- A Prestressed Concrete Beam With A Rectangular Cross Section 800 Mm Deep And 400 Mm Wide Has A Span Of 10 Metres It Is 1 (34.42 KiB) Viewed 35 times
A prestressed concrete beam with a rectangular cross-section 800 mm deep and 400 mm wide has a span of 10 metres. It is post-tensioned by a cable that has a cross-sectional area of 1000 mm² and an eccentricity e that varies para- bolically from zero at the ends to a maximum of 250 mm at mid-span. The prestressing force is 1200 kN. We wish to determine for the mid-span section: • the stresses due to prestress acting alone; • the decompression moment; and • the stresses due to prestress, self-weight and a uniformly applied live load of 30 kN/m. All loads act shortly after prestressing, so that the one value of Ec is used throughout these calculations. Other Data 2 320x10 mm; Ig 17.07×10 mm; 3 Zbot = Ztop = 1/(D/2) = 17.07×10/400 = 42.67×106 mm³ The unit weight of reinforced concrete is taken as 25 kN/m³, so that the self- weight is wG = 25 x 0.32 = 8.0 kN/m.