POISSON EFFECT IN REINFORCED CONCRETE MEMBRANE ELEMENTS

RC shear elements behave very differently before vs. after cracking. The Poisson effect before cracking is characterized by the Poisson's ratio, but after cracking is characterized by 2 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 0. This study describes the experiments performed to measure these 2 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 vs. shear strain curves of membrane elements, including the postpeak descending branches.