Question

A culvert is constructed with pretensioned inverted $T$ section and subsequent in situ concrete. Concrete grade corresponds to ${\sigma }_c=7MPa.$ For the section shown in the given figure, the maximum prestressing force will be

• A. 620 kN
• B. 890 kN
• C. 970 kN
• D. 1060 kN

Answer 1

The correct option is C 970 kN

The stress varies from zero at one extreme fiber to ${\sigma }_c$ at other extreme fiber.
${\sigma }_c=\frac{5}{7}{\sigma }_c=5MPa{P}_0=\left[\frac{600\times 200\times \left(\frac{5+7}{2}\right)+200\times 500\times \frac{5}{2}}{100}\right]=970kN$