welcome to the new ge ppt template!...mode-superposition method: principal coordinates...
TRANSCRIPT
![Page 1: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/1.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Structural DynamicsLecture Eleven: Dynamic Response of MDOF Systems: (Chapter 11) By: H. [email protected]
![Page 2: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/2.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Dynamic Response of MDOF Systems: Mode-Superposition MethodMode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with
Modal Damping: Frequency-Response AnalysisMode-Displacement Solution for the Response of
MDOF SystemsMode-Acceleration Solution for the Response of
Undamped MDOF Systems Dynamic Stresses by Mode SuperpositionMode Superposition for Undamped Systems with
Rigid-Body Modes
![Page 3: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/3.jpg)
School of Mechanical EngineeringIran University of Science and Technology
MODE-DISPLACEMENT SOLUTION FOR THE RESPONSE OF MDOF SYSTEMS
In many cases only a subset of the modes is availableWe examine modal truncation and determine the
factors to be considered in deciding how many modes to include.
![Page 4: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/4.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Mode-displacement solution
The mode-displacement solution ignores completely the contribution of modes not included in the set The "kept“ modes are not restricted to the
lowest-frequency modes if some modes of higher frequency are available and are considered to be important.
![Page 5: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/5.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Example
What conclusions can you draw concerning truncation to one mode, to two modes, or to three modes?
![Page 6: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/6.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Example: Modal masses and stiffnesses
![Page 7: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/7.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Example: The modal forces
![Page 8: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/8.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Example: The mode-displacement
![Page 9: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/9.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Example: The mode-displacement
![Page 10: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/10.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Mode-acceleration solution
![Page 11: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/11.jpg)
School of Mechanical EngineeringIran University of Science and Technology
ExampleDetermine an expression for u1 using Mode
Acceleration Method, Compare the results with the results of mode-
displacement method.
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School of Mechanical EngineeringIran University of Science and Technology
Example: The mode-acceleration solution
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School of Mechanical EngineeringIran University of Science and Technology
Example: The mode-acceleration solution
![Page 14: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/14.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Example: The mode-acceleration solution
![Page 15: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/15.jpg)
School of Mechanical EngineeringIran University of Science and Technology
DYNAMIC STRESSES BY MODE SUPERPOSITIONFor the mode-displacement method, the internal stresses are given by:
For the mode-acceleration method for an undamped system, the displacement approximation leads to the stress approximation:
![Page 16: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/16.jpg)
School of Mechanical EngineeringIran University of Science and Technology
ExampleFor the shear building, write an expression for
the shear force at the ith story corresponding to mode r.
![Page 17: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/17.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Dynamic Response of MDOF Systems: Mode-Superposition MethodMode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with
Modal Damping: Frequency-Response AnalysisMode-Displacement Solution for the Response of
MDOF SystemsMode-Acceleration Solution for the Response of
Undamped MDOF Systems Dynamic Stresses by Mode SuperpositionMode Superposition for Undamped Systems with
Rigid-Body Modes
![Page 18: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/18.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Structural DynamicsLecture 12: Dynamic Response of MDOF Systems: (Chapter 11) By: H. [email protected]
![Page 19: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/19.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Dynamic Response of MDOF Systems: Mode-Superposition MethodMode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with
Modal Damping: Frequency-Response AnalysisMode-Displacement Solution for the Response of
MDOF SystemsMode-Acceleration Solution for the Response of
Undamped MDOF Systems Dynamic Stresses by Mode SuperpositionMode Superposition for Undamped Systems with
Rigid-Body Modes
![Page 20: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/20.jpg)
School of Mechanical EngineeringIran University of Science and Technology
DYNAMIC STRESSES BY MODE SUPERPOSITIONFor the mode-displacement method, the internal stresses are given by:
For the mode-acceleration method for an undamped system, the displacement approximation leads to the stress approximation:
![Page 21: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/21.jpg)
School of Mechanical EngineeringIran University of Science and Technology
ExampleFor the shear building, write an expression for
the shear force at the ith story corresponding to mode r.
![Page 22: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/22.jpg)
School of Mechanical EngineeringIran University of Science and Technology
MODE SUPERPOSITION FOR UNDAMPED SYSTEMS WITH RIGID-BODY MODES
![Page 23: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/23.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Mode-Displacement Method for Systems with Rigid-Body Modes
All rigid-body modes are employed, Included are number of elastic modes.
Rigid-body displacements do not give rise to internal stresses:
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School of Mechanical EngineeringIran University of Science and Technology
Mode-Acceleration Method for Systems with Rigid-Body Modes
The stiffness matrix is singular and cannot be inverted, The mode-acceleration method cannot be employed in
the straightforward manner
Must include all flexible modes.
Truncating the number of elastic modes
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School of Mechanical EngineeringIran University of Science and Technology
Mode-Acceleration Method for Systems with Rigid-Body Modes
In determining the elastic displacements, we use a self-equilibrated force system of applied forces and rigid-body inertia forces.
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School of Mechanical EngineeringIran University of Science and Technology
Mode-Acceleration Method for Systems with Rigid-Body Modes
The Inertia-Relief Matrix
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School of Mechanical EngineeringIran University of Science and Technology
Mode-Acceleration Method for Systems with Rigid-Body Modes
In order to calculate a flexibility matrix we need to impose NR arbitrary constraints.Then let AR be the flexibility matrix of the
system relative to these statically determinate constraints, with zeros filling in the NR rows and columns
corresponding to the constraints.
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School of Mechanical EngineeringIran University of Science and Technology
Mode-Acceleration Method for Systems with Rigid-Body Modes
![Page 29: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/29.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Stresses in Truncated Models of Systems with Rigid-Body Modes
![Page 30: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/30.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Stresses in Truncated Models of Systems with Rigid-Body ModesExample 11.8 Use the mode-displacement method and the mode-acceleration method to determine expressions for the maximum force in each of the two springs shown in Fig.1 due to application of a step force P3(t) = Po. t >0. Compare the convergence of the two methods. The system is at rest at t = 0.
![Page 31: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/31.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Example 11.8 Modes and Natural Frequencies
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School of Mechanical EngineeringIran University of Science and Technology
Example 11.8 Modes and Natural Frequencies
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School of Mechanical EngineeringIran University of Science and Technology
Example 11.8 Initial conditions and generalized forces
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School of Mechanical EngineeringIran University of Science and Technology
Example 11.8 Solutions in modal coordinates
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School of Mechanical EngineeringIran University of Science and Technology
Example 11.8 The modal stress vectors
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School of Mechanical EngineeringIran University of Science and Technology
Example 11.8 The mode-displacement approximation to the spring forces (internal stresses)
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School of Mechanical EngineeringIran University of Science and Technology
Example 11.8 The mode-displacement approximation to the spring forces (internal stresses)
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School of Mechanical EngineeringIran University of Science and Technology
Example 11.8 The mode-acceleration solution for internal stresses
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School of Mechanical EngineeringIran University of Science and Technology
Example 11.8 The mode-acceleration solution for internal stresses
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School of Mechanical EngineeringIran University of Science and Technology
Example 11.8 Comparison
The two mode solution are identical, since this system has only two elastic modes.The example is too small to indicate improved
"convergence" of the mode acceleration method over the mode-displacement method.
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School of Mechanical EngineeringIran University of Science and Technology
Extra Example
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School of Mechanical EngineeringIran University of Science and Technology
Extra Example
![Page 43: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/43.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Extra Example
![Page 44: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/44.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Dynamic Response of MDOF Systems: Mode-Superposition MethodMode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with
Modal Damping: Frequency-Response AnalysisMode-Displacement Solution for the Response of
MDOF SystemsMode-Acceleration Solution for the Response of
Undamped MDOF Systems Dynamic Stresses by Mode SuperpositionMode Superposition for Undamped Systems with
Rigid-Body Modes
![Page 45: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/45.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Structural DynamicsLecture 13: Mathematical Models of Continuous Systems (Chapter 12) By: H. [email protected]
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School of Mechanical EngineeringIran University of Science and Technology
Mathematical Models of ContinuousSystems
Applications of Newton's Laws: Axial Deformation and Torsion Application of Newton's Laws: Transverse Vibration of
Linearly Elastic Beams (Bernoulli-Euler Beam Theory)Application of Hamilton's Principle: Torsion of a Rod
with Circular Cross SectionApplication of the Extended Hamilton's Principle:
Beam Flexure Including Shear Deformation and Rotatory Inertia (Timoshenko Beam Theory)
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School of Mechanical EngineeringIran University of Science and Technology
APPLICATIONS OF NEWTON'S LAWS: AXIAL DEFORMATION AND TORSIONThe axial deformation assumptions, The axis of the member remains straight. Cross sections remain plane and remain perpendicular to the axis of
the member. The material is linearly elastic. ' The material properties (E, p) are constant at a given cross section,
but may vary with x.
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Constitutive Equation
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Applications of Newton's Laws:
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School of Mechanical EngineeringIran University of Science and Technology
Common Boundary Conditions:
Tip mass
Elastic Support
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School of Mechanical EngineeringIran University of Science and Technology
Torsional Deformation of Rods with Circular Cross Section The axis of the member, which is labeled the x axis, remains
straight. Cross sections remain plane and remain perpendicular to the axis of
the member. Radial lines in each cross section remain straight and radial as the
cross section rotates through angle e about the axis. The material is linearly elastic. The shear modulus is constant at a given cross section but may
vary with x.
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School of Mechanical EngineeringIran University of Science and Technology
Newton's Law for moments
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School of Mechanical EngineeringIran University of Science and Technology
Common Boundary Conditions:
An example:Rod-disk system
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School of Mechanical EngineeringIran University of Science and Technology
TRANSVERSE VIBRATION OF LINEARLY ELASTIC EULER-BERNOULLI BEAMSThe Euler-Bernoulli assumptions of elementary beam theory are:
The x-y plane is a principal plane of the beam, and it remains plane as the beam deforms in the y direction.
There is an axis of the beam, which undergoes no extension or contraction. This is called the neutral axis, and it is labeled the x axis. The original xz plane is called the neutral surface.'
Cross sections, which are perpendicular to the neutral axis in the undeformed beam, remain plane and remain perpendicular to the deformed neutral axis; that is, transverse shear deformation is neglected.
The material is linearly elastic, with modulus of elasticity E(x); that is, the beam is homogeneous at any cross section. (Generally, E is constant throughout the beam.) .
Normal stresses along y and z are negligible compared to that of x
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School of Mechanical EngineeringIran University of Science and Technology
TRANSVERSE VIBRATION OF LINEARLY ELASTIC EULER-BERNOULLI BEAMS
The following dynamics assumptions will also be made:The rotatory inertia of the beam may be
neglected in the moment equation.The mass density is constant at each cross
section, so that the mass center coincides with the centroid of the cross section.
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School of Mechanical EngineeringIran University of Science and Technology
TRANSVERSE VIBRATION OF LINEARLY ELASTIC EULER-BERNOULLI BEAMS
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School of Mechanical EngineeringIran University of Science and Technology
Common Boundary Conditions:
Fixed end at x = xe:
Simply supported end at x = xe :
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School of Mechanical EngineeringIran University of Science and Technology
Common Boundary Conditions:
Free end
The tip mass at x=L:
![Page 59: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/59.jpg)
School of Mechanical EngineeringIran University of Science and Technology
A Beam Subjected to Compressive End Load
![Page 60: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/60.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Mathematical Models of ContinuousSystems
Applications of Newton's Laws: Axial Deformation and Torsion Application of Newton's Laws: Transverse Vibration of
Linearly Elastic Beams (Bernoulli-Euler Beam Theory)Application of Hamilton's Principle: Torsion of a Rod
with Circular Cross Section Application of the Extended Hamilton's Principle:
Beam Flexure Including Shear Deformation and Rotatory Inertia (Timoshenko Beam Theory)
![Page 61: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/61.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Structural DynamicsLecture 14: Mathematical Models of Continuous Systems (Chapter 12) By: H. [email protected]
![Page 62: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/62.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Mathematical Models of ContinuousSystems
Applications of Newton's Laws: Axial Deformation and Torsion Application of Newton's Laws: Transverse Vibration of
Linearly Elastic Beams (Bernoulli-Euler Beam Theory)Application of Hamilton's Principle: Torsion of a Rod
with Circular Cross Section Application of the Extended Hamilton's Principle:
Beam Flexure Including Shear Deformation and Rotatory Inertia (Timoshenko Beam Theory)
![Page 63: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/63.jpg)
School of Mechanical EngineeringIran University of Science and Technology
APPLICATION 'OF HAMILTON'S PRINCIPLE: TORSION OF A CIRCULAR ROD
![Page 64: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/64.jpg)
School of Mechanical EngineeringIran University of Science and Technology
APPLICATION 'OF HAMILTON'S PRINCIPLE: TORSION OF A CIRCULAR ROD
![Page 65: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/65.jpg)
School of Mechanical EngineeringIran University of Science and Technology
APPLICATION 'OF HAMILTON'S PRINCIPLE: TORSION OF A CIRCULAR ROD
![Page 66: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/66.jpg)
School of Mechanical EngineeringIran University of Science and Technology
APPLICATION 'OF HAMILTON'S PRINCIPLE: TORSION OF A CIRCULAR ROD
![Page 67: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/67.jpg)
School of Mechanical EngineeringIran University of Science and Technology
APPLICATION 'OF HAMILTON'S PRINCIPLE: TORSION OF A CIRCULAR ROD
![Page 68: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/68.jpg)
School of Mechanical EngineeringIran University of Science and Technology
BEAM FLEXURE INCLUDING SHEARDEFORMATION AND ROTATORY INERTIA
![Page 69: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/69.jpg)
School of Mechanical EngineeringIran University of Science and Technology
BEAM FLEXURE INCLUDING SHEARDEFORMATION AND ROTATORY INERTIA
![Page 70: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/70.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Application of the Extended Hamilton's Principle
![Page 71: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/71.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Application of the Extended Hamilton's Principle
![Page 72: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/72.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Timoshenko Beam Theory
![Page 73: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/73.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Timoshenko Beam TheoryIf the beam has uniform cross-sectional properties, the two coupled PDEs may be combined to give a single equation in v:
![Page 74: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/74.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Mathematical Models of ContinuousSystems
Applications of Newton's Laws: Axial Deformation and Torsion Application of Newton's Laws: Transverse Vibration of
Linearly Elastic Beams (Bernoulli-Euler Beam Theory)Application of Hamilton's Principle: Torsion of a Rod
with Circular Cross Section Application of the Extended Hamilton's Principle:
Beam Flexure Including Shear Deformation and Rotatory Inertia (Timoshenko Beam Theory)
![Page 75: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/75.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Structural DynamicsLecture 15: Free Vibration of Continuous Systems (Chapter 13) By: H. [email protected]
![Page 76: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/76.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Free Vibration of Continuous Systems
Free Axial and Torsional Vibration Free Transverse Vibration of Bernoulli-Euler Beams Rayleigh's Method for Approximating the
Fundamental Frequency of a Continuous SystemFree Transverse Vibration of Beams Including
Shear Deformation and Rotatory Inertia Some Properties of Natural Modes of Continuous
SystemsFree Vibration of Thin Flat Plates
![Page 77: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/77.jpg)
School of Mechanical EngineeringIran University of Science and Technology
FREE AXIAL VIBRATION
![Page 78: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/78.jpg)
School of Mechanical EngineeringIran University of Science and Technology
FREE AXIAL VIBRATION
Fixed end: Free end:
End conditions
![Page 79: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/79.jpg)
School of Mechanical EngineeringIran University of Science and Technology
FREE AXIAL VIBRATIONExample:
![Page 80: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/80.jpg)
School of Mechanical EngineeringIran University of Science and Technology
FREE AXIAL VIBRATIONExample:
![Page 81: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/81.jpg)
School of Mechanical EngineeringIran University of Science and Technology
FREE TRANSVERSE VIBRATION OFBERNOULLI-EULER BEAMS
Free vibration of a uniform beam,
![Page 82: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/82.jpg)
School of Mechanical EngineeringIran University of Science and Technology
FREE TRANSVERSE VIBRATION OFBERNOULLI-EULER BEAMS
There are five constants in the general solution: the four amplitude constants and the eigenvalue.
![Page 83: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/83.jpg)
School of Mechanical EngineeringIran University of Science and Technology
FREE TRANSVERSE VIBRATION OFBERNOULLI-EULER BEAMS: Example
![Page 84: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/84.jpg)
School of Mechanical EngineeringIran University of Science and Technology
FREE TRANSVERSE VIBRATION OFBERNOULLI-EULER BEAMS: Example
![Page 85: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/85.jpg)
School of Mechanical EngineeringIran University of Science and Technology
FREE TRANSVERSE VIBRATION OFBERNOULLI-EULER BEAMS: Example
![Page 86: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/86.jpg)
School of Mechanical EngineeringIran University of Science and Technology
FREE TRANSVERSE VIBRATION OFBERNOULLI-EULER BEAMS: Example
![Page 87: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/87.jpg)
School of Mechanical EngineeringIran University of Science and Technology
![Page 88: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/88.jpg)
School of Mechanical EngineeringIran University of Science and Technology
RAYLEIGH'S METHOD FOR APPROXIMATING THE FUNDAMENTAL FREQUENCY OF A CONTINUOUS SYSTEMLord Rayleigh observed that for undamped free vibration, the motion is simple harmonic motion. Thus,
Rayleigh also observed that energy is conserved.the maximum kinetic energy is equal to the
maximum potential energy, that is,
![Page 89: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/89.jpg)
School of Mechanical EngineeringIran University of Science and Technology
RAYLEIGH'S METHOD FOR APPROXIMATING THE FUNDAMENTAL FREQUENCY OF A CONTINUOUS SYSTEM
![Page 90: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/90.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Example : Approximate fundamental frequencyof a uniform cantilever beam
The shape function
![Page 91: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/91.jpg)
School of Mechanical EngineeringIran University of Science and Technology
FREE TRANSVERSE VIBRATION OF BEAMS INCLUDING SHEAR DEFORMATION AND ROTATORY INERTIAConsider a uniform, simply supported beam:
Equations of motion:
Geometric boundary conditions:
Natural boundary conditions:
![Page 92: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/92.jpg)
School of Mechanical EngineeringIran University of Science and Technology
FREE TRANSVERSE VIBRATION OF BEAMS INCLUDING SHEAR DEFORMATION AND ROTATORY INERTIA
So the boundary conditions reduce, respectively, to
![Page 93: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/93.jpg)
School of Mechanical EngineeringIran University of Science and Technology
FREE TRANSVERSE VIBRATION OF BEAMS INCLUDING SHEAR DEFORMATION AND ROTATORY INERTIA
The simply supported beam mode shape satisfies both the boundary conditions, and the equation of motion:
![Page 94: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/94.jpg)
School of Mechanical EngineeringIran University of Science and Technology
FREE TRANSVERSE VIBRATION OF BEAMS INCLUDING SHEAR DEFORMATION AND ROTATORY INERTIA
Bernoulli-Euler beam characteristic equation
The rotatory inertia correction term
The shear correction term
![Page 95: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/95.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Free Vibration of Continuous Systems
Free Axial and Torsional Vibration Free Transverse Vibration of Bernoulli-Euler Beams Rayleigh's Method for Approximating the
Fundamental Frequency of a Continuous SystemFree Transverse Vibration of Beams Including
Shear Deformation and Rotatory InertiaSome Properties of Natural Modes of Continuous
SystemsFree Vibration of Thin Flat Plates
![Page 96: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/96.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Structural DynamicsLecture 16: Free Vibration of Continuous Systems (Chapter 13) By: H. [email protected]
![Page 97: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/97.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Free Vibration of Continuous Systems
Free Axial and Torsional Vibration Free Transverse Vibration of Bernoulli-Euler Beams Rayleigh's Method for Approximating the
Fundamental Frequency of a Continuous SystemFree Transverse Vibration of Beams Including
Shear Deformation and Rotatory Inertia Some Properties of Natural Modes of Continuous
SystemsFree Vibration of Thin Flat Plates
![Page 98: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/98.jpg)
School of Mechanical EngineeringIran University of Science and Technology
SOME PROPERTIES OF NATURAL MODESOF CONTINUOUS SYSTEMS
Following properties associated with the modes are considered: scaling (or normalization), orthogonality, the expansion theorem, and the Rayleigh quotient.
These are illustrated by using the Bernoulli-Euler beam equations.
![Page 99: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/99.jpg)
School of Mechanical EngineeringIran University of Science and Technology
SOME PROPERTIES OF NATURAL MODESOF CONTINUOUS SYSTEMS: scaling
Orthononnal modes
![Page 100: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/100.jpg)
School of Mechanical EngineeringIran University of Science and Technology
SOME PROPERTIES OF NATURAL MODESOF CONTINUOUS SYSTEMS: orthogonality
![Page 101: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/101.jpg)
School of Mechanical EngineeringIran University of Science and Technology
SOME PROPERTIES OF NATURAL MODESOF CONTINUOUS SYSTEMS: orthogonality
![Page 102: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/102.jpg)
School of Mechanical EngineeringIran University of Science and Technology
SOME PROPERTIES OF NATURAL MODESOF CONTINUOUS SYSTEMS: orthogonalityTo demonstrate the orthogonality relations for beams with loaded boundaries, we consider two distinct solutions of the eigenvalue problem:
![Page 103: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/103.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Orthogonality relations for beams
![Page 104: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/104.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Orthogonality relations for beams
![Page 105: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/105.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Expansion Theorem:Any function V(x) that satisfies the same boundary conditions as are satisfied by a given set of orthonormal modes, and is such that (EI V")" is a continuous function, can be represented by an absolutely and uniformly convergent series of the form
![Page 106: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/106.jpg)
School of Mechanical EngineeringIran University of Science and Technology
RESPONSE TO INITIAL EXCITATIONS:Beams in Bending Vibration
![Page 107: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/107.jpg)
School of Mechanical EngineeringIran University of Science and Technology
RESPONSE TO INITIAL EXCITATIONS:Beams in Bending Vibration
To demonstrate that every one of the natural modes can be excited independently of the other modes we select the initials as:
![Page 108: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/108.jpg)
School of Mechanical EngineeringIran University of Science and Technology
RESPONSE TO INITIAL EXCITATIONS:Response of systems with tip masses
Boundary conditions
Initial conditions
![Page 109: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/109.jpg)
School of Mechanical EngineeringIran University of Science and Technology
RESPONSE TO INITIAL EXCITATIONS:Response of systems with tip masses
Observing from boundary condition
![Page 110: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/110.jpg)
School of Mechanical EngineeringIran University of Science and Technology
RESPONSE TO INITIAL EXCITATIONS:Response of systems with tip masses
Similarly,
![Page 111: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/111.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Example:Response of a cantilever beam with a lumped mass at the end to the initial velocity:
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School of Mechanical EngineeringIran University of Science and Technology
Example:
![Page 113: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/113.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Example:
Because initial velocity resembles the 2nd mode
![Page 114: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/114.jpg)
School of Mechanical EngineeringIran University of Science and Technology
RESPONSE TO EXTERNAL EXCITATIONS
The various types of distributed-parameter systems differ more in appearance than in vibrational characteristics.We consider the response of a beam in
bending supported by a spring of stiffness k at x=0 and pinned at x=L.
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School of Mechanical EngineeringIran University of Science and Technology
RESPONSE TO EXTERNAL EXCITATIONS
Orthonormal modes
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RESPONSE TO EXTERNAL EXCITATIONS: Harmonic Excitation
Controls which mode is excited.
Controls the resonance.
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RESPONSE TO EXTERNAL EXCITATIONS: Arbitrary Excitation
The developments remain essentially the same for all other boundary conditions, and the same can be said about other systems.
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ExampleDerive the response of a uniform pinned-pinned beam to a concentrated force of amplitude F0acting at x = L/2 and having the form of a step function.
Orthonormal Modes
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Example
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Free Vibration of Continuous Systems
Free Axial and Torsional Vibration Free Transverse Vibration of Bernoulli-Euler Beams Rayleigh's Method for Approximating the
Fundamental Frequency of a Continuous SystemFree Transverse Vibration of Beams Including
Shear Deformation and Rotatory Inertia Some Properties of Natural Modes of Continuous
SystemsFree Vibration of Thin Flat Plates
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School of Mechanical EngineeringIran University of Science and Technology
Structural DynamicsLecture 17: Free Vibration of Continuous Systems (Chapter 13) By: H. [email protected]
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School of Mechanical EngineeringIran University of Science and Technology
Free Vibration of Continuous Systems
Free Axial and Torsional Vibration Free Transverse Vibration of Bernoulli-Euler Beams Rayleigh's Method for Approximating the
Fundamental Frequency of a Continuous SystemFree Transverse Vibration of Beams Including
Shear Deformation and Rotatory Inertia Some Properties of Natural Modes of Continuous
SystemsFree Vibration of Thin Flat Plates
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Rayleigh Quotient:
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Example: Lowest natural frequency of the fixed-free tapered rod in axial vibration
The 1st mode of a uniform clamped-free rod as a trial function:
A comparison function
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THE RAYLEIGH-RITZ METHODThe method was developed by Ritz as an extension of Rayleigh's energy method. Although Rayleigh claimed that the method
originated with him, the form in which the method is generally used is due to Ritz.
The first step in the Rayleigh-Ritz method is to construct the minimizing sequence:
independent trial functionsundetermined coefficients
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THE RAYLEIGH-RITZ METHOD
The independence of the trial functions implies the independence of the coefficients, which in turn implies the independence of the variations
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THE RAYLEIGH-RITZ METHOD
Solving the equations amounts to determining the coefficients, as wellas to determining
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Example : Solve the eigenvalue problem for the fixed-free tapered rod in axial vibration
The comparison functions
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Example :
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Example : n = 2
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Example : n = 2
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Example : n = 3
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Example : n = 3
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Example : The Ritz eigenvalues for the two approximations are:
The improvement in the first two Ritz natural frequencies is very small, indicates the chosen comparison functions
resemble very closely the actual natural modes.Convergence to the lowest eigenvalue with six
decimal places accuracy is obtained with 11 terms:
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Truncation
Approximation of a system with an infinite number of DOFs by a discrete system with n degrees of freedom implies truncation:
Constraints tend to increase the stiffness of a system:
The nature of the Ritz eigenvalues requires further elaboration.
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TruncationA question of particular interest is how the eigenvalues of the (n +1)-DOF approximation relate to the eigenvalues of the n-DOF approximation.
We observe that the extra term in series does not affect the mass and stiffness coefficients computed on the basis of an n-term series (embedding property):
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TruncationFor matrices with embedding property the eigenvalues satisfy the separation theorem:
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School of Mechanical EngineeringIran University of Science and Technology
Free Vibration of Continuous Systems
Free Axial and Torsional Vibration Free Transverse Vibration of Bernoulli-Euler Beams Rayleigh's Method for Approximating the
Fundamental Frequency of a Continuous SystemFree Transverse Vibration of Beams Including
Shear Deformation and Rotatory Inertia Some Properties of Natural Modes of Continuous
SystemsFree Vibration of Thin Flat Plates
![Page 139: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/139.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Structural DynamicsLecture 18: Free Vibration of Continuous Systems (Chapter 13) By: H. [email protected]
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School of Mechanical EngineeringIran University of Science and Technology
Free Vibration of Continuous Systems
> Free Axial and Torsional Vibration > Free Transverse Vibration of Bernoulli-Euler Beams > Rayleigh's Method for Approximating the
Fundamental Frequency of a Continuous System> Free Transverse Vibration of Beams Including
Shear Deformation and Rotatory Inertia > Some Properties of Natural Modes of Continuous
Systems> Free Vibration of Thin Flat Plates
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School of Mechanical EngineeringIran University of Science and Technology
VIBRATION OF PLATES
> Plates have bending stiffness in a manner similar to beams in bending.
> In the case of plates one can think of two planes of bending, producing in general two distinct curvatures.
> The small deflection theory of thin plates, called classical plate theory or Kirchhoff theory, is based on assumptions similar to those used in thin beam or Euler-Bernoulli beam theory.
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EQUATION OF MOTION: CLASSICAL PLATE THEORYThe elementary theory of plates is based on the following assumptions:> The thickness of the plate (h) is small compared to its lateral
dimensions.> The middle plane of the plate does not undergo in-plane
deformation. Thus, the midplane remains as the neutral plane after deformation or bending.
> The displacement components of the midsurface of the plate are small compared to the thickness of the plate.
> The influence of transverse shear deformation is neglected. This implies that plane sections normal to the midsurface before deformation remain normal to the rnidsurface even after deformation or bending.
> The transverse normal strain under transverse loading can be neglected. The transverse normal stress is small and hence can be neglected compared to the other components of stress.
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Moment - Shear Force Resultants:
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Equation of motion
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BOUNDARY CONDITIONS
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BOUNDARY CONDITIONS
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BOUNDARY CONDITIONS: Free Edge
> There are three boundary conditions, whereas the equation of motion requires only two:
> Kirchhoff showed that the conditions on the shear force and the twisting moment are not independent and can be combined into only one boundary condition.
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BOUNDARY CONDITIONS: Free Edge
Replacing the twisting moment by an equivalent vertical force.
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BOUNDARY CONDITIONS
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BOUNDARY CONDITIONS
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BOUNDARY CONDITIONS
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FREE VIBRATION OF RECTANGULAR PLATES
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School of Mechanical EngineeringIran University of Science and Technology
FREE VIBRATION OF RECTANGULAR PLATES
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FREE VIBRATION OF RECTANGULAR PLATES
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Solution for a Simply Supported Plate
We find that all the constants Ai except A1 and
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Solution for a Simply Supported Plate
The initial conditions of the plate are:
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Solution for a Simply Supported Plate
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Solution for a Simply Supported Plate
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Solution for a Simply Supported Plate
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School of Mechanical EngineeringIran University of Science and Technology
Free Vibration of Continuous Systems
> Free Axial and Torsional Vibration > Free Transverse Vibration of Bernoulli-Euler Beams > Rayleigh's Method for Approximating the
Fundamental Frequency of a Continuous System> Free Transverse Vibration of Beams Including
Shear Deformation and Rotatory Inertia > Some Properties of Natural Modes of Continuous
Systems> Free Vibration of Thin Flat Plates
![Page 161: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/161.jpg)
School of Mechanical EngineeringIran University of Science and Technology
Structural DynamicsLecture 19: Free Vibration of Continuous Systems (Chapter 13) By: H. [email protected]
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School of Mechanical EngineeringIran University of Science and Technology
Free Vibration of Continuous Systems
> Free Axial and Torsional Vibration > Free Transverse Vibration of Bernoulli-Euler Beams > Rayleigh's Method for Approximating the
Fundamental Frequency of a Continuous System> Free Transverse Vibration of Beams Including
Shear Deformation and Rotatory Inertia > Some Properties of Natural Modes of Continuous
Systems> Free Vibration of Thin Flat Plates
![Page 163: Welcome to the new GE PPT template!...Mode-Superposition Method: Principal Coordinates Mode-Superposition Solutions for MDOF Systems with Modal Damping: Frequency- Response Analysis](https://reader035.vdocuments.us/reader035/viewer/2022062606/5fe6ce580edb7525477ac7e8/html5/thumbnails/163.jpg)
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Vibrations of Rectangular Plates
The functions X(x) and Y(y) can be separated provided either of the followings are satisfied:
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Vibrations of Rectangular Plates
These equations can be satisfied only by the trigonometric functions:
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Vibrations of Rectangular Plates
Assume that the plate is simply supported along edges x =0 and x =a:
Implying:
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Vibrations of Rectangular PlatesThe various boundary conditions can be stated,
SS-SS-SS-SS, SS-C-SS-C, SS-F-SS-F, SS-C-SS-SS, SS-F-SS-SS, SS-F-SS-C
Assuming:
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Vibrations of Rectangular Plates
y = 0 and y = b are simply supported:
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School of Mechanical EngineeringIran University of Science and Technology
Vibrations of Rectangular Plates
y = 0 and y = b are simply supported:
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Vibrations of Rectangular Plates
y = 0 and y = b are clamped:
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Vibrations of Rectangular Plates
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Vibrations of Rectangular Plates
Exact characteristic equations for some of classical boundary conditions of vibrating moderately thick rectangular platesShahrokh Hosseini Hashemi and M. Arsanjani ,International Journal of Solids
and Structures Volume 42, Issues 3-4, February 2005, Pages 819-853
Exact solution for linear buckling of rectangular Mindlin platesShahrokh Hosseini-Hashemi, Korosh Khorshidi, and Marco Amabili, Journal of
Sound and Vibration Volume 315, Issues 1-2, 5 August 2008, Pages 318-342
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FORCED VIBRATION OF RECTANGULAR PLATES
the normal modes
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School of Mechanical EngineeringIran University of Science and Technology
FORCED VIBRATION OF RECTANGULAR PLATES
Using a modal analysis procedure:
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School of Mechanical EngineeringIran University of Science and Technology
FORCED VIBRATION OF RECTANGULAR PLATESThe response of simply supported rectangular plates:
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School of Mechanical EngineeringIran University of Science and Technology
Free Vibration of Continuous Systems
> Free Axial and Torsional Vibration > Free Transverse Vibration of Bernoulli-Euler Beams > Rayleigh's Method for Approximating the
Fundamental Frequency of a Continuous System> Free Transverse Vibration of Beams Including
Shear Deformation and Rotatory Inertia > Some Properties of Natural Modes of Continuous
Systems> Free Vibration of Thin Flat Plates