What is the difference between shock load and gradually applied loads and suddenly applied Load?

The only difference between a shock load and a gradually applied load is something called an impulse; defined as the integral of a force with respect to time. When a force is applied to a rigid body it changes the momentum of that body. A small force applied for a long time can produce the same momentum change as a large force applied briefly, because it is the product of the force and the time for which it is applied that is important.