Expert: Ray Wilkinson - 11/11/2006

Question
Mr. Wilkinson,

The helicopter subfloor structure has to be designed so as to limit the deceleration forces during crushing, transmitted to passengers. This is achieved through a series of beams and bulkheads. The beams are I-beams but the web is in the shape of a sine-wave when viewed in planform.

It is these beams I am concerned with. Why is the sine-wave shape so efficient at absorbing crash loads? What about a trapazoid-wave or other such shape? Is the efficiency of the web a function of the wavelength, amplitude etc., of the wave shape? Could you point in the direction of e.g. a drop test involving these beams or, ideally, the efficiency of the web shape etc.

If you could offer some experience or comments I would be very grateful.

Thanks for your time,

Answer
Hi Eoin

Sorry for the delay in responding to this one. It's not in direct area of experience so I asked one of my colleagues and I'm still waiting for a response. If and when I get an answer I'll forward it to you. If I haven't come back again within a week or so, please nag me, and I'll give him a prompt.

Regards

Ray
R.Wilkinson@herts.ac.uk