The study of the nonlinear behaviour of end blocks of post-tensioned prestressed concrete units by finite element method

Investigations have been carried out into the nonlinear behaviour of the end blocks for post-tensioned prestressed concrete units using the three dimensional finite element method. As most of the nonlinear behaviour in the end block can be attributed to cracking in the concrete, detailed studies were made into the deformational behaviour and failure of concrete at both the structural and phenomenological levels. The equations of the constitutive stress-strain relation and failure criterion derived from exhaustive experimental tests were adopted. The initial stress finite element procedure for nonlinear material analysis was adopted for the computer program. Computer runs were carried out for various end blocks up to the loading level where the Onset of Unstable Fracture Propagation (about 70%- 90% of ultimate strength) was reached. In addition to jobs with external anchors, the stress distri- butions and regions of cracking were also studied for end blocks with different types of embedded anchorages. Some end blocks'were also tested with steel reinforcement present. Comparions have been made between the results obtained and the experimental results of various researchers.