قوة احتكاك القص لمفاصل البناء الخرسانية عالية الأداء

Shear Friction Strength of Ultra- High Performance Concrete Construction Joints

Abstract

In this study, the shear friction behavior of UHPC was investigated both experimentally and numerically by conducting tests on 9 push-off specimens using ultra-high performance concrete (UHPC). UHPC is distinguished from other types of concrete by lack of coarse aggregate, steel fiber reinforcing, low water-to-cement ratio, low permeability, compressive strength exceeding 120 MPa, and average tensile strength 10.77 MPa. To maximize the benefits of UHPC in joints, new model guidelines for its application are required. In order to employ hybrid design approaches with this novel material without putting anyone safety at risk, the contact between the UHPC has to be described. The major parameters considered are the types of interfacing and using of shear reinforcement through the shear plane. Key factors affecting shear performance of individual construction joint were investigated in terms of shear strength, failure mechanism, and slip responses.
The observations from experimental tests showed that the increase in the shear reinforcement improves shear resistance, the grooved interfacing wear was discovered to be a successful approach compared to other interfacing techniques for increasing the shear capacity of a contact, in contrast to the exposed fibers specimens, which were shown to be ineffective in increasing the shear strength. The finite element method using (ABAQUS) was utilized to create a model for the structural behavior of push-off specimen. In terms of the maximum slip and the ultimate load capacity, the findings revealed that there was a good agreement between experimental and the numerical results. The mean differences in the ultimate load capacity were (7.56) %. Various new parameters were suggested to be investigated numerically by the verified model, such as the number of dowel bars, and the concrete strength.
The numerical findings showed that increasing the number of dowel bars from one to two and from three to four was able to enhance the final load capacity by 23% and 14 %, respectively, in contrast with one dowel bar and three dowel bars. Furthermore, increasing the concrete strength from (120 to 200 MPa) had a clear performance and more efficient to obtain higher ultimate load by (59 and 60 %) for the specimens with rectangle and circular grooves respectively. Finally, an interaction formula for the shear friction strength was proposed on the basis of the experimental results, to predict the shear load-carrying capacity of the UHPC structures.