Inclination of cracks and bearing behaviour of prestressed UHPFRC girders subjected to shear

Research topics

Design and construction with ultra-high performance concrete (UHPC), shear bearing behaviour of reinforced concrete members

Person in charge

Kevin Metje, M.Sc.

Project description

Unlike for reinforced concrete members with shear reinforcement, a generally accepted model, which is able to describe the shear bearing behaviour of specimens without shear reinforcement consistently, does not exist until this day. Comparing different models shows that the relevant shear bearing mechanisms, namely the uncracked concrete compressive zone, the aggregate interlock, and the dowel action of the longitudinal reinforcement, are interpreted and weighted differently.

For steel fibre reinforced girders, a bearing mechanism of the fibres is added which, in the case of UHPFRC specimens, can result in a multiplication of the shear bearing capacity compared to members without any shear reinforcement. Here, the inclination angle of the shear crack determines its length and thus the actual contribution of the fibres activated in the shear crack.

In previous research on the bearing behaviour of steel fibre reinforced girders engineering models have been developed, which were empirically calibrated using individual test results. However, in terms of formation and propagation of the critical shear crack, bearing mechanism of the fibres in this crack, and interaction with the other bearing mechanisms, these models are lacking physical basis.

Within the scope of the research project, the influence of the fibre content and the influence of a longitudinal compressive force (prestressing) on the inclination of the shear crack and the shear bearing capacity of UHPFRC girders are investigated experimentally and numerically. The aim is to identify the mechanisms, which are responsible for the formation and propagation of shear cracks, as well as to gain insights into the interaction of the various bearing mechanisms.

Publications

METJE, K.; LÜTTICKE, S.; LEUTBECHER, T., 2024. Statistical Evaluation of UHPFRC Shear Verification Methods. In: FEHLING, E.; MIDDENDORF, B.; THIEMICKE, J., eds. Proceedings of HiPerMat 2024, 6th International Symposium on Ultra-High Performance Concrete and High Performance Construction Materials. Kassel, March 6-8, 2024. Kassel: kassel university press, pp. 141-144. Structural Materials and Engineering Series, Vol. 40. ISBN 978-3-7376-1159-6
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METJE, K.; LEUTBECHER, T., 2023. Verification of the shear resistance of UHPFRC beams - Design method for the German DAfStb Guideline and database evaluation. Engineering Structures. 277, 115439. doi:10.1016/j.engstruct.2022.115439
Appendix A. Supplementary Data 1. UHPC and UHPFRC Shear Data Base

METJE, K.; LEUTBECHER, T., 2022. Querkrafttragverhalten stahlfaserverstärkter UHFB-Biegeträger mit Kompaktquerschnitt. Beton- und Stahlbetonbau. 117(10), 812-825. doi:10.1002/best.202200046

METJE, K.; LEUTBECHER, T., 2022. Zur Querkraftbemessung von Biegeträgern aus stahlfaserverstärktem ultrahochfesten Beton – Teil 2: Datenbankauswertung und Überprüfung des Bemessungsansatzes/Design of ultra-high performance fibre-reinforced concrete girders subjected to shear – Part 2: database evaluation and review of design approach. Bauingenieur. 97(4), 122-130. doi:10.37544/0005-6650-2022-04-66 

METJE, K.; LEUTBECHER, T., 2022. Zur Querkraftbemessung von Biegeträgern aus stahlfaserverstärktem ultrahochfesten Beton – Teil 1: Bemessungsansatz und Datenbank/Design of ultra-high performance fibre-reinforced concrete girders subjected to shear – Part 1: design approach and database. Bauingenieur. 97(3), 83-90-12. doi:10.37544/0005-6650-2022-03-67 

METJE, K.; LEUTBECHER, T., 2021. Experimental investigations on the shear bearing behavior of prestressed ultra-high performance fiber-reinforced concrete beams with compact cross-section. Structural Concrete. 22(6), 3746-3762. doi:10.1002/suco.202100337
Supporting Information: Data S1. A: Shear tests / B: Time-dependent deformation and loss of prestress

METJE, K.; LEUTBECHER, T., 2020. Experimental investigations on the shear bearing capacity of UHPFRC beams with compact cross-section. In: MIDDENDORF, B.; FEHLING, E.; WETZEL, A., eds. Proceedings of HiPerMat 2020, 5th International Symposium on Ultra-High Performance Concrete and High Performance Construction Materials. Kassel, March 11-13, 2020. Kassel: kassel university press, pp. 9-10. Structural Materials and Engineering Series, Vol. 32. ISBN 978-3-7376-0828-2
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