Can Different Design Codes Give the Accurate Prediction of Moment Capacities of High-Strength Concrete Members?

The availability and advancement of material technology and the acceptance has led to the production of higher grades of concrete. High strength concrete (HSC) offers superior engineering properties i.e. compressive strength, tensile strength, durability, modulus of elasticity and overall better performance when compared to the conventional concrete. Due to its enhanced strength and improved structural properties, high strength concrete has been increasingly used for the past two decades. In this research, many published studies on the behavior of HSC beams have been discussed and analyzed. High strength concrete used in this study is defined as concrete with compressive strength exceeding 50MPa. Although there are many publications proposing stress block models for HSC beams, a universally accepted stress block model is yet to be developed. In most design standards, the conventional rectangular stress block developed for normal strength concrete (NSC) is still being used for design of HSC beams. In this paper, published work has been analyzed to establish some understanding of flexural behavior of HSC beams. Models proposed in various design codes and standards have been analyzed to compare the experimental and theoretical moment capacities. A number of spreadsheets in Excel were developed using available data and various graphs were plotted to determine the accuracy of the code provisions for calculating the ultimate moment capacity of beams. Based on this, conclusions are drawn for the design of high strength concrete beams in flexure utilizing different code provisions.