Experimental and Numerical Investigation of Different Types of Jacketing Effect on Retrofitting RC Short Columns Using ECC Concrete

Given the deterioration of civil infrastructure throughout the world, developing more efficient repair and strengthening is essential. Jacketing is one of the most common methods for retrofitting reinforced concrete (RC) columns. Notably, using engineered cementitious composite (ECC) within the jacketing area increases the bearing capacity and significantly enhances the ductility of the columns. The recent development of ECC concrete with suitable compressive strength and higher ductility of about 5 % can significantly enhance the performance of reinforced concrete structures. The behavior of retrofitted RC columns depends heavily on the cohesion between the jacket and the original column as well as the mechanical properties of the jacketing materials. This study investigates jacketed square and circular RC columns using ECC and conventional/normal concrete (NC) using different casing techniques to retrofit RC columns, namely galvanized mesh, U and L-shape joints, removing the cover, core drilling, and integrated models. All specimens were subjected to a compression test. The results indicate that in both square and circular specimens, the use of ECC as a super ductile material and vertical U-shaped elements to connect the longitudinal rebars of the casing and the core leads to much higher ductility and bearing capacity than in NC specimens. These elements also showed suitable ductility because of using ECC as a super ductile material. In order to optimize these methods, finite element analysis (FEA) was conducted using Abaqus software to verify experimental models, as well as a parametric study to achieve an optimum design of the jacketing

Studying the compressive, tensile and flexural properties of binary and ternary fiber-reinforced UHPC using experimental, numerical and multi-target digital image correlation methods

Compressive, tensile, and flexural properties of ultra-high-performance concrete (UHPFRC) specimens were studied in this research. Binary and ternary combinations of micro steel (MS), round crimped (RC), crimped (C), hooked-end (H), and polypropylene (PP) fibers were used in overall ratios of 2 % by volume of concrete. For this purpose, 100×200 mm cylindrical specimens, dog-bone specimens (length: 330 mm, width: 80 mm, thickness: 40 mm), and prismatic beams with a dimension of 100×100×500 mm (clear span: 450 mm) were cast and tested under compressive, tensile, and four-point bending tests (4PBT). A digital image correlation (DIC)-based method namely, multi-target digital image correlation (MT-DIC) was used to record the displacement and deflection values in tension and flexure tests. Furthermore, experimental findings were used in numerical simulations and additional analyses were carried out as complementary studies to provide a better understanding of the governing parameters; length, width, depth, and overall size of the beams. Results revealed that a hybrid combination of micro and macro steel fibers performs better than other specimens in all the investigated parameters and the MT-DIC method proved to be a very useful tool in capturing the displacement and deflection values. Furthermore, the inverse analysis approach for the numerical simulation of beams and nonlinear regression-based models captured the direct tension and flexural results with coefficient of determination (R2) values above 0.90