Flexural behavior and crack width prediction of UHPC-steel strip composite decks under sagging moments

The UHPC-steel strip composite deck is a novel technique for strengthening in-service orthotropic steel decks with numerous fatigue cracks penetrating the steel deck plate. However, the anti-cracking behavior of the new composite decks under sagging moments is still unclear and formulas for prediction of the crack width at the bottom surface of the UHPC layer is unavailable. In this study, the flexural behavior of the UHPC-steel strip composite deck under sagging moments was investigated through a series of experimental tests. In the tests, the width of the steel strips and the thickness of the UHPC layer were considered as the two primary parameters. The responses of the UHPC-steel strip composite specimens, including the load–deflection curve, failure mode of the specimens, interfacial slippage, and nominal cracking stress of UHPC, were systematically analyzed and discussed. The test results indicate that the specimens with steel strips possessed a better anti-cracking performance compared to that of the specimens without steel strips. This phenomenon implies that the steel strips should impede the initiation and propagation of cracks in UHPC. Moreover, an increase to the width of the steel strips could reduce the average crack spacing and maximum crack width of UHPC. Further, theoretical formulas were proposed to calculate the maximum crack width at the bottom surface of the UHPC layer. The theoretical results obtained via the proposed formulas agreed well with the test results, confirming that the proposed analysis method should be suitable for the UHPC-steel strip composite deck. So the proposed method could be utilized to calculate the crack width at the bottom surface of the UHPC layer under sagging moments.