A Proposed Formula for Predicting Size Effect on Shear Strength of Concrete Beams Without Coarse Aggregate

Abstract

In this research, the size effect on shear strength of concrete beams without coarse aggregate has been studied by evaluating the ACI 318-14, ACI 318-19, and Eurocode 2 formulas. The beam specimens had the width, length, a/d, and maximum aggregate size of 6 cm, 110 cm, 2.744, and 0.6 mm, respectively. The beam's depths had been set to have a range from 6 to 18 cm. The compressive strengths of the beam were in between 58.51 and 99.80 MPa. The beams had been tested under two concentrated loads. The longitudinal reinforcement consisted of two diameter 16 mm. The beams were designed without any stirrups. Based on the analysis, the ACI 318-19 approach provides the best prediction with the mean strength ratio and coefficient of variation of 1.5086 and 0.26, respectively. The ACI 318-19 also indicates insignificant downward trend on the strength ratio vs. effective depth. The test results show that the size effect is in good agreement with the Bažant’s size effect law. In this paper, modifications to the existing formula are given to provide more accurate prediction.