chapter  8
66 Pages

Time-dependent mechanics of structural concrete

This chapter fi rst presents a new time-dependent constitutive model which encompasses both near-and post-peak regions in concrete compression. In order to contribute towards a better evaluation of structural collapse under extreme loads, a coupled plastic-damaging law is presented and applied to non-linear collapse analysis in line with the multi-scale concept, and its applicability is verifi ed. Repetition of higher stresses apparently causes progressive damage, which is also rate-dependent on strain and stress. Second, this chapter discusses the separate time-dependent cumulative non-linearity and the effect of repetition of the strain path on the overall damage evolution of concrete in compression. Third, this transient non-linear analysis is also proposed as a way of predicting the long-term deformation and safety performance of structural concrete with and without cracking, and a mechanistic creep constitutive model for pre-and post-cracking tension stiffness is presented. The effect of drying shrinkage is integrated into the predictive scheme using the thermo-hydro physics of porous media discussed in Chapter 3 and Chapter 7, and a simple equivalent method of analysis is discussed for the practical durability performance assessment of structural concrete. Careful verifi cation of the model is carried out with respect to the creep defl ection of reinforced concrete (RC) beams and slabs subjected to multi-axial fl exure. Three-dimensional fi ber and plate and shell elements are used for the space discretization of the analysis domain.