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Re: Re: Steel vs. Aluminum

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Posted By<" ">Neil Moran on March 15, 2002 at 04:45:42:

In Reply to: Re: Steel vs. Aluminum posted bydavid schenken on March 14, 2002 at 00:13:04:

Hi,

I am a structural/mechanical design engineer and get involved in all types of structures for the Theatre and Stage industries. While I would agree with you all, that a structural grade of aluminium can be as strong, or even stronger than steel, this is only one consideration to cater for. What about the deflection of the structure?

The modulus of elasticity of aluminium (whatever grade) is only about 1/3 that of steel. So the deflection of an aluminium structure will be 3x that of a similar steel structure. If deflection is important you will need 3x more `second moment of area` (approx 3x more weight) of aluminium in order to achieve the same deflection as the steel structure. Aluminium is also 1/3 the weight of steel so both structures would now weigh the same.

There is only an advantage in using aluminium where deflection is un-important. Steel is also easier to weld than aluminium.

Regards,
Neil Moran

Follow Ups

Re: Re: Re: Steel vs. Aluminum Dave Schenken 23:49:13 4/04/2002 (0)

Subject: Re: Re: Re: Steel vs. Aluminum

Comments:: Hi, : I am a structural/mechanical design engineer and get involved in all types of structures for the Theatre and Stage industries. While I would agree with you all, that a structural grade of aluminium can be as strong, or even stronger than steel, this is only one consideration to cater for. What about the deflection of the structure? : The modulus of elasticity of aluminium (whatever grade) is only about 1/3 that of steel. So the deflection of an aluminium structure will be 3x that of a similar steel structure. If deflection is important you will need 3x more `second moment of area` (approx 3x more weight) of aluminium in order to achieve the same deflection as the steel structure. Aluminium is also 1/3 the weight of steel so both structures would now weigh the same. : There is only an advantage in using aluminium where deflection is un-important. Steel is also easier to weld than aluminium. : Regards, : Neil Moran

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