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Steel Designers' Manual - 6th Edition (2003)
analysis, where ‘mass’ is applied as loading. It is important to ensure that all the
mass present is correctly included as mass (not loading) in the dynamic analysis.
Clearly, dynamically consistent units must be used throughout, and these units
may not be the same as those used for a static analysis using the same model. A
hand check of the first mode frequency using an approximate or empirical method
is strongly advisable to ensure that the results are realistic. In addition, there is even
more need than with static analysis to view computer analysis results as approximate.
It is very difficult to predict natural frequencies of real structures with a high
degree of precision unless the real boundary conditions and structural stiffness can
be defined with confidence. This is rarely the case and these are uncertainties that
finite element analysis cannot resolve.
12.6 Dynamic testing
Calculation of the dynamic properties and dynamic responses of structures still presents
some difficulties, and testing and monitoring of structures has a significant role
in structural dynamics. Testing is the only way by which the damping of structures
can be obtained, by which analytical methods can be calibrated and many forms of
dynamic loading can be estimated. It is often an essential part of the assessment and
improvement of structures where dynamic response is found to be excessive in practice.
Further details are contained in references 9 and 10.
References to Chapter 12
Dynamic testing 371
1. Clough R.W. & Penzien J. (1993) Dynamics of Structures, 2nd edn. McGraw-
Hill.
2. Dowrick D.J. (1987) Earthquake Resistant Design for Engineers and Architects,
2nd edn. John Wiley & Sons.
3. Warburton G.B. (1976) The Dynamical Behaviour of Structures, 2nd edn.
Pergamon Press, Oxford.
4. Harris C.M. & Crede C.E. (1976) Shock and Vibration Handbook. McGraw-
Hill.
5. Roark R.J. & Young W.C. (1989) Formulas for Stress and Strain, 6th edn.
McGraw-Hill.
6. Construction Industry Research & Information Association (CIRIA)/The Steel
Construction Institute (SCI) (1989) Design Guide on the Vibration of Floors.
SCI Publication 076, SCI, Ascot, Berks.
7. Bathe K.J. (1996) Finite Element Procedures. Prentice Hall, Englewood Cliffs,
NJ.
8. Bachmann H. (1995) Vibration Problems in Structures. Birkhauser Verlag AG.
9. Ewins D.J. & Inman D.J. (2001) Structural dynamics @2000: Current status and
future directions. Research Studies Press, Baldock.