If the maximum dip of a parabolic tendon carrying tension P is h and the effective length of the pre-stressed beam is L, the upward uniform pressure will be A. $$\frac{{8{\text{hP}}}}{l}$$ B. $$\frac{{8{\text{hP}}}}{{{l^2}}}$$ C. $$\frac{{8{\text{h}}l}}{{\text{P}}}$$ D. $$\frac{{8{\text{h}}l}}{{{{\text{P}}^2}}}$$

The correct answer is $\boxed{\frac{{8{\text{hP}}}}{{{l^2}}}}$.

The upward uniform pressure is the force per unit area that is exerted by the tendon on the beam. It is equal to the tension in the tendon divided by the effective length of the beam. The tension in the tendon is equal to the product of the maximum dip of the tendon and the effective length of the beam. The effective length of the beam is the distance from the point where the tendon is attached to the beam to the point where the tendon is attached to the support.

The upward uniform pressure can be calculated using the following formula:

$$\text{Upward uniform pressure} = \frac{{8{\text{hP}}}}{{{l^2}}}$$

where:

• $h$ is the maximum dip of the tendon
• $P$ is the tension in the tendon
• $l$ is the effective length of the beam

The other options are incorrect because they do not take into account the effective length of the beam.