BCGBC4010A Apply structural principles to residential low-rise constructions

Structural principles - Properties

Section properties

Calculating the section modulus
Question 1
Based on a rectangle with the dimensions of b = 50 mm and d = 200 mm, use the formula Zxx = (b by d to the power of two) divided by six, mm3 to calculate the section modules for beam A
A.	3.33 x 103 mm3
B.	33.3 x 103 mm3 
C.	83.3 x 103 mm3
D.	333.3 x 103 mm3
The correct answer is D - 333.3 x 103 mm3.  

Question 2
Based on a rectangle with the dimensions of b = 200 m and d = 50 mm use the formula Zxx = (b by d to the power of two) divided by six, mm3 to calculate the section modulus for beam B.
A.	8.33 x 103 mm3
B.	33.3 x 103 mm3
C.	83.3 x 103 mm3
D.	833.3 x 103 mm3
The correct answer is C - 83.3 x 103 mm3. Beam A has an elastic modulus Z = 333.3 x 103 mm3. Beam B has an elastic modulus Z = 83.3 x 103 mm3. As beam A has a greater value for Z the elastic modulus, beam A is stiffer than beam B even though they are exactly the same shape and cross-section.

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