Flexural Behavior of Unbonded Prestressed Concrete Composite Beams Manufactured with Glass-Fiber-Reinforced Lightweight Aggregate Concrete and Conventional Concrete

Light aggregate concrete beams are prone to wide cracks and brittle failure. In response to these shortcomings, the objective of the present study is to propose unbonded prestressed concrete composite beams manufactured with glass-fiber-reinforced lightweight aggregate concrete and conventional concrete and verify the reliability of the design provisions of JBJ 12-2006 for such beams. Flexural performance tests were conducted on 11 such beams, showing that this structural form can reduce component self-weight by about 20%. Joining the two types of concrete using a ridged interface can effectively prevent bond-slip damage. The model code used in JBJ 12-2006 significantly overestimates maximum crack width for such beams. Theoretical analysis found that the influences on the stress increment of prestressed reinforcement are the comprehensive reinforcement index and prestressed reinforcement index. A theoretical model of this stress increment was obtained by fitting test data, ultimately resulting in a formula for flexural bearing capacity. Based on regression modeling of test data, the average crack spacing and strain uneven coefficient of steel bars were adjusted, while a method for calculating the average crack width was also obtained. On this basis, a model of maximum crack width was obtained by modifying the crack width amplification coefficient (adjusted from 1.5 specified in JBJ 12-2006 to 1.42). The proposed beam model and calculation methods have valuable engineering applications.