Compressive behavior of large-size square PEN FRP-concrete-steel hybrid multi-tube concrete columns

Fiber-reinforced polymer (FRP)-concrete-steel hybrid multi-tube concrete column (MTCC) is a new type of composite column and comprises a number of steel inner tubes, an FRP external tube and concrete fillings for the space inside all the tubes. This paper presents a series of experimental tests on four large-size square PEN (polyethylene naphthalate) FRP-MTCCs, of which the PEN fibers were extracted from recycled plastic bottles. The parameters of interest include the FRP thickness and the steel tube configuration. The experimental results showed that the large-size square MTCCs with PEN FRP exhibited excellent ductility due to the effective confinement provided by PEN FRP jacket and steel tubes. A prediction method for the square PEN FRP-MTCCs has been developed in the present study to consider the unique characteristics of the column and is able to produce reasonable predictions for the experimental results. This study serves to present an innovative alternative in an environmentally friendly way that can replace the conventional bridge piers in coastal and salina regions.