Structural Mechanics Distinction Task

[Terra_Bitz]

Homework Statement

Hi,

I'm stuck on answering the attached question, I know how to find the axial within the column however I do know what the question means by justifying a chosen material, help would be much appreciated.

Thanks in advance!

Alfie

Relevant Equations

The way how I found out calculate axial load is here: https://www.hunker.com/13400857/how-to-calculate-the-axial-load

To find axial load , 5m / 6m = 0.83
Arc tangent , tan-1(0.83) = 39.69
Cosine of the force , Cos(39.69) = 0.77
Sine of the force , Sin(39.69) = 0.64
Axial load in the vertical direction , (200kN/m X 6 = 1200kN / 2 = 600kN + self weight of 6kN = 606kN) So 606kN X 0.77 = 466.62kN
Axial load in the horizontal direction , (200kN/m X 6 = 1200kN / 2 = 600kN + self weight of 6kN = 606kN) So 606kN X 0.64 = 387.84kN

 

[phinds]

I do know what the question means by justifying a chosen material

Well, do you think that balsawood, for example, or perhaps styrofoam, would be good materials to use? Why or why not?

 

[Terra_Bitz]

Well, do you think that balsawood, for example, or perhaps styrofoam, would be good materials to use? Why or why not?

Ah right, so essentially choose a suitable material, such as steel or RC, and talk about its pro's and cons.

I was confused when it say's 'justify' I wasn't sure as to whether it was asking me to choose a material then design a section.

Thank you Phinds

 

[phinds]

Ah right, so essentially choose a suitable material, such as steel or RC, and talk about its pro's and cons.

I was confused when it say's 'justify' I wasn't sure as to whether it was asking me to choose a material then design a section.

Thank you Phinds

yes, but I think "justify" is perhaps a bit more firm than you are taking it to be. I would say it's not just choosing and discussing a material, it's specifically showing that it has strength properties that are at has a good safety factor in excess of what your calculations show is needed. I realize you may have already had that in mind without specifically saying so.

 

[Terra_Bitz]

yes, but I think "justify" is perhaps a bit more firm than you are taking it to be. I would say it's not just choosing and discussing a material, it's specifically showing that it has strength properties that are at least a good safety factor in excess of what your calculations show is needed. I realize you may have already had that in mind without specifically saying so.

Apologies but I'm not sure I follow, I've researched what the safety factor is for structural steelwork in building, being 4-6 ( https://www.engineeringtoolbox.com/factors-safety-fos-d_1624.html ), however how do I apply this to my previous calculations?

 

[phinds]

how do I apply this to my previous calculations?

No idea. Maybe someone else here will chime in.

 

[CivilSigma]

I'm not sure why you are calculating the angle: arctan(5/6) ??
The axial load on the column is just 606 kN, and there are no lateral forces on the column.

Safety factors are used when it comes to material design. I don't think the purpose of this problem is to design a section. You don't apply safety factors to structural analysis