measuring and calculating the dynamic response of simple structures aoe 3054 e. nikolaidis
TRANSCRIPT
Measuring and Calculating the Dynamic
Response of Simple Structures
AOE 3054
E. Nikolaidis
Outline
1 Introduction
2 Analysis of Dynamical Behavior of Structures
3 Dynamic Testing of Structures
4 Summary/Concluding Remarks
1 Introduction
• a. Dynamic loading
Dynamic means time varying
Examples:
• Aircraft wing-gust loads
• Offshore platform-waves
• Car on rough pavement
• Earthquake loads
Terminology
• Vibration: ?
b. Static versus dynamic analysis
Static• Constant load,
response• No inertia
forces
Dynamic• ?• Inertia forces
c. Steps in a dynamical investigation
• Design
• Analysis
• Testing/correction of model
• Redesign
2 Analysis of Dynamical Behavior of Structures
• Define ? model
• Derive ? model
• Solve for dynamical behavior
3 Dynamical Testing of Structures
Why dynamical testing:
• ?
• ?
• Full-scale structure
• Reduced scale physical models (use in early design stages)
Frequency response function
Basic property of linear systems: Sine in-Sine out
Scos(t) ?
Beam that can be modeled as a SDOF
system
Observations
=0 then ?
• At resonance:
Amplitude ratio=Q=AK=1/2Phase angle= ?
• For frequencies of excitation much higher than natural frequency the response amplitude is close to zero
• Example: Large space structures
4 Summary/Concluding Remarks
• Dynamic loading
• Steps in dynamical investigation
• Test
Motivation
Examples