Ultimate analysis of prestressed and partially prestressed sections by strain compatibility

A non-linear analysis procedure which attempts to predict the behavior at ultimate of prestressed and partially prestressed sections is presented. It takes into consideration the non-linear characteristics of the steel but assumes that the strains and forces in the concrete at ultimate are well approximated by the ACI specifications. The numerical techniques and the computer program implementing the proposed procedure are rapidly reviewed. They help analyze the influence on ultimate behavior of major variables such as type of prestressing steel, amount of non- prestressed reinforcement, ultimate compressive strain and stress block dimensional coefficients of the concrete. Examples of applications and typical results are presented. It is shown that although the ACI recommended procedure to predict ultimate moment capacity is reasonably accurate and conservative, it may lead to substantial error in predicting strain in the prestressing steel and the corresponding curvature of the section. /Author/