Flexural Performance of Post-tensioned Rectangular Concrete-Filled FRP Tubes (CFFT) Beams Using High and Normal Strength Concrete

Abstract

AbstractThis paper presents the test results of an experimental study aimed at investigating the flexural behavior of prestressed high and normal strength concrete filled fibre-reinforced polymer (FRP)- rectangular tubes (CFFT) beams. Two unbonded post-tensioned (PCFFT) beams were constructed with different concrete compressive strength ranged from 40 to 70 MPa. All beams had identical cross-sectional of 305 × 406 mm2. The beams were tested under a four-point bending. The test results confirm the feasibility of using post-tensioned rectangular CFFT system for flexural members. The results indicate that the PCFFTs beams are capable of developing very high inelastic flexural deformations and ultimate capacity. High-strength and normal-strength concrete prestressed CFFT beams show almost similar inelastic load-deflection behaviors. While increasing the concrete compressive strength from 40 to 70 MPa enhanced the initial stiffness and load before cracking. After cracking, however, prestressed CFFT beam constructed with high-strength concrete exhibit only a 7% increase in the ultimate flexural moment capacity with no significant change in the ultimate deflection compare to normal-strength concrete beam. The proposed analytical model based on partially confined concrete model successfully predicts the flexural moment capacity of the tested beams with satisfactory accuracy on average of 1.08 ± 0.03. However, further experimental tests are needed to better understand the flexural behavior of PCFFTs with a wide range of concrete compressive strength.KeywordsPrestressedConcrete-filled tubePost-tensioningHigh-strength concreteConfinement