Many devastating earthquakes exceeding the design basis levels have occurred in the past. Safety assessment of equipments and piping systems of industrial/nuclear safety related structures subjected to earthquakes beyond design basis levels necessitates consideration of the structural nonlinearity. The Instructure or floor response spectra (FRS) are the input required for qualification of these systems and hence it is essential to generate this input considering structural nonlinearity. This paper addresses the experimental and analytical work on generation of FRS for nonlinear Reinforced Cement Concrete (RCC) structure. Push over and shake table experiments are performed on three storeyed RCC framed structure. A simplified analytical approach is proposed to derive earthquake-induced In-structure response spectra for the structure deforming beyond elastic limits. In this approach, initially, the performance of the structure is evaluated using pushover analysis. Floor spectra of the structure are then obtained considering the degraded stiffness and increased damping evaluated at each performance level iteratively from pushover curve. The floor spectra of the structure generated by the proposed method are validated using experimentally simulated results from shake table tests.