Novel 3D printed bars for retrofitting heat damaged RC beams

Abstract

Three-dimensional (3D) printing is a novel technique that has been recently used in producing printed composites for strengthening and rehabilitating complex structures. This research investigates the applicability of printed bars in strengthening and repairing unheated and heat-damaged reinforced concrete (RC) beams. The printed bars were made using Polylactic Acid (PLA) and 20% of carbon fibers. Beams were subjected to a high temperature of 700 °C for 3 h. The Near-surface mounted technique (NSM) was then adopted to strengthen the ordinary RC beams and repair the heat damaged beams using the 3D printed bars. Test results have shown that strengthening and repairing RC beams using the 3D printed bars can increase the load-carrying capacity and the initial stiffness of the beams. The 3D printed bars increased the load-carrying capacity of the heat-damaged beams up to 34%, and hence they restored their load-carrying capacity. The flexural strength was then predicted using the ACI-440 code and compared to the experimental results. The formulations proposed by the ACI-440 for calculating the flexural strength of RC beams strengthened using NSM-FRP bars are applicable but conservative in predicting the flexural strength of the beams strengthened using NSM-3D printed bars.