors, nonlinear hydrodynamic forces induced by seals and internal rotor damping. The methodology of the partitioned direct integration method (PDIM) is described for reducing the computational efforts efficiently. Combining the PDIM and the shooting method, a nonlinear stability analysis of the rotor system is performed effectively. The numerical results, which are in good agreement with test data, indicate that the effects of flexible Support Stiffness k on the dynamic characteristics and stability of the rotor system are significant. The first critical speed of the rotor system rises as a nonlinear function of k markedly. The second critical speed varies slightly and approximates a linear variation as k increases. The onset speed of instability of the rotor system rises initially and then reduces as k increases. The effect of seal nonlinearities at low k is contrary to that at high k and the effect of seal length on the system stability is more significant than that of seal radius. The results explain the nature of the subsynchronous motion of a turbopump rotor system with flexible Support and can be used in the design and operation of a liquid fuel turbopump rotor system to eliminate its rotordynamic problem.

David Thambiratnam - One of the best experts on this subject based on the ideXlab platform.

  • analysis of plate resting on elastic Supports and elastic foundation by finite strip method
    Computers & Structures, 2001
    Co-Authors: Minghui Huang, David Thambiratnam
    Abstract:

    Abstract A procedure incorporating the finite strip method together with spring systems is proposed in this paper for treating plates on elastic Supports. The spring systems can simulate different elastic Supports, such as elastic foundation, line and point elastic Supports, and also mixed boundary conditions. To illustrate the application of this procedure, two numerical examples are presented. A three-span simply Supported plate is first considered and the effects of Support Stiffness on the static and free vibration responses and on the critical buckling stress are discussed. A plate resting on Winkler elastic foundation is next studied and the effects of dimension ratio on the static and free vibration responses are discussed. Numerical results show that the spring system can successfully simulate different kinds of elastic Supports.

Yozo Fujino - One of the best experts on this subject based on the ideXlab platform.

  • design formulas for damping of a stay cable with a damper
    Journal of Structural Engineering-asce, 2008
    Co-Authors: Yozo Fujino, Nam Hoang
    Abstract:

    The performance of a damper in controlling large-amplitude vibrations of a stay cable in a bridge is influenced by essential parameters such as the amount of sag and flexural rigidity of the cable, and the Stiffness of the damper Support. In this paper, accurate asymptotic formulas are analytically derived for the modal damping ratio of a general cable. The formulation includes the parameters mentioned above and is appropriate for a damper having a finite Support Stiffness. For a viscous damper, the influential parameters are explicitly incorporated as reduction and modification factors in the modal damping formula, which significantly simplifies the design procedure for stay cables. The analytical results are also extended to high-damping rubber dampers which have recently been encountered in practice. Finally, important formulas relevant to the design of both types of dampers are tabulated.

P Fromme - One of the best experts on this subject based on the ideXlab platform.

  • scour influence on the fatigue life of operational monopile Supported offshore wind turbines
    Wind Energy, 2018
    Co-Authors: Ramtin Rezaei, Philippe Duffour, P Fromme
    Abstract:

    Offshore wind turbines Supported on monopiles are an important source for renewable energy. Their fatigue life is governed by the environmental loads and in the dynamic behavior, depending on the Support Stiffness and thus soil-structure interaction. The effects of scour on the short-term and long-term responses of the NREL 5-MW wind turbine under operational conditions have been analyzed by using a finite element beam model with Winkler springs to model soil-structure interaction. It was found that due to scour, the modal properties of the wind turbine do not change significantly. However, the maximum bending moment in the monopile increases, leading to a significant reduction in fatigue life. Backfilling the scour hole can recover the fatigue life, depending mostly on the depth after backfilling. An approximate fatigue analysis method is proposed, based on the full time-domain analysis for 1 scour depth, predicting with good accuracy the fatigue life for different scour depths from the quasi-static changes in the bending moment.