Comparative study of the flexural behavior of steel fiber-reinforced lightweight aggregate concrete beams reinforced and prestressed with CFRP tendons

A comparative experimental investigation of flexural behavior of lightweight aggregate concrete (LWC) beams reinforced and prestressed with carbon fiber reinforced polymer (CFRP) bars was presented and an unbonded prestressing anchorage system for CFRP tendons was introduced. A total of four beams prestressed with unbonded CFRP bars and four reinforced with CFRP bars were tested under four-point bending, taking into account the effect of steel fiber content and clear span length. Based on the experimental results, the application of prestressing force and the addition of steel fibers reduced the deflection and crack width of the beams. The larger clear span length resulted in wider crack width and lower tendon stress increment in the prestressed specimens. A geometry-based model was proposed to calculate the tendon stress increment in terms of deflection. Accordingly, decomposing analytical procedure into a bonded beam analysis and an unbonded member analysis, an iterative algorithm for the deflection of beams prestressed with unbonded FRP tendons was developed. The proposed models yielded reasonable stress increment and deflection predictions at service load level.

Automated summary

The experimental investigation compared the flexural behavior of lightweight aggregate concrete beams reinforced and prestressed with CFRP bars, showing that prestressing force and steel fibers can reduce deflection and crack width, while longer clear span length results in wider cracks. A geometry-based model and iterative algorithm were proposed for calculating the deflection and stress increment of beams prestressed with unbonded FRP tendons.