Natural Frequency Bridge Beam 1

[damo74]

Has anyone any idea on how I could calculate the natural frequency of a concrete bridge beam?

 

[GregLocock]

Sure.

Best way, to be honest, is FEA, but if it is a single span uniform beam supported at each end then the first mode is given by

f=1/2/pi*A*sqrt(E*I/mu/L^4) Hz

For simply supported A=9.81, for fixed fixed A=22.4

mu=mass per unit length

All units are consistent.

The book you need is by Robert D Blevins






Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Bbird]

Normally the first nat freq would lie somewhere in between simpply supported and fully fixed conditions, both are well defined by the textbooks. Should use them for sanity check after FEA work.