QUESTION 1 (17 marks) A steel section made of Grade 300, heavily welded steel pl

Question

QUESTION 1 (17 marks) A steel section made of Grade 300, heavily welded steel plates is used for a steel beam bending about the horizontal plastic neutral (or equal area) axis X-X as shown in Figure 1. The top flange has a thickness of 14 mm and the bottom flange a thickness of 8 mm. (4 marks) (a) Determine the location h of the plastic neutral axis X-X (b) Hence calculate the plastic section modulus S for the section (c) Determine the slenderness (that is, compact, non-compact or slender) for each component and 5 marks) the whole section. Hence calculate the effective section modulus Z and the moment capacity , for the section. The elastic section modulus Z of the section 1956347 mm3 (8 marks) 14 10 10 10 240 240 Figure 1 (All dimensions in mm)

Explanation / Answer

a)The plastic netral axis will be such that it divides the section into two equal areas

In terms of 'h', the equal area axis can be determined as

14*(240+240+10+10+10)+3*10*(320-h) =

3*h*10 +8*(240+240+10+10+10)

7140+9600-30h=30h+4080

h=211

In the above calculation,h is calculated from the top of bottom plate. Therefore, value of h per the figure on question=211+8=219 mm

b)plastic section modulus=14*510*(109+7)+3*10*109²/2 + 3*10*211²/2+8*510*(211+4)=2551470 mm³

c) since I do not know which country's design code has to be followed, I am not able to solve part c

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