Effects of concrete-to-concrete surface treatment methods on the bending behavior of rc buildings: A numerical investigation

Abstract

The RC formwork technique is increasingly used for retrofitting existing structural members and constructing new ones. One critical factor influencing the bending capacity of reinforced concrete (RC) buildings is the slippage between concrete substrates. This study investigates the effectiveness of two surface treatment methods, shear connectors and surface irregularities, in enhancing the flexural behavior of RC structures. Specifically, the study examines the impact of different ratios of Pi-shaped shear connectors on concrete-to-concrete interfaces in RC frames built with formworks. Various ratios of these shear dowels are implemented to improve bending capacity. Additionally, the effectiveness of surface irregularities is assessed. Three-dimensional (3D) models of RC frames are simulated, with as-cast (smooth) surfaces modeled using the Coulomb friction model, characterized by a uniform friction coefficient. The numerical results indicate that the lateral bending capacity of frames constructed with RC formworks is approximately 91 % of that of a monolithic counterpart due to surface slippage. Clamping stress from shear links at the interfaces improves the nonlinear response, with an optimal shear tie ratio of around 0.4 %. Furthermore, rectangular-shaped surface irregularities more effectively enhance bending capacity than shear connectors. Both surface treatment methods not only increase bending capacity but also improve displacement ductility compared to monolithic structures, with surface irregularities providing a more significant contribution due to reduced slippage.