Fatigue Behaviour of Keyed Dry Joints for Segmental Structures Made of Ultra-High Performance Fiber-Reinforced Concrete

• Applicant: Professor Dr.-Ing. Vincent Oettel
• Subject Area: Structural Engineering, Building Informatics and Construction Operation
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 538139593

Numerous bridges will have to be replaced in the coming years due to damage and increased traffic loads. Segmental bridge constructions with keyed dry joints made of ultra-high performance fiber-reinforced concrete (UHPFRC) are highly effective and forward-looking and, above all, they are far more economical and ecological and therefore more sustainable than conventional in-situ constructions using normal concrete. They combine the advantages of segmental constructions, which can be prefabricated independently of weather conditions, with higher quality, in shorter construction time and, even more, less labour-intensive than on-site constructions with the advantages of UHPFRC with its very high compressive strength, post-cracking tensile strength and durability. Thus, extremely slender, thin-walled, resource-saving as well as weight-, mass- and transport-optimised segmental bridges with very high load-bearing capacity, outstanding durability and long service life can be built. It must be taken into account that segmental joints are areas of discontinuity. Thus the load-bearing capacity of the keyed dry joint is decisive for the load-bearing safety of the entire segmental construction. Furthermore, slender and filigree constructions are more susceptible to fatigue loads. In case of thin-walled UHPFRC-structures, the lower dead loads result in a larger ratio between cyclic and static loads compared to normal concretes, which can lead to less favourable fatigue loading. It is unclear to what extent cyclic loads affect the load-bearing capacity of keyed dry joints made of UHPFRC. Basically, the degradation behaviour of keyed UHPFRC dry joints under cyclic loading has not even rudimentarily been understood, yet. Within this research project the damage processes and mechanisms of keyed UHPFRC dry joints shall be investigated under fatigue loading. Systematically graded experimental investigations are to be carried out on small- and large-format test specimens under cyclic loading, such as compression, bending, shear and segmental beam tests. The tests are to be documented, evaluated and analysed by mechanical measuring methods and imaging techniques and supplemented by numerical investigations (FEM). On the basis of the results, an approach to describe the fatigue resistance of keyed dry joints made of UHPFRC will be derived. The main goal of this research project is to record, to understand, to describe and to predict the degradation behaviour of keyed, segmental dry-joints made of ultra-high performance fiber-reinforced concrete under cyclic loading.

• DFG Programme: Research Grants