Characterization of interface properties for modeling the shear behavior of T-beams strengthened with ultra high-performance concrete

AbstractThe application of Ultra high-performance concrete (UHPC) lateral layers on normal-strength concrete (NSC) beams substantially improves their shear performance. However, the impact of the NSC-UHPC interface properties on the shear performance has been scarcely studied and may hinder the strengthening efficiency and modify the failure mode. This study has characterized the complete shear and tensile behavior of interface specimens and evaluated the effect of anchors at the interface. Then, the complete curves of the interface allowed calibration of an interface concrete fracture (CF) model that was introduced in finite element (FE) simulations replicating the shear behavior of UHPC-strengthened T-beams tested in the same project. Parametric studies were then made with FE simulations. Results showed the FE simulations with the CF model better capture the stiffness evolution and failure mode of strengthened beams than that with the perfect bond model. The increase of UHPC layer thickness up to 80 mm and anchor spacing at the interface smaller than 300 mm considerably increased the stiffness and shear capacity of the strengthened beams. Existing dead load on beams did not impair UHPC strengthening and a substantial increase in shear capacity can still be achieved in real-size strengthened T-beams.Keywords: Anchor arrangementbeam preloadingbeam sizeconcrete fracture modelfinite-element simulationsinterface lawUHPC layer thicknessultra high-performance concrete Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThe authors would like to acknowledge the financial support obtained from NSERC and MITACS (Canadian granting agencies), and industrial partners involved in the research project (BPDL, City of Montreal, Euclid, Jacques-Cartier, and Champlain Bridges Inc., Sika and St-Lawrence Seaway). The authors also gratefully acknowledge the financial support from the China Scholarship Council (CSC) and the help of the technical staff of Polytechnique Montreal Structural Laboratory.