# Help Needed with HNC Engineering Assignment..

Thread starter 5 years ago
#1
Evening everyone, looking for some help with an assignment, just to make sure i'm heading down the right track..

The questions is as follows:

A structural engineer is looking for a material to design a structural member in compression. The engineer needs to compare the behaviour of timber, steel and reinforced concrete structural members under compression. If steel has a maximum allowable compressive strength of 300 N/mm^2, concrete 40 N/mm^2, reinforced concrete 48 N/mm^2 and timber class C24 parallel to the grain 21.0 N/mm^2.

1) What is the maximum load a test piece of each material of dimensions 50mm x 75mm made from each of these materials can carry?

2) What would be an acceptable factor of safety.

For part 1, am i right in saying I simply find the total area of a test piece (3750mm^2) , then multiply this by each maximum allowable compressive strength? So for Steel, it would be 3750 x 300 n/mm^2 , giving me a max load of 1125 kN?

For part 2, I'm not quite sure where to start - with the information provided there is nothing to suggest there is any imposed load. So i'd simply looking for a factor of safety for each material? I know the Euro code suggests a factor of safety of 1.35 for dead loads, but the question suggests I need it for the specific materials, so any ideas where I can find these?

Thanks in advance for any guidance
0
5 years ago
#2
(Original post by b4rn5ey)
For part 1, am i right in saying I simply find the total area of a test piece (3750mm^2) , then multiply this by each maximum allowable compressive strength? So for Steel, it would be 3750 x 300 n/mm^2 , giving me a max load of 1125 kN?
Yes, stress = force/area. Find the area (in this case the cross sectional area) and then, using the max stress, find the force.

For part 2, I'm not quite sure where to start - with the information provided there is nothing to suggest there is any imposed load. So i'd simply looking for a factor of safety for each material? I know the Euro code suggests a factor of safety of 1.35 for dead loads, but the question suggests I need it for the specific materials, so any ideas where I can find these?

Thanks in advance for any guidance
I think for this they may be asking you to use some "engineering sense" to suggest an acceptable factor of safety.

As far as I am aware, the deadload factor from Eurocode is for applying to loads to make them larger, rather than to downgrade the strength of a material by, but I think you may be on the right track. I would look at the approach Eurocode takes to different materials.
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Thread starter 5 years ago
#3
cheers for the response
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