Longitudinal joints of tubbings with newly designed high‐strength reinforcement

Abstract

Continuous tunneling using a tunnel‐boring machine is a very popular method when it comes to the construction of large tunnel projects. The use of precast reinforced concrete elements, called tubbings, is a highly economical way to secure the tunnel post excavation. Unfortunately, a loss of the load‐bearing capacity has been observed in the past in the joints between the tubbings. Reasons for that are among others the required reduction of the cross section in the longitudinal joint area and, above all, the high normal compressive forces that arise due to soil pressure. This paper describes experimental testing of longitudinal joints of tubbings conducted at TU Wien. The increase of the load‐bearing capacity of a newly designed and optimized tubbing with high‐strength joint‐compressive reinforcement, which was developed and patented by the Institute of Structural Engineering at TU Wien, is presented. The high‐strength steel is characterized by its high yield strength of 670 MPa, as well as the very large available bar diameters of up to 75 mm. This new optimized tubbing enables the production of thinner tubbings compared to conventional designs, and can thus achieve a reduction in material, transport and excavation costs.

Optimized reinforcement in longitudinal joints of segmental tunnel linings

“…Throughout the experiment, the forces were measured using four load cells and the deformations using four inductive displacement transducers (one per corner). Additionally, the vertical displacements were measured throughout the experiments in four different locations [20]. A photogrammetric measuring system allowed the continuous recording of the crack propagation.…”

“…The origin of the idea, the development and the experimental tests carried out with the new design are briefly summarized in this section of the paper. Detailed information of the experimental investigations are presented in Wolfger et al [20].…”

“…A photogrammetric measuring system allowed the continuous recording of the crack propagation. For the interpretation of the photogrammetric measurements and the concluded positive effect on the SLS for the newly designed longitudinal joint it is referred to Wolfger et al [20],…”

Hochbelastete Lastübertragungszonen mit stumpf gestoßener Bewehrung: Experimentelle Untersuchungen und numerische Simulationen

“…Erste Großversuche von zentrisch beanspruchten Tübbinglängsfugen unter Verwendung des neuartigen Bewehrungskonzepts der TU Wien werden in Wolfger et al [4] und Proksch‐Weilguni et al [5] vorgestellt. In Abschnitt 2.1 aus [5] wurden auch alternative Konzepte zur Traglaststeigerung von Tübbinglängsfugen vorgestellt.…”

“…4 durch η sl = 100 % beschrieben. Dies unterstreicht die Ergebnisse der in[4,5] vorgestellten Großversuche, in denen mit stumpf gestoßenen Längsbe wehrungsstäben eine Traglaststeigerung der Lastübertra gungszone im Ausmaß der Tragfähigkeit der Längsbe wehrungsstäbe nachgewiesen wurde.Bei Vorhandensein einer Exzentrizität e und/oder eines Abstands a ergab sich bei den experimentellen Untersu chungen ein Ausnutzungsgrad der Längsbewehrung η sl von 14-29 %, was einer deutlichen Reduktion der Effekti vität der traglaststeigernden Wirkung des Längsbeweh rungsstabs entspricht. Am Beispiel der Versuchsreihe D bedeutet der Abstand a von 50 mm des Längsstabs, dass…”