Sir .. what is the use of -ve reinforcement?

I am constructing a 6m span continuous 500mm x 500mm RC beam with a clear span of 3.6m between RC column supports. I noticed that the top bars at the support(negative moment) is only 3- 20mm diameter deformed bars while the bottom bars is 5  20mm diameter. Is it possible to have more bars in the compression side than the tension side of the RC beam? The beam is to be constructed in a place with no history of earthquake.