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Structural dynamics of overhead cranes

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Greetings,


I'm searching info about dynamic requirements in the design of overhead
traveling cranes.   I'm interested in design specifications or
recommendations for considering dynamic effects and vibrations in the
structure of bridge cranes (especially, regarding to admissible natural
frequencies of girders).

I've nearly checked all the Standards on this subject:  European (CEN,
FEM...), American (CMAA), International (ISO) and even some national
standards (DIN, AS...).   So far I've just found one reference regarding
this matter:  in an Australian Standard [AS 1418.1- Cranes, Hoists and
Winches ? Bridge, gantry, portal (including container cranes) and jib
cranes:], which specifies a minimum value of 2.4 Hz for the natural
frequency of the structure (for vertical and lateral first modes of
vibration).   From the point of view of some crane designers, for large
span values this criterium implies a disproportionate increase of the
stiffness of girders, so the structure becomes overdimensioned (in some
cases this requirement could be equivalent to a deflection limit around
1/2000 span)

I've also come across an annex of a project of an European Norm (prEN),
which points out the same minimum value (2.4 Hz) of vertical frequency for
span<25 m.  But for longer span values, the recommended vertical frecuency
decreases exponentially (for Span=50 m, fv=1.8 Hz).   For horizontal
frequencies the recommended minimum value is fh=1.8 Hz.

Can someone help me by providing some guidances or recommendations for
considering dynamic requirements in safe design of overhead cranes?  I've
seen that there is no much legislation or literature about it.


Thank you.

Regards,

____________________________________________________

Celia Gómez <cgomezga(--nospam--at)bilbao.idom.es>
IDOM Ingeniería, Arquitectura y Consultoría
Área de Análisis y Diseño Avanzados
Lehendakari Aguirre,3 - 48014 Bilbao   (Spain)







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