Flexural behavior of lightweight concrete beams reinforced with GFRP bars and prestressed with steel strands

The present research is focused on developing efficient, durable flexural members by combining the use of lightweight concrete (LWC), fiber-reinforced polymer (FRP) bars, and prestressing. The use of LWC reduces the structural weight while providing suitable thermal insulation whereas using FRP bars instead of steel reinforcement provides corrosion resistance, light weight, high tensile strength, and fatigue resistance. Both materials possess smaller moduli of elasticity compared to those in materials within conventional construction, which may cause large deflections and excessive crack widths that are addressed via prestressing. Six LWC beam specimens were fabricated and tested, all of which contained FRP bars. Two specimens were not prestressed, one in under-reinforced and the other in over-reinforced conditions. The other four specimens contained different configurations of prestressing steel in addition to FRP bars. The experimental results were used to validate nonlinear finite element models in Abaqus. Results showed that of a prestress level of 6 MPa in concrete reduced the beam deflection at failure by 28% and increased the cracking load by three times. Therefore, a relatively small prestress level could compensate for the increase in deflection and possible cracking, which shows the merits of this combination in providing an optimal solution for the structural members of the future.