determination of moment parameters of rectangular stress block for high-strength prestressed concrete

Various structural design codes for reinforced and prestressed concrete propose different equations and recommendations for the parameters of the rectangular stress block. however, these formulations are often valid only for a specific ultimate strain and are primarily based on concrete with a compressive strength below 50 mpa. in this study, with the aim of evaluating the accuracy and adequacy of these parameters for high-strength prestressed concrete, the stress-strain curve and equivalent stress block parameters were calculated throughout the entire loading process. to achieve this, a simplified third-degree polynomial stress-strain relationship was proposed and compared with experimental data for both compressed (high-strength) and non-compressed (normal-strength) concretes. the results demonstrated that the proposed model has acceptable accuracy in predicting the actual behavior of both compressed and non-compressed concretes, and it can be used to derive instantaneous parameters of the stress block. the obtained stress block parameters were compared with code-based relationships and previous studies, revealing that certain code assumptions require modification when applied to high-strength concrete.