Assessing beam shear behavior with distributed longitudinal strains
Jack J. Poldon, Evan C. Bentz, Neil A. Hoult
Abstract
Abstract The demand on the longitudinal reinforcement due to shear has been traditionally based on statics but has rarely been measured. Empirical assumptions needed for the concrete stiffness and the variability of reinforcement strain due to cracking and disturbed regions complicate these measurements, and make the use of conventional strain gauges impractical. This paper investigates the use of distributed measurements from a large reinforced concrete beam test to study the effects of disturbed regions, forces at a crack, shrinkage, and the in situ modulus of elasticity of concrete. The increased demand due to shear on the longitudinal reinforcement was observed, and the Canadian code was shown to provide an accurate upper bound to the measured strain at service loads. The measured longitudinal strains were also used to estimate the average angle of principal compressive stress, and it was observed to decrease with applied load, reaching values as low as 14° near failure.