Model test research on the concrete creep and shrinkage effects on the long-time deflection of steel concrete composite beam

This paper presents a model test research on long-term deflection of prestressed steel-concrete composite beams caused by creep and shrinkage effects of concrete. The model is designed based on a 20.8m length segment of a service composite beam bridge in Guangzhou. Geometric scale between the model and prototype is 1:8. Long-term deflection of the test model was obtained through 300 days of uninterrupted test. In addition, using the CEB-FIP (1990) criterion, effective modulus of concrete was calculated considering the effect of the concrete creep and shrinkage. Uniform the effective modulus of concrete to the modulus of steel, the value of structure's time varying stiffness was calculated with single material theory and the relationship between stiffness and deflection by introducing stiffness adjustment coefficients was established, then the value of deflection changing with time was calculated.