ABSTRACT
Formulations are presented by which a smeared rotating crack model, incorporated into an iterative total-load secant-stiffness framework, is employed to analyse reinforced concrete structures subjected to reversed cyclic loading. The analytical studies are performed using the two-dimensional nonlinear finite element program VecTor2, which employs the Disturbed Stress Field Model (DSFM) as its concrete model. Emphasis is placed on the crack-slip mechanism which calculates the slip as a function of the shear stress along the crack, accounting for cyclic degradation due to load reversals. Most smeared rotating crack models, such as the DSFM, make certain assumptions which may render them unconservative under cyclic load conditions. The crack-slip model presented in this paper addresses these assumptions, and its implementation within smeared crack formulations increases their suitability for the analysis of RC structures subjected to cyclic and reversed cyclic loading. The crack-slip model described keeps track of two distinct and alternately active cracks within one element by monitoring the change in direction of the principal stress field. A cyclic degradation law is empirically derived from tests performed on push-off specimens and included in the formulation. The slip strains in each loading cycle, calculated accordingly, are treated as independent plastic deformations. The analytical procedure is initially verified against a series of shell specimens tested under reversed cyclic shear loading. Shear wall specimens tested in the laboratory are then analysed with the new model. Better estimates of the energy dissipation, failure mode, and deformation response are obtained when accounting for cyclic crack-slip degradation.
