Structural performance of new fully and partially concrete-filled rectangular FRP-tube beams

• Full-scale rectangular partially and fully-CFFT beams were tested under flexure.
• The strength-to-weight ratio of partially-CFFT beams reaches 370% higher than RC beams.
• The ductility of fully-CFFT beams is 12 times that of RC beams in average.
• The ductility of partially-CFFT beams is 5 times that of RC beams in average.
• The structural cracking, yield, and ultimate moments of CFFT beams can be predicted theoretically.

This research introduces rectangular partially concrete-filled fiber-reinforced polymer (FRP) tube (CFFT) beams with inner voids and steel rebar. The beams contain an outer rectangular filament-wound FRP tube with an inner hollow circular or square FRP tube shifted toward the tension zone. The flexural behavior of the partially-CFFT beams was compared with a fully-CFFT beam, and another conventional steel-reinforced concrete (RC) beam having identical dimensions and flexural steel reinforcement. The results indicated that, the partially-CFFT beams had an overall strength-to-weight ratio 370% higher than that of the RC beam, while their weight was 30% lighter than the RC beam. In addition, the failure of the partially-CFFT beams was ductile in compression. The inner circular void indicated a slightly better performance than the square void in this partially-CFFT beam. Theoretical-section analysis has been conducted and compared with the experimental results.