Analytical approach to factors affecting long-term tension stiffening

It is widely accepted that tension stiffening of reinforced concrete reduces in the long term. In the codes of practice, this is accounted for by means of a modification in the empirical parameters to interpolate the average response of the reinforced member between the states I (uncracked) and II (bare steel). This average response is actually the result of the interaction of the different time-dependent mechanisms which develop in the element. In a tension member, the behaviour is mainly influenced by concrete creep and shrinkage and time-dependent bond deterioration. The role played by these processes is still unknown. An analytical approach is developed in this paper in order to understand the influence of such processes in the long-term decay of tension stiffening in tension members. The model is able to explain the experimental response of specimens tested in the literature and the results show the major influence of the time-dependent bond deterioration (bond creep and bond stiffness modification), rather than concrete creep and shrinkage.