Experimental study and theoretical analysis on the flexural performance of steel–bamboo composite beams strengthened with externally prestressed steel strands

The influence of prestress techniques on the flexure performance of steel–bamboo​ composite beams was investigated by testing twelve specimens, considering the prestressing scheme, and loading scheme as parameters. The experimental performances, failure modes, and mechanical characteristics were observed and analyzed. The effects of different parameters on deformation performance, failure modes, and load-bearing capacity were explored, and theoretical methods were proposed for estimating deformation and resistance. The results indicated that the failure of the test specimens was mainly material damage due to the tearing of bamboo flanges, interface debonding, and local buckling of steel sheets, depending on the choice of prestressing and loading schemes. The prestressed composite beams exhibited a relatively better deformation performance than ordinary beams. The equivalent bending stiffness increased by up to 30% in the serviceability limit state; therefore, the prestressed specimens generated smaller deflections under the same vertical load. Moreover, the two-point prestressed specimens exhibited better deformation performance than the one-point prestressed specimens. Finally, a comparison of the results indicated that the proposed methods provided feasible estimations of the deformation in the serviceability limit state and load-bearing capacity in the ultimate limit state, with relative errors of approximately 5% on average.