Respected Researcher I simulated behavior of FRP jacketed circular columns using confined concrete 01 material model which is available in Open Sees. I observed that the time period of column after applying FRP is not reducing and also If I increase the number of layers, the time period is not changing. why it is happening like this?. I am thinking that the material model is not taking in to consideration of stiffness enhancement due to FRP. Because of this reason, time period is not reducing. Please correct me if I am wrong. Thank you Sai