Cracking of pre-tensioned beams

At the serviceability limit state international standards require for partially prestressed concrete members the decompression of the section under quasi-permanent loads or the limitation of the cracking under frequent loads, depending on the environmental exposure class. The calculation of crack width needs to tackle two fundamental problems: the calculation of stresses and the different bond properties of ordinary reinforcement and prestressing steel. Some attempts to deal with these aspects can be found in the literature and in international standards (Eurocode 2, Model Code 1990), but some improvements are needed to permit applications. Structural behaviour is analyzed in this paper distinguishing two phases, that is, the single crack formation phase and the stabilized cracking phase. A crack width calculation method is proposed as an improvement to the methods introduced by international standards.