Strengthening of reinforced concrete (RC) structures with fiber-reinforced polymer (FRP) composites has become an attractive alternative for the construction industry in recent years. Unfortunately, the cost of carbon FRP or glass FRP in strengthening/repairing of RC structures is expensive. In this paper, reliability of a cheap polypropylene fiber in strengthening of RC columns and shear walls under seismic loads is investigated. For the sake of comparison, the responses of twin large-scale RC models subjected to various simulated earthquakes on a large shaking table are investigated. The columns and shear wall of the first story of one of the twin models are strengthened with 3-D woven polypropylene fiber-reinforced polymer (3-D PP-FRP). However, the other RC model is not strengthened. The results show that the PP-FRP enhances the performance of the strengthened model to sustain relatively high dynamic excitations due to significant increase in confinement, shear capacity and consequently lateral resistance of its supporting elements. This results in the postponing of structural failure. Also, even after two additional simulated earthquakes, the mode of failure of the columns is changed from the total collapse in un-strengthened model to structural damage at columns’ end connections for the strengthened one. Thus, the used material is promising in strengthening or rehabilitation of RC structures, since it is very cheap and light relative to other composite materials.