Shear model mSM-c for slender reinforced concrete members without shear reinforcement subjected to fatigue loads

摘要

Research on shear behaviour and shear capacity of reinforced concrete members without shear reinforcement is always of particular interest, especially the development of a general model for design of shear capacity of various reinforced concrete members under different load actions. One of the recent solutions to this problem is the mechanical shear model mSM, previously developed by the author, which was derived exclusively based on mechanical principles and mathematical formulations. In this paper, an extend formulation of this model, named mSM-c, for members under cyclic loads is presented. In contrast to existing methods, the new approach considers the fatigue degradation of shear capacity on the material level, taking into account the mechanical properties of concrete in detail, including the tensile strength, the fracture energy and the bond between concrete and reinforcement. The model is extensively verified using the results of shear tests published by other authors. An evaluation of the experimental-to-calculated ratio V-exp/V-cal for a shear test database of 108 simply supported beams under concentrated loads using mSM-c yielded a mean value of 1.02 and a corresponding coefficient of variation of 11%, showing a notable improvement in prediction accuracy when compared to some existing shear models. In addition, an analysis of the fatigue shear capacity of concrete members included in the shear test database shows that fatigue creep of the bond between concrete and reinforcement reduces the shear capacity by about 3%.