First of all you have to distinguish between the "stiffness" of a building, which conditions mainly the frequencies of the system and the "stiffness" of an element, or the Elastic Modulus of the material in which the building is made. For what concerns buildings, it is not true that you can directly correlate stiffness with strength, but your question is very ill-posed. The main effect of changing the stiffness is to change the periods of a building, and an increase in stiffness is not always a good idea if you move your periods along the response spectrum. Though, it is true that, generally speaking, if you increase the stiffness of a building you lower the periods of the building, this leading to low-require of displacements. This results, though, in very high force levels in the structural elements. 

If the answer to your question was a yes, the easier way to design a building would be to just design it a stiff as possible, because the higher the stiffness, the higher the resistance, but this is not true.

First of all you have to distinguish between the "stiffness" of a building, which conditions mainly the frequencies of the system and the "stiffness" of an element, or the Elastic Modulus of the material in which the building is made. For what concerns buildings, it is not true that you can directly correlate stiffness with strength, but your question is very ill-posed. The main effect of changing the stiffness is to change the periods of a building, and an increase in stiffness is not always a good idea if you move your periods along the response spectrum. Though, it is true that, generally speaking, if you increase the stiffness of a building you lower the periods of the building, this leading to low-require of displacements. This results, though, in very high force levels in the structural elements. 

If the answer to your question was a yes, the easier way to design a building would be to just design it a stiff as possible, because the higher the stiffness, the higher the resistance, but this is not true.

Generally speaking, a sufficient lateral stiffness of  buildings is required to reduce inter-storey drift which in turn will result in lower damaging non structural  elements under wind and seismic excitations.

In reinforced concrete structures, the stiffness of the elements is not closely correlated with the resistance level. Moreover, in buildings a low lateral stiffness will also result in P-Delta and second order effects due to the eccentricity of gravity loads related to drifts.

On the other hand, it is true that most of the earthquakes produces lower actions for more flexible systems having a higher natural vibration period. To combine  these conflicting aspects was developed the strategy of Base Isolation System which reduces the equivalent stiffness of special bearings at the base in a part located outside the body of the construction.

Dear Dr. Bruno Palazzo

Regarding base isolation system, we can't use it for high rise building. It can be used only for limited height (many articles recommended to use base isolation up to five floors)

Dear Dr. Dia Eddin Nassani,

I agree that base isolation strategy is not indicated for high rise building since to realize the isolation you should move the natural vibration period around 3 time the fixed  base one reaching too high base isolated period.  

May be you question is "Does strength of concrete (Compressive strength) affects the stiffness of high rise structures?"

Compressive strength is empirically related to modulus of elasticity (E) of concrete. Stiffness depends on E. Thus compressive strength can be empirically related to the stiffness of the structure.

Dear Dr. Dia Eddin Nassani,

I am not agree with the term you have used the number of floors. The terms of limitation would be used for flexible structures. Even there are usage of base isolation with more number of floors. 

Stiffness of a building does not affect the strength of concrete.

Strength of concrete is independent from the building design.