Two active control systems, the active mass damper and active tendon are proposed, for reduction of the along-wind response of tall buildings. the optimal control forces for both control systems are found using an ins...
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Two active control systems, the active mass damper and active tendon are proposed, for reduction of the along-wind response of tall buildings. the optimal control forces for both control systems are found using an instantaneous open-loop or an instantaneous closed-loop algorithm. the wind excitation is simulated by artificial wind pressures, generated using wind design spectra, which are spatially correlated by means of an experimental coherence function. Numerical examples demonstrate the effectiveness of both control systems in reducing the building's response and improving the comfort of its occupants.
the dynamic substructure method has been successfully used in eigenvalue solutions and dynamic response analysis of large complex structure systems. More than half of computer time is expended on obtaining the normal ...
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the dynamic substructure method has been successfully used in eigenvalue solutions and dynamic response analysis of large complex structure systems. More than half of computer time is expended on obtaining the normal modes of components. this paper applies the method of Ritz vectors to the dynamic substructure instead of eigenvalue solution of components, and in response analysis as well. In this paper, discussions have been made on how to define the force vector to automatically generate Ritz vectors without external loading for eigensolution, and on the conditions to generate complete base vectors.
Existing formulations associated with residual flexibility result in systems where the generalized coordinates for normal modes and residual flexibility are always coupled. thus an additional mode synthesis is necessa...
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Existing formulations associated with residual flexibility result in systems where the generalized coordinates for normal modes and residual flexibility are always coupled. thus an additional mode synthesis is necessary to uncouple the resulting systems. this paper presents a new formulation to apply residual flexibility to structural dynamics. In this new formulation, the generalized coordinates for residual flexibility are orthogonal to those for normal modes. they can be added to the modal model as an independent component and do not disturb the original modal model. therefore, the costly additional mode synthesis needed in the existing formulations is completely eliminated in the new formulation. this paper also provides a proof that the new formulation can be transformed into existing formulations.
To confirm the usefulness of dynamic-absorber design in multi-degree-of-freedom systems proposed in report 1, we demonstrate that the first three resonances of a cantilever-beam structure with negligible internal damp...
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To confirm the usefulness of dynamic-absorber design in multi-degree-of-freedom systems proposed in report 1, we demonstrate that the first three resonances of a cantilever-beam structure with negligible internal damping are suppressed effectively by three dynamic absorbers designed using the method we propose. the transfer matrix is used to determine suitable locations for installing dynamic absorbers and to estimate equivalent masses. After a complex transfer matrix is formed for the dynamic absorber, a complex transfer matrix is used to calculate the frequency response of a beam structure withthree dynamic absorbers. Boththeoretical and experimental analysis show that dynamic absorbers can greatly reduce resonant vibration in beam structures.
this paper presents a recursive method to accomplish pole placement for control of large-order vibrating systems. the pole placement is based on matrix perturbation theory, where the controls are considered as a first...
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this paper presents a recursive method to accomplish pole placement for control of large-order vibrating systems. the pole placement is based on matrix perturbation theory, where the controls are considered as a first-order perturbation on the uncontrolled system. the difference between the open-loop poles and the desired closed-loop poles is divided into regions small enough to maintain validity of the perturbation assumption. Control gains are then calculated in each region, resulting in a stepwise design. the method presented here is also applicable to any linear, time-invariant system.
the dynamic response of large structural systems is often analyzed using component mode synthesis (CMS) techniques. CMS is widely accepted for predicting coupled system response with increased modeling efficiency and ...
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the dynamic response of large structural systems is often analyzed using component mode synthesis (CMS) techniques. CMS is widely accepted for predicting coupled system response with increased modeling efficiency and flexibility over conventional methods. Parameter identification (PID) techniques can be used to improve predicted response when experimental data are available. this study explores combining CMS and PID methods to improve the analytical modeling of the connections in a component mode synthesis model. the approach involves modeling components with either finite elements or experimental modal data and then joining the components with physical connecting elements at their interface points.
the finite element method has advantages for dynamic analysis of large, complex rotor systems when applied in an efficient manner. Algorithms for beam elements with shear deflection and gyroscopics have been developed...
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the finite element method has advantages for dynamic analysis of large, complex rotor systems when applied in an efficient manner. Algorithms for beam elements with shear deflection and gyroscopics have been developed and reported earlier, along with techniques for using matrix reduction approaches prior to solution of the dynamic matrix equations. this paper describes extension of these techniques to the microcomputer (PC-DOS) in a FORTRAN environment. the paper includes a description of the capability of the program, the computational techniques used, implementation of graphics, and a discussion on the difficulties encountered in the PC development relative to earlier mainframe and minicomputer implementations. the general utility of the microcomputer for rotor dynamics analysis is confirmed, providing efficient matrix reduction and solution approaches are used.
the dynamic analysis for a large turbine machine is complex, mainly due to the couple of the rotor system and the flexible foundation. In this paper the rotor system and foundation are treated as two independent subst...
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the dynamic analysis for a large turbine machine is complex, mainly due to the couple of the rotor system and the flexible foundation. In this paper the rotor system and foundation are treated as two independent substructures, and the oil-film bearings are modeled as a particular substructure with coupling forces and neglectable inertia. the modal synthesis technique is applied to the analysis of dynamic properties for the whole system consisting of rotor, oil-film bearings and foundation. Because the oil-film stiffness and damping may be nonconservative, it is necessary to study the stability for the system. the eigenvalues for free vibration equation of systems are calculated. Various factors such as the asymmetry of oil-film properties are included. then complex modes and complex eigenvalues are obtained.
A procedure was preocously developed, to create detailed finite element models of pump components and to assemble a dynamic model, for determining the complex dynamic behavior of components and the pump system. this p...
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A procedure was preocously developed, to create detailed finite element models of pump components and to assemble a dynamic model, for determining the complex dynamic behavior of components and the pump system. this paper presents the approach for determining the natural frequencies and mode shapes of pump components and the system. Effect of design changes on system natural frequencies is studied. Pump system dynamics is reviewed for variations in casing, impeller, pedestal, and line shafting. Computed natural frequencies are compared withthe frequencies obtained from laboratory and field data. Typical mode shape plots of pump components and the pump system are provided for illustration.
A method for performing frequency analysis of multicylinder engines having any number of cylinders in any angular orientation with respect to each other is developed. Cylinder axes may also have linear offsets with re...
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A method for performing frequency analysis of multicylinder engines having any number of cylinders in any angular orientation with respect to each other is developed. Cylinder axes may also have linear offsets with respect to the crankshaft axis. A three-dimensional flexural finite-line element with joint freedom irregularity is developed and used to formulate the eigenvalue equations of motion for the system considering true geometries of the crank-throws and the slider-crank linkage loops. the lumped mass system is used. the element can be restrained to perform coupled torsional and flexural frequency analysis as well as pure flexural or pure torsional frequency analysis of geared rotor models of engines. Flexibilities of geared connections and bearings can be considered. A generalized computer program is made available for industrial use.
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