The arch of a bridge over a river is in the form of a semi-circle of radius 3 m. The bridge width is 10 m. Due to a flood the water level raises 1.5 m above the crest of the arch. Calculate (a) The upward force the arch, (b) the horizontal thrust on the half of the arch.

1. The upward force will be the imaginary volume of water held over the surface.

Now, the imaginary volume of water =

Total upward force = 128.7 x 9810 = 1.26 MN

2. The horizontal force on each side,

         

   Answer: 1.26 MN; 0.883 MN