Analytical study on the mechanical behavior of longitudinal joints in shield tunnel strengthened by a steel ultra-high performance concrete composite

Abstract

A mechanical calculation model for longitudinal joints strengthened by steel ultra-high performance concrete (UHPC) composites was first proposed and validated against the numerical results. This method can continuously calculate the mechanical response of the whole process by real-time monitoring and adjusting the stress stage of each material, eliminating the need to divide stages based on experimental phenomena. Parameter analysis was performed to explored the influence of strengthening parameter and axial force level. The strengthening mechanism under sagging and hogging moments was investigated and compared. Under sagging moments, the strengthening effect is significant, boosting the load-bearing capacity by 4.14 times and increasing the flexural stiffness by 2.93 times. Under hogging moments, a more pronounced improvement in flexural stiffness is observed. For sagging moments, the primary factors influencing structural bearing capacity and stiffness are the thickness of the steel plate and UHPC, respectively. Under hogging moments, the axial force level emerged as the most critical factor for enhancing structural mechanical performance. The strengthening mechanisms differ under sagging and hogging moments, with the former effectively leveraging the mechanical properties of the strengthening material, while the latter further explore the bending resistance of the bolts. These findings contribute to the theoretical foundation for practical engineering strengthening.

Graphical abstract

Keywords

longitudinal joint / analytical solution / strengthening mechanism / steel UHPC composite

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Acknowledgements

The present work was carried out with the support of National Natural Science Foundation of China (Grant Nos. 51938005, 52090082, and 52378395). These financial supports are gratefully acknowledged.

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11709-025-1150-2 and is accessible for authorized users.

Competing interests

The authors declare that they have no competing interests.

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