Analytical prediction of the pinching mechanism of RC elements under cyclic shear using a rotation-angle softened truss model

In this paper, two RC elements subjected to reversed cyclic shear stresses are considered to study the effect of the steel grid orientation on the shape of the cyclic shear stress-strain curves. The presence and absence of the pinching mechanism in the post-yield shear hysteretic loops is studied using the Rotating Angle Softened Truss Model (RA-STM) theory [Hsu TTC. Softened truss model theory for shear and torsion. ACI Structural Journal 1988;85(6):624-35]. It is found that the RA-STM when combined with newly proposed cyclic material constitutive relationships can rationally predict the presence and absence of the pinching effect in the shear hysteretic loops of RC shear elements but is still incapable of predicting the descending envelopes.