Experimental and Analytical Investigation of Ultra-High-Performance Reinforced Concrete (UHPRC) Rectangular Slender Columns Under Uni-Axial Loading and Bi-Axial Bending

Ultra-high-performance reinforced concrete (UHPRC) is seen to be a potential material that could be used for modern construction purposes due to its high strength, durability, and better mechanical characteristics. This research explores the behaviour of ultra-high-performance reinforced concrete rectangular slender columns when subject to axial load and flexural stresses using both experiments and computational modeling. In total, eighty-one samples of columns have been investigated using concentrated, uniaxially eccentric and biaxially eccentric loading. For each case, three strength levels (M60, M70, and M80) and three longitudinal steel ratios (1.34%, 2.09%, and 3.01%) have been considered. From the experiment, it can be seen that an increase in the concrete strength led to a substantial increase in carrying capacity, up to 29% in M80 samples compared to M60 samples with respect to uniaxial eccentric loading. Moreover, an increased steel ratio added to the load-bearing capacity by 17–20%. In order to confirm the experimental results, some non-linear finite element analyses were carried out, incorporating important aspects of non-linearity like cracking and crushing. The analysis results showed an agreement of about 4–9% with the experiment. These conclusions led to the development of an interaction diagram and a simplified analytical approach to design slender UHPRC columns under eccentric loads.