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The shown girder is made from plain stone concrete and four 25 mm diameter steel wires. Including the weight of steel wires, determine self weight of the girder if its length is 12.5 m. Neglect the volume of concrete displaced by steel wires
My answer, area of concrete = ((150*1200)+ 4((200*100)+(0.5*100*150))-(4*pi*(12.5)^2))*(1×10^-3)^2=70.44m^2
area of steel = (4*pi*(12.5)^2))*(1×10^-3)^2 = 1.963×10^-3m^2
W = [(70.44×22.6)+(1.96×10^-3×77.3)] = 1.59×10^3KN/m
This is not a question of reverse engineering, but anyway this is how you can proceed.
Divide the cross-section into 5 parts - 3 rectangles and 2 trapezoids.
Area of rectangle and trapezoids can be calculated with their respective formulae. Multiply by the length (12.5m) to get the volume. The product of volume and density would give the mass.
Similarly, you can calculate the mass for the 4 steel wires.
