Connection of the prefabricated updeck of road tunnels by a short lap-spliced joint using ultra-high-performance fiber-reinforced concrete

Abstract

Prefabricated internal structures of road tunnels, consisting of precast elements and the connections between them, provide advantages in terms of quality control and manufacturing costs. However, the limited construction space in tunnels creates challenges for on-site assembly. To identify feasible connecting joints, flexural tests of precast straight beams connected by welding-spliced or lap-spliced reinforcements embedded in normal concrete or ultra-high-performance fiber-reinforced concrete (UHPFRC) are first performed and analyzed. With an improvement in the strength grade of the closure concrete for the lap-spliced joint, the failure of the beam transforms from a brittle splitting mode to a ductile flexural mode. The beam connected by UHPFRC100 with short lap-spliced reinforcements can achieve almost equivalent mechanical performance in terms of the bearing capacity, ductility, and stiffness as the beam connected by normal concrete with welding-spliced reinforcements. This favorable solution is then applied to the connection of neighboring updeck slabs resting on columns in a double-deck tunnel. The applicability is validated by flexural tests of T-shaped joints, which, fail in a ductile fashion dominated by the ultimate bearing capacity of the precast elements, similar to the corresponding straight beam. The utilization of UHPFRC significantly reduces the required lap-splice length of reinforcements owing to its strong bonding strength.

Graphical abstract

Keywords

UHPFRC / prefabricated updeck / road tunnel / lap-spliced rebars / flexural tests

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Acknowledgements

The work of the first author was sponsored by the Shanghai Pujiang Program (No. 20PJ1406100) and the National Natural Science Foundation of China (Grant No. 52208398). In addition, the financial support from the Sino-German Center for Research Promotion, provided within project GZ 1574, is gratefully acknowledged. The last author acknowledges financial support from the Science and Technology Commission of Shanghai Municipality (No. 21DZ1203504) and the National Natural Science Foundation of China (Grant No. 51808336). Moreover, the interesting discussions with Mr. Enjie HU are gratefully acknowledged.

Conflict of Interest

The authors declare that they have no conflict of interest.

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