In the high-rise buildings, describ in brief the structural behavior of " flat slab building structures " ?

The flat slab it self though relatively flexible provides strength to the system because of the continuty with the shear walls and columns.One can visualize that the portion of the slab will act as a shallow beam continuous with the columns thus behaving as  a rigid frame. Hence the behavior of the total system is similar to that a core frame system also serves to show the behavior of flat slab buildings.

The lateral forces are primarily resisted  by frame action in the upper portion of the structure and by the shear walls or core system in the lower portion. 

the problem with the flat slab system ... although it provids continuity because it acts as a diaphragm ... is the lack of redundancy : a flat slab is a beamless slab where there are no beams so if one column fails for a reason (say earthquake  damage) ,the load sustained by that column will not be transfered to the nearby columns because the beams , which are the "means of transportation" dont exist ! so in severe seismic regions dual systems (frames (special and intermediate) and shear walls) are advisable !

The flat slab structures are needed to connect the vertical shear elements, so you not only calculate them as slabs but also as horizontal beams

This is done according to the solid base and flexible sheets, and taking the natural factors as having a strong impact on tall buildings, such as the wind