Kern Zone

Q. The below figure represents a section of a prestressed beam. For a no-tension design where ${\sigma }_c$ is the permissible stress in concrete, the total moment carrying capacity is

1. $\frac{b{d}^2{\sigma }_c}{3}$
2. $\frac{b{d}^2{\sigma }_c}{4}$
3. $\frac{b{d}^2{\sigma }_c}{6}$
4. $\frac{b{d}^2{\sigma }_c}{12}$

Q. A pre-tensioned (assume no losses) concrete rectangular $(b\times d)$ beam is designed on the basis of no tension. Concrete strength is ${\sigma }_c.$ The maximum moment that the beam can carry is

1. ${\sigma }_c.\frac{b{d}^2}{2}$
2. ${\sigma }_c.\frac{b{d}^2}{3}$
3. ${\sigma }_c.\frac{b{d}^2}{4}$
4. ${\sigma }_c.\frac{b{d}^2}{6}$

Q. What is the distance between the kerns for the section given below?

1. 100 units
2. > 100 units, < 150 units
3. < 100 units
4. > 150 units

Q. The prestress profile in mass-produced pretensioned slab units of 2.8 m span for normal residential slab units of 2.8 m span for normal residential buildings would generally be

1. axial along centroidal axis
2. parabolic below centroidal axis with zero eccentricity at ends
3. straight along top kern
4. straight along bottom kern

Q. A reinforced concrete beam is to be post-tensioned in such a way that no tensile stress develops at the time of post-tensioning. The distance of the tendon from the nearest face must be

1. $\text{between}\frac{d}{5}\text{and}\frac{d}{4}$
   where $d$ is the depth of the beam
2. $<\frac{d}{6}$
   where $d$ is the depth of the beam
3. $\text{between}\frac{d}{4}\text{and}\frac{d}{3}$
   where $d$ is the depth of the beam
4. $>\frac{d}{3}$
   where $d$ is the depth of the beam