Pipe racks are important part of Industrial Structures such as oil refineries, petrochemical sector, as they are used to support piping systems that transports fluids from one place to the other. The aim of this study is to carry out Linear Dynamic Analysis of Ethanol gas plant pipe rack considering coupled and decoupled case (for both pipe empty and operating conditions), using ANSYS and validating with Staad Pro. While analysing pipe rack generally, the point masses calculated due to the weight of piping system and fluid are applied on the pipe rack structure, which usually satisfies the seismic mass criteria, but the stiffness added due to piping system and their supports are been neglected. The effect on seismic demand of Pipe rack, due to additional masses and stiffness of piping system have been checked. It is observed that in coupled case the modal frequencies of the structure is higher due to additional pipe stiffness, but at the same time base shear values are lower as compared to decoupled case