Poisson Effect in Reinforced Concrete Membrane Elements

Reinforced concrete shear elements behave very differently before and after cracking. The Poisson effect before cracking is characterized by the well-known Poisson's ratio, but after cracking is characterized by two Hsu/Zhu ratios. In the postyield range, the Hsu/Zhu ratio V sub 12 (tensile strain caused by perpendicular compressive strain) was found to be a constant of 1.9, and the Hsu/Zhu ratio V sub 21 (compressive strain caused by perpendicular tensile strain) was measured to be zero. This study describes the experiments performed to measure these two Hsu/Zhu ratios, which provide the basis for the establishment of the softened membrane model (SMM). This new theory, reported in a companion paper, can predict the entire shear stress versus shear strain curves of membrane elements, including the postpeak descending branches.