Causes of Stiffness Degradation in Steel–UHPC Composite Beam-Bolted Connections

This groundbreaking study conducts the first_ever field push test on anchor bolts in steel–UHPC composite pavement in China, providing researchers with the opportunity to obtain the true mechanical performance of the anchor bolts after more than a decade of operation. As a result, the study comprehensively studies the long-term performance of anchor bolts in steel–UHPC composite pavement. The study established a finite element model of steel–UHPC pavement based on the mechanical properties of studs obtained from the field push-back tests, and the mechanical properties of studs were modeled by COMBIN39 and COMBIN14 elements. The reasons for the degradation of the bolt performance were analyzed by combining the anchorage force transfer model of the composite beam and the fatigue formula of the stiffness degradation of the bolt, based on the results of the finite element method. The study revealed that the stress of the anchor bolts gradually equilibrates along the longitudinal direction after prolonged service, with the end anchor bolts experiencing an offloading phenomenon and the middle span anchor bolts experiencing an increasing load phenomenon. Furthermore, the study identified the residual slip at the interface of the anchor bolt as a significant factor in the longitudinal stress redistribution of the anchor bolt, and construction errors further promoted stress redistribution. The study’s findings contribute to advancing the design and construction of steel–UHPC composite pavement. Additionally, the study proposes a novel approach to accurately evaluate the stiffness of pavements by combining the anchor bolt extrapolation test with a finite element model, with a maximum error of no more than 5 percent, which can be applied in future pavement design and construction.

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