Numerical investigation on shear behaviour of old-to-new concrete interface with rectangular roughness tooth

Tey, Yee Chean (2024) Numerical investigation on shear behaviour of old-to-new concrete interface with rectangular roughness tooth. Final Year Project, UTAR.

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Abstract

The interface between old and new concrete in structural extension and repair is crucial for maintaining structural integrity and load-bearing capacity. Previous studies have focused on the impact of surface roughness texture on the behaviour of the concrete-to-concrete interface, but there is limited research on the effect of manipulating the roughness tooth parameter on the shear behaviour. To address this research gap, this study conducts a numerical investigation to examine the effectiveness of rectangular roughness tooth on the shear behaviour of the old-to-new concrete interface. This study used a double shear test setup and the finite element method to conduct a parametric study, exploring the relationship between tooth thickness and shear capacity, as well as the effect of confining pressure on the effectiveness of the rectangular tooth. The concrete interface parameter is calibrated using two reference specimens, followed by 18 test specimens with varying roughness tooth thickness (ranging from 30 mm to 70 mm) to conduct the parametric study. The findings indicate that increasing the tooth thickness positively impacts the ultimate shear capacity of the concrete interface. Specifically, there is a significant increase of 15.81% for the specimen batch without confining pressure and 14.87% for the specimen batch with confining pressure as tooth thickness increased from 30 mm to 70 mm. These results are supported by high coefficients of determination (R2) of 0.9206 and 0.9976, respectively. Additionally, the presence of confining pressure leads to an average increase of 19% in shear capacity. Interestingly, the results demonstrate that the existence of confining pressure does not affect the degree of influence of tooth thickness on shear strength, as the increase in ultimate shear capacity in both batches is not significantly different. Hence, it underscores the importance of considering the tooth thickness, when designing the surface roughness texture of concrete in structural extension and repair projects to achieve optimal structural performance.

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