Experimental Study on the Long-Term Behaviour of RBPC T-Beams

This study compares the mechanical properties of the retard-bonded and conventionally bonded prestressed concrete (RBPC and BPC, respectively) under uniform loads. Results show that the prestressed strands and concrete of the RBPC T-beams are firmly bonded with harden of retard-bonded materials, thereby exhibiting the same mechanical properties as that of the BPC beams. The growth rate of the long-term deflections of the RBPC T-beam is slightly lower than that of the BPC T-beam. Given the effect of concrete shrinkage, creep and time variation of prestress loss, the regular patterns of deflection growth of the RBPC T-beam mid-spans are analysed based on the age-adjusted effective modulus method, method of equivalent prestress load and calculation model of prestress loss. Accordingly, the long-term deflection development curves of the RBPC T-beam mid-spans under self-weight, prestressing force and external loads are obtained. Calculation results are in good agreement with the test results. This method has immense applicability for the computation of the RBPC T-beams, and can be used to estimate the long-term deflection growth of regular patterns of the RBPC components.