This paper provides a distinct study on the performance of different residential buildings with different height and length spans under the influence of applied loads according to the Turkish standard TS498. The research paper presents the nonlinear performance of the buildings and provides a clear picture of the plastic and its stages throughout the construction. The study explains the effect of the various stages of plastic and how it affects the rigidity of the building. The results portray the building's stiffness values and how they change. The results show that stiffness increases with length-increase and decreases by decreasing the height of buildings. All stiffness values were calculated according to the first plastic hinge formation. Software used is ETABS 2018 and all calculations and parameters used according to FEMA356-2000, ASCE 7-16, ACI-318, EURO code 8, and Turkish standard.

Slabs are one of the most basic components concerning the cost of the structure, because of the number of building materials utilized. It is of incentive to think about the current technologies available, meaning to make these slabs cost less or even improve its behaviour. Cobiax and post-tension slabs systems show up as an appropriate alternative. In light of this reason, this paper focuses on demonstrating the advantages and disadvantages of both Cobiax and post-tension systems. Nowadays, these systems are very popular all around the world. It is very necessary to have a wide understanding of the differences in cost and the construction duration between these two systems and have good knowledge about the advantages and disadvantages of both types. Firstly, the properties of these types of slabs have been reported and the advantages and disadvantages for both systems and then the cost and time has been compared, which are the most important factors for the owners. Finally, it has been made a comparison between the reinforcement quantities, concrete quantities, final cost and duration to finalize the construction stage.  As a result, it has been found that the post-tension system is more economical than the Cobiax system according to reinforcement quantities, on the other hand, Cobiax system is more economical in concrete quantities which leads to lighter buildings and fewer reinforcement quantities in foundations. When the construction duration has been considered, it has been found that the post-tension is the quickest system in the construction field because it is increasing the strength and durability of the structure which the Cobiax system cannot provide.